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Activation of constitutive androstane receptor (CAR) transcription factor by xenobiotics promotes hepatocellular proliferation, promotes hypertrophy without liver injury, and induces drug metabolism genes. Previous work demonstrated that lymphocyte-specific protein-1 (LSP1), an F-actin binding protein and gene involved in human hepatocellular carcinoma, suppresses hepatocellular proliferation after partial hepatectomy. The current study investigated the role of LSP1 in liver enlargement induced by chemical mitogens, a regenerative process independent of tissue loss. 1,4-Bis [2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP), a direct CAR ligand and strong chemical mitogen, was administered to global Lsp1 knockout and hepatocyte-specific Lsp1 transgenic (TG) mice and measured cell proliferation, hypertrophy, and expression of CAR-dependent drug metabolism genes. TG livers displayed a significant decrease in Ki-67 labeling and liver/body weight ratios compared with wild type on day 2. Surprisingly, this was reversed by day 5, due to hepatocyte hypertrophy. There was no difference in CAR-regulated drug metabolism genes between wild type and TG. TG livers displayed increased Yes-associated protein (YAP) phosphorylation, decreased nuclear YAP, and direct interaction between LSP1 and YAP, suggesting LSP1 suppresses TCPOBOP-driven hepatocellular proliferation, but not hepatocyte volume, through YAP. Conversely, loss of LSP1 led to increased hepatocellular proliferation on days 2, 5, and 7. LSP1 selectively suppresses CAR-induced hepatocellular proliferation, but not drug metabolism, through the interaction of LSP1 with YAP, supporting the role of LSP1 as a selective growth suppressor.
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Neoplasias Hepáticas , Xenobióticos , Animales , Proliferación Celular , Receptor de Androstano Constitutivo , Hepatocitos/metabolismo , Hipertrofia/metabolismo , Hígado/metabolismo , Neoplasias Hepáticas/patología , Linfocitos , Ratones , Proteínas de Microfilamentos , Xenobióticos/metabolismo , Xenobióticos/farmacología , Proteínas Señalizadoras YAPRESUMEN
Using nerve guide conduits (NGCs) to promote the regeneration of PNI is a feasible alternative to autograft. Compared with NGCs made of single material, composite NGCs have a greater development prospect. Our previous research has confirmed that poly(D, L-lactic acid)/ß-tricalcium phosphate/hyaluronic acid/chitosan/nerve growth factor (PDLLA/ß-TCP/HA/CHS/NGF) NGCs have excellent physical and chemical properties, which can slowly release NGF and support cell adhesion and proliferation. In this study, PDLLA/ß-TCP/HA/CHS/NGF NGCs were prepared and used to bridge a 10 mm sciatic nerve defect in 200-250 g Sprague-Dawley (SD) rat to verify the performance of the NGCs in vivo. Substantial improvements in nerve regeneration were observed after using the PDLLA/ß-TCP/HA/CHS/NGF NGCs based on gross post-operation observation, triceps wet weight analysis and nerve histological assessment. In vivo studies illustrate that the PDLLA/ß-TCP/HA/CHS/NGF sustained-release NGCs can effectively promote peripheral nerve regeneration, and the effect is similar to that of autograft.
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Introduction: Surufatinib (also known as HMPL-012, sulfatinib) is a novel oral tyrosine kinase inhibitor (TKI), which has the dual activity of anti-angiogenesis and immune regulation. In December 2020, surufatinib was approved as a monotherapy for unresectable locally advanced or metastatic, progressive nonfunctioning, well differentiated (grade 1 or 2) extrapancreatic neuroendocrine tumors (epNETs) in China.Areas covered: In this paper, the chemical properties, mechanism of action, pharmacokinetics, clinical efficacy, safety, and tolerability of surufatinib for treatment of advanced extrapancreatic NETs are introduced in detail. We performed a systematic review of the literature in PubMed and the following keywords were used: 'surufatinib,' 'sulfatinib' and 'HMPL-012.'Expert opinion: Surufatinib is a potent, selective, and small-molecule TKI that targets vascular endothelial growth factor receptor (VEGFR), fibroblast growth factor receptor 1 (FGFR1) and colony stimulating factor 1 receptor (CSF1R). Surufatinib showed an acceptable safety profile and encouraging antitumor activity in patients with advanced epNETs. The most frequently observed adverse events (AEs) were hypertension and proteinuria. Surufatinib provides a new treatment option for patients with advanced epNETs. More clinical trials of surufatinib are ongoing to develop a combination of therapy strategies and new indications for malignancies.
