RESUMEN

Conventional live virus research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of coronavirus disease-19 (COVID-19), requires Biosafety Level 3 (BSL-3) facilities. SARS-CoV-2 pseudotyped viruses have emerged as valuable tools in virology, mimicking the entry process of the SARS-CoV-2 virus into human cells by expressing its spike glycoprotein in a surrogate system using recombinant plasmids. One significant application of this tool is in functional assays for the evaluation of neutralizing antibodies. Pseudotyped viruses have the advantage of being competent for only a single cycle of infection, providing better safety and versatility and allowing them to be studied in BSL-2 laboratories. Here, we describe three protocols for the detection of SARS-CoV-2 neutralizing antibodies through a pseudotyped virus assay. First, SARS-CoV-2 S pseudotyped viruses (PV SARS-CoV-2 S) are produced using a Moloney murine leukemia virus (MuLV) three-plasmid system. The plasmids are designed to express the GagPol packing proteins, enhanced green fluorescent protein (eGFP) as a readout system, and the SARS-CoV-2 S protein modified to remove the endoplasmic reticulum retention domain and to improve infection. Next, the internalization of PV SARS-CoV-2 S protein in human embryonic kidney 293T (HEK-293T) cells overexpressing angiotensin-converting enzyme 2 (HEK-293T-ACE2) is confirmed by fluorescence microscopy and quantified using flow cytometry. Finally, PV SARS-CoV-2 S is used to screen neutralizing antibodies in serum samples from convalescent COVID-19 patients; it can also be used for studying the cell entry mechanisms of different SARS-CoV-2 variants, evaluating antiviral agents, and designing vaccines. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Generation of PV SARS-CoV-2 S pseudotyped virus Basic Protocol 2: Assay of PV SARS-CoV-2 S internalization in target cells. Basic Protocol 3: Detection of neutralizing antibodies in serum samples.

Asunto(s)

Anticuerpos Neutralizantes , Anticuerpos Antivirales , COVID-19 , SARS-CoV-2 , Humanos , Anticuerpos Neutralizantes/inmunología , Anticuerpos Neutralizantes/sangre , SARS-CoV-2/inmunología , Anticuerpos Antivirales/inmunología , Anticuerpos Antivirales/sangre , COVID-19/virología , COVID-19/inmunología , COVID-19/diagnóstico , COVID-19/sangre , Pruebas de Neutralización/métodos , Células HEK293 , Pseudotipado Viral , Glicoproteína de la Espiga del Coronavirus/inmunología , Glicoproteína de la Espiga del Coronavirus/genética

RESUMEN

Connexins (Cxs) function as gap junction (GJ) channels and hemichannels that mediate intercellular and transmembrane signaling, respectively. Here, we investigated the proximal segment of the first extracellular loop, E1, of two closely related Cxs, Cx26 and Cx30, that share widespread expression in the cochlea. Computational studies of Cx26 proposed that this segment of E1 contains a parahelix and functions in gating. The sequence of the parahelix is identical between Cx26 and Cx30 except for an Ala/Glu difference at position 49. We show through cysteine-scanning and mutational analyses that position 49 is pore-lining and interacts with the adjacent Asp50 residue to impact hemichannel functionality. When both positions 49 and 50 are charged, as occurs naturally in Cx30, the hemichannel function is dampened. Co-expression of Cx30 with Cx26(D50N), the most common mutation associated with keratitis-ichthyosis-deafness syndrome, results in robust hemichannel currents indicating that position 49-50 interactions are relevant in heteromerically assembled hemichannels. Cysteine substitution at position 49 in either Cx26 or Cx30 results in tonic inhibition of hemichannels, both through disulfide formation and high-affinity metal coordination, suggestive of a flexible region of the pore that can narrow substantially. These effects are absent in GJ channels, which exhibit wild-type functionality. Examination of postnatal cochlear explants suggests that Cx30 expression is associated with reduced propagation of Ca2+ waves. Overall, these data identify a pore locus in E1 of Cx26 and Cx30 that impacts hemichannel functionality and provide new considerations for understanding the roles of these connexins in cochlear function.

Asunto(s)

Conexina 26 , Conexina 30 , Conexinas , Conexina 26/metabolismo , Conexina 26/genética , Animales , Conexina 30/metabolismo , Conexina 30/genética , Humanos , Conexinas/metabolismo , Conexinas/genética , Dominios Proteicos , Uniones Comunicantes/metabolismo , Ratones , Células HEK293 , Cóclea/metabolismo , Cóclea/fisiología

