Modulation of Leukocyte Adhesion by P-selectin/PSGL-1 Signaling

描述（由申请人提供）：通过P-选择素/PSGL-1信号传导调节白细胞粘附白细胞募集需要级联的细胞事件，包括响应细胞的滚动和牢固粘附。P-选择素（CD 62 P）、P-选择素糖蛋白配体-1（PSGL-1、CD 162）和β 2-整联蛋白是先天免疫和炎症所必需的内皮和白细胞粘附分子。P-选择素与PSGL-1的相互作用介导白细胞滚动，在此期间，它们通过局部释放或展示的细胞因子和化学引诱物原位充分活化，用于β 2-整联蛋白介导的牢固粘附。然而，P-选择素粘附活性的反馈调节和P-选择素诱导的β 2-整联蛋白活化的机制仍然不确定。Nef相关因子1（Nafl）是NF-κ B活化的内源性抑制剂。血清淀粉样蛋白P组分（SAP）是由肝细胞响应于各种炎症介质而快速合成和分泌的急性时相蛋白。在前期研究中，我们发现Naf 1与PSGL-1的胞质尾区形成了稳定的复合物。P-selectin与PSGL-1的结合使Naf 1的Y552 PPM基序磷酸化，以募集磷脂酰肌醇-3激酶（PI 3 K）的p85亚基并触发信号级联反应，最终激活α M β 2（CD 11b CD 18，Mac-1）。此外，我们观察到SAP与P-选择素相互作用，并作为PSGL-1的内源性抑制剂识别P-选择素。在本授权申请中，我们提出1）确定P-选择素诱导的α M β 2活化的功能重要性; 2）确定PSGL-1-Naf 1-p85信号通路调节α M β 2活性的生物学意义; 3）探索SAP对P-选择素粘附活性的调节。总体而言，这项研究不仅将增强我们对在白细胞募集的多步骤范例中精确决定白细胞命运的分子机制的理解，而且还将发现用于预防和治疗炎症性疾病的新的治疗靶点。

DESCRIPTION (provided by applicant): Modulation of Leukocyte Adhesion by P-selectin/PSGL-1 Signaling Leukocyte recruitment entails a cascade of cellular events, including rolling and firm adhesion of responding cells. P-selectin (CD62P), P-selectin glycoprotein ligand-1 (PSGL-1, CD162) and beta2-integrins are endothelial and leukocyte cell adhesion molecules essential for innate immunity and inflammation. The interaction of P-selectin with PSGL-1 mediates leukocyte rolling, during which they become sufficiently activated in situ by locally released or displayed cytokines and chemoattractants for beta2-integrin-mediated firm adhesion. However, the mechanisms for feedback regulation of P-selectin adhesion activity and P- selectin-induced beta2-integrin activation remain undetermined. Nef-associated factor 1 (Nafl) is an endogenous inhibitor for NF-kappaB activation. Serum amyloid P component (SAP) is an acute phase protein synthesized and secreted rapidly by hepatocytes in response to various inflammatory mediators. In the preliminary studies, we found that Naf1 formed a stable complex with the cytoplasmic tail of PSGL-1. Engagement of PSGL-1 by P-selectin phosphorylated the Y552PPM motif of Naf1 for recruiting p85 subunit of phosphatidylinositol-3 kinase (PI3K) and triggering the signaling cascade that culminated in activation of alphaMbeta2 (CD11bCD18, Mac-1). In addition, we observed that SAP interacted with P-selectin and acted as an endogenous inhibitor of PSGL-1 for P-selectin recognition. In this grant application, we propose 1) to define the functional importance of P-selectin-induced activation of alphaMbeta2; 2) to determine the biological significance of the PSGL-1-Naf1-p85 signaling pathway for modulation of alphaMbeta2 activity; and 3) to explore the regulation of P-selectin adhesion activity by SAP. Overall, this study will not only enhance our understanding of molecular mechanisms that precisely determine leukocyte fates in the multi- step paradigm of leukocyte recruitment, but also discover novel therapeutic targets for prevention and treatment of inflammatory disorders.