The hepatic WASH complex is required for efficient plasma LDL and HDL cholesterol clearance
Melinde Wijers, Paolo Zanoni, Nalan Liv, Dyonne Y. Vos, Michelle Y. Jäckstein, Marieke Smit, Sanne Wilbrink, Justina C. Wolters, Ydwine T. van der Veen, Nicolette Huijkman, Daphne Dekker, Niels Kloosterhuis, Theo H. van Dijk, Daniel D. Billadeau, Folkert Kuipers, Judith Klumperman, Arnold von Eckardstein, Jan Albert Kuivenhoven, Bart van de Sluis
Melinde Wijers, Paolo Zanoni, Nalan Liv, Dyonne Y. Vos, Michelle Y. Jäckstein, Marieke Smit, Sanne Wilbrink, Justina C. Wolters, Ydwine T. van der Veen, Nicolette Huijkman, Daphne Dekker, Niels Kloosterhuis, Theo H. van Dijk, Daniel D. Billadeau, Folkert Kuipers, Judith Klumperman, Arnold von Eckardstein, Jan Albert Kuivenhoven, Bart van de Sluis
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Research Article Hepatology Metabolism

The hepatic WASH complex is required for efficient plasma LDL and HDL cholesterol clearance

Abstract

The evolutionary conserved Wiskott-Aldrich syndrome protein and SCAR homolog (WASH) complex is one of the crucial multiprotein complexes that facilitates endosomal recycling of transmembrane proteins. Defects in WASH components have been associated with inherited developmental and neurological disorders in humans. Here, we show that hepatic ablation of the WASH component Washc1 in chow-fed mice increases plasma concentrations of cholesterol in both LDLs and HDLs, without affecting hepatic cholesterol content, hepatic cholesterol synthesis, biliary cholesterol excretion, or hepatic bile acid metabolism. Elevated plasma LDL cholesterol was related to reduced hepatocytic surface levels of the LDL receptor (LDLR) and the LDLR-related protein LRP1. Hepatic WASH ablation also reduced the surface levels of scavenger receptor class B type I and, concomitantly, selective uptake of HDL cholesterol into the liver. Furthermore, we found that WASHC1 deficiency increases LDLR proteolysis by the inducible degrader of LDLR, but does not affect proprotein convertase subtilisin/kexin type 9–mediated LDLR degradation. Remarkably, however, loss of hepatic WASHC1 may sensitize LRP1 for proprotein convertase subtilisin/kexin type 9–induced degradation. Altogether, these findings identify the WASH complex as a regulator of LDL as well as HDL metabolism and provide in vivo evidence for endosomal trafficking of scavenger receptor class B type I in hepatocytes.

Authors

Melinde Wijers, Paolo Zanoni, Nalan Liv, Dyonne Y. Vos, Michelle Y. Jäckstein, Marieke Smit, Sanne Wilbrink, Justina C. Wolters, Ydwine T. van der Veen, Nicolette Huijkman, Daphne Dekker, Niels Kloosterhuis, Theo H. van Dijk, Daniel D. Billadeau, Folkert Kuipers, Judith Klumperman, Arnold von Eckardstein, Jan Albert Kuivenhoven, Bart van de Sluis

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Figure 4

The WASH complex is required for normal cell surface expression of LDLR and LRP1.

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The WASH complex is required for normal cell surface expression of LDLR ...
(A) Representative immunoblot of whole-cell and cell-surface protein levels of LDLR and LRP1 in WT and Washc1–/– primary hepatocytes. (B) Quantification of total and cell surface levels of LDLR and LRP1 (n = 4). (C) Representative immunoblot of hepatic LDLR and LRP1 3 weeks after AAV-PCSK9-D377Y administration. (D) Quantification of hepatic LRP1 protein levels in male WT and Washc1ΔHep mice 3 weeks after AAV-PCSK9-D377Y administration as determined by immunoblotting (n = 6–7). (E) Hepatic Lrp1 mRNA expression in the experimental groups of mice depicted in D. (F) Total plasma cholesterol levels in male WT and Washc1ΔHep mice before and 3 weeks after AAV-PCSK9-D377Y administration (n = 6–7). (G) TC levels of FPLC fractionated pooled plasma of WT and Washc1ΔHep 3 weeks after AAV-PCSK9-D377Y administration. CR, chylomicron remnants (n = 6–7). (H) Relative plasma apolipoprotein levels in WT and Washc1ΔHep mice after AAV-PCSK9-D377Y administration as measured by targeted proteomics. (I) Coomassie blue staining of ApoB100 and ApoB48 in WT and Washc1ΔHep plasma before and after AAV-PCSK9-D377Y administration. Data are presented as the mean ± SEM, **P < 0.01, ***P < 0.001 as determined by Student’s t test.