RhoA Stimulates p27Kip Degradation through Its Regulation of Cyclin E/CDK2 Activity

Hu, Weimin; Bellone, Clifford J.; Baldassare, Joseph J.

doi:10.1074/jbc.274.6.3396

Cited by 111 publications

(89 citation statements)

References 35 publications

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“…radation of the Cdk2 inhibitor p27 (37,38). However, induction of Cdc42V12 expression had no effect on the accumulation of p27 in serum-starved cells (Fig.…”

Section: Fig 2 Cv12/lap3 Cells Exhibit Accelerated Cyclin E-cdk2 Acmentioning

confidence: 99%

Cdc42 Promotes G1 Progression through p70 S6 Kinase-mediated Induction of Cyclin E Expression

Chou¹,

Robens

Gupta³

2003

Journal of Biological Chemistry

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The Rho family GTPase Cdc42 is recognized for its role in cellular proliferation and transformation. However, the mechanism by which it promotes cell cycle progression has remained undefined. Using an inducible expression system, we show that constitutively active Cdc42 (Cdc42V12) is sufficient by itself to induce anchorage-independent but not mitogen-independent growth in NIH3T3 cells. However, Cdc42V12 markedly accelerates activation of cyclin E-Cdk2 in response to mitogen. These effects were highly specific, as the kinetics of cyclin D-Cdk4 activation was unaltered. Cdc42V12 promotes Cdk2 activation by selectively inducing cyclin E expression without affecting other regulatory proteins such as the p27 Cdk inhibitor or Cdc25A. Furthermore, Cdc42V12 was able to activate a reporter gene driven by the cyclin E promoter in the absence of exogenous mitogen or adhesion. Cyclin E induction was sensitive to rapamycin but not inhibitors of mitogen-activated protein kinases, implicating p70 S6 kinase (p70S6k) as the relevant mediator. Consistent with this notion, wild type and constitutively active alleles of p70S6k were sufficient to activate the cyclin E promoter. In sum, these studies provide novel insights into the mechanism by which Cdc42 promotes G 1 progression.

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“…radation of the Cdk2 inhibitor p27 (37,38). However, induction of Cdc42V12 expression had no effect on the accumulation of p27 in serum-starved cells (Fig.…”

Section: Fig 2 Cv12/lap3 Cells Exhibit Accelerated Cyclin E-cdk2 Acmentioning

confidence: 99%

Cdc42 Promotes G1 Progression through p70 S6 Kinase-mediated Induction of Cyclin E Expression

Chou¹,

Robens

Gupta³

2003

Journal of Biological Chemistry

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“…For transient transfections IIC9 cells were grown to subconfluency (80%). The cells were transfected as previously described (51). After 12 h the cells were serum-arrested for 48 h before stimulation.…”

Section: Methodsmentioning

confidence: 99%

Expression of Cyclin E Renders Cyclin D-CDK4 Dispensable for Inactivation of the Retinoblastoma Tumor Suppressor Protein, Activation of E2F, and G1-S Phase Progression

Keenan

Lents

Baldassare

2004

Journal of Biological Chemistry

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The activation of CDK2-cyclin E in late G 1 phase has been shown to play a critical role in retinoblastoma protein (pRb) inactivation and G 1 -S phase progression of the cell cycle. The phosphatidylinositol 3-OH-kinase inhibitor LY294002 has been shown to block cyclin D1 accumulation, CDK4 activity and, thus, G 1 progression in ␣-thrombin-stimulated IIC9 cells (Chinese hamster embryonic fibroblasts). Our previous results show that expression of cyclin E rescues S phase progression in ␣-thrombin-stimulated IIC9 cells treated with LY294002, arguing that cyclin E renders CDK4 activity dispensable for G 1 progression. In this work we investigate the ability of ␣-thrombin-induced CDK2-cyclin E activity to inactivate pRb in the absence of prior CDK4-cyclin D1 activity. We report that in the absence of CDK4-cyclin D1 activity, CDK2-cyclin E phosphorylates pRb in vivo on at least one residue and abolishes pRb binding to E2F response elements. We also find that expression of cyclin E rescues E2F activation and cyclin A expression in cyclin D kinase-inhibited, ␣-thrombin-stimulated cells. Furthermore, the rescue of E2F activity, cyclin A expression, and DNA synthesis by expression of E can be blocked by the expression of either CDK2(D145N) or Rb ⌬CDK , a constitutively active mutant of pRb. However, restoring four known cyclin E-CDK2 phosphorylation sites to Rb ⌬CDK renders it susceptible to inactivation in late G 1 , as assayed by E2F activation, cyclin A expression, and S phase progression. These data indicate that CDK2-cyclin E, without prior CDK4-cyclin D activity, can phosphorylate and inactivate pRb, activate E2F, and induce DNA synthesis.The mammalian cell cycle is controlled by two important families of proteins, the cyclins and the cyclin-dependent kinases (CDKs) 1 (for reviews, see Refs. 1 and 2). Progression through the cell cycle is governed by the kinase activities of specific CDKs, which are regulated by association with the regulatory cyclin subunits. The sequential activation of early G 1 CDK activity, CDK4 or CDK6 together with cyclin D1, D2, or D3, and the late G 1 CDK activity, CDK2 together with cyclin E1 or E2, is believed to be required for progression through G 1 and into S phase. Because IIC9 cells contain CDK4, but not CDK6, and cyclin D1, but not D2 or D3, CDK4-cyclin D1 activation in early G 1 is required for the expression of cyclin E, CDK2 activity, and G 1 -S phase progression (3-5).In most cell types inactivation of the retinoblastoma (pRb) protein is essential for passage through G 1 and transition of cells into S phase (2, 6 -9). pRb regulates this progression by its association with the E2F family of transcription factors (10 -13). In quiescent cells (G 0 phase) pRb is unphosphorylated; in early-to mid-G 1 pRb is hypophosphorylated by the D-type CDKs (14, 15). This hypophosphorylated form of pRb, which binds to and inhibits E2F transcription factors, has been shown in vivo to be phosphorylated on 13 of 16 potential CDK phosphorylation sites, suggesting that hypophosphorylated pRb may cons...

