Versatile roles of R-Ras GAP in neurite formation of PC12 cells and embryonic vascular development.
Ras GTPase-activating proteins (GAP) are negative regulators of Ras that convert active Ras-GTP to inactive Ras-GDP. R-Ras GAP is a membrane-associated molecule with stronger GAP activity for R-Ras, an activator of integrin, than H-Ras. We found that R-Ras GAP is down-regulated during neurite formation in rat pheochromocytoma PC12 cells by nerve growth factor (NGF), which is blocked by the transient expression of R-Ras gap or dominant negative R-ras cDNA. By establishing a PC12 subclone that stably expresses exogenous R-Ras GAP, it was found that NGF reduced endogenous R-Ras GAP but not exogenous R-Ras GAP, suggesting that down-regulation of R-Ras GAP occurs at the transcription level. To clarify the physiological role of R-Ras GAP, we generated mice that express mutant Ras GAP with knocked down activity. While heterozygotes are normal, homozygous mice die at E12.5-13.5 of massive subcutaneous and intraparenchymal bleeding, probably due to underdeveloped adherens junctions between capillary endothelial cells. These results show essential roles of R-Ras GAP in development and differentiation: its expression is needed for embryonic development of blood vessel barriers, whereas its down-regulation facilitates NGF-induced neurite formation of PC12 cells via maintaining activated R-Ras.
Iwashita
Shintaro
S
Mitsubishi Kagaku Institute of Life Sciences (MITILS), Machida, Tokyo 194-8511, Japan.
Kobayashi
Mariko
M
Kubo
Yuya
Y
Hinohara
Yoshimi
Y
Sezaki
Mariko
M
Nakamura
Kenji
K
Suzuki-Migishima
Rika
R
Yokoyama
Minesuke
M
Sato
Showbu
S
Fukuda
Mitsunori
M
Ohba
Masayuki
M
Kato
Chieko
C
Adachi
Eijiro
E
Song
Si-Young
SY
D000818:Animals; D049109:Cell Proliferation; D015536:Down-Regulation / Q000235:genetics; D006470:Hemorrhage / Q000196:embryology* / Q000235:genetics / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000235:genetics; D016501:Neurites / Q000378:metabolism* / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D020703:ras GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000172:deficiency / Q000502:physiology*
D020703:ras GTPase-Activating Proteins