Mast cell regulation by PKC and Akt

描述（由申请方提供）：肥大细胞在IgE依赖性过敏性超敏反应和宿主防御某些寄生虫中发挥关键作用。高亲和力IgE受体（FcepsilonRI）与IgE和多价过敏原的交联导致肥大细胞活化，最终释放一组促炎介质。PKC在肥大细胞活化中起关键作用。在通过Fc ε RI交联激活的各种PKC亚型中，PKCa I活性显示出以Btk依赖性方式由蛋白酪氨酸激酶（PTKs）林恩和Syk特异性调节。我们已经证明，在FcnRI刺激后，PKC β I和PKCalpha的C-末端酪氨酸残基Tyr-662和Tyr-658分别被质膜上的Syk磷酸化。这种磷酸化产生了Grb-2（一种衔接蛋白）的Src同源2（SH 2）结构域的结合位点。Grb-2/Sos复合物在Ras附近的募集有助于Ras/ERK通路的激活。Akt也显示在Fc ε RI交联后被激活并参与细胞因子产生。我们的初步数据表明，Akt的活性调节由传统的PKC亚型（α，β 1和β 1）在肥大细胞。基于这些数据，我们假设Syk对几种PKC亚型（a、betal、zeta和lambda/I）的C末端酪氨酸磷酸化招募Grb-2/Sos复合物来激活Ras（假设1），并且传统的PKC亚型磷酸化Akt激活的关键残基Ser-473（假设2）。我们也有初步的数据表明的C-末端疏水基序的底物识别的PKC α的作用（假设3）。为了深入研究PKC亚型和Akt在肥大细胞活化中的作用，我们将在体外和体内实验中评估这些假设。这些研究将为我们对肥大细胞信号转导的理解带来新的见解。鉴于PKC在脱颗粒和其他活化事件中的关键重要性，这些研究也可能为针对过敏性疾病的新治疗方式提供机会。

DESCRIPTION (provided by applicant): Mast cells play a critical role in IgE-dependent allergic hypersensitivity and the host defense against certain parasites. Cross-linking of the high-affinity IgE receptor (FcepsilonRI) with IgE and multivalent allergen elicits mast cell activation, culminating in the release of a panel of proinflammatory mediators. PKC plays critical roles in mast cell activation. Among various PKC isoforms that are activated by FcepsilonRI cross-linking, PKCaI activity was shown to be specifically regulated by protein-tyrosine kinases (PTKs), Lyn and Syk, in a Btk-dependent manner. We have demonstrated that C-terminal tyrosine residues, Tyr-662 and Tyr-658 of PKCbetaI and PKCalpha, respectively, are phosphorylated by Syk at the plasma membrane upon FcnRI stimulation. This phosphorylation creates the binding site for the Src homology 2 (SH2) domain of Grb-2, an adaptor protein. Recruitment of Grb-2/Sos complexes to the vicinity of Ras contributes to activation of the Ras/ERK pathway. Akt was also shown to be activated and involved in cytokine production upon FcepsilonRI cross-linking. Our preliminary data suggest that Akt activity is regulated by conventional PKC isoforms (alpha, betal and betall) in mast cells. Based on these data, we hypothesize that C-terminal tyrosine phosphorylation of several PKC isoforms (a, betal, zeta, and lambda/I) by Syk recruits Grb-2/Sos complexes to activate Ras (Hypothesis 1) and that the conventional PKC isoforms phosphorylate the critical residue Ser-473 for Akt activation (Hypothesis 2). We also have preliminary data suggesting the role of C-terminal hydrophobic motif of PKCa in substrate recognition (Hypothesis 3). To characterize in depth the roles of PKC isoforms and Akt in mast cell activation, we will evaluate these hypotheses in in vitro and in vivo experiments. The proposed studies will bring novel insight into our understanding of mast cell signal transduction. Given the critical importance of PKC in degranulation and other activation events, these studies are also likely to provide an opportunity for novel therapeutic modalities aimed at allergic diseases.