RESUMEN

In this work, we cloned and functionally expressed two novel GABAA receptor subunits from Procambarus clarkii crayfish. These two new subunits, PcGABAA-α and PcGABAA-ß2, revealed significant sequence homology with the PcGABAA-ß subunit, previously identified in our laboratory. In addition, PcGABAA-α subunit also shared a significant degree of identity with the Drosophila melanogaster genes DmGRD (GABA and glycine-like receptor subunits of Drosophila) as well as PcGABAA-ß2 subunit with DmLCCH3 (ligand-gated chloride channel homolog 3). Electrophysiological recordings showed that the expression in HEK cells of the novel subunits, either alone or in combination, failed to form functional homo- or heteromeric receptors. However, the co-expression of PcGABAA-α with PcGABAA-ß evoked sodium- or chloride-dependent currents that accurately reproduced the time course of the GABA-evoked currents in the X-organ neurons from crayfish, suggesting that these GABA subunits combine to form two types of GABA receptors, one with cationic selectivity filter and the other preferentially permeates anions. On the other hand, PcGABAA-ß2 and PcGABAA-ß co-expression generated a chloride current that does not show desensitization. Muscimol reproduced the time course of GABA-evoked currents in all functional receptors, and picrotoxin blocked these currents; bicuculline did not block any of the recorded currents. Reverse transcription polymerae chain reaction (RT-PCR) amplifications and FISH revealed that PcGABAA-α and PcGABAA-ß2 are predominantly expressed in the crayfish nervous system. Altogether, these findings provide the first evidence of a neural GABA-gated cationic channel in the crayfish, increasing our understanding of the role of these new GABAA receptor subunits in native heteromeric receptors.

Asunto(s)

Astacoidea , Clonación Molecular , Receptores de GABA-A , Animales , Astacoidea/genética , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Clonación Molecular/métodos , Humanos , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Células HEK293 , Secuencia de Aminoácidos , Neuronas/metabolismo

RESUMEN

Dronedarone (DRN) is a clinically used drug to mitigate arrhythmias with multichannel block properties, including the sodium channel Nav1.5. Extracellular acidification is known to change the pharmacological properties of several antiarrhythmic drugs. Here, we explore how modification in extracellular pH (pHe) shapes the pharmacological profile of DRN upon Nav1.5 sodium current (INa) and in the ex vivo heart preparation. Embryonic human kidney cells (HEK293T/17) were used to transiently express the human isoform of Nav1.5 α-subunit. Patch-Clamp technique was employed to study INa. Neurotoxin-II (ATX-II) was used to induce the late sodium current (INaLate). Additionally, ex vivo Wistar male rat preparations in the Langendorff system were utilized to study electrocardiogram (ECG) waves. DRN preferentially binds to the closed state inactivation mode of Nav1.5 at pHe 7.0. The recovery from INa inactivation was delayed in the presence of DRN in both pHe 7.0 and 7.4, and the use-dependent properties were distinct at pHe 7.0 and 7.4. However, the potency of DRN upon the peak INa, the voltage dependence for activation, and the steady-state inactivation curves were not altered in both pHe tested. Also, the pHe did not change the ability of DRN to block INaLate. Lastly, DRN in a concentration and pH dependent manner modulated the QRS complex, QT and RR interval in clinically relevant concentration. Thus, the pharmacological properties of DRN upon Nav1.5 and ex vivo heart preparation partially depend on the pHe. The pHe changed the biological effect of DRN in the heart electrical function in relevant clinical concentration.

Asunto(s)

Antiarrítmicos , Dronedarona , Canal de Sodio Activado por Voltaje NAV1.5 , Ratas Wistar , Humanos , Concentración de Iones de Hidrógeno , Dronedarona/farmacología , Animales , Masculino , Células HEK293 , Canal de Sodio Activado por Voltaje NAV1.5/metabolismo , Ratas , Antiarrítmicos/farmacología , Corazón/efectos de los fármacos , Corazón/fisiología , Electrocardiografía/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Espacio Extracelular/metabolismo , Espacio Extracelular/efectos de los fármacos

RESUMEN

Neurotransmission is critical for brain function, allowing neurons to communicate through neurotransmitters and neuropeptides. RVD-hemopressin (RVD-Hp), a novel peptide identified in noradrenergic neurons, modulates cannabinoid receptors CB1 and CB2. Unlike hemopressin (Hp), which induces anxiogenic behaviors via transient receptor potential vanilloid 1 (TRPV1) activation, RVD-Hp counteracts these effects, suggesting that it may block TRPV1. This study investigates RVD-Hp's role as a TRPV1 channel blocker using HEK293 cells expressing TRPV1-GFP. Calcium imaging and patch-clamp recordings demonstrated that RVD-Hp reduces TRPV1-mediated calcium influx and TRPV1 ion currents. Molecular docking and dynamics simulations indicated that RVD-Hp interacts with TRPV1's selectivity filter, forming stable hydrogen bonds and van der Waals contacts, thus preventing ion permeation. These findings highlight RVD-Hp's potential as a therapeutic agent for conditions involving TRPV1 activation, such as pain and anxiety.

