Geranylgeranylated Rho Small GTPase(s) Are Essential for the Degradation of p27Kip1 and Facilitate the Progression from G1 to S Phase in Growth-stimulated Rat FRTL-5 Cells

doi:10.1074/jbc.272.1.13

Geranylgeranylated Rho Small GTPase(s) Are Essential for the Degradation of p27^Kip1 and Facilitate the Progression from G₁ to S Phase in Growth-stimulated Rat FRTL-5 Cells*

From the ^‡ Second Department of Internal Medicine, Chiba University Medical School, Inohana-cho, Chuou-ku, Chiba 260, Japan
the ^¶ Department of Cell Chemistry, Institute of Cellular and Molecular Biology, Okayama University Medical School, Shikata-cho, Okayama 700, Japan, the
the ^∥ Banyu Tsukuba Research Institute in Collaboration with Merck Research Laboratories, Okubo 3, Tsukuba 300-26, Japan
the ** Department of Internal Medicine, Chiba Municipal Hospital, Yahagi, Chuou-ku, Chiba 260, Japan
the ^‡‡ Department of Pharmacology, Kyoto University Faculty of Medicine, Yoshida, Sakyo-ku, Kyoto 606, Japan, and
the ^§§ Cell Regulation Section, Metabolic Disease Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892

^§ To whom correspondence should be addressed:
The Second Dept. of Internal Medicine, Chiba University Medical School, 1-8-1, Inohana-cho, Chuou-ku, Chiba 260, Japan.
Tel.: 81-43-226-2094; Fax: 81-43-226-2095; E-mail: aizan{at}med.m.chiba-u.ac.jp

Abstract

Cyclin-dependent kinase (Cdk) enzymes are activated for entry into the S phase of the cell cycle. Elimination of Cdk inhibitor protein p27^Kip1 during the G₁ to S phase is required for the activation process. An inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase prevents its elimination and leads to G₁ arrest. Mevalonate and its metabolite, geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, restore the inhibitory effect of pravastatin on the degradation of p27 and allow Cdk2 activation. By the addition of geranylgeranyl pyrophosphate, Rho small GTPase(s) are geranylgeranylated and translocated to membranes during G₁/S progression. The restoring effect of geranylgeranyl pyrophosphate is abolished with botulinum C3 exoenzyme, which specifically inactivates Rho. These results indicate (i) among mevalonate metabolites, geranylgeranyl pyrophosphate is absolutely required for the elimination of p27 followed by Cdk2 activation; (ii) geranylgeranylated Rho small GTPase(s) promote the degradation of p27 during G₁/S transition in FRTL-5 cells.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used as are:

Cdk2

cyclin-dependent kinase 2

HMG-CoA

3-hydroxy-3-methylglutaryl coenzyme A

TSH

thyrotropin

GGPP

geranylgeranyl pyrophosphate

FPP

farnesyl pyrophosphate

IPP

isopentenyl pyrophosphate

GST

glutathione S-transferase.
- Received October 9, 1996.