的崎 尚 大阪大学, 医学系研究科, 助手 (80252782)
中西 宏之 大阪大学, 医学系研究科, 助手 (80314318)
SASAKI Takuya Graduate School of Medicine, Osaka University Associate Professor, 医学系研究科, 助教授 (40241278)
SHIRATAKI Hiromichi Graduate School of Medicine, Osaka University Assistant Professor (Present/Dokkyo University School of Medicine, Professor) (90249962)
TANAKA Kazuma Graduate School of Medicine, Osaka University Associate Professor (Present/Hokkaido University, Professor) (60188290)
NOVIEK Peter エール大学, 医学部, 教授
HALL Alan ロンドン大学, 理学部, 教授
|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 1999 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1998 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Small G proteins exist in eukaryotes from yeast to human and constitute a superfamily consisting of more than one hundred members. This superfamily is structurally classified into at least five families : the Ras, Rho, Rab, Sarl/Arf, and Ran families. They regulate a wide variety of cell functions : The Ras family regulates gene expression; the Rho family regulates reorganization of cytoskeleton and gene expression; the Rab and Sarl/Arf families regulate vesicle trafficking; and the Ran family regulates nucleocytoplasmic transport. Many upstream regulators and downstream effectors of small G proteins have been isolated. In the present research project, we have studied the modes of activation and action of small G proteins, especially the Rab and Rho families.
1. The regulatory mechanism of the Rab family : Rab3A is a member of the Rab family which is particularly implicated in neurotransmitter release from the nerve terminal. We had isolated its regulatory proteins, named Rab GDI, Rab3
GEP, and Rab3 GAP. In this research project, we have shown that these proteins modulate the neurotransmitter release process through regulation of Rab3A.
2. The downstream pathway of the Rab family : We had isolated an effector of Rab3A, named Rabphilin-3A. In this research project, we have shown that Rabphilin-3A actually plays a crucial role in neurotransmitter release using the squid giant axon system. Moreover, we have identified an effector of Rab11, named Rabphilin-11, and found that the Rab11-Rabphilin-11 system is involved in cell migration through regulation of the vesicle recycling.
3. The regulatory mechanism of the Rho family : We have discovered a novel GDP/GTP exchange protein of Cdc42, named Frabin, and shown that the Frabin-Cdc42 pathway functions as the most upstream regulator for cell migration.
4. The downstream pathway of the Rho family : In S. cerevisiae, we have isolated two downstream effectors of Rho, BNI1 and BNR1, and demonstrated that Rho regulates actin cytoskeleton and microtubules through these targets, leading to budding or cytokinesis. In mammalian cells, ROCK, a serine/threonine protein kinase, and mDia, a mammalian counterpart of BNI1, cooperatively regulate reorganization of the actin cytoskeleton. We have also shown that Rac and Cdc42 regulate cadherin-based cell-cell adhesion. Less