Asunto(s)

Endocannabinoides , Canales Catiónicos TRPV , Humanos , Calcio/metabolismo , Endocannabinoides/farmacología , Endocannabinoides/metabolismo , Endocannabinoides/química , Células HEK293 , Hemoglobinas , Simulación del Acoplamiento Molecular , Simulación de Dinámica Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/farmacología , Fragmentos de Péptidos/metabolismo , Canales Catiónicos TRPV/metabolismo , Canales Catiónicos TRPV/antagonistas & inhibidores

RESUMEN

Mammalian Ste-20-like Kinases 1 and 2 (MST1/2) are core serine-threonine kinases of the Hippo pathway regulating several cellular processes, including cell cycle arrest and cell death. Here, we discovered a novel alternative splicing variant of the MST2 encoding gene, STK3, in malignant cells and tumor datasets. This variant, named STK3∆7 or MST2∆7 (for mRNA or protein, respectively), resulted from the skipping of exon 7. MST2∆7 exhibited increased ubiquitylation and interaction with the E3 ubiquitin-protein ligase CHIP compared to the full-length protein (MST2FL). Exon 7 in STK3 encodes a segment within the kinase domain, and its exclusion compromised MST2 interaction with and phosphorylation of MOB, a major MST1/2 substrate. Nevertheless, MST2∆7 was capable of interacting with MST1 and MST2FL. Unlike MST2FL, overexpression of MST2∆7 did not lead to increased cell death and growth arrest. Strikingly, we observed the exclusion of STK3 exon 7 in 3.2-15% of tumor samples from patients of several types of cancer, while STK3∆7 was seldomly found in healthy tissues. Our study identified a novel STK3 splicing variant with loss of function and the potential to disturb tissue homeostasis by impacting on MST2 activities in the regulation of cell death and quiescence.

Asunto(s)

Empalme Alternativo , Proliferación Celular , Proteínas Serina-Treonina Quinasas , Serina-Treonina Quinasa 3 , Humanos , Proteínas Adaptadoras Transductoras de Señales , Línea Celular Tumoral , Exones/genética , Células HEK293 , Factor de Crecimiento de Hepatocito/genética , Factor de Crecimiento de Hepatocito/metabolismo , Neoplasias/genética , Neoplasias/patología , Neoplasias/metabolismo , Fosforilación , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Serina-Treonina Quinasa 3/genética , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitinación/genética

RESUMEN

Aberrant activation of the Hedgehog (Hh) signalling pathway has been associated with the development and progression of pancreatic cancer. For this reason, blockade of Hh pathway by inhibitors targeting the G protein-coupled receptor Smoothened (SMO) has been considered as a therapeutic target for the treatment of this cancer. In our previous work, we obtained a new SMO ligand based on a purine scaffold (compound I), which showed interesting antitumor activity in several cancer cell lines. In this work, we report the design and synthesis of 17 new purine derivatives, some of which showed high cytotoxic effect on Mia-PaCa-2 (Hh-dependent pancreatic cancer cell lines) and low toxicity on non-neoplastic HEK-293 cells compared with gemcitabine, such as 8f, 8g and 8h (IC50 = 4.56, 4.11 and 3.08 µM, respectively). Two of these purines also showed their ability to bind to SMO through NanoBRET assays (pKi = 5.17 for 8f and 5.01 for 8h), with higher affinities to compound I (pKi = 1.51). In addition, docking studies provided insight the purine substitution pattern is related to the affinity on SMO. Finally, studies of Hh inhibition for selected purines, using a transcriptional functional assay based on luciferase activity in NIH3T3 Shh-Light II cells, demonstrated that 8g reduced GLI activity with a IC50 = 6.4 µM as well as diminished the expression of Hh target genes in two specific Hh-dependent cell models, Med1 cells and Ptch1-/- mouse embryonic fibroblasts. Therefore, our results provide a platform for the design of SMO ligands that could be potential selective cytotoxic agents for the treatment of pancreatic cancer.

Asunto(s)

Antineoplásicos , Neoplasias Pancreáticas , Purinas , Receptor Smoothened , Humanos , Receptor Smoothened/antagonistas & inhibidores , Receptor Smoothened/metabolismo , Purinas/química , Purinas/farmacología , Purinas/síntesis química , Neoplasias Pancreáticas/tratamiento farmacológico , Neoplasias Pancreáticas/patología , Neoplasias Pancreáticas/metabolismo , Ligandos , Antineoplásicos/farmacología , Antineoplásicos/química , Antineoplásicos/síntesis química , Animales , Ratones , Relación Estructura-Actividad , Ensayos de Selección de Medicamentos Antitumorales , Estructura Molecular , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Células HEK293 , Línea Celular Tumoral , Células 3T3 NIH , Simulación del Acoplamiento Molecular , Proteínas Hedgehog/metabolismo , Proteínas Hedgehog/antagonistas & inhibidores

