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信号调节白细胞粘附涉及一系列细胞事件，包括应答细胞的滚动和牢固粘附。p -选择素（CD62P）、p -选择素糖蛋白配体-1 （PSGL-1, CD162）和β -整合素是内皮细胞和白细胞粘附分子，对先天免疫和炎症至关重要。p -选择素与PSGL-1的相互作用介导白细胞滚动，在此过程中，它们被局部释放或显示的细胞因子和化学引诱剂充分激活，以促进β -整合素介导的牢固粘附。然而，P-选择素粘附活性和P-选择素诱导β -整合素活化的反馈调节机制尚不清楚。nf -associated factor 1 （Nafl）是NF-kappaB激活的内源性抑制剂。血清淀粉样蛋白P组分（SAP）是肝细胞对多种炎症介质的反应中迅速合成和分泌的急性期蛋白。在前期研究中，我们发现Naf1与PSGL-1的胞质尾部形成稳定的复合物。p -选择素参与PSGL-1磷酸化Naf1的Y552PPM基序，募集磷脂酰肌醇-3激酶（PI3K）的p85亚基，并触发信号级联，最终激活α - β 2 （CD11bCD18, Mac-1）。此外，我们观察到SAP与p -选择素相互作用，并作为内源性PSGL-1的p -选择素识别抑制剂。在这项拨款申请中，我们提出1)定义p选择素诱导的α β 2活化的功能重要性；2)确定PSGL-1-Naf1-p85信号通路调节alphabeta2活性的生物学意义；3)探索SAP对p -选择素粘附活性的调控。总之，本研究不仅将加深我们对白细胞募集多步范式中精确决定白细胞命运的分子机制的理解，而且还将发现预防和治疗炎症性疾病的新治疗靶点。

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.