p27^Kip1 modulates cell migration through the regulation of RhoA activation

Abstract

The tumor suppressor p27Kip1 is an inhibitor of cyclin/cyclin-dependent kinase (CDK) complexes and plays a crucial role in cell cycle regulation. However, p27Kip1 also has cell cycle-independent functions. Indeed, we find that p27Kip1 regulates cell migration, as p27Kip1-null fibroblasts exhibit a dramatic decrease in motility compared with wild-type cells. The regulation of motility by p27Kip1 is independent of its cell-cycle regulatory functions, as re-expression of both wild-type p27Kip1 and a mutant p27Kip1 (p27CK–) that cannot bind to cyclins and CDKs rescues migration of p27–/– cells. p27–/– cells have increased numbers of actin stress fibers and focal adhesions. This is reminiscent of cells in which the Rho pathway is activated. Indeed, active RhoA levels were increased in cells lacking p27Kip1. Moreover, inhibition of ROCK, a downstream effector of Rho, was able to rescue the migration defect of p27–/– cells in response to growth factors. Finally, we found that p27Kip1 binds to RhoA, thereby inhibiting RhoA activation by interfering with the interaction between RhoA and its activators, the guanine–nucleotide exchange factors (GEFs). Together, the data suggest a novel role for p27Kip1 in regulating cell migration via modulation of the Rho pathway.

Cyclin D1 Functions in Cell Migration

“…The finding that cyclin D1 directly regulates cell migration are consistent with recent evidence that the cyclin D1-binding proteins p21 CIP1 and p27 KlP1 also regulate migration. p27 KlP1 has been shown to either inhibit 18 or promote cell migration, 19,20 perhaps depending on cell type, context, or other factors. The pro-migratory function of p27 KIP1 has been defined by showing that genetic deletions of p27 KIP1 cause Rho hyperactivation.…”

The E7 protein from human papillomavirus type 16 enhances keratinocyte migration in an Akt-dependent manner

“…Recently, there has been a growing body of evidence supporting the tumor suppressor cyclin-dependent kinase inhibitor p27 kip1 (p27) as a positive regulator of migration and tumor invasion when located in the cytoplasm of cells (Watanabe et al, 2002;McAllister et al, 2003;Besson et al, 2004;Vasko et al, 2004;Li et al, 2006). When mislocalized to the cytoplasm, p27 binds to the small GTPase RhoA and inhibits its association with Rho-GEFs, leading to a loss of RhoA activity and inhibition of its downstream effector Rhoassociated coiled-coil domain containing protein kinase 1 (ROCK) (Besson et al, 2004).…”

“…When mislocalized to the cytoplasm, p27 binds to the small GTPase RhoA and inhibits its association with Rho-GEFs, leading to a loss of RhoA activity and inhibition of its downstream effector Rhoassociated coiled-coil domain containing protein kinase 1 (ROCK) (Besson et al, 2004). Attenuation of the RhoA pathway leads to a decrease in both actin stress fiber and focal adhesion formation, allowing for an increase in migration (Nobes and Hall, 1999).…”

“…Although treatment of E7-expressing cells with LY294002 or AI4 did stabilize total p27 levels, the ratio of phosphorylated to total p27 was similar to that in DXRB-treated pBabe cells (Figure 3c). Cytoplasmic p27 has been demonstrated to increase the migration of cancer cells by an Akt-dependent mechanism and is associated with inhibition of the RhoA pathway (Besson et al, 2004;Vasko et al, 2004;Wu et al, 2006a). To evaluate whether RhoA activity itself was perturbed by E7 under conditions where cytoplasmic retention of p27 is observed, control and E7-expressing keratinocytes were treated with DXRB and RhoA activity was evaluated in a pulldown assay (Figure 4a).…”

Formation of E-Cadherin/β-Catenin–based Adherens Junctions in Hepatocytes Requires Serine-10 in p27(Kip1)

“…Activation of MAPK by OSM also influences the expression of p27(Kip1); see Klausen et al (2000). p27(Kip1) controls cell cycle progression (Polyak et al, 1994) and, interestingly, displays additional non-cell cycle-related functions including differentiation (Deschênes et al, 2001), apoptosis (Drexler, 2003), and migration (McAllister et al, 2003;Besson et al, 2004;Denicourt et al, 2007). The main phosphorylation site in p27(Kip1), Ser10, has been proposed to be an important determinant for non-cell cycle-related cytoplasmic functions of p27(Kip1) (see McAllister et al, 2003;Besson et al, 2006).…”