RESUMEN

Alamandine (ALA) exerts protective effects similar to angiotensin (Ang) (1-7) through Mas-related G protein-coupled receptor type D receptor (MrgDR) activation, distinct from Mas receptor (MasR). ALA induces anti-inflammatory effects in mice but its impact in human macrophages remains unclear. We aimed to investigate the anti-inflammatory effects of ALA in human macrophages. Interleukin (IL)-6 and IL-1ß were measured by ELISA in human THP-1 macrophages and human monocyte-derived macrophages exposed to lipopolysaccharide (LPS). Consequences of MasR-MrgDR heteromerization were investigated in transfected HEK293T cells. ALA decreased IL-6 and IL-1ß secretion in LPS-activated THP-1 macrophages. The ALA-induced decrease in IL-6 but not in IL-1ß was prevented by MasR blockade and MasR downregulation, suggesting MasR-MrgDR interaction. In human monocyte-derived M1 macrophages, ALA decreased IL-1ß secretion independently of MasR. MasR-MrgDR interaction was confirmed in THP-1 macrophages, human monocyte-derived macrophages, and transfected HEK293T cells. MasR and MrgDR formed a constitutive heteromer that was not influenced by ALA. ALA promoted Akt and ERK1/2 activation only in cells expressing MasR-MrgDR heteromers, and this effect was prevented by MasR blockade. While Ang-(1-7) reduced cellular proliferation in MasR -but not MrgDR- expressing cells, ALA antiproliferative effect was elicited in cells expressing MasR-MrgDR heteromers. ALA also induced an antiproliferative response in THP-1 cells and this effect was abolished by MasR blockade, reinforcing MasR-MrgDR interaction. MasR-MrgDR heteromerization is crucial for ALA-induced anti-inflammatory and antiproliferative responses in human macrophages. This study broaden our knowledge of the protective axis of the RAS, thus enabling novel therapeutic approaches in inflammatory-associated diseases.

Asunto(s)

Proliferación Celular , Interleucina-6 , Macrófagos , Proto-Oncogenes Mas , Proteínas Proto-Oncogénicas , Receptores Acoplados a Proteínas G , Sistema Renina-Angiotensina , Humanos , Macrófagos/efectos de los fármacos , Macrófagos/metabolismo , Proliferación Celular/efectos de los fármacos , Células HEK293 , Receptores Acoplados a Proteínas G/metabolismo , Interleucina-6/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Sistema Renina-Angiotensina/efectos de los fármacos , Sistema Renina-Angiotensina/fisiología , Células THP-1 , Multimerización de Proteína/efectos de los fármacos , Oligopéptidos

RESUMEN

The biological clock in eukaryotes controls daily rhythms in physiology and behavior. It displays a complex organization that involves the molecular transcriptional clock and the redox oscillator which may coordinately work to control cellular rhythms. The redox oscillator has emerged very early in evolution in adaptation to the environmental changes in O2 levels and has been shown to regulate daily rhythms in glycerolipid (GL) metabolism in different eukaryotic cells. GLs are key components of lipid droplets (LDs), intracellular storage organelles, present in all living organisms, and essential for energy and lipid homeostasis regulation and survival; however, the cell bioenergetics status is not constant across time and depends on energy demands. Thus, the formation and degradation of LDs may reflect a time-dependent process following energy requirements. This work investigated the presence of metabolic rhythms in LD content along evolution by studying prokaryotic and eukaryotic cells and organisms. We found sustained temporal oscillations in LD content in Pseudomonas aeruginosa bacteria and Caenorhabditis elegans synchronized by temperature cycles, in serum-shock synchronized human embryonic kidney cells (HEK 293 cells) and brain tumor cells (T98G and GL26) after a dexamethasone pulse. Moreover, in synchronized T98G cells, LD oscillations were altered by glycogen synthase kinase-3 (GSK-3) inhibition that affects the cytosolic activity of the metabolic oscillator or by knocking down LIPIN-1, a key GL synthesizing enzyme. Overall, our findings reveal the existence of metabolic oscillations in terms of LD content highly conserved across evolutionary scales notwithstanding variations in complexity, regulation, and cell organization.

