Jing Wang

Northeast Institute of Geography and Agroecology, Beijing, Beijing Shi, China

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Publications (4)41.27 Total impact

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    ABSTRACT: Niemann-Pick C1-like 1 (NPC1L1) is an essential protein for dietary cholesterol absorption. Nonsynonymous (NS) variants of NPC1L1 in humans have been suggested to associate with cholesterol absorption variations. However, information concerning the characteristics and mechanism of these variants in cholesterol uptake is limited. In this study, we analyzed the cholesterol uptake ability of the 19 reported NS variants of NPC1L1 identified from cholesterol low absorbers. Among these variants, L110F, R306C, A395V, G402S, T413M, R693C, R1214H, and R1268H could partially mediate cellular cholesterol uptake and were categorized as partially dysfunctional variants. The other 11 variants including T61M, N132S, D398G, R417W, G434R, T499M, S620C, I647N, G672R, S881L, and R1108W could barely facilitate cholesterol uptake, and were classified into the severely dysfunctional group. The partially dysfunctional variants showed mild defects in one or multiple aspects of cholesterol-regulated recycling, subcellular localization, glycosylation, and protein stability. The severely dysfunctional ones displayed remarkable defects in all these aspects and were rapidly degraded through the ER-associated degradation (ERAD) pathway. In vivo analyses using adenovirus-mediated expression in mouse liver confirmed that the S881L variant failed to localize to liver canalicular membrane, and the mice showed defects in biliary cholesterol re-absorption, while the G402S variant appeared to be similar to wild-type NPC1L1 in mouse liver. This study suggests that the dysfunction of the 19 variants on cholesterol absorption is due to the impairment of recycling, subcellular localization, glycosylation, or stability of NPC1L1.
    Journal of Biological Chemistry 12/2010; 286(9):7397-408. · 4.65 Impact Factor
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    ABSTRACT: Niemann-pick C1 Like 1 (NPC1L1) plays a critical role in the enterohepatic absorption of free cholesterol. Cellular cholesterol depletion induces the transport of NPC1L1 from endocytic recycling compartment (ERC) to plasma membrane (PM); and cholesterol replenishment causes the internalization of NPC1L1 together with cholesterol via clathrin-mediated endocytosis. Although NPC1L1 has been characterized, the other proteins involved in cholesterol absorption and the endocytic recycling of NPC1L1 are largely unknown. Most of the vesicular trafficking events are dependent on the cytoskeleton and motor proteins. Here, we investigated the roles of microfilament and microfilament-associated triple complex composed of myosin Vb, Rab11a and Rab11-FIP2 in the transport of NPC1L1 from ERC to PM. Interference of the dynamics of microfilament by pharmacological treatment delayed the transport of NPC1L1 to the cell surface. Meanwhile, inactivation of any component of the myosin Vb/Rab11a/Rab11-FIP2 triple complex inhibited the export of NPC1L1. Expression of the dominant-negative mutants of myosin Vb, Rab11a or Rab11-FIP2 decreased the cellular cholesterol uptake by blocking the transport of NPC1L1 to PM. These results suggest that the efficient transport of NPC1L1 to PM is dependent on the microfilament-associated myosin Vb/Rab11a/Rab11-FIP2 triple complex.
    Journal of Biological Chemistry 06/2009; · 4.65 Impact Factor
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    ABSTRACT: Niemann-Pick C1-like 1 (NPC1L1) is a polytopic transmembrane protein that plays a critical role in cholesterol absorption. Ezetimibe, a hypocholesterolemic drug, has been reported to bind NPC1L1 and block cholesterol absorption. However, the molecular mechanism of NPC1L1-mediated cholesterol uptake and how ezetimibe inhibits this process are poorly defined. Here we find that cholesterol specifically promotes the internalization of NPC1L1 and that this process requires microfilaments and the clathrin/AP2 complex. Blocking NPC1L1 endocytosis dramatically decreases cholesterol internalization, indicating that NPC1L1 mediates cholesterol uptake via its vesicular endocytosis. Ezetimibe prevents NPC1L1 from incorporating into clathrin-coated vesicles and thus inhibits cholesterol uptake. Together, our data suggest a model wherein cholesterol is internalized into cells with NPC1L1 through clathrin/AP2-mediated endocytosis and ezetimibe inhibits cholesterol absorption by blocking the internalization of NPC1L1.
    Cell metabolism 06/2008; 7(6):508-19. · 17.35 Impact Factor
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    ABSTRACT: The membrane-anchored ubiquitin ligase gp78 promotes degradation of misfolded endoplasmic reticulum (ER) proteins and sterol-regulated degradation of HMG-CoA reductase. It was known previously that Ufd1 plays a critical role in ER-associated degradation (ERAD) together with Npl4 and VCP. The VCP-Ufd1-Npl4 complex recognizes polyubiquitin chains and transfers the ubiquitinated proteins to the proteasome. Here we show that Ufd1 directly interacts with gp78 and functions as a cofactor. Ufd1 enhances the E3 activity of gp78, accelerates the ubiquitination and degradation of reductase, and eventually promotes receptor-mediated uptake of low-density lipoprotein. Furthermore, we demonstrate that the monoubiquitin-binding site in Ufd1 is required for the enhancement of gp78 activity and that the polyubiquitin-binding site in Ufd1 is critical for a postubiquitination step in ERAD. In summary, our study identifies Ufd1 as a cofactor of gp78, reveals an unappreciated function of Ufd1 in the ubiquitination reaction during ERAD, and illustrates that Ufd1 plays a critical role in cholesterol metabolism.
    Cell Metabolism 09/2007; 6(2):115-28. · 14.62 Impact Factor

Publication Stats

158 Citations
41.27 Total Impact Points

Institutions

  • 2010
    • Northeast Institute of Geography and Agroecology
      • State Key Laboratory of Molecular Biology
      Beijing, Beijing Shi, China
  • 2007–2008
    • Shanghai Institutes for Biological Sciences
      Shanghai, Shanghai Shi, China