Cyclin D1 Regulates Cellular Migration through the Inhibition of Thrombospondin 1 and ROCK Signaling

Abstract

Cyclin D1 is overexpressed in human tumors, correlating with cellular metastasis, and is induced by activating Rho GTPases. Herein, cyclin D1-deficient mouse embryo fibroblasts (MEFs) exhibited increased adhesion and decreased motility compared with wild-type MEFs. Retroviral transduction of cyclin D1 reversed these phenotypes. Mutational analysis of cyclin D1 demonstrated that its effects on cellular adhesion and migration were independent of the pRb and p160 coactivator binding domains. Genomewide expression arrays identified a subset of genes regulated by cyclin D1, including Rho-activated kinase II (ROCKII) and thrombospondin 1 (TSP-1). cyclin D1 ؊/؊ cells showed increased Rho GTP and ROCKII activity and signaling, with increased phosphorylation of LIM kinase, cofilin (Ser3), and myosin light chain 2 (Thr18/Ser19). Cyclin D1 repressed ROCKII and TSP-1 expression, and the migratory defect of cyclin D1 ؊/؊ cells was reversed by ROCK inhibition or TSP-1 immunoneutralizing antibodies. cyclin E knockin to the cyclin D1 ؊/؊ MEFs rescued the DNA synthesis defect of cyclin D1 ؊/؊ MEFs but did not rescue either the migration defect or the abundance of ROCKII. Cyclin D1 promotes cellular motility through inhibiting ROCK signaling and repressing the metastasis suppressor TSP-1.The human cyclin D1 gene was initially cloned as a breakpoint rearrangement within parathyroid adenoma (42). Homology of the cyclin D1 cDNA to the CLN gene in yeast suggested the PRAD1 gene encoded the regulatory subunit of a serine threonine kinase. In subsequent studies, cyclin D1 was shown to bind the retinoblastoma (pRb) protein and through physical association with the cyclin-dependent kinase 4 or 6 (cdk4 or cdk6) subunit to phosphorylate pRb. Phosphorylation of pRb by the cyclin D/cdk4 holoenzyme then alters the conformation of pRb, correlating with sequential phosphorylation by cyclin E/cdk2 and the induction of DNA synthesis. The cyclin D1 gene is overexpressed in human cancers, including breast, colon, and prostate cancer, and hematopoietic malignancies (23, 39). Targeted overexpression of cyclin D1 to the mammary gland in transgenic mice was sufficient for the induction of mammary adenocarcinoma. Cyclin D1 is overexpressed in metastatic cells (19,30). Analysis of cyclin D1-deficient mice indicates a role for cyclin D1 in both cellular survival and DNA synthesis (3). Furthermore, cyclin D1-deficient mice are resistant to gastrointestinal tumors induced by mutation of the Apc gene (28) or tumor formation induced by either mammary-targeted Ras or ErbB2 (82). Such observations are consistent with previous studies demonstrating cyclin D1 antisense abrogates epithelial growth of ErbB2-induced tumors in vivo (34).Mutational analysis of the human cyclin D1 cDNA has identified several distinct domains involved in binding either pRb, cdk, the p160 coactivator, and histone deacetylases (22,23,59). The cdk-binding domain of cyclin D1 is required for the association with cdk4 and sequential phosphorylation of pRb, which in turn, leads to the release...

p53-Mediated transactivation of LIMK2b links actin dynamics to cell cycle checkpoint control

“…How stress fibers affect cell cycle progression is not entirely clear; however, emerging evidence suggests that they may be related. For example, cyclin D1, which is often amplified in tumors, inhibits ROCKII expression, and cyclin D1-deficient cells display increased stress fiber formation and reduced cell motility, which can be reversed by ROCK inhibition (Li et al, 2006). Moreover, oncogenic RasV12 inhibits ROCK and uncouples Rho-GTP from stress fiber formation (Sahai et al, 2001;Lee and Helfman, 2004).…”

Nuclear phosphorylated Y142 β-catenin accumulates in astrocytomas and glioblastomas and regulates cell invasion

“…6A). We next addressed whether mutant Y142F b-catenin affects cell adhesion and migration in a cell spreading assay, 44 Invasion experiments were also performed in 2 primary GBM cultures, C65 and C18. HGF increased the invasion of GBM cells expressing WT b-catenin compared to untreated control cells in both GBM cultures.…”

PP2ACdc55regulates G1cyclin stability

“…4 D1 overexpression inhibits Rhoactivated kinase II and thrombospondin 1, factors involved in maintaining proper cell motility and adhesion by regulation of the cytoskeleton. 51 Increased D1 expression also causes enhanced cytokinesis of mammary epithelial cells. 51 A D1-dependent decrease in abundance of the Skp2 component of the SCF complex may be one factor responsible for the increase in cytokinesis.…”

“…51 Increased D1 expression also causes enhanced cytokinesis of mammary epithelial cells. 51 A D1-dependent decrease in abundance of the Skp2 component of the SCF complex may be one factor responsible for the increase in cytokinesis. 51 In S. cerevisiae, loss of Cdc55 results in enhanced activation of the pseudohyphal invasive growth pathway.…”

“…51 A D1-dependent decrease in abundance of the Skp2 component of the SCF complex may be one factor responsible for the increase in cytokinesis. 51 In S. cerevisiae, loss of Cdc55 results in enhanced activation of the pseudohyphal invasive growth pathway. 52,53 Moreover, cdc55 cells have morphological and cytokinesis defects at low temperature, giving rise to elongated daughter cells, some of which lack nuclei.…”