Differential effects of cytohesins 2 and 3 on beta1 integrin recycling.

ADP-ribosylation actor 6 (ARF6) regulates the endocytosis and recycling of a variety of proteins and also promotes peripheral actin rearrangements and cell motility. ARF6 is activated by a large number of guanine nucleotide exchange factors, which likely regulate ARF6 at different locations and during different processes. In this study we investigate the roles of the cytohesin ADP-ribosylation factor (ARF)-guanine nucleotide exchange factors during the recycling of integrin beta1. Intriguingly, we find that knockdown and overexpression of ARNO/cytohesin 2 and GRP1/cytohesin 3 have opposing effects on cell adhesion and spreading on fibronectin and on cell migration. We find that ARNO/cytohesin 2 is required for integrin beta1 recycling, whereas GRP1/cytohesin 3 is dispensable for this process. This is the first demonstration of unique roles for these proteins.