Mechanisms for Blood Cell Adhesion Under Flow

描述（由申请人提供）：本提案采用多学科方法阐明血小板和白细胞如何克服动力学和力学约束，在流动中粘附在血管表面。重点是三种选择素（p -选择素，E-选择素和l-选择素）与p -选择素糖蛋白配体-1 （PSGL-1）和其他细胞表面糖缀合配体的相互作用。这些相互作用介导白细胞在活化血小板、内皮细胞和粘附白细胞上的滚动粘附。我们的总体假设是，选择素与其配体结合的重要动力学性质（例如，捕获键和滑动键）是由这些分子结构决定的特定原子水平相互作用产生的。力通过诱导构象变化和/或在结构中形成新的原子级相互作用来调节功能。传输参数影响内在对接速率对分子相互作用的影响。由于这些动力学特性决定了细胞在流动状态下的功能（例如，系缚、滚动和聚集），相对较小的结构差异会改变这些原子水平的相互作用，从而对生理和病理产生重大影响。这项建议包括四个具体目标。前三个目标使用晶体结构、分子模型、生化和生物物理分析来定义选择素及其配体的特定结构特征如何控制流动细胞的系结、滚动和聚集。第四个目的是利用表达突变选择素的敲入小鼠来揭示体内流动增强细胞粘附的生物学功能。从这项综合研究中获得的信息将阐明分子结构如何满足血液细胞在流体动力学环境中粘附的生物物理要求，并可能提出新的治疗方法来抑制炎症和血栓形成期间的病理性细胞粘附。项目描述：在感染或受伤时，循环中的白细胞和血小板粘附在血管表面，这是控制感染或出血的第一步。这个项目解决了具体的“粘附分子”如何控制这一过程。获得的这一信息可能为治疗心脏病发作、中风、深静脉血栓形成和其他疾病的过度血细胞粘附提供新的方法。

DESCRIPTION (provided by applicant): This proposal employs a multidisciplinary approach to elucidate how platelets and leukocytes overcome kinetic and mechanical constraints to adhere to vascular surfaces under flow. The focus is the interaction of the three selectins (P-selectin, E- selectin, and L-selectin) with P-selectin glycoprotein ligand-1 (PSGL-1) and other cell- surface glycoconjugate ligands. These interactions mediate rolling adhesion of leukocytes on activated platelets, endothelial cells, and adherent leukocytes. Our overall hypothesis is that important kinetic properties (e.g., catch and slip bonds) for binding of selectins to their ligands result from specific atomic-level interactions that are dictated by the structures of these molecules. Force regulates function by inducing conformational changes and/or forming new atomic-level interactions in the structures. Transport parameters influence how intrinsic docking rates affect molecular interactions. Since these kinetic properties determine cellular function under flow (e.g., tethering, rolling, and aggregation), relatively minor structural differences that alter these atomic-level interactions have major consequences for physiology and pathology. The proposal is integrated into four specific aims. The first three aims use crystal structures, molecular modeling, and biochemical and biophysical assays to define how specific structural features of selectins and their ligands govern tethering, rolling, and aggregation of flowing cells. The fourth aim uses knock-in mice expressing a mutant selectin to reveal the biological functions of flow-enhanced cell adhesion in vivo. The information obtained from this integrated study will clarify how molecular structure fulfills the biophysical requirements for blood cells to adhere in a hydrodynamic environment, and may suggest new therapeutic approaches to inhibiting pathological cell adhesion during inflammation and thrombosis. Project Narrative: In response to infection or injury, circulating white blood cells and platelets adhere to blood vessel surfaces, the first step in controlling infection or bleeding. This project addresses how specific "adhesion molecules" control this process. This information obtained may offer new methods to treat excessive blood cell adhesion in heart attacks, strokes, deep venous thrombosis, and other disorders.