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“…GG of RHO proteins is necessary for their proper localization to the cell membrane and subsequent functions. RHOA regulates P27 kip1 by mediating its phosphorylation on Thr187 by CDK2, subsequent translocation of P27 from the nucleus to the cytosol, and enhancing its degradation in the cytoplasm [23,24]. In the absence of GG, RHOA is unable to carry out these functions and P27 kip1 accumulates in the nucleus [25].…”

Section: Mva Blockade Targets Breast Csc Through Rhoa/p27 Kip1 Signalingmentioning

confidence: 99%

Mevalonate Metabolism Regulates Basal Breast Cancer Stem Cells and Is a Potential Therapeutic Target

et al. 2012

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There is increasing evidence that breast tumors are organized in a hierarchy, with a subpopulation of tumorigenic cancer cells, the cancer stem cells (CSCs), which sustain tumor growth. The characterization of protein networks that govern CSC behavior is paramount to design new therapeutic strategies targeting this subpopulation of cells. We have sought to identify specific molecular pathways of CSCs isolated from 13 different breast cancer cell lines of luminal or basal/mesenchymal subtypes. We compared the gene expression profiling of cancer cells grown in adherent conditions to those of matched tumorsphere cultures. No specific pathway was identified to be commonly regulated in luminal tumorspheres, resulting from a minor CSC enrichment in tumorsphere passages from luminal cell lines. However, in basal/mesenchymal tumorspheres, the enzymes of the mevalonate metabolic pathway were overexpressed compared to those in cognate adherent cells. Inhibition of this pathway with hydroxy-3-methylglutaryl CoA reductase blockers resulted in a reduction of breast CSC independent of inhibition of cholesterol biosynthesis and of protein farnesylation. Further modulation of this metabolic pathway demonstrated that protein geranylgeranylation (GG) is critical to breast CSC maintenance. A small molecule inhibitor of the geranylgeranyl transferase I (GGTI) enzyme reduced the breast CSC subpopulation both in vitro and in primary breast cancer xenografts. We found that the GGTI effect on the CSC subpopulation is mediated by inactivation of Ras homolog family member A (RHOA) and increased accumulation of P27 kip1 in the nucleus. The identification of protein GG as a major contributor to CSC maintenance opens promising perspectives for CSC targeted therapy in basal breast cancer. STEM

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RhoA Stimulates p27Kip Degradation through Its Regulation of Cyclin E/CDK2 Activity

Abstract: RhoA has been identified as an important regulator of cell proliferation. We recently showed that the Ras/ RhoA pathway regulates the degradation of p27Kip and the progression of Chinese hamster embryo fibroblasts (IIC9 cells) through G 1 into S phase

Cited by 111 publications

References 35 publications

Cdc42 Promotes G1 Progression through p70 S6 Kinase-mediated Induction of Cyclin E Expression

Cdc42 Promotes G1 Progression through p70 S6 Kinase-mediated Induction of Cyclin E Expression

Expression of Cyclin E Renders Cyclin D-CDK4 Dispensable for Inactivation of the Retinoblastoma Tumor Suppressor Protein, Activation of E2F, and G1-S Phase Progression

Mevalonate Metabolism Regulates Basal Breast Cancer Stem Cells and Is a Potential Therapeutic Target

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