Asunto(s)

Caenorhabditis elegans , Gotas Lipídicas , Pseudomonas aeruginosa , Humanos , Gotas Lipídicas/metabolismo , Animales , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Células HEK293 , Pseudomonas aeruginosa/metabolismo , Pseudomonas aeruginosa/genética , Relojes Biológicos/genética , Evolución Biológica , Metabolismo de los Lípidos/genética , Ritmo Circadiano/genética , Ritmo Circadiano/fisiología

RESUMEN

Polycystic kidney disease (PKD), a disease characterized by the enlargement of the kidney through cystic growth is the fourth leading cause of end-stage kidney disease world-wide. Transient receptor potential Vanilloid 4 (TRPV4), a calcium-permeable TRP, channel participates in kidney cell physiology and since TRPV4 forms complexes with another channel whose malfunction is associated to PKD, TRPP2 (or PKD2), we sought to determine whether patients with PKD, exhibit previously unknown mutations in TRPV4. Here, we report the presence of mutations in the TRPV4 gene in patients diagnosed with PKD and determine that they produce gain-of-function (GOF). Mutations in the sequence of the TRPV4 gene have been associated to a broad spectrum of neuropathies and skeletal dysplasias but not PKD, and their biophysical effects on channel function have not been elucidated. We identified and examined the functional behavior of a novel E6K mutant and of the previously known S94L and A217S mutant TRVP4 channels. The A217S mutation has been associated to mixed neuropathy and/or skeletal dysplasia phenotypes, however, the PKD carriers of these variants had not been diagnosed with these reported clinical manifestations. The presence of certain mutations in TRPV4 may influence the progression and severity of PKD through GOF mechanisms. PKD patients carrying TRVP4 mutations are putatively more likely to require dialysis or renal transplant as compared to those without these mutations.

Asunto(s)

Enfermedades Renales Poliquísticas , Canales Catiónicos TRPV , Canales Catiónicos TRPV/genética , Canales Catiónicos TRPV/metabolismo , Humanos , Enfermedades Renales Poliquísticas/genética , Enfermedades Renales Poliquísticas/patología , Mutación , Femenino , Masculino , Células HEK293 , Mutación con Ganancia de Función , Canales Catiónicos TRPP/genética , Adulto

RESUMEN

BACKGROUND: SARS-CoV2 virus, responsible for the COVID-19 pandemic, has four structural proteins and 16 nonstructural proteins. S-protein is one of the structural proteins exposed on the virus surface and is the main target for producing neutralizing antibodies and vaccines. The S-protein forms a trimer that can bind the angiotensin-converting enzyme 2 (ACE2) through its receptor binding domain (RBD) for cell entry. AIMS: The goal of this study was to express in HEK293 cells a new RBD recombinant protein in a constitutive and stable manner in order to use it as an alternative immunogen and diagnostic tool for COVID-19. MATERIALS & METHODS: The protein was designed to contain an immunoglobulin signal sequence, an explanded C-terminal section of the RBD, a region responsible for the bacteriophage T4 trimerization inducer, and six histidines in the pCDNA-3.1 plasmid. Following transformation, the cells were selected with geneticin-G418 and purified from serum-fre culture supernatants using Ni2+-agarand size exclusion chromatography. The protein was structurally identified by cross-linking and circular dichroism experiments, and utilized to immunize mice in conjuction with AS03 or alum adjuvants. The mice sera were examined for antibody recognition, receptor-binding inhibition, and virus neutralization, while spleens were evaluated for γ-interferon production in the presence of RBD. RESULTS: The protein released in the culture supernatant of cells, and exhibited a molecular mass of 135 kDa with a secondary structure like the monomeric and trimeric RBD. After purification, it formed a multimeric structure comprising trimers and hexamers, which were able to bind the ACE2 receptor. It generated high antibody titers in mice when combined with AS03 adjuvant (up to 1:50,000). The sera were capable of inhibiting binding of biotin-labeled ACE2 to the virus S1 subunit and could neutralize the entry of the Wuhan virus strain into cells at dilutions up to 1:2000. It produced specific IFN-γ producing cells in immunized mouse splenocytes. DISCUSSION: Our data describe a new RBD containing protein, forming trimers and hexamers, which are able to induce a protective humoral and cellular response against SARS-CoV2. CONCLUSION: These results add a new arsenal to combat COVID-19, as an alternative immunogen or antigen for diagnosis.

Asunto(s)

Enzima Convertidora de Angiotensina 2 , Anticuerpos Neutralizantes , Anticuerpos Antivirales , COVID-19 , Proteínas Recombinantes , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus , Animales , Humanos , Glicoproteína de la Espiga del Coronavirus/inmunología , Glicoproteína de la Espiga del Coronavirus/genética , Glicoproteína de la Espiga del Coronavirus/química , Ratones , Anticuerpos Neutralizantes/inmunología , SARS-CoV-2/inmunología , COVID-19/inmunología , COVID-19/prevención & control , Proteínas Recombinantes/inmunología , Proteínas Recombinantes/genética , Proteínas Recombinantes/química , Células HEK293 , Enzima Convertidora de Angiotensina 2/metabolismo , Enzima Convertidora de Angiotensina 2/inmunología , Anticuerpos Antivirales/inmunología , Vacunas contra la COVID-19/inmunología , Ratones Endogámicos BALB C , Femenino , Multimerización de Proteína , Dominios Proteicos/inmunología , Unión Proteica

