MOLECULAR MECHANISMS MEDIATING CD22 ACCESSORY FUNCTION

这项建议的目的是确定体内功能 与B细胞共受体CD22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CD22的转基因小鼠 CD22-/-背景。CD22是一种B细胞特异性跨膜蛋白 调节B细胞信号转导阈值的糖蛋白 抗原受体(BCR)。因此，CD22在人类免疫缺陷中起着重要作用。 调节B细胞耐受性和免疫力之间的平衡。 CD22的胞质结构域包含六个酪氨酸残基，一个或 其中更多的是由于BCR的交联而被磷酸化的。这个 生成的磷酸酪氨酸基序作为对接位置 含有SH2结构域的效应蛋白的募集。研究 已经确定CD22招募了三名 “类”效应蛋白，包括抑制性效应蛋白 SHP-1和刺激效应蛋白PLOGamma、PI3-K、Grb2和 SYK。此外，在这个实验室中进行的研究已经确定 CD22在物理上与AP50相互作用，AP50是其中链亚基 AP-2复合体，通过含有酪氨酸的基序。因此，很有可能 CD22的表达，以及它的功能可能是通过 它与笼状蛋白涂层的窖池有关。尽管很明显， CD22通过BCR负性调节信号转导；问题 关于刺激和抑制的功能作用 与之相关的效应器蛋白。因此，研究是 建议确定效应器蛋白的功能重要性 这些人被招募到CD22。该提案的具体目标包括 1)重组CD22-/-小鼠野生型和 改变形式的小鼠CD22不再与选定的效应器结合 2)利用CD22转基因小鼠检测 效应蛋白与细胞质结合的生理意义 CD22的结构域；3)定义分子和生化过程 调节CD22的表达；以及4)确定生理上的 CD22与AP-2复合体在体内相互作用的重要性。 拟议的研究将准确地确定 CD22在体内调节BCR信号转导。这些研究的结果 研究将提供信息，以加深我们对 调节耐受和耐受之间平衡的分子过程 豁免权。然后可以使用这些信息来帮助 免疫调节生物治疗剂的研究进展 控制疾病的系统。

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.