title: p27Kip1 modulates cell migration through the regulation of RhoA activation.
abstract: The tumor suppressor p27(Kip1) is an inhibitor of cyclin/cyclin-dependent kinase (CDK) complexes and plays a crucial role in cell cycle regulation. However, p27(Kip1) also has cell cycle-independent functions. Indeed, we find that p27(Kip1) regulates cell migration, as p27(Kip1)-null fibroblasts exhibit a dramatic decrease in motility compared with wild-type cells. The regulation of motility by p27(Kip1) is independent of its cell-cycle regulatory functions, as re-expression of both wild-type p27(Kip1) and a mutant p27(Kip1) (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 p27(Kip1). 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 p27(Kip1) 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 p27(Kip1) in regulating cell migration via modulation of the Rho pathway.
authors.affiliation: Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Division of Basic Science, Seattle, WA 98109, USA.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Besson
authors.forename: Mark
authors.initials: M
authors.lastname: Gurian-West
authors.forename: Anja
authors.initials: A
authors.lastname: Schmidt
authors.forename: Alan
authors.initials: A
authors.lastname: Hall
authors.forename: James M
authors.initials: JM
authors.lastname: Roberts
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism; D051379:Mice; D022502:Stress Fibers / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D020742:rhoA GTP-Binding Protein