This project focuses on SRPK1 and SRPK2, major kinases responsible for the phosphorylation of SR proteins and RS domain-containing splicing factors and regulators in mammalian cells. We demonstrated that both of these splicing kinases are anchored in the cytoplasm through interactions with molecular chaperons and that they can be induced to translocate to the nucleus in response to cellular signaling. We recently discovered that these kinases are direct substrates of activated Akt, representing a new branch of the EGF pathway to regulate SR protein phosphorylation and alternative splicing in the nucleus. Interestingly, these splicing kinases also modulate the functional state of Akt via a novel feedback mechanism, and as a functional consequence, we found that depletion of SRPK1 is sufficient to transform immobilized MEFs. Based on these recent findings, we now propose three specific aims to (1) define SRPKs as signal transducers for regulated splicing using global approaches in combination with biochemical dissection of key signal transduction pathways involved, (2) elucidate the mechanism underlying SRPK-mediated signaling by characterizing specific molecular switches induced by upstream signaling events, and (3) determine the function and regulatory role of SRPKs in tumorigenesis by pursuing the hypotheses that SRPKs may regulate Akt and synergize with other key regulators in the Akt pathway to determine cell fate and promote tumorigenesis. The proposed studies are expected to have broad implications on regulated splicing, signal transduction and cancer biology.
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