Regulation of RNA metabolism and cell growth control by SR protein kinases

描述（由申请人提供）： 该项目的重点是SRPK1和SRPK2，主要激酶负责SR蛋白磷酸化和RS域包含剪接因子和调节剂在哺乳动物细胞。我们证明了这两种剪接激酶都通过与分子伴侣的相互作用锚定在细胞质中，并且它们可以被诱导易位到细胞核中以响应细胞信号。我们最近发现，这些激酶是激活Akt的直接底物，代表EGF途径的一个新的分支，以调节SR蛋白磷酸化和选择性剪接在细胞核中。有趣的是，这些剪接激酶还通过一种新的反馈机制调节Akt的功能状态，作为一个功能性的结果，我们发现SRPK1的耗尽足以转化固定的MEFs。基于这些最新发现，我们现在提出三个具体目标：（1）使用全局方法结合对所涉及的关键信号转导途径的生化解剖来定义SRPK作为调节剪接的信号转导子，（2）通过表征由上游信号事件诱导的特定分子开关来阐明SRPK介导的信号转导的潜在机制，以及（3）通过以下假设确定SRPKs在肿瘤发生中的功能和调节作用：SRPKs可以调节Akt并与Akt途径中的其他关键调节剂协同作用以决定细胞命运并促进肿瘤发生。这些研究将对调控剪接、信号转导和肿瘤生物学产生广泛的影响。

DESCRIPTION (provided by applicant): 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.