Signal Transduction of Type 1 Interferons in Malignant Cells

DESCRIPTION: (provided by applicant) This is a competitive grant-renewalapplication, in which the overall goal is to understand the mechanisms of TypeI IFN signaling in malignant cells. During the previous funding period, weidentified several novel-IFN activated signaling cascades involving theCrkL-adapter and demonstrated that CrkL plays a critical role in Type I IFNsignal transduction. We will now undertake studies to establish the functionalroles of the different domains of CrkL in the context of its signaling capacityand define the contribution of distinct CrkL-cascades in the generation of thebiological effects of IFNs. A major goal of this grant application is also todetermine the mechanisms of regulation of Stat-serine phosphorylation. Inaddition to tyrosine phosphorylation, IFNalpha-dependent phosphorylation ofStat1 and Stat3 on serine 727 is required for transcriptional activation oftarget genes. Although it is well established that Jak-kinases regulatetyrosine phosphorylation of Stats, the IFNalpha-activated serine kinase thatphosphorylates Stat-proteins is not known. The identification of such a serinekinase is an important outstanding issue, required to complete ourunderstanding on the IFN-activated Jak-Stat pathway. Our data have establishedthat a member of the protein kinase C-family of proteins, PKC-delta, isactivated in a Type I IFN-dependent manner and regulates serine phosphorylationof Stat1. These findings, for the first time, provide the identity of theIFNalpha-activated Stat-serine kinase and form the basis for further studies.The objective of this section of this proposal is to define the mechanisms bywhich PKC-delta is activated by the Type I IFN receptor and interacts withStat1, and possibly Stat3, to effect their phosphorylation on serine 727.Studies will be also performed to define the role of PKC-deltaactivation/Stat-serine phosphorylation in the induction of theantiproliferative, antiviral and immunomodulatory effects of Type I IFNs, aswell as the induction of suppressive effects of IFNalpha on bone marrowleukemic progenitors from patients with chronic myelogenous leukemia.Altogether, this proposal will address important aspects of the mechanisms ofType I IFN-signal transduction and generation of antileukemic effects.