Regulatory mechanism of β3 integrin function via signaling molecules

β_3整合素（β_3 integrin，β_3 integrin）包括α_<IIb>β_3和α_vβ_3，在动脉粥样硬化和血栓形成中起重要作用。因此，阐明整合素功能的调节机制是控制这些血管事件的关键问题。本研究尝试建立一种不同于血小板的新的实验模型来研究β_3整合素的功能调控。基于β-螺旋桨模型，我们采用丙氨酸扫描突变检测了αv亚基中的配体结合位点。我们证明了W3 2-3环中的178 Tyr是配体结合的关键残基之一。第二，我们检测了脐血单个核细胞和某些巨核细胞系的早期巨核细胞，发现CD 42 b（GPIb）阳性细胞<IIb>在TRAP和/或PMA刺激后几分钟内就能激活α_ β_3。我们一直在寻找负责整合素激活的分子之间的差异显示方法在某些巨核细胞系的CD 42 b阳性和CD 42 b阴性细胞。第三，我们检测了血小板中的Na^+/Ca^&lt;2+&gt;交换体，我们首次证明它是整合素活化的重要信号分子。我们证明了一个新的70 kD的亚型，而不是110 kD的形式在血小板。70 kD NCX的功能意义正在研究中。

β_3 integrins, which contain α_<IIb>β_3 and α_vβ_3, play critical roles in atherosclerosis as well as thrombosis. Therefore, the elucidation of the regulatory mechanisms for integrin function is a critical issue to control these vascular events. In this research project, we have tried to establish a new experimental model other than platelets to examine the regulation of β_3 integrin function.Firstly, we have analyzed structural and functional analyses of αvβ_3 integrin. Based on the β-propeller model we have examined ligand-binding sites in the αv subunit employing alanine-scanning mutagenesis. We demonstrated that 178Tyr in the W3 2-3 loop is one of the critical residues for ligand-binding. Secondly, we have examined early megakaryocytes derived from umbilical cord blood mononuclear cells and certain megakaryocytic cell lines and demonstrated that CD42b(GPIb)-positive cells could activate α_<IIb>β_3 within several minutes after TRAP and/or PMA stimulation. We have been searching molecules responsible for integrin activation employing differential display method between CD42b-positive and CD42b-negative cells in a certain megakaryocytic cell line. Thirdly, we have examined Na^+/Ca^<2+> exchanger in platelets which we have firstly demonstrated as an important signaling molecule for integrin activation. We demonstrated a new 70 kD isoform in platelets instead of 110-kD form. The functional significance of the 70 kD NCX is under investigation.