RESUMEN

The extremely halophilic archaeon Haloarcula japonica accumulates the C50 carotenoid, bacterioruberin (BR). To reveal the BR biosynthetic pathway, unidentified phytoene desaturase candidates were functionally characterized in the present study. Two genes encoding the potential phytoene desaturases, c0507 and d1086, were found from the Ha. japonica genome sequence by a homology search using the Basic Local Align Search Tool. Disruption mutants of c0507 and d1086 and their complemented strains transformed with expression plasmids for c0507 and d1086 were subsequently constructed. High-performance liquid chromatography (HPLC) ana-lyses of carotenoids produced by these strains revealed that C0507 and D1086 were both bifunctional enzymes with the same activities as both phytoene desaturase (CrtI) and 3,4-desaturase (CrtD). C0507 and D1086 complemented each other during BR biosynthesis in Ha. japonica. This is the first study to identify two distinct enzymes with both CrtI and CrtD activities in an extremely halophilic archaeon.

Asunto(s)

Carotenoides , Haloarcula , Oxidorreductasas , Carotenoides/metabolismo , Haloarcula/genética , Haloarcula/enzimología , Haloarcula/metabolismo , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Vías Biosintéticas/genética , Proteínas Arqueales/genética , Proteínas Arqueales/metabolismo , Prueba de Complementación Genética , Filogenia

RESUMEN

Dihydroceramide Δ4-desaturase 1 (DEGS1) enzymatic activity is inhibited with N-(4-hydroxyphenyl)-retinamide (4-HPR). We reported previously that 4-HPR suppresses severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry through a DEGS1-independent mechanism. However, it remains unclear whether DEGS1 is involved in other SARS-CoV-2 infection processes, such as virus replication and release. Here we established DEGS1 knockout (KO) in VeroE6TMPRSS2 cells. No significant difference was observed in virus production in the culture supernatant between wild-type (WT) cells and DEGS1-KO cells, although the levels of dihydroceramide (DHCer), a DEGS1 substrate, were significantly higher in DEGS1-KO cells than WT cells. Furthermore, the virus-induced cytopathic effect was also observed in DEGS1-KO cells. Importantly, the EC50 value of 4-HPR in DEGS1-KO cells was almost identical to the value reported previously in WT cells. Our results indicated the lack of involvement of DEGS1 in SARS-CoV-2 infection.

Asunto(s)

COVID-19 , Fenretinida , Animales , Ceramidas , Chlorocebus aethiops , Ácido Graso Desaturasas , Fenretinida/farmacología , Humanos , Oxidorreductasas , SARS-CoV-2 , Células Vero

RESUMEN

Atherosclerosis is a chronic multifactorial cardiovascular disease. Western diets have been reported to affect atherosclerosis through regulating adipose function. In high cholesterol diet-fed ApoE -/- mice, adipocyte HIF-1α deficiency or direct inhibition of HIF-1α by the selective pharmacological HIF-1α inhibitor PX-478 alleviates high cholesterol diet-induced atherosclerosis by reducing adipose ceramide generation, which lowers cholesterol levels and reduces inflammatory responses, resulting in improved dyslipidemia and atherogenesis. Smpd3, the gene encoding neutral sphingomyelinase, is identified as a new target gene directly regulated by HIF-1α that is involved in ceramide generation. Injection of lentivirus-SMPD3 in epididymal adipose tissue reverses the decrease in ceramides in adipocytes and eliminates the improvements on atherosclerosis in the adipocyte HIF-1α-deficient mice. Therefore, HIF-1α inhibition may constitute a novel approach to slow atherosclerotic progression.

RESUMEN

Glycosylceramides are abundant membrane components in vascular plants and are associated with cell differentiation, organogenesis, and protein secretion. Long-chain base (LCB) Δ4-desaturation is an important structural feature for metabolic channeling of sphingolipids into glycosylceramide formation in plants and fungi. In Arabidopsis thaliana, LCB Δ4-unsaturated glycosylceramides are restricted to pollen and floral tissue, indicating that LCB Δ4-desaturation has a less important overall physiological role in A. thaliana. In the bryophyte Physcomitrium patens, LCB Δ4-desaturation is a feature of the most abundant glycosylceramides of the gametophyte generation. Metabolic changes in the P. patens null mutants for the sphingolipid Δ4-desaturase (PpSD4D) and the glycosylceramide synthase (PpGCS), sd4d-1 and gcs-1, were determined by ultra-performance liquid chromatography coupled with nanoelectrospray ionization and triple quadrupole tandem mass spectrometry analysis. sd4d-1 plants lacked unsaturated LCBs and the most abundant glycosylceramides. gcs-1 plants lacked all glycosylceramides and accumulated hydroxyceramides. While sd4d-1 plants mostly resembled wild-type plants, gcs-1 mutants were impaired in growth and development. These results indicate that LCB Δ4-desaturation is a prerequisite for the formation of the most abundant glycosylceramides in P. patens. However, loss of unsaturated LCBs does not affect plant viability, while blockage of glycosylceramide synthesis in gcs-1 plants causes severe plant growth and development defects.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis , Bryopsida , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Polen , Esfingolípidos

RESUMEN

Lipotoxic cardiomyopathy (LCM) is characterized by cardiac steatosis, including the accumulation of fatty acids, triglycerides and ceramides. Model systems have shown the inhibition of ceramide biosynthesis to antagonize obesity and improve insulin sensitivity. Sphingosine Δ4 desaturase (encoded by ifc in Drosophila melanogaster) enzymatically converts dihydroceramide into ceramide. Here, we examine ifc mutants to study the effects of desaturase deficiency on cardiac function in Drosophila Interestingly, ifc mutants exhibited classic hallmarks of LCM: cardiac chamber dilation, contractile defects and loss of fractional shortening. This outcome was phenocopied in global ifc RNAi-mediated knockdown flies. Surprisingly, cardiac-specific ifc knockdown flies exhibited cardiac chamber restriction with no contractile defects, suggesting heart autonomous and systemic roles for ifc activity in cardiac function. Next, we demonstrated that ifc mutants exhibit suppressed Sphingosine kinase 1 (Sk1) expression. Ectopic overexpression of Sk1 was sufficient to prevent cardiac chamber dilation and loss of fractional shortening in ifc mutants. Partial rescue was also observed with cardiac- and fat-body-specific Sk1 overexpression. Finally, we showed that cardiac-specific expression of Drosophila inhibitor of apoptosis (dIAP) also prevented cardiac dysfunction in ifc mutants, suggesting a role for caspase activity in the observed cardiac pathology. Collectively, we show that spatial regulation of sphingosine Δ4 desaturase activity differentially affects cardiac function in heart autonomous and systemic mechanisms through tissue interplay.

Asunto(s)

Cardiomiopatías/enzimología , Ceramidas/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , Proteínas de la Membrana/metabolismo , Contracción Miocárdica , Miocardio/enzimología , Triglicéridos/metabolismo , Animales , Animales Modificados Genéticamente , Cardiomiopatías/genética , Cardiomiopatías/patología , Cardiomiopatías/fisiopatología , Cardiotoxicidad , Modelos Animales de Enfermedad , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas Inhibidoras de la Apoptosis/genética , Proteínas Inhibidoras de la Apoptosis/metabolismo , Proteínas de la Membrana/genética , Mutación , Miocardio/patología , Fosfotransferasas (Aceptor de Grupo Alcohol)/genética , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo

RESUMEN

Cone photoreceptors are essential for vision under moderate to high illuminance and allow color discrimination. Their fast dark adaptation rate and resistance to saturation are believed to depend in part on an intraretinal visual cycle that supplies 11- cis-retinaldehyde to cone opsins. Candidate enzymes of this pathway have been reported, but their physiologic contribution to cone photoresponses remains unknown. Here, we evaluate the role of a candidate retinol isomerase of this pathway, sphingolipid δ4 desaturase 1 (Des1). Single-cell RNA sequencing analysis revealed Des1 expression not only in Müller glia but also throughout the retina and in the retinal pigment epithelium. We assessed cone functional dependence on Müller cell-expressed Des1 through a conditional knockout approach. Floxed Des1 mice, on a guanine nucleotide-binding protein subunit α transducin 1 knockout ( Gnat1-/-) background to allow isolated recording of cone-driven photoresponses, were bred with platelet-derived growth factor receptor α (Pdgfrα)-Cre mice to delete Des1 in Müller cells. Conditional knockout of Des1 expression, as shown by tissue-selective Des1 gene recombination and reduced Des1 catalytic activity, caused no gross changes in the retinal structure and had no effect on cone sensitivity or dark adaptation but did slightly accelerate the rate of cone phototransduction termination. These results indicate that Des1 expression in Müller cells is not required for cone visual pigment regeneration in the mouse.-Kiser, P. D., Kolesnikov, A.V., Kiser, J. Z., Dong, Z., Chaurasia, B., Wang, L., Summers, S. A., Hoang, T., Blackshaw, S., Peachey, N. S., Kefalov, V. J., Palczewski, K. Conditional deletion of Des1 in the mouse retina does not impair the visual cycle in cones.

