Competitive Nuclear Export of Cyclin D1 and Hic-5 Regulates Anchorage-Dependence of Cell Growth and Survival

Abstract

Anchorage dependence of cell growth and survival is a critical trait that distinguishes nontransformed cells from transformed cells. We demonstrate that anchorage dependence is determined by anchorage-dependent nuclear retention of cyclin D1, which is regulated by the focal adhesion protein, Hic-5, whose CRM1-dependent nuclear export counteracts that of cyclin D1. An adaptor protein, PINCH, interacts with cyclin D1 and Hic-5 and potentially serves as an interface for the competition between cyclin D1 and Hic-5 for CRM1. In nonadherent cells, the nuclear export of Hic-5, which is redox-sensitive, was interrupted due to elevated production of reactive oxygen species, and cyclin D1 was exported from the nucleus. When an Hic-5 mutant that was continuously exported in a reactive oxygen species-insensitive manner was introduced into the cells, cyclin D1 was retained in the nucleus under nonadherent conditions, and a significant population of cells escaped from growth arrest or apoptosis. Interestingly, activated ras achieved predominant cyclin D1 nuclear localization and thus, growth in nonadherent cells. We report a failsafe system for anchorage dependence of cell growth and survival. INTRODUCTIONAnchorage dependence of cell growth is the phenomenon whereby nontransformed cells adhere to the substratum for cell cycle progression from G1 to S phase. Numerous studies have defined the roles of adhesion signals mediated by the integrin-extracellular matrix (ECM) interaction in cell cycle progression. Basically, integrin-ECM-mediated signaling potentiates and prolongs the growth factor receptor-mediated mitogenic signaling and is required from mid-to late-G1 phase in various events associated with cell cycle progression, such as up-regulation of G1-phase CDK activity, Cip/Kips down-regulation, association of cyclin E with CDK2, pRb phosphorylation, and cyclin A expression (Fang et al., 1996;Zhu et al., 1996;Assoian, 1997;Schwartz and Assoian, 2001). As a result, loss of adhesion generally causes complete G1-phase cell cycle arrest in nontransformed cells; moreover, in susceptible cells, it leads to anoikis, a specific type of apoptosis caused by the detachment of a cell from its supportive matrix, which was first described in epithelial and endothelial cells (Frisch and Screaton, 2001;Reddig and Juliano, 2005).In contrast, transformed cells usually circumvent the anchorage requirement in cell cycle progression. Their anchorage-independent survival and growth is well known as a hallmark of cellular transformation and correlates with tumorigenicity in vivo (Freedman and Shin, 1974). Mechanistically, the anchorage-independent growth is considered to be based on an abnormal activation of the G1-phase cyclincyclin-dependent kinases (CDKs) uncoupled from anchorage. In general, an oncogenic pathway activates a robust and/or constitutive mitogenic signal, which is presumed to reduce the requirement for integrin-ECM-mediated signaling and its importance as a booster of growth factor receptor-mediated mitogenic signaling in the tra...

A mitochondrial ROS pathway controls matrix metalloproteinase 9 levels and invasive properties in RAS‐activated cancer cells

“…Hydrogen peroxide‐inducible clone‐5 is a multidomain protein that comprises four Leu‐ and Asp‐rich LD and LIM domains and serves as a molecular adaptor in a range of cellular activities from integrin signaling at focal adhesions to transcriptional activities in the nucleus . Our recent work suggested that HIC‐5 is involved in the regulation of anchorage dependence in cell growth . In this study, we examined its involvement in tumor growth and/or metastasis using cells established from MDA‐MB‐231 breast cancer cells by viral transduction of shRNA for HIC‐5 (sequence #1 and #2).…”

“…Hydrogen peroxide‐inducible clone‐5 is a molecular adaptor that features redox‐sensitive expression and functions. In particular, it traffics in and out of the nucleus with the redox‐sensitive nuclear export signal and modulates cellular responses to redox changes . In this study, we tested the possible association of the emerging role of HIC‐5 with redox changes in cells.…”

Reviewing once more the c-myc and Ras collaboration

“…1). Ras activates the cycD1 promoter via an AP-1 like sequence 69 and achieves predominant cycD1 nuclear localization; as a consequence, the cells may acquire an ability for non-adherent growth 70 or anchorageindependent cell cycle progression. 71,72 For this reason, cycD1 is regarded as a mitogenic sensor that relays and amplifies extracellular growth signals.…”

Regulation of mitochondrial ROS production by HIC‐5: a common feature of oncogene‐induced senescence and tumor invasiveness?

“…One of the necessary steps preceding tumor invasion of transformed epithelial cells is the detachment from its matrix attachment sites, which is controlled by integrin receptors linked to the focal adhesion complex. Detachment has been shown to lead to an increase of intracellular ROS production and is facilitated by epithelial–mesenchymal transition and loss of focal adhesions. Shibanuma and colleagues now propose that, under these conditions, HIC‐5 might be a key regulator for adapting cells to ROS‐mediated cellular stress.…”