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: 5.04). 07/2006; 26(12):4612-27. DOI: 10.1128/MCB.02061-05
Source: PubMed

ABSTRACT 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.

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Available from: Daniel Croft, Apr 16, 2014
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    • "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. "
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    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.
    Molecular Neurobiology 10/2013; 49(2). DOI:10.1007/s12035-013-8568-6 · 5.29 Impact Factor
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    • "As described above, P61A6 induces decreased levels of cyclin D1 together with increased G1 and decreased proliferation. A number of studies in lung cancer cells suggest that RhoA plays important roles in cyclin D1 and cell cycle progression [25,26]. To rigorously test the hypothesis that RhoA is a key target of the growth inhibitory effects of P61A6, we transfected H358 cells with the wild type RhoA (3xHA-RhoA) or a mutant form of RhoA, RhoA-F (3xHA-RhoA-F), which can be farnesylated instead of geranylgeranylated, because the C-terminal leucine has been changed to serine. "
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    ABSTRACT: Background Lung cancer is the leading cause of cancer-related mortality. Therapies against non-small cell lung cancer (NSCLC) are particularly needed, as this type of cancer is relatively insensitive to chemotherapy and radiation therapy. We recently identified GGTI compounds that are designed to block geranylgeranylation and membrane association of signaling proteins including the Rho family G-proteins. One of the GGTIs is P61A6 which inhibits proliferation of human cancer cells, causes cell cycle effects with G1 accumulation and exhibits tumor-suppressing effects with human pancreatic cancer xenografts. In this paper, we investigated effects of P61A6 on non-small cell lung cancer (NSCLC) cells in vitro and in vivo. Methods Three non-small cell lung cancer cell lines were used to test the ability of P61A6 to inhibit cell proliferation. Further characterization involved analyses of geranylgeranylation, membrane association and activation of RhoA, and anchorage-dependent and –independent growth, as well as cell cycle effects and examination of cell cycle regulators. We also generated stable cells expressing RhoA-F, which bypasses the geranylgeranylation requirement of wild type RhoA, and examined whether the proliferation inhibition by P61A6 is suppressed in these cells. Tumor xenografts of NSCLC cells growing in nude mice were also used to test P61A6’s tumor-suppressing ability. Results P61A6 was shown to inhibit proliferation of NSCLC lines H358, H23 and H1507. Detailed analysis of P61A6 effects on H358 cells showed that P61A6 inhibited geranylgeranylation, membrane association of RhoA and caused G1 accumulation associated with decreased cyclin D1/2. The effects of P61A6 to inhibit proliferation could mainly be ascribed to RhoA, as expression of the RhoA-F geranylgeranylation bypass mutant rendered the cells resistant to inhibition by P61A6. We also found that P61A6 treatment of H358 tumor xenografts growing in nude mice reduced their growth as well as the membrane association of RhoA in the tumors. Conclusion Thus, P61A6 inhibits proliferation of NSCLC cells and causes G1 accumulation associated with decreased cyclin D1/2. The result with the RhoA-F mutant suggests that the effect of P61A6 to inhibit proliferation is mainly through the inhibition of RhoA. P61A6 also shows efficacy to inhibit growth of xenograft tumor.
    BMC Cancer 04/2013; 13(1):198. DOI:10.1186/1471-2407-13-198 · 3.32 Impact Factor
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    • "For example, polyploidization naturally occurs in megakaryocytes due to an incomplete mitosis, which is related to a partial defect in Rho-ROCK activation, and leads to an abnormal contractile ring lacking myosin IIA (Lordier et al. 2008). Moreover, Rho-ROCK signaling increases cyclin D1 and Cip1 protein levels, stimulating G1/S cell cycle progression (Croft and Olson 2006). Despite a high degree of homology between the two ROCKs, as well as the fact that they share several common substrates, studies have clearly shown that the two ROCK isoforms also have distinct and non-redundant functions. "
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    ABSTRACT: Cancer-associated changes in cellular behavior, such as modified cell-cell contact, increased migratory potential, and generation of cellular force, all require alteration of the cytoskeleton. Two homologous mammalian serine/threonine kinases, Rho-associated protein kinases (ROCK I and II), are key regulators of the actin cytoskeleton acting downstream of the small GTPase Rho. ROCK is associated with cancer progression, and ROCK protein expression is elevated in several types of cancer. ROCKs exist in a closed, inactive conformation under quiescent conditions, which is changed to an open, active conformation by the direct binding of guanosine triphosphate (GTP)–loaded Rho. In recent years, a number of ROCK isoform-specific binding partners have been found to modulate the kinase activity through direct interactions with the catalytic domain or via altered cellular localization of the kinases. Thus, these findings demonstrate additional modes to regulate ROCK activity. This review describes the molecular mechanisms of ROCK activity regulation in cancer, with emphasis on ROCK isoform-specific regulation and interaction partners, and discusses the potential of ROCKs as therapeutic targets in cancer.
    Journal of Histochemistry and Cytochemistry 11/2012; 61(3). DOI:10.1369/0022155412470834 · 2.40 Impact Factor
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