Cdc37 in Fcgamma R-induced Growth Arrest in B Cells

描述（由申请人提供）：这一新的长期目标 应用是为了了解B细胞抗原受体 (BCR)与IG受体（Fc γ RIIB）同时抑制B细胞 增殖Fc γ RIIB功能丧失可导致自身抗体产生 并可能导致自身免疫性疾病因此了解 生长停滞的分子基础对 与Fc γ RIIB相关的体液免疫应答和病理学 失调D型细胞周期蛋白/细胞周期蛋白依赖性激酶（cdk）4-视网膜母细胞瘤 (pRb)途径是生长因子信号和功能的主要靶点， 调节G1至S期进程。我们的结果表明BCR-Fc γ RIIB 共交联部分地通过信号传导来发挥其生长抑制作用， Cdc 37的磷酸化。Cdc 37沿着hsp 90，在 导致D型细胞周期蛋白-cdk 4复合物组装的途径。研究 本文提出的方法将检验Cdc 37的磷酸化在 对BCR-Fc γ RIIB共接合的应答：a）阻止hsp 90/Cdc 37的靶向 至cdk 4; B）阻断D型细胞周期蛋白激酶复合物的组装;和c）促进 成熟B淋巴细胞生长停滞。这些假设将在三个测试 具体目标包括：1）质谱法，以确定 Cdc 37上的BCR-Fc γ RIIB诱导型磷酸受体位点; 2）体外结合 丙氨酸点突变的GSTCdc 37的体内异位表达， 不能被阴性信号磷酸化，将用于评估作用 Hsp 9 O/Cdc 37靶向cdk 4和D型细胞周期蛋白中的磷酸化 激酶组装;和3）天冬氨酸取代的 FLAG-Cdc 37将被用于模拟磷酸化并迫使细胞分裂。 D型细胞周期蛋白激酶复合物并促进生长停滞。的信息 从这些研究中获得的信息将指导未来的研究， 自身免疫性疾病的治疗干预。

DESCRIPTION (provided by applicant): The long-term objective of this new application is to understand how engagement of the B-cell antigen receptor (BCR), simultaneously with the Ig receptor (FcgammaRIIB), inhibits B-cell proliferation. Loss of FcgammaRIIB function can lead to autoantibody production and may contribute to autoimmune disease. Therefore, understanding the molecular basis that underlies growth arrest has significant implications for both humoral immune responses and pathology associated with FcgammaRIIB dysregulation. The D-type cyclin/cyclin dependent kinase(cdk) 4-retinoblastoma (pRb) pathway is a primary target for growth factor signals and functions to regulate G1-to-S phase progression. Our results indicate that BCR-FcgammaRIIB co-cross-linking exerts its growth inhibitory effect, in part, by signaling the phosphorylation of Cdc37. Cdc37, along with hsp9O, plays an essential role in the pathway leading to D-type cyclin-cdk4 complex assembly. The research proposed herein will test the hypotheses that phosphorylation of Cdc37 in response to BCR-FcgammaRIIB coengagement: a) prevents targeting of hsp9O/Cdc37 to cdk4; b) blocks assembly of D-type cyclin kinase complexes; and c) promotes growth arrest in mature B lymphocytes. These hypotheses will be tested in three specific aims that include: 1) mass spectrometry to identify BCR-FcgammaRIIB-inducible phosphoacceptor sites on Cdc37; 2) in vitro binding assays and in vivo ectopic expression of alanine point-mutated GSTCdc37, that cannot be phosphorylated by negative signals, will be used to evaluate the role of phosphorylation on targeting of hsp9O/Cdc37 to cdk4 and in D-type cyclin kinase assembly; and 3) ectopic expression of aspartic acid substituted FLAG-Cdc37 will be used to mimic phosphorylation and force the disruption of D-type cyclin kinase complexes and promote growth arrest. The information obtained from these studies will serve to direct future studies aimed at therapeutic interventions in autoimmune disease.