RESUMEN

Protein ADP-ribosylation plays important but ill-defined roles in antiviral signalling cascades such as the interferon response. Several viruses of clinical interest, including coronaviruses, express hydrolases that reverse ADP-ribosylation catalysed by host enzymes, suggesting an important role for this modification in host-pathogen interactions. However, which ADP-ribosyltransferases mediate host ADP-ribosylation, what proteins and pathways they target and how these modifications affect viral infection and pathogenesis is currently unclear. Here we show that host ADP-ribosyltransferase activity induced by IFNγ signalling depends on PARP14 catalytic activity and that the PARP9/DTX3L complex is required to uphold PARP14 protein levels via post-translational mechanisms. Both the PARP9/DTX3L complex and PARP14 localise to IFNγ-induced cytoplasmic inclusions containing ADP-ribosylated proteins, and both PARP14 itself and DTX3L are likely targets of PARP14 ADP-ribosylation. We provide evidence that these modifications are hydrolysed by the SARS-CoV-2 Nsp3 macrodomain, shedding light on the intricate cross-regulation between IFN-induced ADP-ribosyltransferases and the potential roles of the coronavirus macrodomain in counteracting their activity.

Asunto(s)

ADP-Ribosilación , Interferón gamma , Poli(ADP-Ribosa) Polimerasas , Humanos , Poli(ADP-Ribosa) Polimerasas/metabolismo , Interferón gamma/metabolismo , Interacciones Huésped-Patógeno , Células HEK293 , ADP Ribosa Transferasas/metabolismo , ADP Ribosa Transferasas/genética , Procesamiento Proteico-Postraduccional , SARS-CoV-2/metabolismo , Proteínas de Neoplasias , Ubiquitina-Proteína Ligasas

RESUMEN

The development of cell-based fluorescent assays has resulted in an incredible tool for searching new ion channels' modulators with a biophysical and clinical profile. Among all the ion channels, potassium (K+)-permeable channels represent the most diverse and relevant for cell function, making them attractive targets for drug discovery. Some of the cell-based assays for K+ channels take advantage of a thallium-sensitive dye whose fluorescence increased upon the binding of thallium (Tl+), an ion able to move through K+ channels. We optimize the FLIPR Potassium Assay Kit based on thallium influx to measure the Kv10.1 activity.

Asunto(s)

Talio , Talio/metabolismo , Humanos , Colorantes Fluorescentes/química , Células HEK293 , Fluorescencia , Canales de Potasio Éter-A-Go-Go

RESUMEN

MAIN CONCLUSION: We generated transplastomic tobacco lines that stably express a human Basic Fibroblast Growth Factor (hFGFb) in their chloroplasts stroma and purified a biologically active recombinant hFGFb. MAIN: The use of plants as biofactories presents as an attractive technology with the potential to efficiently produce high-value human recombinant proteins in a cost-effective manner. Plastid genome transformation stands out for its possibility to accumulate recombinant proteins at elevated levels. Of particular interest are recombinant growth factors, given their applications in animal cell culture and regenerative medicine. In this study, we produced recombinant human Fibroblast Growth Factor (rhFGFb), a crucial protein required for animal cell culture, in tobacco chloroplasts. We successfully generated two independent transplastomic lines that are homoplasmic and accumulate rhFGFb in their leaves. Furthermore, the produced rhFGFb demonstrated its biological activity by inducing proliferation in HEK293T cell lines. These results collectively underscore plastid genome transformation as a promising plant-based bioreactor for rhFGFb production.

Asunto(s)

Cloroplastos , Factor 2 de Crecimiento de Fibroblastos , Nicotiana , Plantas Modificadas Genéticamente , Proteínas Recombinantes , Nicotiana/genética , Nicotiana/metabolismo , Humanos , Factor 2 de Crecimiento de Fibroblastos/genética , Factor 2 de Crecimiento de Fibroblastos/metabolismo , Cloroplastos/metabolismo , Cloroplastos/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Células HEK293 , Proliferación Celular , Hojas de la Planta/metabolismo , Hojas de la Planta/genética

RESUMEN

LPA3 receptors were expressed in TREx HEK 293 cells, and their signaling and phosphorylation were studied. The agonist, lysophosphatidic acid (LPA), increased intracellular calcium and ERK phosphorylation through pertussis toxin-insensitive processes. Phorbol myristate acetate, but not LPA, desensitizes LPA3-mediated calcium signaling, the agonists, and the phorbol ester-induced LPA3 internalization. Pitstop 2 (clathrin heavy chain inhibitor) markedly reduced LPA-induced receptor internalization; in contrast, phorbol ester-induced internalization was only delayed. LPA induced rapid ß-arrestin-LPA3 receptor association. The agonist and the phorbol ester-induced marked LPA3 receptor phosphorylation, and phosphorylation sites were detected using mass spectrometry. Phosphorylated residues were detected in the intracellular loop 3 (S221, T224, S225, and S229) and in the carboxyl terminus (S321, S325, S331, T333, S335, Y337, and S343). Interestingly, phosphorylation sites are within sequences predicted to constitute ß-arrestin binding sites. These data provide insight into LPA3 receptor signaling and regulation.

