Cell type-specific regulation of RhoA activity during cytokinesis.
Rho family GTPases play pivotal roles in cytokinesis. By using probes based on the principle of fluorescence resonance energy transfer (FRET), we have shown that in HeLa cells RhoA activity increases with the progression of cytokinesis. Here we show that in Rat1A cells RhoA activity remained suppressed during most of the cytokinesis. Consistent with this observation, the expression of C3 toxin inhibited cytokinesis in HeLa cells but not in Rat1A cells. Furthermore, the expression of a dominant negative mutant of Ect2, a Rho GEF, or Y-27632, an inhibitor of the Rho-dependent kinase ROCK, inhibited cytokinesis in HeLa cells but not in Rat1A cells. In contrast to the activity of RhoA, the activity of Rac1 was suppressed during cytokinesis and started increasing at the plasma membrane of polar sides before the abscission of the daughter cells in both HeLa and Rat1A cells. This type of Rac1 suppression was shown to be essential for cytokinesis because a constitutively active mutant of Rac1 induced a multinucleated phenotype in both HeLa and Rat1A cells. Moreover, the involvement of MgcRacGAP/CYK-4 in this suppression of Rac1 during cytokinesis was shown by the use of a dominant negative mutant. Because ML-7, an inhibitor of myosin light chain kinase, delayed the cytokinesis of Rat1A cells and because Pak, a Rac1 effector, is known to suppress myosin light chain kinase, the suppression of the Rac1-Pak pathway by MgcRacGAP may play a pivotal role in the cytokinesis of Rat1A cells.
Department of Tumor Virology, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Suita-shi, Osaka 565-0871, Japan.
Hisayoshi
H
Yoshizaki
Yusuke
Y
Ohba
Maria-Carla
MC
Parrini
Natalya G
NG
Dulyaninova
Anne R
AR
Bresnick
Naoki
N
Mochizuki
Michiyuki
M
Matsuda
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001905:Botulinum Toxins / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D048749:Cytokinesis; D018076:DNA, Complementary / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D016193:G1 Phase; D016195:G2 Phase; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry; D006801:Humans; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D009281:Naphthalenes / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D020742:rhoA GTP-Binding Protein / Q000096:biosynthesis*
D000577:Amides; D001381:Azepines; D018076:DNA, Complementary; C489850:ECT2 protein, human; D006576:Heterocyclic Compounds, 4 or More Rings; D009281:Naphthalenes; D011518:Proto-Oncogene Proteins; D011725:Pyridines; C070571:ML 7; C108830:Y 27632; D049452:Green Fluorescent Proteins; C472645:blebbistatin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020742:rhoA GTP-Binding Protein