Chemokines integrate JAK/STAT and G-protein pathways during chemotaxis and calcium flux responses

Abstract

The JAK/STAT (Janus kinase / signaling transducer and activator of transcription) signaling pathway is implicated in converting stationary epithelial cells to migratory cells. In mammals, migratory responses are activated by chemoattractant proteins, including chemokines. We found that by binding to seven-transmembrane G-protein-coupled receptors, chemokines activate the JAK/STAT pathway to trigger chemotactic responses. We show that chemokine-mediated JAK/STAT activation is critical for G-protein induction and for phospholipase C-β dependent Ca2+, flux; in addition, pharmacological inhibition of JAK or mutation of the JAK kinase domain causes defects in both responses. Furthermore, Gαi association with the receptor is dependent on JAK activation, and the chemokine-mediated Ca2+ flux that requires phospholipase C-β activity takes place downstream of JAK kinases. The chemokines thus employ a mechanism that links heterologous signaling pathways - G proteins and tyrosine kinases - in a network that may be essential for mediating their pleiotropic responses.