title: Human homolog of Drosophila tumor suppressor Scribble negatively regulates cell-cycle progression from G1 to S phase by localizing at the basolateral membrane in epithelial cells.
abstract: Drosophila tumor suppressor Scribble has been identified as an apical-basolateral polarity determinant in epithelia. A human homolog of Drosophila Scribble, human Scribble (hScrib), has been identified as a protein targeted by human papillomavirus E6 for the ubiquitin-mediated degradation dependent on E6AP, a cellular ubiquitin-protein ligase. Human Scribble is classified as a LAP protein, having leucine-rich repeats (LRRs) and PDZ domains. We investigated whether hScrib, which is thought to have a role in polarity determination based on the data of its Drosophila homolog, is involved in cell-cycle regulation and proliferation control of epithelia. Transfection of hScrib inhibits cell-cycle progression from G1 to S phase, and it up- and down-regulates expression of adenomatous polyposis coli and cyclins A and D1, respectively. Knockdown of hScrib expression by siRNA leads to cell-cycle progression from G1 to S phase. We explored functional domain mapping to reveal which domains of hScrib are critical for its cellular proliferation control and localization at the basolateral membrane. We found that LRRs and PDZ domain 1 are indispensable for hScrib to inhibit cell growth by blocking cell-cycle progression and to keep its proper localization. These data indicate that basolateral membrane localization of hScrib is closely related to its proliferation control. Our findings suggest the possibility that hScrib is involved in signal transduction to negatively regulate cell proliferation by localizing at the basolateral membrane of epithelial cells through LRRs and PDZ domains.
authors.affiliation: Department of Obstetrics and Gynecology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nagasaka
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Tetsu
authors.initials: T
authors.lastname: Yano
authors.forename: Shin
authors.initials: S
authors.lastname: Takizawa
authors.forename: Yoko
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Tsuruga
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Takeo
authors.initials: T
authors.lastname: Minaguchi
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Oda
authors.forename: Osamu
authors.initials: O
authors.lastname: Hiraike-Wada
authors.forename: Hajime
authors.initials: H
authors.lastname: Ooishi
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yasugi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Taketani
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D004331:Drosophila melanogaster; D004847:Epithelial Cells / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D016193:G1 Phase; D016147:Genes, Tumor Suppressor; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016196:S Phase; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C480591:SCRIB protein, human; D025521:Tumor Suppressor Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins