PYK2 links Gqα and G13α signaling to NF-κB activation

Signaling via a variety of G-protein-coupled receptors (GPCRs) leads to activation of nuclear factor (NF)-kappaB. Evidence exists for a signaling pathway initiated by the B2 type bradykinin receptor via G(q) activation, which leads to the sequential stimulation of phosphoinositide 3-kinase (PI3K), the serine/threonine kinase Akt, I kappaB kinases, and finally nuclear factor NF-kappaB-dependent transcription. GPCR-mediated G(q)alpha or G(13)alpha activation also potently stimulates the tyrosine kinase PYK2. In this study we tested whether G(q)alpha- and/or G(13)alpha -induced PYK2 activation contributes to GPCR-mediated NF-kappaB activation. Among the GTPase-deficient forms of G alpha tested, G(13)alpha and G(q)alpha most potently stimulated an NF-kappaB-dependent reporter gene. PYK2 activated the same reporter gene and synergized with either G(q)alpha Q209L (QL) or G(13)alpha Q226L (QL). Placing PYK2 upstream of both PI3K and Akt activation, PYK2 activated Aht through a PI3K-dependent pathway, and either a dominant negative form of Aht or the PI3K inhibitor LY294002 blocked PYK2-stimulated NF-kappaB-dependent transcription. Placing PYK2 downstream of G-protein activation, a kinase-dead form of PYK2, PYK2 (KD), blocked NF-kappaB-dependent transcription triggered by signaling through the muscarinic receptor type 1 and either G(q)alpha QL or G(13)alpha QL. PYK2 (KD) also blocked Akt activation by the same stimuli. These results indicate that PYK2 can link G-protein activation through PI3K, Akt, and I kappaB kinase to NF-kappaB activation.