BIG2, an ARF guanine nucleotide‐exchange protein, regulates cell migration via effects integrin β1 cycling and actin cytoskeleton remodeling

Abstract

Brefeldin A‐inhibited guanine nucleotide‐exchange protein (BIG)2 activates ADP‐ribosylation factors (ARFs), a family of ~20‐kDa GTPase proteins involved in regulation of vesicular trafficking, by accelerating the replacement of ARF‐bound GDP with GTP. Mechanisms of additional BIG2 function(s) are less clear. We identified an involvement of BIG2 in integrin β1 action during cell migration using small interfering RNA (siRNA) and Difference Gel Electrophoresis (DIGE) analysis. Amounts of Arp2, Arp3, and cofilin, proteins known to act downstream of integrin β1 in cell movement, were increased in the cytosol fraction after BIG2 depletion. Treatment of HeLa cells with BIG2 siRNA, but not control siRNAs, resulted in perinuclear accumulation of integrin β1 and delayed return of internalized integrin β1 to the cell surface. At the same time, motility of BIG2‐depleted cells was decreased, and formation of the actin‐based membrane protrusions at leading edges of migrating cells was blocked, as was recruitment of Arp2, Arp3, and cofilin to the leading edge. Taken together, these data reveal a novel mechanism through which BIG2 may serve to coordinate cytoskeleton and membrane traffic, in cell migration, via integrin β1 action.