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Tumores Neuroendocrinos , Humanos , Indoles , Tumores Neuroendocrinos/tratamiento farmacológico , Tumores Neuroendocrinos/patología , Inhibidores de Proteínas Quinasas/efectos adversos , Pirimidinas/uso terapéutico , Sulfonamidas , Factor A de Crecimiento Endotelial VascularRESUMEN
Hepatocellular carcinoma (HCC) is the fifth most common type of cancer and the third leading cause of cancer-related deaths worldwide. Liver resection or liver transplantation is the most effective therapy for HCC because drugs approved by the US Food and Drug Administration to treat patients with unresectable HCC have an unfavorable overall survival rate. Therefore, the development of biomarkers for early diagnosis and effective therapy strategies are still necessary to improve patient outcomes. Fibroblast growth factor (FGF) 19 was amplified in patients with HCC from various studies, including patients from The Cancer Genome Atlas. FGF19 plays a syngeneic function with other signaling pathways in primary liver cancer development, such as epidermal growth factor receptor, Wnt/ß-catenin, the endoplasmic reticulum-related signaling pathway, STAT3/IL-6, RAS, and extracellular signal-regulated protein kinase, among others. The current review presents a comprehensive description of the FGF19 signaling pathway involved in liver cancer development. The use of big data and bioinformatic analysis can provide useful clues for further studies of the FGF19 pathway in HCC, including its application as a biomarker, targeted therapy, and combination therapy strategies.
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Carcinoma Hepatocelular/metabolismo , Factores de Crecimiento de Fibroblastos/metabolismo , Neoplasias Hepáticas/metabolismo , Animales , Biomarcadores de Tumor/metabolismo , Humanos , Transducción de Señal/fisiologíaRESUMEN
BACKGROUND AND AIMS: Constitutive androstane receptor (CAR) agonists, such as 1,4-bis [2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP), are known to cause robust hepatocyte proliferation and hepatomegaly in mice along with induction of drug metabolism genes without any associated liver injury. Yes-associated protein (Yap) is a key transcription regulator that tightly controls organ size, including that of liver. Our and other previous studies suggested increased nuclear localization and activation of Yap after TCPOBOP treatment in mice and the potential role of Yap in CAR-driven proliferative response. Here, we investigated a direct role of Yap in CAR-driven hepatomegaly and hepatocyte proliferation using hepatocyte-specific Yap-knockout (KO) mice. APPROACH AND RESULTS: Adeno-associated virus 8-thyroxine binding globulin promoter-Cre recombinase vector was injected to Yap-floxed mice for achieving hepatocyte-specific Yap deletion followed by TCPOBOP treatment. Yap deletion did not decrease protein expression of CAR or CAR-driven induction of drug metabolism genes (including cytochrome P450 [Cyp] 2b10, Cyp2c55, and UDP-glucuronosyltransferase 1a1 [Ugt1a1]). However, Yap deletion substantially reduced TCPOBOP-induced hepatocyte proliferation. TCPOBOP-driven cell cycle activation was disrupted in Yap-KO mice because of delayed (and decreased) induction of cyclin D1 and higher expression of p21, resulting in decreased phosphorylation of retinoblastoma protein. Furthermore, the induction of other cyclins, which are sequentially involved in progression through cell cycle (including cyclin E1, A2, and B1), and important mitotic regulators (such as Aurora B kinase and polo-like kinase 1) was remarkably reduced in Yap-KO mice. Microarray analysis revealed that 26% of TCPOBOP-responsive genes that were mainly related to proliferation, but not to drug metabolism, were altered by Yap deletion. Yap regulated these proliferation genes through alerting expression of Myc and forkhead box protein M1, two critical transcriptional regulators of CAR-mediated hepatocyte proliferation. CONCLUSIONS: Our study revealed an important role of Yap signaling in CAR-driven hepatocyte proliferation; however, CAR-driven induction of drug metabolism genes was independent of Yap.
