title: Direct binding of RalA to PKCη and its crucial role in morphological change during keratinocyte differentiation.
abstract: During differentiation, keratinocytes undergo a dramatic shape change from small and round to large and flat, in addition to production of proteins necessary for the formation of epidermis. It has been shown that protein kinase C (PKC) η is crucial for keratinocyte differentiation. However, its role in this process has yet to be fully elucidated. Here, we show that catalytic activity is not necessary for enlarged and flattened morphology of human keratinocytes induced by overexpression of PKCη, although it is important for gene expression of the marker proteins. In addition, we identify the small G protein RalA as a binding partner of PKCη, which binds to the C1 domain, an indispensable region for the morphological change. The binding led activation of RalA and actin depolymerization associated with keratinocyte differentiation. siRNA techniques proved that RalA is involved in not only the keratinocyte differentiation induced by PKCη overexpression but also normal keratinocyte differentiation induced by calcium and cholesterol sulfate. These results provide a new insight into the molecular mechanism of cytoskeletal regulation leading to drastic change of cell shape.
authors.affiliation: Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan. shirai@kobe-u.ac.jp
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Shirai
authors.forename: Shoko
authors.initials: S
authors.lastname: Morioka
authors.forename: Megumi
authors.initials: M
authors.lastname: Sakuma
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yoshino
authors.forename: Chihiro
authors.initials: C
authors.lastname: Otsuji
authors.forename: Norio
authors.initials: N
authors.lastname: Sakai
authors.forename: Kaori
authors.initials: K
authors.lastname: Kashiwagi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Chida
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Shirakawa
authors.forename: Hisanori
authors.initials: H
authors.lastname: Horiuchi
authors.forename: Chikako
authors.initials: C
authors.lastname: Nishigori
authors.forename: Takehiko
authors.initials: T
authors.lastname: Ueyama
authors.forename: Naoaki
authors.initials: N
authors.lastname: Saito
mesh_terms: D000199:Actins / Q000378:metabolism; D000256:Adenoviridae; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002788:Cholesterol Esters / Q000494:pharmacology; D004789:Enzyme Activation; D000078404:Epidermal Cells; D004817:Epidermis / Q000201:enzymology; D004926:Escherichia coli; D015870:Gene Expression / Q000502:physiology; D020868:Gene Silencing; D057809:HEK293 Cells; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology; D009154:Mutation; D011485:Protein Binding / Q000502:physiology; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D020725:ral GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D002788:Cholesterol Esters; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C081975:protein kinase C eta; D011493:Protein Kinase C; C492198:RALA protein, human; D020725:ral GTP-Binding Proteins; C007045:cholesteryl sulfate; D002118:Calcium