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Gankyrin plays an essential role in Ras-induced tumorigenesis through regulation of the RhoA/ROCK pathway in mammalian cells.

ABSTRACT: Activating mutations in Ras proteins are present in about 30% of human cancers. Despite tremendous progress in the study of Ras oncogenes, many aspects of the molecular mechanisms underlying Ras-induced tumorigenesis remain unknown. Through proteomics analysis, we previously found that the protein Gankyrin, a known oncoprotein in hepatocellular carcinoma, was upregulated during Ras-mediated transformation, although the functional consequences of this were not clear. Here we present evidence that Gankyrin plays an essential role in Ras-initiated tumorigenesis in mouse and human cells. We found that the increased Gankyrin present following Ras activation increased the interaction between the RhoA GTPase and its GDP dissociation inhibitor RhoGDI, which resulted in inhibition of the RhoA effector kinase Rho-associated coiled coil-containing protein kinase (ROCK). Importantly, Gankyrin-mediated ROCK inhibition led to prolonged Akt activation, a critical step in activated Ras-induced transformation and tumorigenesis. In addition, we found that Gankyrin is highly expressed in human lung cancers that have Ras mutations and that increased Gankyrin expression is required for the constitutive activation of Akt and tumorigenesis in these lung cancers. Our findings suggest that Gankyrin is a key regulator of Ras-mediated activation of Akt through inhibition of the downstream RhoA/ROCK pathway and thus plays an essential role in Ras-induced tumorigenesis.

SUBMITTER: Man JH

PROVIDER: S-EPMC2912196 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Gankyrin plays an essential role in Ras-induced tumorigenesis through regulation of the RhoA/ROCK pathway in mammalian cells.

Man Jiang-Hong JH Liang Bing B Gu Yue-Xi YX Zhou Tao T Li Ai-Ling AL Li Tao T Jin Bao-Feng BF Bai Bing B Zhang Hai-Ying HY Zhang Wei-Na WN Li Wei-Hua WH Gong Wei-Li WL Li Hui-Yan HY Zhang Xue-Min XM

The Journal of clinical investigation 20100712 8

Activating mutations in Ras proteins are present in about 30% of human cancers. Despite tremendous progress in the study of Ras oncogenes, many aspects of the molecular mechanisms underlying Ras-induced tumorigenesis remain unknown. Through proteomics analysis, we previously found that the protein Gankyrin, a known oncoprotein in hepatocellular carcinoma, was upregulated during Ras-mediated transformation, although the functional consequences of this were not clear. Here we present evidence that ...[more]

PMID: 20628200

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Project description:AimsTo determine the mechanisms by which the ?1A-adrenergic receptor (AR) regulates cardiac contractility.BackgroundWe reported previously that transgenic mice with cardiac-restricted ?1A-AR overexpression (?1A-TG) exhibit enhanced contractility but not hypertrophy, despite evidence implicating this G?q/11-coupled receptor in hypertrophy.MethodsContractility, calcium (Ca(2+)) kinetics and sensitivity, and contractile proteins were examined in cardiomyocytes, isolated hearts and skinned fibers from ?1A-TG mice (170-fold overexpression) and their non-TG littermates (NTL) before and after ?1A-AR agonist stimulation and blockade, angiotensin II (AngII), and Rho kinase (ROCK) inhibition.ResultsHypercontractility without hypertrophy with ?1A-AR overexpression is shown to result from increased intracellular Ca(2+) release in response to agonist, augmenting the systolic amplitude of the intracellular Ca(2+) concentration [Ca(2+)]i transient without changing resting [Ca(2+)]i. In the absence of agonist, however, ?1A-AR overexpression reduced contractility despite unchanged [Ca(2+)]i. This hypocontractility is not due to heterologous desensitization: the contractile response to AngII, acting via its G?q/11-coupled receptor, was unaltered. Rather, the hypocontractility is a pleiotropic signaling effect of the ?1A-AR in the absence of agonist, inhibiting RhoA/ROCK activity, resulting in hypophosphorylation of both myosin phosphatase targeting subunit 1 (MYPT1) and cardiac myosin light chain 2 (cMLC2), reducing the Ca(2+) sensitivity of the contractile machinery: all these effects were rapidly reversed by selective ?1A-AR blockade. Critically, ROCK inhibition in normal hearts of NTLs without ?1A-AR overexpression caused hypophosphorylation of both MYPT1 and cMLC2, and rapidly reduced basal contractility.ConclusionsWe report for the first time pleiotropic ?1A-AR signaling and the physiological role of RhoA/ROCK signaling in maintaining contractility in the normal heart.

Dataset Information

Gankyrin plays an essential role in Ras-induced tumorigenesis through regulation of the RhoA/ROCK pathway in mammalian cells.

Publications

Gankyrin plays an essential role in Ras-induced tumorigenesis through regulation of the RhoA/ROCK pathway in mammalian cells.

Similar Datasets

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