title: Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium.
abstract: Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.
authors.affiliation: Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA. jennifer.black@roswellpark.org
authors.forename: M R
authors.initials: MR
authors.lastname: Frey
authors.forename: J A
authors.initials: JA
authors.lastname: Clark
authors.forename: O
authors.initials: O
authors.lastname: Leontieva
authors.forename: J M
authors.initials: JM
authors.lastname: Uronis
authors.forename: A R
authors.initials: AR
authors.lastname: Black
authors.forename: J D
authors.initials: JD
authors.lastname: Black
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D018797:Cell Cycle Proteins; D002460:Cell Line; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation; D049452:Green Fluorescent Proteins; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism; D008164:Luminescent Proteins / Q000032:analysis; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016192:Resting Phase, Cell Cycle; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D025521:Tumor Suppressor Proteins
chemical_list: C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007527:Isoenzymes; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D049452:Green Fluorescent Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C497260:Prkcd protein, rat; C497257:Prkce protein, rat; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D018844:Cyclin-Dependent Kinases; D013755:Tetradecanoylphorbol Acetate