title: CLIC4 mediates and is required for Ca2+-induced keratinocyte differentiation.
abstract: Keratinocyte differentiation requires integrating signaling among intracellular ionic changes, kinase cascades, sequential gene expression, cell cycle arrest, and programmed cell death. We now show that Cl(-) intracellular channel 4 (CLIC4) expression is increased in both mouse and human keratinocytes undergoing differentiation induced by Ca(2+), serum and the protein kinase C (PKC)-activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Elevation of CLIC4 is associated with signaling by PKCdelta, and knockdown of CLIC4 protein by antisense or shRNA prevents Ca(2+)-induced keratin 1, keratin 10 and filaggrin expression and cell cycle arrest in differentiating keratinocytes. CLIC4 is cytoplasmic in actively proliferating keratinocytes in vitro, but the cytoplasmic CLIC4 translocates to the nucleus in keratinocytes undergoing growth arrest by differentiation, senescence or transforming growth factor beta (TGFbeta) treatment. Targeting CLIC4 to the nucleus of keratinocytes via adenoviral transduction increases nuclear Cl(-) content and enhances expression of differentiation markers in the absence of elevated Ca(2+). In vivo, CLIC4 is localized to the epidermis in mouse and human skin, where it is predominantly nuclear in quiescent cells. These results suggest that CLIC4 participates in epidermal homeostasis through both alterations in the level of expression and subcellular localization. Nuclear CLIC4, possibly by altering the Cl(-) and pH of the nucleus, contributes to cell cycle arrest and the specific gene expression program associated with keratinocyte terminal differentiation.
authors.affiliation: Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Suh
authors.forename: Michihiro
authors.initials: M
authors.lastname: Mutoh
authors.forename: Tomoko
authors.initials: T
authors.lastname: Mutoh
authors.forename: Luowei
authors.initials: L
authors.lastname: Li
authors.forename: Andrew
authors.initials: A
authors.lastname: Ryscavage
authors.forename: John M
authors.initials: JM
authors.lastname: Crutchley
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Dumont
authors.forename: Christina
authors.initials: C
authors.lastname: Cheng
authors.forename: Stuart H
authors.initials: SH
authors.lastname: Yuspa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000302:isolation & purification / Q000378:metabolism*; D000091344:Filaggrin Proteins; D015870:Gene Expression; D006801:Humans; D007381:Intermediate Filament Proteins / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism; D007633:Keratins / Q000378:metabolism; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: C464459:CLIC4 protein, human; D018118:Chloride Channels; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D020033:Protein Isoforms; D018808:Transcription Factor AP-1; D007633:Keratins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium