Biotin
Hepatitis C virus (HCV) infection is a major cause of chronic liver diseases such as steatosis, cirrhosis, and hepatocellular carcinoma. HCV particles have been found to associate with apolipoproteins, and apolipoproteins not only participate in the HCV life cycle, but also help HCV escape recognition by the host immune system, which pose challenges for the development of both HCV treatments and vaccines. However, no study has reported on the comprehensive identification of apolipoprotein associations with HCV particles. In the present study, we performed proteome analysis by affinity purification coupled with mass spectrometry (AP-MS) to comprehensively identify the apolipoprotein associations with HCV particles, and ApoM was first identified by AP-MS besides the previously reported ApoE, ApoB, ApoA-I and ApoC-I. Additionally, three assays further confirmed that ApoM was a novel virus particle associated protein. We also showed that ApoM was required for HCV production, especially for the assembly/release step of HCV life cycle. Furthermore, ApoM interacted with the HCV E2 protein. Finally, HCV infection reduced ApoM expression both in vitro and in vivo. Collectively, our study demonstrates that ApoM, identified as a novel HCV particle associated protein, contributes to HCV assembly/release and interacts with HCV E2 protein. It provides new insights on how HCV and the host apolipoproteins are reciprocally influenced and lays a basis for research in developing innovative antiviral strategies.
Objective: High-density lipoprotein (HDL) from nondiabetic patients with metabolic syndrome (MetS) displays abnormalities in their lipidome, such as triglyceride enrichment and sphingosine-1-phosphate depletion. We hypothesized that these abnormalities could impair the ability of HDL to stimulate endothelial nitric oxide synthase (eNOS).
Approach and results: Compared with HDL from control subjects, HDL from normoglycemic patients with MetS was 39% richer in triglycerides (P<0.01) and 15% poorer in sphingosine-1-phosphate (P<0.05; n=23 in each group). eNOS activity, assessed by the conversion of L-[3H]arginine to L-[3H]citrulline, was 69% lower in human umbilical vein endothelial cells incubated with HDL from MetS patients than in cells incubated with HDL from controls (P<0.0001). In addition, the activating phosphorylation of eNOS at serine (Ser) 1177 and of Akt (protein kinase B) at Ser473 was 37% (P<0.001) and 39% (P<0.05) lower, respectively, with HDL from MetS patients. Sphingosine-1-phosphate enrichment of HDL from MetS patients restored their ability to stimulate eNOS activity (P<0.05), in relation with a significant increase in eNOS phosphorylation at Ser1177 (P<0.05) and in Akt phosphorylation at Ser473 (P=0.05). By contrast, triglyceride enrichment of HDL from control subjects did not modify eNOS activity (P=0.90) and phosphorylation at Ser1177 (P=0.87).
Conclusions: We provide evidence that the activation of eNOS by HDL is decreased in MetS patients before the appearance of diabetes mellitus and that sphingosine-1-phosphate depletion of HDL is the main factor responsible for this defect. This has important consequences on the impairment of HDL functionality and antiatherogenic properties in these patients.