Asunto(s)

Lisofosfolípidos , Receptores del Ácido Lisofosfatídico , Transducción de Señal , Humanos , beta-Arrestinas/metabolismo , Sitios de Unión , Señalización del Calcio , Células HEK293 , Lisofosfolípidos/metabolismo , Fosforilación , Receptores del Ácido Lisofosfatídico/metabolismo

RESUMEN

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that causes severe outbreaks in human populations. ZIKV infection leads to the accumulation of small non-coding viral RNAs (known as sfRNAs) that are crucial for evasion of antiviral responses and for viral pathogenesis. However, the mechanistic understanding of how sfRNAs function remains incomplete. Here, we use recombinant ZIKVs and ribosome profiling of infected human cells to show that sfRNAs block translation of antiviral genes. Mechanistically, we demonstrate that specific RNA structures present in sfRNAs trigger PKR activation, which instead of limiting viral replication, enhances viral particle production. Although ZIKV infection induces mRNA expression of antiviral genes, translation efficiency of type I interferon and interferon stimulated genes were significantly downregulated by PKR activation. Our results reveal a novel viral adaptation mechanism mediated by sfRNAs, where ZIKV increases its fitness by repurposing the antiviral role of PKR into a proviral factor.

Asunto(s)

Biosíntesis de Proteínas , ARN Viral , Replicación Viral , Infección por el Virus Zika , Virus Zika , eIF-2 Quinasa , Virus Zika/genética , Humanos , eIF-2 Quinasa/metabolismo , eIF-2 Quinasa/genética , ARN Viral/metabolismo , ARN Viral/genética , Infección por el Virus Zika/virología , Infección por el Virus Zika/genética , Infección por el Virus Zika/inmunología , Replicación Viral/genética , ARN no Traducido/genética , ARN no Traducido/metabolismo , Animales , Chlorocebus aethiops , Células HEK293 , Línea Celular

RESUMEN

N-glycosylation is the most common protein modification in the eukaryotic secretory pathway. It involves the attachment a high mannose glycan to Asn residues in the context of Asn-X-Ser/Thr/Cys, a motif known as N-glycosylation sequon. This process is mediated by STT3A and STT3B, the catalytic subunits of the oligosaccharyltransferase complexes. STT3A forms part of complexes associated with the SEC61 translocon and functions co-translationally. Vacant sequons have another opportunity for glycosylation by complexes carrying STT3B. Local sequence information plays an important role in determining N-glycosylation efficiency, but non-local factors can also have a significant impact. For instance, certain proteins associated with human genetic diseases exhibit abnormal N-glycosylation levels despite having wild-type acceptor sites. Here, we investigated the effect of protein stability on this process. To this end, we generated a family of 40 N-glycan acceptors based on superfolder GFP, and we measured their efficiency in HEK293 cells and in two derived cell lines lacking STT3B or STT3A. Sequon occupancy was highly dependent on protein stability, improving as the thermodynamic stability of the acceptor proteins decreases. This effect is mainly due to the activity of the STT3B-based OST complex. These findings can be integrated into a simple kinetic model that distinguishes local information within sequons from global information of the acceptor proteins.

Asunto(s)

Hexosiltransferasas , Proteínas de la Membrana , Procesamiento Proteico-Postraduccional , Humanos , Glicosilación , Células HEK293 , Hexosiltransferasas/metabolismo , Hexosiltransferasas/genética , Proteínas de la Membrana/metabolismo , Proteínas de la Membrana/genética , Estabilidad Proteica , Polisacáridos/metabolismo

RESUMEN

L-type calcium channels are essential for the excitation-contraction coupling in cardiac muscle. The CaV1.2 channel is the most predominant isoform in the ventricle which consists of a multi-subunit membrane complex that includes the CaV1.2 pore-forming subunit and auxiliary subunits like CaVα2δ and CaVß2b. The CaV1.2 channel's C-terminus undergoes proteolytic cleavage, and the distal C-terminal domain (DCtermD) associates with the channel core through two domains known as proximal and distal C-terminal regulatory domain (PCRD and DCRD, respectively). The interaction between the DCtermD and the remaining C-terminus reduces the channel activity and modifies voltage- and calcium-dependent inactivation mechanisms, leading to an autoinhibitory effect. In this study, we investigate how the interaction between DCRD and PCRD affects the inactivation processes and CaV1.2 activity. We expressed a 14-amino acid peptide miming the DCRD-PCRD interaction sequence in both heterologous systems and cardiomyocytes. Our results show that overexpression of this small peptide can displace the DCtermD and replicate the effects of the entire DCtermD on voltage-dependent inactivation and channel inhibition. However, the effect on calcium-dependent inactivation requires the full DCtermD and is prevented by overexpression of calmodulin. In conclusion, our results suggest that the interaction between DCRD and PCRD is sufficient to bring about the current inhibition and alter the voltage-dependent inactivation, possibly in an allosteric manner. Additionally, our data suggest that the DCtermD competitively modifies the calcium-dependent mechanism. The identified peptide sequence provides a valuable tool for further dissecting the molecular mechanisms that regulate L-type calcium channels' basal activity in cardiomyocytes.

