Abstract
IL-4 is survival factor for lymphocytes and other hematopoietic cells. Whether there are mechanisms of pro-survival signaling induced by IL-4 apart from PI3K-Akt activation is not fully clear. Our laboratory identified PARP-14, a poly-ADP-ribose polymerase subfamily member, as a Stat6-interacting protein. PARP-14 is highly expressed in lymphoid organs, influences B cell subset ratios as well as the IgA response to antigen, and has intrinsic ADP-ribosyltransferase activity. ADP-ribosyltransferases and PARPs catalyze mono- and poly-ADP-ribosylation, transferring ADP from NAD+ to target proteins. ADP-ribosylation is a post-translational modification used by bacterial exotoxins to impact signal transduction, or, in the case of the mammalian PARP-1, to influence gene transcription and DNA repair or trigger apoptosis. Almost nothing is known about biological roles or mechanisms of action of other mammalian PARPs. We now show that PARP-14 is essential for full survival signaling despite normal Akt activation in B cells. Investigation of the mechanism(s) revealed that PARP-14 mediates IL-4 induction of gene products known to promote cell survival, and also metabolic functions of B cells. Moreover, intervention that restored glycolytic activity in IL-4-treated B cells also rescued pro-survival signaling. These results reveal a novel link to metabolic regulation via a mammalian ADP-ribosyltransferase.
