CLIC4 regulates cell adhesion and β1 integrin trafficking

Abstract

BSTRACTChloride intracellular channel protein 4 (CLIC4) exists in both soluble and membrane-associated forms, and is implicated in diverse cellular processes, ranging from ion channel formation to intracellular membrane remodeling. CLIC4 is rapidly recruited to the plasma membrane by lysophosphatidic acid (LPA) and serum, suggesting a possible role for CLIC4 in exocytic-endocytic trafficking. However, the function and subcellular target(s) of CLIC4 remain elusive. Here, we show that in HeLa and MDA-MB-231 cells, CLIC4 knockdown decreases cell-matrix adhesion, cell spreading and integrin signaling, whereas it increases cell motility. LPA stimulates the recruitment of CLIC4 to b1 integrin at the plasma membrane and in Rab35-positive endosomes. CLIC4 is required for both the internalization and the serum-or LPA-induced recycling of b1 integrin, but not for EGF receptor trafficking. Furthermore, we show that CLIC4 suppresses Rab35 activity and antagonizes Rab35-dependent regulation of b1 integrin trafficking. Our results define CLIC4 as a regulator of Rab35 activity and serum-and LPAdependent integrin trafficking.

Emerging biological roles of Cl− intracellular channel proteins

“…CLIC1, CLIC3 and CLIC4 colocalize with integrin subunits α5, β1 and β3, and with distinct Rab GTPases upon growth factor stimulation or integrin engagement (Argenzio et al, 2014;Dozynkiewicz et al, 2012;Gurski et al, 2015). Both CLIC3 and CLIC4 regulate the trafficking of α5β1 integrin and promote the recycling of activated α5β1 integrin from different cellular compartments back to plasma membrane (Argenzio et al, 2014;Dozynkiewicz et al, 2012) (Fig.…”

“…(3, 4) CLIC2 and CLIC4 undergo rapid translocation to the plasma membrane upon GPCR stimulation (Lecat et al, 2015). (4) Upon stimulation with LPA, CLIC4 colocalizes with NHERF2 and β1 integrin at the plasma membrane and in a subset of Rab35-positive recycling endosome (Argenzio et al, 2014;Ponsioen et al, 2009). CLIC4 contributes to the internalization of β1 integrin (5) and its LPA-induced recycling back to the plasma membrane (Argenzio et al, 2014) (6).…”

“…G-protein-coupled receptor (GPCR) agonists, such as lysophosphatidic acid (LPA), in diverse cell types (Argenzio et al, 2014;Lecat et al, 2015;Ponsioen et al, 2009). CLIC2 shows a similarly rapid translocation upon GPCR stimulation (Lecat et al, 2015) (Fig.…”

“…Both CLIC3 and CLIC4 regulate the trafficking of α5β1 integrin and promote the recycling of activated α5β1 integrin from different cellular compartments back to plasma membrane (Argenzio et al, 2014;Dozynkiewicz et al, 2012) (Fig. 2).…”

“…CLICs are small globular proteins (∼28 kDa) that are structurally related to the omega-class of glutathione S-transferases (GSTs) but appear to have distinct, but still poorly understood, cellular functions. Contrary to their original name, CLIC proteins do not function as conventional Cl − channels but, instead, have roles in such diverse biological processes as tubulogenesis (Berry et al, 2003;Ulmasov et al, 2009), actin-dependent membrane remodeling (Berryman and Bretscher, 2000;Berryman et al, 2004;Bohman et al, 2005;Singh et al, 2007), endosomal trafficking (Argenzio et al, 2014;Chou et al, 2016;Dozynkiewicz et al, 2012), vacuole formation and fusion (Berry et al, 2003), as well as intravesicular pH regulation (Berry et al, 2003;Jiang et al, 2012;Ulmasov et al, 2009), among others. Moreover, they show intrinsic glutaredoxinlike activity in vitro (Al Khamici et al, 2015).…”