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Proliferación Celular/fisiología , Receptor de Androstano Constitutivo/fisiología , Hepatocitos/fisiología , Inactivación Metabólica/genética , Proteínas Señalizadoras YAP/fisiología , Animales , Ciclo Celular , Femenino , Regulación de la Expresión Génica , Genes/genética , Hepatocitos/metabolismo , Humanos , Inactivación Metabólica/fisiología , Regeneración Hepática , Ratones Noqueados , TranscriptomaRESUMEN
INTRODUCTION: Camrelizumab (also known as SHR-1210), a humanized monoclonal antibody against PD-1, has been shown to block the binding of PD-1 to PD-L1 and consequently inhibit the immune escape of tumor cells. Recently, camrelizumab was approved as a second-line drug for previously treated advanced hepatocellular carcinoma in China. AREAS COVERED: In this paper, the chemical properties, mechanism of action, pharmacokinetics, clinical efficacy, safety, and tolerability of camrelizumab for the treatment of advanced hepatocellular carcinoma are introduced in detail. The strategy for combination therapy and the potential application of camrelizumab in other solid tumors are briefly described. We performed a systematic review of the literature in PubMed and the following keywords were used: 'SHR-1210,' 'Camrelizumab,' and 'hepatocellular carcinoma.' EXPERT OPINION: Camrelizumab is a selective, humanized, high-affinity IgG4 kappa mAb against PD-1. Camrelizumab showed promising antitumor activity and manageable toxicities and offers a new second-line drug option for patients with advanced hepatocellular carcinoma. Reactive cutaneous capillary endothelial proliferation is a novel but prevalent immune-related dermatologic toxicity of camrelizumab, which is mild, reversible, and predictable. More clinical trials of camrelizumab are ongoing to develop combination therapy strategies and new indications for malignancies.
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Anticuerpos Monoclonales Humanizados/uso terapéutico , Carcinoma Hepatocelular/tratamiento farmacológico , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Neoplasias Hepáticas/tratamiento farmacológico , Receptor de Muerte Celular Programada 1/antagonistas & inhibidores , Animales , Anticuerpos Monoclonales Humanizados/efectos adversos , Anticuerpos Monoclonales Humanizados/farmacocinética , Carcinoma Hepatocelular/inmunología , Carcinoma Hepatocelular/mortalidad , Carcinoma Hepatocelular/patología , Interacciones Farmacológicas , Humanos , Inhibidores de Puntos de Control Inmunológico/efectos adversos , Inhibidores de Puntos de Control Inmunológico/farmacocinética , Neoplasias Hepáticas/inmunología , Neoplasias Hepáticas/mortalidad , Neoplasias Hepáticas/patología , Receptor de Muerte Celular Programada 1/inmunología , Resultado del TratamientoRESUMEN
The application of hollow nerve conduits in the repair of peripheral nerve defects is effected by inferior recovery, and nerve extension is hampered by the scar tissue generated during the repair process. In this study, the filler in hollow nerve conduit, chitosan/oxidized hydroxyethyl cellulose (CS/OHEC) hydrogel loaded asiaticoside liposome and the conductive reduced graphene oxide (rGO) were developed and used to reform the microenvironment for peripheral nerve regeneration. The physiochemical properties of CS/OHEC/rGO/asiaticoside liposome hydrogel were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and compressive modulus, porosity, swelling ratio, degradation and conductivity. In addition, the asiaticoside release profiles in vitro were investigated. The hydrogel had a continuous porous network structure with pore size distribution in the range of 50-250 µm. The majority of the hydrogels had porosities above 70%, and a compressive modulus of 0.45 MPa. The weight loss rate of hydrogel reached 76.14 ± 4.45% within 8 weeks. The conductivity of the hydrogel was 5.27 ± 0.42 × 10-4 S/cm. The hydrogel was non-toxic and suitable for adhesion and proliferation of nerve cells in vitro. In addition, the application of electrical stimulation after the addition of rGO can promote the differentiation and proliferation of nerve cells, accelerating nerve regeneration. The asiaticoside released from the hydrogel had a significant inhibitory effect on the growth and collagen secretion of fibroblasts, eliminating scars for regenerative nerves, which can promote the function recovery of defected peripheral nerve. Together, these positive results indicate that the hydrogel would be a promising candidate for peripheral nerve regeneration.
