腺嘌呤核苷二磷酸核醣化相似因子四C (ARL4C)與其結合蛋白之特性探討

Abstract

ADP-ribosylation factor-like (ARL) 4C is a member of Ras-related small G protein family. Previous studies have shown that ARL4C plays potential roles in actin dynamics and cholesterol secretion process. However the cellular function of ARL4C remains unclear. We found that exogenous wild type ARL4C and active form ARL4C-Q72L induced filopodia and reduced stress fiber intensity in HeLa cell. Overexpression of Cdc42-T17N or Rac1-T17N did not affect ARL4C-induced filopodia. We found that the expression level of ARL4C mRNA could be detected by RT-PCR in human lung adenocarcinoma cell line (CL1-5). Wound-healing assay showed that migration ability was decreased in ARL4C-depleted CL1-5. To identify potential effectors of ARL4C, We performed yeast two-hybrid screening in human fetal brain cDNA library by using ARL4C-Q72L as bait and identified a putative effector of ARL4C, an actin-binding protein filamin A (FLNa). Yeast two‐hybrid analysis showed that the C-terminus of FLNa interacted with wild type ARL4C and ARL4C-Q72L, but not with ARL4C inactive form T27N. GST-Pull down assay and immunoprecipitation demonstrated that ARL4C interacted with the FLNa in vitro and in vivo. Immunofluorescence analysis showed that wild type ARL4C and ARL4C-Q72L colocalized with endogenous FLNa at plasma membrane and ARL4C-induced filopodia in HeLa cells. Knockdown of FLNa by siRNA did not affect the localization of ARL4C or ARL4C-induced filopodia. In the future, we will study the roles of ARL4C and FLNa in CL1-5 cell migration ability.