title: Rho/ROCK signaling in regulation of corneal epithelial cell cycle progression.
abstract: OBJECTIVE
  The authors' previous study showed that the expression of a Rho-associated serine/threonine kinase (ROCK) is regulated during cell cycle progression in corneal epithelial cells. The present study was conducted to determine whether and how Rho/ROCK signaling regulates cell cycle progression.
  
  
  METHODS
  Rabbit corneal epithelial cells (RCECs) in culture were arrested in the G(0) phase of the cell cycle by serum deprivation and then allowed to re-enter the cell cycle in the presence or absence of the ROCK inhibitor (Y27632) in serum-supplemented medium. The number of cells in the S phase, the relative levels of specific cyclins and CDKs and their intracellular distribution, and the relative levels of mRNAs were determined by BrdU labeling, Western blot and immunocytochemical analyses, and real-time RT-PCR, respectively.
  
  
  RESULTS
  ROCK inhibition delayed the progression of G(1) to S phase and led to a decrease in the number of RCECs entering the S phase between 12 and 24 hours from 31.5% +/- 4.5% to 8.1% +/- 2.6%. During the cell cycle progression, protein and mRNA levels of cyclin-D1 and -D3 and cyclin-dependent kinases CDK4 and CDK6 were significantly lower, whereas the protein levels of the CDK inhibitor p27(Kip1) were higher in ROCK-inhibited cells. Intracellular mRNA or protein levels of cyclin-E and protein levels of CDK2 were not significantly affected, but their nuclear translocation was delayed by ROCK inhibition.
  
  
  CONCLUSIONS
  ROCK signaling is involved in cell cycle progression in RCECs, possibly by upregulation of cyclin-D1 and -D3 and CDK4, -6, and -2; nuclear translocation of CDK2 and cyclin-E; and downregulation of p27(Kip1).
authors.affiliation: UPMC Eye Center, Ophthalmology and Visual Science Research Center, Eye and Ear Institute, Department of Ophthalmology, University of Pittsburgh School of Medicine, 203 Lothrop Street, Pittsburgh, PA 15213, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Emily
authors.initials: E
authors.lastname: Guerriero
authors.forename: Kira
authors.initials: K
authors.lastname: Lathrop
authors.forename: Nirmala
authors.initials: N
authors.lastname: SundarRaj
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000166:cytology* / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D007150:Immunohistochemistry; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D000577:Amides; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D011725:Pyridines; D012333:RNA, Messenger; C108830:Y 27632; D054460:rho-Associated Kinases