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Celulosa/análogos & derivados , Quitosano , Cicatriz/prevención & control , Terapia por Estimulación Eléctrica , Grafito , Regeneración Nerviosa/efectos de los fármacos , Traumatismos de los Nervios Periféricos/terapia , Nervios Periféricos/fisiología , Triterpenos , Animales , Celulosa/química , Celulosa/farmacología , Quitosano/química , Quitosano/farmacología , Grafito/química , Grafito/farmacocinética , Hidrogeles/química , Hidrogeles/farmacología , Liposomas , Ratones , Células 3T3 NIH , Triterpenos/química , Triterpenos/farmacologíaRESUMEN
Obesity is a major risk factor for type 2 diabetes because of chronic hepatic inflammation and resultant insulin resistance. Hepatocyte growth factor (HGF) is responsible for resetting hepatic homeostasis after injury following activation by urokinase-type plasminogen activator (u-PA; encoded by the PLAU gene). Plasminogen activator inhibitor type-1 (PAI-1; encoded by the SERPINE1 gene), a u-PA inhibitor and antifibrinolytic agent, is often elevated in obesity and is linked to cardiovascular events. We hypothesized that, in addition to its role in preventing fibrinolysis, elevated PAI-1 inhibits HGF's activation by u-PA and the resultant anti-inflammatory and hepatoprotective properties. Wild-type and PAI-1 knockout (KO) mice on a high-fat diet both became significantly heavier than lean controls; however, the obese KO mice demonstrated improved glucose metabolism compared with wild-type mice. Obese KO mice also exhibited an increase in conversion of latent single-chain HGF to active two-chain HGF, coinciding with an increase in the phosphorylation of the HGF receptor (HGFR or MET, encoded by the MET gene), as well as dampened inflammation. These results strongly suggest that, in addition to its other functions, PAI-mediated inhibition of HGF activation prohibits the resolution of inflammation in the context of obesity-induced type 2 diabetes.
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Diabetes Mellitus Tipo 2/metabolismo , Obesidad/metabolismo , Inhibidor 1 de Activador Plasminogénico/metabolismo , Animales , Diabetes Mellitus Tipo 2/inducido químicamente , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/patología , Grasas de la Dieta/efectos adversos , Grasas de la Dieta/farmacología , Factor de Crecimiento de Hepatocito/genética , Factor de Crecimiento de Hepatocito/metabolismo , Inflamación/inducido químicamente , Inflamación/genética , Inflamación/metabolismo , Inflamación/patología , Masculino , Ratones , Ratones Noqueados , Obesidad/inducido químicamente , Obesidad/genética , Obesidad/patología , Inhibidor 1 de Activador Plasminogénico/genética , Proteínas Proto-Oncogénicas c-met/genética , Proteínas Proto-Oncogénicas c-met/metabolismoRESUMEN
Epidermal growth factor receptor (EGFR) is a critical regulator of hepatocyte proliferation and liver regeneration. Our recent work indicated that EGFR can also regulate lipid metabolism during liver regeneration after partial hepatectomy. Based on these findings, we investigated the role of EGFR in a mouse model of nonalcoholic fatty liver disease (NAFLD) using a pharmacological inhibition strategy. C57BL6/J mice were fed a chow diet or a fast-food diet (FFD) with or without EGFR inhibitor (canertinib) for 2 months. EGFR inhibition completely prevented development of steatosis and liver injury in this model. In order to study if EGFR inhibition can reverse NAFLD progression, mice were fed the FFD for 5 months, with or without canertinib treatment for the last 5 weeks of the study. EGFR inhibition remarkably decreased steatosis, liver injury, and fibrosis and improved glucose tolerance. Microarray analysis revealed that ~40% of genes altered by the FFD were differentially expressed after EGFR inhibition and, thus, are potentially regulated by EGFR. Several genes and enzymes related to lipid metabolism (particularly fatty acid synthesis and lipolysis), which were disrupted by the FFD, were found to be modulated by EGFR. Several crucial transcription factors that play a central role in regulating these lipid metabolism genes during NAFLD, including peroxisome proliferator-activated receptor gamma (PPARγ), sterol regulatory element-binding transcription factor 1 (SREBF1), carbohydrate-responsive element-binding protein, and hepatocyte nuclear factor 4 alpha, were also found to be modulated by EGFR. In fact, chromatin immunoprecipitation analysis revealed that PPARγ binding to several crucial lipid metabolism genes (fatty acid synthase, stearoyl-coenzyme A desaturase 1, and perilipin 2) was drastically reduced by EGFR inhibition. Further upstream, EGFR inhibition suppressed AKT signaling, which is known to control these transcription factors, including PPARγ and SREBF1, in NAFLD models. Lastly, the effect of EGFR in FFD-induced fatty-liver phenotype was not shared by receptor tyrosine kinase MET, investigated using MET knockout mice. Conclusion: Our study revealed a role of EGFR in NAFLD and the potential of EGFR inhibition as a treatment strategy for NAFLD.
