ORITANI Kenji Osaka University, Graduate School of Medicine, Assistant Professor, 医学系研究科, 助手 (70324762)
SHIRAGA Masamichi Osaka University, Graduate School of Medicine, Assistant Professor, 医学系研究科, 助手
|Budget Amount *help
¥13,700,000 (Direct Cost : ¥13,700,000)
Fiscal Year 2004 : ¥5,500,000 (Direct Cost : ¥5,500,000)
Fiscal Year 2003 : ¥8,200,000 (Direct Cost : ¥8,200,000)
β3 integrins, which contain αIIbβ3 and αvβ3, 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 β3 integrin function and their ligand-binding sites.
We examined ligand-binding sites within the αvβ-propeller domain employing alanine-scanning mutagenesis within W3 and W4 loops. We demonstrated that 178Tyr and Asp128 are the critical residues for ligand-binding.. In addition Ala215Tyr αv increased the integrin affinity.
We next demonstrated that in a megakaryocytic cell line, CMK,CD42b(GPIb)-positive cells could activate αIIbβ3 after PMA stimulation. We then searched molecules responsible for integrin activation employing differential display method and/or cDNA micrarray During CMK maturation expression levels of 306 genes increased. Among them we were interested in β1-tublin, CKIP-1, cortactin, PKCδ, PKCβ1, WAVE-1, Rab27B etc. Employing bryostatin-1 we suggested that PKCα and β play a role in integrin activation. Employing primary megakaryocytic cells derived from cord blood, we confirmed that WAVE-1 expression, but not WAVE-2 or -3, increased during megakaryocytic differentiation. In adhered platelets both WAVE-1 and WAVE-2 were localized at the edge of the lamellipodia, suggesting that these molecules may regulate actin reorganization during platelet spreading.