title: Hsp40 regulates the amount of keratin proteins via ubiquitin-proteasome             pathway in cultured human cells.
abstract: Keratins represent important structural components of intermediate filament             proteins. Their expression profiles are remarkably tissue-specific. Recent data             have shown that keratins associate with many proteins including heat shock proteins             (HSP). We recently identified cell-specific keratin and HSP expression. We aimed             to gain further insight into the regulation of keratins by specific inhibition             through knockdown of Hsp40 in human keratinocyte cells. Keratin-HSP interaction             in HaCaT cell lysate was evaluated by immunoprecipitation followed by Western             blotting. Immunofluorescence, was used to examine the co-localization of keratins             and Hsp40. Hsp40 depletion led to an increase in the levels of keratin proteins             (K5, K14, K10) and a decrease in keratin ubiquitination without influencing keratin             gene expression. Our results demonstrate direct or indirectly association of Hsp40             and imply that expressed keratin proteins were regulated by Hsp40 depending on             the ubiquitin-proteasome pathway in HaCaT. Furthermore, the K10 differentiation             marker was increased by knockdown of Hsp40. The results presented in this study             indicate that Hsp40 is related to the differentiation exchange of keratin pairs.
authors.affiliation: Department of Biochemistry and Biotechnology, Faculty of Agriculture                     and Life Science, Hirosaki University, Hirosaki 036-8561, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Asato
authors.initials: A
authors.lastname: Uchiumi
authors.forename: Yohtaro
authors.initials: Y
authors.lastname: Katagata
mesh_terms: D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D020868:Gene Silencing; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007633:Keratins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D034741:RNA, Small Interfering / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D050956:HSP40 Heat-Shock Proteins; D034741:RNA, Small Interfering; D025801:Ubiquitin; D007633:Keratins; D046988:Proteasome Endopeptidase Complex