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Receptores ErbB/antagonistas & inhibidores , Comida Rápida , Morfolinas/farmacología , Morfolinas/uso terapéutico , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Animales , Modelos Animales de Enfermedad , Metabolismo de los Lípidos/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
The gene leukocyte-specific protein-1 (LSP1), encodes an F-actin binding protein that directly interacts with the mitogen-activated protein kinase pathway. LSP1 has copy number variations in 52% of human hepatocellular carcinoma (HCC). LSP1 suppresses proliferation and migration in hepatocytes. LSP1 binds to the rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein/extracellular signal-regulated kinase (ERK)/ERK signaling cassette, the target for sorafenib, a crucial chemotherapeutic agent for HCC. This study addresses the role of LSP1 in liver regeneration and sensitivity to sorafenib in normal and neoplastic hepatocytes. Two mouse models, an Lsp1 global knockout (LSP1KO) and a hepatocyte-specific Lsp1 transgenic (LSP1TG) mouse, were used. After two-thirds hepatectomy (PHx), LSP1KO mice displayed increased proliferation and ERK activation, whereas LSP1TG mice displayed suppressed proliferation and decreased ERK activation. LSP1KO hepatocytes cultured without growth factors exhibited increased proliferation, whereas LSP1TG hepatocytes showed decreased proliferation. Rat and human hepatoma cells expressing Lsp1 shRNA displayed increased sensitivity to sorafenib, as evidenced by decreased cell numbers and phosphorylated ERK expression compared with control. LSP1 KO mice treated with sorafenib before PHx displayed decreased hepatocyte proliferation. Our data show that loss of LSP1 function, observed in HCC, leads to increased sensitivity to sorafenib treatment and enhanced hepatocellular proliferation after PHx in vivo and in cultured cells.
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Proteínas de Unión al Calcio/fisiología , Resistencia a Medicamentos/efectos de los fármacos , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Hepatocitos/citología , Hepatocitos/efectos de los fármacos , Sorafenib/farmacología , Animales , Antineoplásicos/farmacología , Proliferación Celular , Femenino , Células Hep G2 , Hepatocitos/metabolismo , Humanos , Regeneración Hepática/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas de Microfilamentos , FosforilaciónRESUMEN
Hepatic stellate cell (HSC) activation and trans-differentiation into myofibroblast (MFB)-like cells is key for fibrogenesis after liver injury and a potential therapeutic target. Recent studies demonstrated that low-density lipoprotein receptor-related protein 1 (LRP1)-dependent signaling by tissue-type plasminogen activator (t-PA) is a pro-fibrotic regulator of the MFB phenotype in kidney. This study investigated whether LRP1 signaling by t-PA is also relevant to HSC activation following injury. Primary and immortalized rat HSCs were treated with t-PA and assayed by western blot, MTT, and TUNEL. In vitro results were then verified using an in vivo, acute carbon tetrachloride (CCl4) injury model that examined the phenotype and recovery kinetics of MFBs from wild-type animals vs mice with a global (t-PA) or HSC-targeted (LRP1) deletion. In vitro, in contrast to kidney MFBs, exogenous, proteolytically inactive t-PA suppressed, rather than induced, activation markers in HSCs following phosphorylation of LRP1. This process was mediated by LRP1 as inhibition of t-PA binding to LRP1 blocked the effects of t-PA. In vivo, following acute injury, phosphorylation of LRP1 on activated HSCs occurred immediately prior to their disappearance. Mice lacking t-PA or LRP1 retained higher densities of activated HSCs for a longer time period compared with control mice after injury cessation. Hence, t-PA, an FDA-approved drug, contributes to the suppression of activated HSCs following injury repair via signaling through LRP1. This renders t-PA a potential target for exploitation in treating patients with fibrosis.
