Received for publication August 18, 2004.
Revised December 21, 2004.
Accepted for publication December 29, 2004.

-arrestin 2 Dependent AT_1A Receptor Mediated Pathway of Chemotaxis Uncoupled from G-Protein Signaling

Abstract

ABSTRACT Chemotaxis is a cellular response that directs cell migration toward a chemical gradient and is fundamental to a variety of cellular processes. The receptors for most known chemokines belong to the seven transmembrane spanning superfamily and signal through members of the G_i family. -arrestins, in addition to regulating desensitization, have emerged as potential mediators of G-protein independent signaling pathways and have been implicated in several chemotactic pathways. Here we report a system wherein chemotaxis is stimulated in a -arrestin 2-dependent and apparently G-protein-independent manner. HEK293 cells with stable expression of the angiotensin II receptor type 1A (AT_1AR) undergo chemotaxis in response to Ang II. An Ang II peptide analogue S¹I⁴I⁸ Ang II that is unable to activate G-protein mediated responses induces chemotaxis in these cells that is unaffected by pertussis toxin-mediated suppression of G _i. Suppression of -arrestin 2 expression using siRNA essentially eliminated AT_1AR mediated chemotaxis induced by either Ang II or the S¹I⁴I⁸ Ang II peptide, while having no effect on EGF induced chemotaxis. It also abolished chemotaxis induced by LPA, which was completely sensitive to pertussis toxin. In contrast, reduction of G_q/11 through siRNA and inhibition of PKC, ERK1/2, or PI-3 kinase did not diminish AT_1AR mediated chemotaxis. Inhibiting p38 MAPK decreased AT_1AR mediated chemotaxis and eliminated EGF mediated chemotaxis, suggesting that p38 plays a role in chemotaxis that is not specific to the AT_1AR in this system. These data provide compelling evidence that - arrestin 2 can mediate chemotaxis through mechanisms which are G-protein independent (Ang II receptors) or dependent (LPA receptors).

Key words: Chemotactic peptides, Angiotensin, NGF/EGF, Gi family, Gq/11 family, GRKs, barrestins