The Small GTPase Cdc42 Interacts with Niemann-Pick C1-like 1 (NPC1L1) and Controls Its Movement from Endocytic Recycling Compartment to Plasma Membrane in a Cholesterol-dependent Manner

Abstract

Niemann-Pick C1-like 1 (NPC1L1) is a multi-transmembrane protein that mediates the absorption of dietary and biliary cholesterol through vesicular endocytosis. The subcellular localization of NPC1L1 is regulated by cholesterol. Cholesterol depletion induces the transport of NPC1L1 to plasma membrane (PM) from endocytic recycling compartment that requires MyoVb⅐Rab11a⅐Rab11-FIP2 triple complex, and cholesterol-replenishment renders the internalization of NPC1L1 together with cholesterol. Here, we find that GTP-bound Cdc42 interacts with NPC1L1. Cholesterol depletion regulates the activation of Cdc42 and enhances NPC1L1-Cdc42 interaction. Overexpression of constitutive GTP-bound Cdc42 mutant form or knockdown of Cdc42 inhibits the transport of NPC1L1 to the PM and disturbs the cholesterol-regulated binding of NPC1L1 to Rab11a, MyoVb, and actin. Knockdown of Cdc42 downstream effectors N-WASP or Arp3 also leads to the similar results. In liver-specific Cdc42 knock-out (Cdc42 LKO) mice, NPC1L1 fails to localize to bile canaliculi, and the biliary cholesterol cannot be efficiently reabsorbed. These results indicate that Cdc42 controls the cholesterol-regulated transport and localization of NPC1L1, and plays a role in cholesterol absorption.

Ezetimibe blocks the internalization of NPC1L1 and cholesterol in mouse small intestine

“…Unlike what has been observed in cultured cells whose recycling endosomes were gathered into condensed complex at the perinuclear region ( 9,13,15,16 ), these recycling endosomes labeled by Rab11 in intestinal tissues were localized along the brush border membrane at the subapical intestinal lumen are different between mouse and rat. Mice have more hydrophilic bile acids pool ( 50 ), mainly taurocholate and tauro-␤ -muricholate, which are poor cholesterol solubilizers and probably lead to less effi cient cholesterol absorption.…”

“…The ERC is a cellular cholesterol pool and a Rab11a-positive compartment ( 9, 12-14 ). When the ERC cholesterol level drops, NPC1L1 moves to plasma membrane to mediate another round of cholesterol transport ( 9,13,(15)(16)(17). Ezetimibe, a cholesterol absorption inhibitor, blocks the internalization of NPC1L1-Flotillin-cholesterol microdomains and therefore decreases cholesterol uptake in cultured cells ( 9,11,17,18 ).…”

The GTPase-deficient Rnd Proteins Are Stabilized by Their Effectors

“…This chimera showed a Ͼ10-fold higher protein level compared with wild-type Rnd3 and is primarily localized to internal membranes (Fig. 4E) (44). We conclude that in part the correct localization of Rnd3 via its C terminus is required for its turnover.…”

LTP-triggered cholesterol redistribution activates Cdc42 and drives AMPA receptor synaptic delivery

“…They may be related to the displacement of Cdc42 from lipid rafts (Fessler et al, 2004;Jaksits et al, 2004). Interestingly, concomitant Cdc42 activation and mobilization of Rab11 recycling endosomes has been observed in hepatic cells upon cholesterol removal (Xie et al, 2011). Additionally, reduction in cholesterol levels has been linked to the activation of the phosphoinositide 3-kinase pathway (Martin et al, 2008(Martin et al, , 2011, which may in turn lead to Cdc42 activation via phosphatidylinositol (3,4,5)-trisphosphate-sensitive Cdc42 GEFs, such as Vav2 and Vav3 (Aoki et al, 2005).…”