IDENTIFICATION OF PUTATIVE PROTEIN CANDIDATES IN THE EXPORT MECHANISM OF ANNEXI

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。膜联蛋白2是纤溶酶原和组织纤溶酶原激活剂的纤溶原共受体，刺激细胞表面主要纤溶酶（纤溶酶）的活化。在人类受试者中，急性早幼粒细胞白血病中膜联蛋白2的过度表达导致出血素质，反映了细胞表面膜联蛋白2依赖性产生过多的纤溶酶。此外，完全缺乏膜联蛋白2的小鼠在血管内表现出纤维蛋白积聚和损伤性血栓清除受损。我们之前已经证明，内皮细胞膜联蛋白2（一种缺乏典型信号肽的蛋白）在体外和体内短暂的温度胁迫下，在没有细胞死亡或细胞裂解的情况下，从细胞质转移到胞质外质膜。这种受调节的反应不依赖于新蛋白或mRNA的合成，也不需要经典的内质网高尔基通路。温度胁迫诱导的膜联蛋白2易位既依赖于蛋白p11 （S100A10）的表达，也依赖于膜联蛋白2的酪氨酸磷酸化，因为在p11缺失、酪氨酸激酶失活或酪氨酸23突变时，膜联蛋白2的释放被完全消除。膜联蛋白2在细胞表面的易位显著增加了组织纤溶酶原激活剂依赖的纤溶酶原激活电位，可能代表了一种新的应激诱导蛋白分泌途径。我们已经通过免疫亲和试验和质谱鉴定了至少四种可能与膜联蛋白2到细胞表面的易位机制有关的蛋白质。目前正在对这些可能的候选蛋白进行研究。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Annexin 2 is a profibrinolytic co-receptor for plasminogen and tissue plasminogen activator that stimulates activation of the major fibrinolysin, plasmin, at cell surfaces. In human subjects, over-expression of annexin 2 in acute promyelocytic leukemia leads to a bleeding diathesis reflective of excessive cell surface annexin 2-dependent generation of plasmin. In addition, mice completely deficient in annexin 2 display fibrin accumulation within blood vessels and impaired clearance of injury-induced thrombi. We have previously shown that endothelial cell annexin 2, a protein that lacks a typical signal peptide, translocates from the cytoplasm to the extracytoplasmic plasma membrane in response to brief temperature stress both in vitro and in vivo in the absence of cell death or cell lysis. This regulated response is independent of new protein or mRNA synthesis and does not require the classical endoplasmic reticulum¿Golgi pathway. Translocation of annexin 2 induced by temperature stress is dependent on both expression of protein p11 (S100A10) and tyrosine phosphorylation of annexin 2 because the release of annexin 2 is completely eliminated on depletion of p11, inactivation of tyrosine kinase, or mutation of tyrosine 23. Translocation of annexin 2 to the cell surface dramatically increases tissue plasminogen activator-dependent plasminogen activation potential and may represent a novel stress-induced protein secretion pathway. We have identified by immunoaffinity assays and mass spectrometry at least four proteins that may be associated with the translocation mechanism of annexin 2 to the cell surface. These putative protein candidates are currently being investigated.