The Rho GTPase effector ROCK regulates Cyclin A, Cyclin D1, and p27Kip1 levels by distinct mechanisms

The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow G61 1BD, United Kingdom.
Molecular and Cellular Biology (Impact Factor: 4.78). 07/2006; 26(12):4612-27. DOI: 10.1128/MCB.02061-05
Source: PubMed


The members of the Rho GTPase family are well known for their regulation of actin cytoskeletal structures. In addition, they influence progression through the cell cycle. The RhoA and RhoC proteins regulate numerous effector proteins, with a central and vital signaling role mediated by the ROCK I and ROCK II serine/threonine kinases. The requirement for ROCK function in the proliferation of numerous cell types has been revealed by studies utilizing ROCK-selective inhibitors such as Y-27632. However, the mechanisms by which ROCK signaling promotes cell cycle progression have not been thoroughly characterized. Using a conditionally activated ROCK-estrogen receptor fusion protein, we found that ROCK activation is sufficient to stimulate G1/S cell cycle progression in NIH 3T3 mouse fibroblasts. Further analysis revealed that ROCK acts via independent pathways to alter the levels of cell cycle regulatory proteins: cyclin D1 and p21(Cip1) elevation via Ras and the mitogen-activated protein kinase pathway, increased cyclin A via LIM kinase 2, and reduction of p27(Kip1) protein levels. Therefore, the influence of ROCK on cell cycle regulatory proteins occurs by multiple independent mechanisms.

Download full-text


Available from: Daniel Croft, Apr 16, 2014
  • Source
    • "Rho and ROCK are necessary for Ras-GTP loading and lead to increased to increased cyclin D1 transcription following growth factor stimulation (Swant et al., 2005; Welsh et al., 2001). Inhibition of Rho or ROCK function inhibits cyclin A expression and blocks cell proliferation in atrial myofibroblasts (Porter et al., 2004; Croft and Olson, 2006). Moreover, Rho GTPase activity is necessary for cyclin E expression in rat astrocytes (Tanaka et al., 1998). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Selective activation of Rho GTPase cascade requires the release of Rho from RhoGDI (GDP-dissociation inhibitors) complexes. Our previous studies identified RhoGDIα SUMOylation at Lys-138 and its function in the regulation of cancer cell invasion. In the current study, we demonstrate that RhoGDIα SUMOylation has a crucial role in the suppression of cancer cell anchorage-independent growth as well as the molecular mechanisms underlying this suppression. We found that ectopic expression of RhoGDIα resulted in marked inhibition of an anchorage-independent growth with induction of G0/G1 cell cycle arrest, while point mutation of RhoGDIα SUMOylation at residue Lys-138 (K138R) abrogated this growth suppression and G0/G1 cell cycle arrest in cancer cells. Further studies showed that SUMOylation at Lys-138 was critical for RhoGDIα down-regulation of cyclin D1 protein expression and that MEK1/2-Erk was a specific downstream target of SUMOylated RhoGDIα for its inhibition of C-Jun/AP-1 cascade, cyclin d1 transcription, and cell cycle progression. These results strongly demonstrate that SUMOylated RhoGDIα suppressed C-Jun/AP-1-dependent transactivation specifically via targeting MEK1/2-Erk, subsequently leading to the down-regulation of cyclin D1 expression and anti-cancer activity. Our results provide new mechanistic insights into the understanding of essential role of SUMOylation at Lys-138 in RhoGDIα's biological function.
    Preview · Article · Dec 2013 · Molecular oncology
  • Source
    • "Inhibition of ROCK1 resulted in a decreased proliferation, whereas inhibition of ROCK2 had the opposite effect, significantly enhancing proliferation relative to the control cells and regulating cyclin D1, whose role is also apparent in fibroblasts [22], corneal epithelial cells, and hepatic stellate cells [23, 24], to mediate the canonical Wnt/TCF pathways involving β-catenin [25, 26]. In contrast to the opposing effects of the ROCKs described here, only ROCK2 was involved in cell proliferation changes in SH-SY5Y cells [27], indicating different pathways among cell lines. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite current advances in therapy, the prognosis of patients with glioblastoma has not improved sufficiently in recent decades. This is due mainly to the highly invasive capacity of glioma cells. Little is known about the mechanisms underlying this particular characteristic. While the Rho-kinase (ROCK)-dependent signaling pathways involved in glioma migration have yet to be determined, they show promise as one of the candidates in targeted glioblastoma therapy. There are two ROCK isoforms: ROCK1, which is upregulated in glioblastoma tissue compared to normal brain tissue, and ROCK2, which is also expressed in normal brain tissue. Blockage of both of these ROCK isoforms with pharmacologic inhibitors regulates the migration process. We examined the activities of ROCK1 and ROCK2 using knockdown cell lines and the newly developed stripe assay. Selective knockdown of either ROCK1 or ROCK2 exerted antidromic effects on glioma migration: while ROCK1 deletion altered the substrate-dependent migration, deletion of ROCK2 did not. Furthermore, ROCK1 knockdown reduced cell proliferation, whereas ROCK2 knockdown enhanced it. Along the signaling pathways, key regulators of the ROCK pathway are differentially affected by ROCK1 and ROCK2. These data suggest that the balanced activation of ROCKs is responsible for the substrate-specific migration and the proliferation of glioblastoma cells.
    Full-text · Article · Oct 2013 · Molecular Neurobiology
  • Source
    • "These results suggest that ROCK signaling and TPPP1 regulate cell proliferation through modulation of b-catenin expression and its transcriptional targets. This is supported by previous studies demonstrating that b-catenin levels are increased during S-phase [23] and that activation of ROCK is necessary for cells to transit into S-phase [2]. Moreover, we demonstrated that inhibition of TPPP1- mediated HDAC6 regulation promotes S-phase entry [22]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Rho-associated coiled-coil kinase (ROCK) family of proteins, including ROCK1 and ROCK2, are key regulators of actin and intermediate filament morphology. The newly discovered ROCK substrate Tubulin polymerization promoting protein 1 (TPPP1) promotes microtubule polymerization and inhibits the activity of Histone deacetylase 6 (HDAC6). The effect of TPPP1 on HDAC6 activity is inhibited by ROCK signaling. Moreover, it was recently demonstrated that ROCK activity increases the cellular expression of the oncogene β-catenin, which is a HDAC6 substrate. In this study, we investigated the interplay between ROCK-TPPP1-HDAC6 signaling and β-catenin expression. We demonstrate that β-catenin expression is increased with ROCK signaling activation and is reduced with increased TPPP1 expression in U2OS cells. Further investigation revealed that ROCK-mediated TPPP1 phosphorylation, which prevents its binding to HDAC6, negates TPPP1-mediated reduction in β-catenin expression. We also show that increased HDAC6 activity resulting from ROCK signaling activation reduced β-catenin acetylation at Lys-49, which was also accompanied by its decreased phosphorylation by Caesin kinase 1 (CK1) and Glycogen Synthase kinase 3β (GSK3β), thus preventing its proteasomal degradation. Overall, our results suggest that ROCK regulates β-catenin stability in cells via preventing TPPP1-mediated inhibition of HDAC6 activity, to reduce its acetylation and degradation via phosphorylation by CK1 and GSK3β.
    Preview · Article · May 2013 · Biochemical and Biophysical Research Communications
Show more