| Beta arrestin 2 is critically involved in CXCR 4 mediated chemotaxis , and this is mediated by its enhancement of p 38 MAPK activation . ^^^ We have demonstrated previously that beta arrestin 2 functions to attenuate CXCR 4 mediated G protein activation and to enhance CXCR 4 internalization . ^^^ Here we show further that the expression of beta arrestin 2 in both HeLa and human embryonic kidney 293 cells significantly enhances the chemotactic efficacy of stromal cell derived factor 1alpha , the specific agonist of CXCR 4 , whereas the suppression of beta arrestin 2 endogenous expression by antisense or RNA mediated interference technology considerably attenuates stromal cell derived factor 1alpha induced cell migration . ^^^ Further analysis reveals that expression of beta arrestin 2 strengthened CXCR 4 mediated activation of both p 38 MAPK and ERK , and the suppression of beta arrestin 2 expression blocked the activation of two kinases . ^^^ The results of our study suggest that beta arrestin 2 can function not only as a regulator of CXCR 4 signaling but also as a mediator of stromal cell derived factor 1alpha induced chemotaxis and that this activity probably occurs via the ASK1 / p38 MAPK pathway . . ^^^ |