Activation of cyclin-dependent kinase 2 (Cdk2) in growth-stimulated rat astrocytes. Geranylgeranylated Rho small GTPase(s) are essential for the induction of cyclin E gene expression.
The role of the mevalonate cascade in the control of cell cycle progression in astrocytes has been investigated. Serum stimulation of rat astrocytes in primary culture induces the expression of cyclin E followed by the activation of cyclin-dependent kinase 2 (Cdk2) during G1/S transition. The expression of p27, cyclin D1, and the activities of Cdk4 and Cdk-activating kinase (CAK), composed of Cdk7 and cyclin H, were not affected. Serum did, however, stimulate the expression of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase mRNA at mid-G1 phase. Moreover, an inhibitor of HMG-CoA reductase, pravastatin, reduced cyclin E expression and Cdk2 activation and caused G1 arrest in the astrocytes. In contrast, mevalonate and its metabolite, geranylgeranylpyrophosphate (GGPP) but not farnesylpyrophosphate (FPP), reversed the inhibitory effects of pravastatin on cyclin E expression and Cdk2 activation and allowed G1/S transition. Rho small GTPase(s) were geranylgeranylated and translocated to membranes in the presence of GGPP during G1/S transition. The effect of GGPP on cyclin E expression was abolished by botulinum C3 exoenzyme, which specifically inactivates Rho. These data indicate that geranylgeranylated Rho small GTPase(s) are essential for the induction of cyclin E expression, Cdk2 activation, and G1/S transition in rat astrocytes.
Second Department of Internal Medicine, Chiba University School of Medicine, Chiba 260,, Japan. tomoaki@intmed02.m.chiba-u.ac.jp
T
T
Tanaka
I
I
Tatsuno
Y
Y
Noguchi
D
D
Uchida
T
T
Oeda
S
S
Narumiya
T
T
Yasuda
H
H
Higashi
M
M
Kitagawa
K
K
Nakayama
Y
Y
Saito
A
A
Hirai
D036002:ADP Ribose Transferases / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000201:enzymology*; D001692:Biological Transport; D001769:Blood; D001905:Botulinum Toxins; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division; D019927:Cyclin E / Q000235:genetics; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004261:DNA Replication; D004789:Enzyme Activation; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D017035:Pravastatin / Q000494:pharmacology; D011247:Pregnancy; D017368:Protein Prenylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D019927:Cyclin E; D006903:Hydroxymethylglutaryl CoA Reductases; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D001905:Botulinum Toxins; D020558:GTP Phosphohydrolases; D017035:Pravastatin