Published online before print July 20, 2009
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* Pulmonary, Allergy and Critical Care and
Hematology and Oncology Divisions, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
1. Correspondence: Pulmonary, Allergy and Critical Care Division, Department of Medicine, University of Pennsylvania School of Medicine, 522 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104-6061, USA. E-mail: collmanr{at}mail.med.upenn.edu
ABSTRACT
MIP-1β/CCL4 is a principal regulator of macrophage migration and signals through CCR5. Several protein kinases are linked to CCR5 in macrophages including the src kinase Lyn, PI3K, focal adhesion related kinase Pyk2, and members of the MAPK family, but whether and how these kinases regulate macrophage chemotaxis are not known. To define the role of these signaling molecules, we examined the functions and interactions of endogenous proteins in primary human macrophages. Using siRNA gene silencing and pharmacologic inhibition, we show that chemotaxis in response to CCR5 stimulation by MIP-1β requires activation of Pyk2, PI3K p85, and Lyn, as well as MAPK ERK. MIP-1β activation of CCR5 triggered translocation of Pyk2 and PI3K p85 from the cytoplasm to colocalize with Lyn at the plasma membrane with formation of a multimolecular complex. We show further that arrestins were recruited into the complex, and arrestin down-regulation impaired complex formation and macrophage chemotaxis toward MIP-1β. Together, these results identify a novel mechanism of chemokine receptor regulation of chemotaxis and suggest that arrestins may serve as scaffolding proteins linking CCR5 to multiple downstream signaling molecules in a biologically important primary human cell type.
Key Words: CCR5 • chemokine • PI3K • Pyk2 • Lyn • MAPK