Asunto(s)

Canales de Calcio Tipo L , Miocitos Cardíacos , Canales de Calcio Tipo L/metabolismo , Canales de Calcio Tipo L/genética , Canales de Calcio Tipo L/química , Animales , Miocitos Cardíacos/metabolismo , Humanos , Células HEK293 , Ratas , Dominios Proteicos

RESUMEN

Cannabidiol (CBD), one of the main Cannabis sativa bioactive compounds, is utilized in the treatment of major epileptic syndromes. Its efficacy can be attributed to a multimodal mechanism of action that includes, as potential targets, several types of ion channels. In the brain, CBD reduces the firing frequency in rat hippocampal neurons, partly prolonging the duration of action potentials, suggesting a potential blockade of voltage-operated K+ channels. We postulate that this effect might involve the inhibition of the large-conductance voltage- and Ca2+-operated K+ channel (BK channel), which plays a role in the neuronal action potential's repolarization. Thus, we assessed the impact of CBD on the BK channel activity, heterologously expressed in HEK293 cells. Our findings, using the patch-clamp technique, revealed that CBD inhibits BK channel currents in a concentration-dependent manner with an IC50 of 280 nM. The inhibition is through a direct interaction, reducing both the unitary conductance and voltage-dependent activation of the channel. Additionally, the cannabinoid significantly delays channel activation kinetics, indicating stabilization of the closed state. These effects could explain the changes induced by CBD in action potential shape and duration, and they may contribute to the observed anticonvulsant activity of this cannabinoid.

Asunto(s)

Cannabidiol , Cannabis , Canales de Potasio de Gran Conductancia Activados por el Calcio , Cannabidiol/farmacología , Cannabis/química , Humanos , Canales de Potasio de Gran Conductancia Activados por el Calcio/antagonistas & inhibidores , Canales de Potasio de Gran Conductancia Activados por el Calcio/efectos de los fármacos , Células HEK293 , Animales , Técnicas de Placa-Clamp , Cannabinoides/farmacología , Ratas , Estructura Molecular

RESUMEN

Lysophosphatidic acid (LPA) type 3 (LPA3) receptor mutants were generated in which the sites detected phosphorylated were substituted by non-phosphorylatable amino acids. Substitutions were made in the intracellular loop 3 (IL3 mutant), the carboxyl terminus (Ctail), and both domains (IL3/Ctail). The wild-type (WT) receptor and the mutants were expressed in T-REx HEK293 cells, and the consequences of the substitutions were analyzed employing different functional parameters. Agonist- and LPA-mediated receptor phosphorylation was diminished in the IL3 and Ctail mutants and essentially abolished in the IL3/Ctail mutant, confirming that the main phosphorylation sites are present in both domains and their role in receptor phosphorylation eliminated by substitution and distributed in both domains. The WT and mutant receptors increased intracellular calcium and ERK 1/2 phosphorylation in response to LPA and PMA. The agonist, Ki16425, diminished baseline intracellular calcium, which suggests some receptor endogenous activity. Similarly, baseline ERK1/2 phosphorylation was diminished by Ki16425. An increase in baseline ERK phosphorylation was detected in the IL3/Ctail mutant. LPA and PMA-induced receptor interaction with ß-arrestin 2 and LPA3 internalization were severely diminished in cells expressing the mutants. Mutant-expressing cells also exhibit increased baseline proliferation and response to different stimuli, which were inhibited by the antagonist Ki16425, suggesting a role of LPA receptors in this process. Migration in response to different attractants was markedly increased in the Ctail mutant, which the Ki16425 antagonist also attenuated. Our data experimentally show that receptor phosphorylation in the distinct domains is relevant for LPA3 receptor function.

Asunto(s)

Lisofosfolípidos , Receptores del Ácido Lisofosfatídico , Transducción de Señal , Humanos , Fosforilación , Receptores del Ácido Lisofosfatídico/metabolismo , Receptores del Ácido Lisofosfatídico/genética , Células HEK293 , Lisofosfolípidos/metabolismo , Calcio/metabolismo , Endocitosis , Mutación