Interleukin (IL)-7 induces rapid activation of Pyk2, which is bound to Janus kinase 1 and IL-7R alpha

Interleukin-7 (IL-7) receptor signaling begins with activation of the Janus tyrosine kinases Jak1 and Jak3, which are associated with the receptor com plex. To identify potential targets of these kinases, we examined Pyk2 (a m ember of the focal adhesion kinase family) using an IL-7-dependent murine t hymocyte line, D1. We demonstrate that stimulation of D1 (or normal pro-T) cells by IL-7 rapidly increased tyrosine phosphorylation and enzymatic acti vity of Pyk2, with kinetics slightly lagging that of Jak1 and Jak3 phosphor ylation. Conversely, IL-7 withdrawal resulted in a marked decrease of Pyk2 phosphorylation. Pyk2 was found to be physically associated with Jak1 prior to IL-7 stimulation and to increase its association with lL-7R alpha chain following IL-7 stimulation. Pyk2 appeared to be involved in cell survival, because antisense Pyk2 accelerated the cell death process. Activation of P yk2 via the muscarinic and nicotinic receptors using carbachol or via intra cellular Ca2+ rise using ionomycin/phorbol myristate acetate promoted survi val in the absence of IL-7. These data support a role for Pyk2 in coupling Jak signaling to the trophic response.