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Fibrinolíticos/farmacología , Células Estrelladas Hepáticas/efectos de los fármacos , Proteína 1 Relacionada con Receptor de Lipoproteína de Baja Densidad/agonistas , Miofibroblastos/efectos de los fármacos , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Activador de Tejido Plasminógeno/farmacología , Animales , Tetracloruro de Carbono/antagonistas & inhibidores , Tetracloruro de Carbono/toxicidad , Intoxicación por Tetracloruro de Carbono/tratamiento farmacológico , Intoxicación por Tetracloruro de Carbono/metabolismo , Intoxicación por Tetracloruro de Carbono/patología , Línea Celular Transformada , Transdiferenciación Celular/efectos de los fármacos , Células Cultivadas , Fibrinolíticos/metabolismo , Fibrinolíticos/uso terapéutico , Células Estrelladas Hepáticas/citología , Células Estrelladas Hepáticas/metabolismo , Células Estrelladas Hepáticas/patología , Humanos , Ligandos , Proteína 1 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Proteína 1 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Miofibroblastos/citología , Miofibroblastos/metabolismo , Miofibroblastos/patología , Fosforilación/efectos de los fármacos , Ratas , Ratas Endogámicas F344 , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/farmacología , Proteínas Recombinantes/uso terapéutico , Solventes/química , Solventes/toxicidad , Activador de Tejido Plasminógeno/genética , Activador de Tejido Plasminógeno/metabolismo , Activador de Tejido Plasminógeno/uso terapéuticoRESUMEN
UNLABELLED: Hepatocellular carcinoma (HCC) is the most commonly diagnosed form of liver cancer with high morbidity and mortality. Copy number variation (CNV) analysis of human HCC revealed that leukocyte-specific protein 1 (LSP1) had the highest number of cases with CNV. LSP1, a F-actin-binding protein, is expressed in hematopoietic cells and interacts with kinase suppressor of Ras (KSR), a scaffold for the extracellular signal-related kinase/mitogen-activated protein kinase pathway. Expression of LSP1 in liver, and its role in normal hepatocellular function and carcinogenesis, remains unknown. Therefore, LSP1 messenger RNA and protein levels were analyzed in normal hepatocytes in culture, rat liver following partial hepatectomy (PHx), and hepatoma cell lines. In culture and after PHx, LSP1 increased after the termination of hepatocyte proliferation. To investigate LSP1 function in HCC, short hairpin RNA was utilized to stably knock down LSP1 expression in the JM1 rat hepatoma cell line. Loss of LSP1 in JM1 cells resulted in dramatic up-regulation of cyclin D1 and phosphorylated ERK2, increased cell proliferation, and migration. Coimmunoprecipitation and immunofluorescence analysis displayed an interaction and colocalization between LSP1, KSR, and F-actin in JM1 cells and liver during regeneration. Conversely, expression of LSP1 in the JM2 rat hepatoma cell line led to decreased proliferation. Enhanced expression of LSP1 in mouse hepatocytes during liver regeneration after injection of an LSP1 expression plasmid also led to decreased hepatocyte proliferation. CONCLUSION: LSP1 is expressed in normal hepatocytes and liver after PHx after termination of proliferation. In rat hepatoma cell lines and mouse liver in vivo, LSP1 functions as a negative regulator of proliferation and migration. Given the high frequency of LSP1 CNV in human HCC, LSP1 may be a novel target for diagnosis and treatment of HCC.
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Carcinoma Hepatocelular/metabolismo , Hepatocitos/fisiología , Neoplasias Hepáticas/metabolismo , Regeneración Hepática , Proteínas de Microfilamentos/metabolismo , Actinas/metabolismo , Animales , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Humanos , Masculino , Ratones , Metástasis de la Neoplasia , Proteínas Quinasas/metabolismo , Ratas Endogámicas F344RESUMEN
Proximal tubule epithelial cells have a highly sophisticated endocytic machinery to retrieve the albumin in the glomerular filtrate. The megalin-cubilin complex and the endocytic adaptor disabled-2 (Dab2) play a pivotal role in albumin endocytosis. We previously demonstrated that protein kinase B (Akt) regulates albumin endocytosis in the proximal tubule through an interaction with Dab2. Here, we examined the nature of Akt-Dab2 interaction. The pleckstrin homology (PH) and catalytic domains (CD) of Akt interacted with the proline-rich domain (PRD) of Dab2 based on yeast-two hybrid (Y2H) experiments. Pull-down experiments utilizing the truncated constructs of Dab2 demonstrated that the initial 11 amino acids of Dab2-PRD were sufficient to mediate the interaction between Akt and Dab2. Endocytosis experiments utilizing Akt1- and Akt2-silencing RNA revealed that both Akt1 and Akt2 mediate albumin endocytosis in proximal tubule epithelial cells; therefore, Akt1 and Akt2 may play a compensatory role in albumin endocytosis. Furthermore, both Akt isoforms phosphorylated Dab2 at Ser residues 448 and 449. Ser-to-Ala mutations of these Dab2 residues inhibited albumin endocytosis and resulted in a shift in location of Dab2 from the peripheral to the perinuclear area, suggesting the physiological relevance of these phosphorylation sites in albumin endocytosis. We conclude that both Akt1 and Akt2 are involved in albumin endocytosis, and phosphorylation of Dab2 by Akt induces albumin endocytosis in proximal tubule epithelial cells. Further delineation of how Akt affects expression/phosphorylation of endocytic adaptors and receptors will enhance our understanding of the molecular network triggered by albumin overload in the proximal tubule.
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Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Albúminas/metabolismo , Endocitosis , Túbulos Renales Proximales/enzimología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Proteínas Reguladoras de la Apoptosis , Células HEK293 , Humanos , Masculino , Ratones Noqueados , Fosforilación , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Mapeo de Interacción de Proteínas , Proteínas Proto-Oncogénicas c-akt/deficiencia , Proteínas Proto-Oncogénicas c-akt/genética , Interferencia de ARN , Transfección , Proteínas Supresoras de Tumor/genéticaRESUMEN
Albumin in the glomerular filtrate is normally retrieved by concerted efforts of clathrin, LDL-type receptor megalin- and clathrin-associated sorting proteins. In glomerular diseases, albumin overload triggers a proapoptotic and inflammatory response contributing to tubulointerstitial fibrosis and tubular atrophy. The relationship between albumin overload-induced proximal tubule injury and albumin endocytosis remains to be discovered. We investigated presence of a possible overlap between endocytosis and cell survival. We showed a novel interaction between prosurvival protein, protein kinase B (PKB/Akt), and adaptor protein, disabled 2 (Dab2), with coimmunoprecipitation. Further delineation of this interaction by GST pull-down experiments utilizing different Dab2 constructs identified proline-rich domain as the interacting partner. Expression of Dab2 and PKB/Akt was downregulated at high concentrations of albumin associated with apoptosis. We then examined the physiological relevance of this interaction with functional studies. Overexpression of PKB/Akt increased albumin uptake in human proximal tubule cells. Conversely, inhibition of PKB/Akt with a nonselective Akt/PKB signaling inhibitor-2 and a dominant negative construct of PKB/Akt resulted in a decrease in albumin uptake. Inhibition of Dab2 by silencing RNA abolished PKB/Akt-induced albumin uptake demonstrating the physiological importance of this novel interaction. We concluded that PKB/Akt is part of an endocytic machinery and it mediates albumin uptake through its interaction with Dab2. The role that PKB/Akt plays in the endocytic cascade may dictate its decreased expression in proteinuric states in an attempt to limit albumin endocytosis that may tilt the balance between cell survival and apoptosis toward cell death.