MOLECULAR MECHANISMS MEDIATING CD22 ACCESSORY FUNCTION

本提案的目的是确定体内功能性 与B细胞共受体CD 22相互作用的效应蛋白的作用 通过产生表达野生型或改变的CD 22的转基因小鼠， CD 22背景 CD 22是一种B细胞特异性的跨膜 调节通过B细胞的信号阈值的糖蛋白 抗原受体（BCR）。因此，CD 22在 调节B细胞中耐受性和免疫力之间的平衡。 CD 22的胞质结构域含有六个酪氨酸残基，一个或多个。 其中更多的是响应于BCR交联而磷酸化。的 得到的磷酸酪氨酸基序作为对接位点， 募集含有SH 2结构域的效应蛋白。研究 在这个实验室进行的研究已经确定，CD 22招募了三个 效应蛋白的“类别”，包括抑制性效应蛋白 SHP-1和刺激性效应蛋白PL 0 γ、PI 3-K、Grb 2和 西克 此外，在该实验室进行的研究已经确定， CD 22与AP 50（CD 22的中链亚基）发生物理相互作用， AP-2复合物，通过含酪氨酸基序。 因此， CD 22的表达以及推测其功能是通过以下方式调节的 它与网格蛋白包被的凹坑有关。 虽然很明显， CD 22通过BCR负调节信号转导;问题 仍然关于刺激和抑制的功能作用， 与之相关的效应蛋白。因此， 提出确定效应蛋白的功能重要性 被募集到CD 22上建议的具体目标包括： 1）用野生型重组CD 22-/-小鼠， 不再与选定效应子结合的鼠CD 22的改变形式 2）利用CD 22转基因小鼠来确定CD 22蛋白的表达。 效应蛋白与细胞质结合的生理重要性 CD 22的结构域; 3）定义分子和生物化学过程 调节CD 22表达;和4）确定生理性的 CD 22和AP-2复合物在体内相互作用的重要性。 拟议的研究将准确地确定 CD 22在体内调节BCR信号转导。 结果从这些 研究将提供信息，以进一步了解 调节耐受性和耐受性之间平衡的分子过程， 免疫力 然后，可以使用该信息来促进 开发生物制剂， 系统控制疾病。

The objective of this proposal is to determine the in vivo functional role of effector proteins that interact with the B cell co-receptor CD22 by generating transgenic mice that express wild type or altered CD22 on the CD22-/- background. CD22 is a B cell specific transmembrane glycoprotein that regulates the threshold of signaling via the B cell antigen receptor (BCR). Therefore, CD22 plays an important role in regulating the balance between tolerance and immunity in the B cell. The cytoplasmic domain of CD22 contains six tyrosine residues, one or more of which are phosphorylated in response to BCR cross-linking. The resultant phosphotyrosine motifs function as docking sites for the recruitment of SH2 domain-containing effector proteins. Studies performed in this laboratory have determined that CD22 recruits three "classes" of effector proteins including the inhibitory effector protein SHP-1 and the stimulatory effector proteins PLOgamma, PI 3-K, Grb2 and Syk. Additionally, studies performed in this laboratory have determined that CD22 physically interacts with AP50, the medium chain subunit of the AP-2 complex, via a tyrosine-containing motif. Thus it is likely that CD22 expression, and presumably its function, are regulated through its association with clathrin-coated pits. Although it is apparent the CD22 negatively regulates signal transduction via the BCR; questions remain regarding the functional role of stimulatory and inhibitory effector proteins that associate with it. Therefore, studies are proposed to determine the functional importance of effector proteins that are recruited to CD22. The specific aims of the proposal include the following: 1) to reconstitute CD22-/- mice with wild type and altered forms of murine CD22 that no longer bind to selected effector proteins; 2) to utilize the CD22 transgenic mice to determine the physiologic importance of effector protein binding to the cytoplasmic domain of CD22; 3) to define the molecular and biochemical processes that regulate CD22 expression; and 4) to determine the physiologic importance of the interaction between CD22 and the AP-2 complex in vivo. The proposed studies will precisely determine the mechanism by which CD22 regulates BCR signal transduction in vivo. The results from these studies will provide information to further our understanding of the molecular processes that regulate the balance between tolerance and immunity. This information can then be used to facilitate the development of biotherapeutic agents that will modulate the immune system to control disease.