title: Cdc42Hs, but not Rac1, inhibits serum-stimulated cell cycle progression at G1/S through a mechanism requiring p38/RK.
abstract: Antimitogenic stimuli such as environmental or genotoxic stress, transforming growth factor-beta, and the inflammatory cytokines tumor necrosis factor and interleukin-1 activate two extracellular signal-regulated kinase (ERK)-based signaling pathways: the stress-activated protein kinase (SAPK/JNK) pathway and the p38 pathway. Activated p38 phosphorylates transcription factors important in the regulation of cell growth and apoptosis, including activating transcription factor 2 (ATF2), Max, cAMP response element-binding protein-homologous protein/growth arrest DNA damage 153 (CHDP/GADD153). In turn, p38 lies downstream of the Rho family GTPases Cdc42Hs and Rac1, as well as at least three mitogen-activated protein kinase (MAPK)/ERK-kinases (MEKs): MAPK kinases-3, -6, and SAPK/ERK-kinase-1. Although many of the stimuli that activate p38 can also inhibit cell cycle progression, a clear-cut role for the p38 pathway in cell cycle regulation has not been established. Using a quantitative microinjection approach, we show here that Cdc42Hs, but not Rac1 or RhoA, can inhibit cell cycle progression at G1/S through a mechanism requiring activation of p38. These results suggest a novel role for Cdc42Hs in cell cycle inhibition. Furthermore, these results suggest that although both Cdc42Hs and Rac1 can activate p38 in situ, the effects of Cdc42Hs and Rac1 on cell cycle progression are, in fact, quite distinct.
authors.affiliation: Diabetes Research Laboratory, Massachusetts General Hospital East, Charlestown, Massachusetts 02129, USA.
authors.forename: A
authors.initials: A
authors.lastname: Molnár
authors.forename: A M
authors.initials: AM
authors.lastname: Theodoras
authors.forename: L I
authors.initials: LI
authors.lastname: Zon
authors.forename: J M
authors.initials: JM
authors.lastname: Kyriakis
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016193:G1 Phase; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D016196:S Phase; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins
chemical_list: D018797:Cell Cycle Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins