Differential contribution of M(r) 120 kDa rasGTPase-activating protein and neurofibromatosis type 1 gene product during the transition from growth phase to arrested state in human fibroblasts accompanied by a unique rasGTPase-activating activity.
Using octyl glucoside-solubilized cell extracts from human fibroblasts during growth phase to G0/G1 arrest state, we found that while the number of M(r) 120 kDa rasGTPase-activating protein (p120GAP) molecules per cell decreases to half its original levels, the amount of neurofibromatosis type 1 gene product (NF1, a neurofibromin) remains constant during the transition. The contribution of p120GAP to the total rasGTPase-activating (rasGA) activity in growing cells was found to be larger than that observed in arrested cells (84% vs 53%). On the other hand, NF1 contributes less than 15% of the total rasGA activity in either extract. These results indicate that the qualitative changes occur in the contributors to rasGA activity during transition. They also suggest that a unique rasGA activity exists in the arrested cells, which was obtained separately from both p120GAP and NF1 by heparin-Sepharose column chromatography.
Kobayashi
M
M
Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Hashimoto
N
N
Hoshino
M
M
Hattori
S
S
Iwashita
S
S
D000818:Animals; D001921:Brain / Q000201:enzymology; D002452:Cell Count; D002453:Cell Cycle; D002455:Cell Division; D002478:Cells, Cultured; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000166:cytology; D020690:GTPase-Activating Proteins; D006493:Heparin; D006801:Humans; D008970:Molecular Weight; D025542:Neurofibromin 1; D011506:Proteins / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D009418:S100 Proteins / Q000378:metabolism
D020690:GTPase-Activating Proteins; D025542:Neurofibromin 1; D011506:Proteins; D009418:S100 Proteins; D006493:Heparin