title: Rho-associated kinase connects a cell cycle-controlling anchorage signal to the mammalian target of rapamycin pathway.
abstract: When deprived of anchorage to the extracellular matrix, fibroblasts arrest in G(1) phase at least in part due to inactivation of G(1) cyclin-dependent kinases. Despite great effort, how anchorage signals control the G(1)-S transition of fibroblasts remains highly elusive. We recently found that the mammalian target of rapamycin (mTOR) cascade might convey an anchorage signal that regulates S phase entry. Here, we show that Rho-associated kinase connects this signal to the TSC1/TSC2-RHEB-mTOR pathway. Expression of a constitutively active form of ROCK1 suppressed all of the anchorage deprivation effects suppressible by tsc2 mutation in rat embryonic fibroblasts. TSC2 contains one evolutionarily conserved ROCK target-like sequence, and an alanine substitution for Thr(1203) in this sequence severely impaired the ability of ROCK1 to counteract the anchorage loss-imposed down-regulation of both G(1) cell cycle factors and mTORC1 activity. Moreover, TSC2 Thr(1203) underwent ROCK-dependent phosphorylation in vivo and could be phosphorylated by bacterially expressed active ROCK1 in vitro, providing biochemical evidence for a direct physical interaction between ROCK and TSC2.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Jung-ha
authors.initials: JH
authors.lastname: Park
authors.forename: Shiho
authors.initials: S
authors.lastname: Arakawa-Takeuchi
authors.forename: Shigeki
authors.initials: S
authors.lastname: Jinno
authors.forename: Hiroto
authors.initials: H
authors.lastname: Okayama
mesh_terms: D000818:Animals; D002460:Cell Line; D016193:G1 Phase / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D051381:Rats; D016196:S Phase / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: C000624652:Tsc1 protein, rat; C000624655:Tsc2 protein, rat; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D054460:rho-Associated Kinases