title: Autophagy negatively regulates keratinocyte inflammatory responses via scaffolding protein p62/SQSTM1.
abstract: The scaffolding adaptor protein p62/SQSTM1 (p62) has been shown to be an autophagy receptor that acts as a link between the ubiquitination and autophagy machineries. However, the roles of autophagy and p62 in human keratinocytes are not well understood. In this study, we show that keratinocyte autophagy negatively regulates p62 expression, which is essential for the prevention of excessive inflammation and the induction of cathelicidin in human keratinocytes. Stimulation of TLR2/6 or TLR4 in primary human keratinocytes robustly activated autophagy pathways and up-regulated p62 expression through induction of NADPH oxidases 2 and 4 and the generation of reactive oxygen species. MyD88 and TNFR-associated factor 6, key signaling molecules that mediate TLR activation, played an essential role in the induction of autophagy and p62 expression. Additionally, blockade of autophagy significantly increased the generation of inflammatory cytokines and expression of p62 in primary human keratinocytes. Notably, silencing hp62 through RNA interference resulted in a significant decrease in NF-κB activation, inflammatory cytokine production, cathelicidin expression, and cell proliferation (as well as cyclin D1 expression) in keratinocytes. Epidermal expression of p62 was further found to be significantly higher in psoriatic skin than in skin affected by atopic dermatitis or from healthy controls. Collectively, our data provide new insights into the roles of autophagy and p62 in controlling cutaneous inflammation.
authors.affiliation: Department of Microbiology, Chungnam National University, Daejeon 301-747, South Korea.
authors.forename: Hye-Mi
authors.initials: HM
authors.lastname: Lee
authors.forename: Dong-Min
authors.initials: DM
authors.lastname: Shin
authors.forename: Jae-Min
authors.initials: JM
authors.lastname: Yuk
authors.forename: Ge
authors.initials: G
authors.lastname: Shi
authors.forename: Dae-Kyoung
authors.initials: DK
authors.lastname: Choi
authors.forename: Sang-Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Song Mei
authors.initials: SM
authors.lastname: Huang
authors.forename: Jin-Man
authors.initials: JM
authors.lastname: Kim
authors.forename: Chang Deok
authors.initials: CD
authors.lastname: Kim
authors.forename: Jeung-Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Eun-Kyeong
authors.initials: EK
authors.lastname: Jo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000502:physiology*; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis; D001343:Autophagy / Q000276:immunology*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D003876:Dermatitis, Atopic / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015536:Down-Regulation / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D018836:Inflammation Mediators / Q000502:physiology*; D015603:Keratinocytes / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D016328:NF-kappa B / Q000502:physiology; D011565:Psoriasis / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D051195:Toll-Like Receptor 2 / Q000378:metabolism / Q000502:physiology; D051216:Toll-Like Receptor 6 / Q000378:metabolism / Q000502:physiology; D054804:Cathelicidins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D023181:Antimicrobial Cationic Peptides; D016207:Cytokines; D018836:Inflammation Mediators; D016328:NF-kappa B; D017382:Reactive Oxygen Species; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; C495342:TLR2 protein, human; C495368:TLR6 protein, human; D051195:Toll-Like Receptor 2; D051216:Toll-Like Receptor 6; D054804:Cathelicidins