Asunto(s)

Proteínas de la Membrana/metabolismo , Oxidorreductasas/metabolismo , Retina/metabolismo , Células Fotorreceptoras Retinianas Conos/metabolismo , Visión Ocular/fisiología , Animales , Células Ependimogliales/metabolismo , Masculino , Ratones , Ratones Noqueados , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Epitelio Pigmentado de la Retina/metabolismo , Células Fotorreceptoras Retinianas Bastones/metabolismo , Retinaldehído/metabolismo , Transducina/metabolismo

RESUMEN

Despite the potential of vegetable oils as aquafeed ingredients, a major drawback associated with their utilization is the inferior level of beneficial n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Echium oil (EO), which is rich in stearidonic acid (SDA, 18:4n-3), could potentially improve the deposition of n-3 LC-PUFA as the biosynthesis of LC-PUFA is enhanced through bypassing the rate-limiting ∆6 desaturation step. We report for the first time an attempt to investigate whether the presence of a desaturase (Fads2) capable of ∆4 desaturation activities and an elongase (Elovl5) will leverage the provision of dietary SDA to produce a higher rate of LC-PUFA bioconversion. Experimental diets were designed containing fish oil (FO), EO or linseed oil (LO) (100FO, 100EO, 100LO), and diets which comprised equal mixtures of the designated oils (50EOFO and 50EOLO) were evaluated in a 12-week feeding trial involving striped snakeheads (Channa striata). There was no significant difference in growth and feed conversion efficiency. The hepatic fatty acid composition and higher expression of fads2 and elovl5 genes in fish fed EO-based diets indicate the utilization of dietary SDA for LC-PUFA biosynthesis. Collectively, this resulted in a higher deposition of muscle eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to LO-based diets. Dietary EO improved the ratio of n-3 LC-PUFA to n-6 LC-PUFA in fish muscle, which is desirable for human populations with excessive consumption of n-6 PUFA. This study validates the contribution of SDA in improving the content of n-3 LC-PUFA and the ratio of EPA to arachidonic acid (ARA, 20:4n-6) in a freshwater carnivorous species.

Asunto(s)

Echium , Ácido Graso Desaturasas/genética , Ácidos Grasos Omega-3/metabolismo , Lino , Perciformes/metabolismo , Aceites de Plantas/farmacología , Acetiltransferasas/genética , Animales , Encéfalo/metabolismo , Elongasas de Ácidos Grasos , Proteínas de Peces/genética , Regulación de la Expresión Génica/efectos de los fármacos , Hígado/metabolismo , Músculos/metabolismo , Perciformes/genética

RESUMEN

The γ-carotenoids, such as myxol and saproxanthin, have a high potential to be utilized in nutraceutical and pharmaceutical industries for their neuro-protective and antioxidant effects. CrtD is involved in the production of γ-carotenoids by desaturating the C3'-C4' position of 1'-OH-γ-carotenoid. We determined the crystal structure of CrtD from Nonlabens dokdonensis DSW-6 (NdCrtD), the first structure of CrtD family enzymes. The NdCrtD structure was composed of two distinct domains, an FAD-binding domain and a substrate-binding domain, and the substrate-binding domain can be divided into two subdomains, a Rossmann fold-like subdomain and a lid subdomain. Although the FAD-binding domain showed a structure similar to canonical FAD-containing enzymes, the substrate-binding domain exhibited a novel structure to constitute a long and hydrophobic tunnel with a length of ∼40 Å. The molecular docking-simulation reveals that the tunnel provides an appropriate substrate-binding site for the carotenoid such as 1'-OH-γ-carotene with a length of ∼35 Å. We could predict residues related to recognize the 1'-hydroxyl group and to stabilize the hydrophobic end without hydroxyl group. Moreover, we suggest that the flexible entrance loop may undergo an open-closed formational change during the binding of the substrate.

Asunto(s)

Proteínas Bacterianas/química , Flavobacteriaceae/enzimología , Oxidorreductasas/química , Secuencia de Aminoácidos , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Dominio Catalítico , Cristalografía por Rayos X , Flavina-Adenina Dinucleótido/metabolismo , Flavobacteriaceae/genética , Modelos Moleculares , Simulación de Dinámica Molecular , Datos de Secuencia Molecular , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Pantoea/enzimología , Pantoea/genética , Conformación Proteica , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido , Especificidad de la Especie , Electricidad Estática

RESUMEN

The endogenous production of long-chain polyunsaturated fatty acids (LC-PUFA) in carnivorous teleost species inhabiting freshwater environments is poorly understood. Although a predatory lifestyle could potentially supply sufficient LC-PUFA to satisfy the requirements of these species, the nutrient-poor characteristics of the freshwater food web could impede this advantage. In this study, we report the cloning and functional characterisation of an elongase enzyme in the LC-PUFA biosynthesis pathway from striped snakehead (Channa striata), which is a strict freshwater piscivore that shows high deposition of LC-PUFA in its flesh. We also functionally characterised a previously isolated fatty acyl desaturase cDNA from this species. Results showed that the striped snakehead desaturase is capable of Δ4 and Δ5 desaturation activities, while the elongase showed the characteristics of Elovl5 elongases. Collectively, these findings reveal that striped snakehead exhibits the genetic resources to synthesise docosahexaenoic acid (DHA; 22:6n-3) from eicosapentaenoic acid (EPA; 20:5n-3). Both genes are expressed at considerable levels in the brain and the liver. In liver, both genes were up-regulated by dietary C18 PUFA, although this increase did not correspond to a significant rise in the deposition of muscle LC-PUFA. Brain tissue of fish fed with plant oil diets showed higher expression of fads2 gene compared to fish fed with fish oil-based diet, which could ensure DHA levels remain constant under limited dietary DHA intake. This suggests the importance of DHA production from EPA via the ∆4 desaturation step in order to maintain an optimal reserve of DHA in the neuronal tissues of carnivores.

Asunto(s)

Acetiltransferasas/metabolismo , Ácidos Docosahexaenoicos/biosíntesis , Ácido Eicosapentaenoico/biosíntesis , Ácido Graso Desaturasas/metabolismo , Proteínas de Peces/metabolismo , Perciformes/metabolismo , Acetiltransferasas/genética , Secuencia de Aminoácidos , Animales , Encéfalo/metabolismo , Carnivoría , Clonación Molecular , Dieta , Escherichia coli/genética , Escherichia coli/metabolismo , Ácido Graso Desaturasas/genética , Elongasas de Ácidos Grasos , Aceites de Pescado/administración & dosificación , Proteínas de Peces/genética , Regulación de la Expresión Génica , Hígado/metabolismo , Datos de Secuencia Molecular , Músculos/metabolismo , Especificidad de Órganos , Perciformes/clasificación , Perciformes/genética , Filogenia , Aceites de Plantas/administración & dosificación , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alineación de Secuencia

RESUMEN

1.6 kb ?4-desaturase gene(FAD4)was amplified by PCR using plasmid pGEM-TFAD4 as template.The fragment was subcloned into the HindⅢ/XbaⅠrestriction site of pYES2.0 vector.Recombinant plasmid pYFAD4 was transformed into Saccharomyces cerevisiae strain INVScl for expression.It was found to exhibit ?4-fatty acid desaturase activity in the recombinant S.cerevisiae YFAD4 in the presence of exogenous fatty acid substrate docosapentaenoic acid(100?mol/L)under introduction of GAL1.Expression of the FAD4 under appropriate media and temperature conditions led to the production of DHA and it reached 41.13% of the total yeast fatty acid by GC detection.It was suggested that the protein encoded by FAD4 could specifically catalyze DPA into DHA.