title: Mesotrypsin and caspase-14 participate in prosaposin processing: potential relevance to epidermal permeability barrier formation.
abstract: A proteomics-based search for molecules interacting with caspase-14 identified prosaposin and epidermal mesotrypsin as candidates. Prosaposin is a precursor of four sphingolipid activator proteins (saposins A-D) that are essential for lysosomal hydrolysis of sphingolipids. Thus, we hypothesized that caspase-14 and mesotrypsin participate in processing of prosaposin. Because we identified a saposin A sequence as an interactor with these proteases, we prepared a specific antibody to saposin A and focused on saposin A-related physiological reactions. We found that mesotrypsin generated saposins A-D from prosaposin, and mature caspase-14 contributed to this process by activating mesotrypsinogen to mesotrypsin. Knockdown of these proteases markedly down-regulated saposin A synthesis in skin equivalent models. Saposin A was localized in granular cells, whereas prosaposin was present in the upper layer of human epidermis. The proximity ligation assay confirmed interaction between prosaposin, caspase-14, and mesotrypsin in the granular layer. Oil Red staining showed that the lipid envelope was significantly reduced in the cornified layer of skin from saposin A-deficient mice. Ultrastructural studies revealed severely disorganized cornified layer structure in both prosaposin- and saposin A-deficient mice. Overall, our results indicate that epidermal mesotrypsin and caspase-14 work cooperatively in prosaposin processing. We propose that they thereby contribute to permeability barrier formation in vivo.
authors.affiliation: From the Shiseido Innovative Science Research Center, 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama 224-8558, the Department of Dermatology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, and.
authors.forename: Mami
authors.initials: M
authors.lastname: Yamamoto-Tanaka
authors.affiliation: From the Shiseido Innovative Science Research Center, 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama 224-8558.
authors.forename: Akira
authors.initials: A
authors.lastname: Motoyama
authors.affiliation: From the Shiseido Innovative Science Research Center, 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama 224-8558.
authors.forename: Masashi
authors.initials: M
authors.lastname: Miyai
authors.affiliation: From the Shiseido Innovative Science Research Center, 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama 224-8558.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Matsunaga
authors.affiliation: the Institute of Glycoscience, Tokai University, Kitakinnmoku 4-1-1, Hiratsuka, Kanagawa 259-1292, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Matsuda
authors.affiliation: the Department of Dermatology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, and.
authors.forename: Ryoji
authors.initials: R
authors.lastname: Tsuboi
authors.affiliation: From the Shiseido Innovative Science Research Center, 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama 224-8558, toshihiko.hibino1@to.shiseido.co.jp.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Hibino
mesh_terms: D000818:Animals; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D010539:Permeability; D011499:Protein Processing, Post-Translational; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D049231:Saposins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012867:Skin / Q000378:metabolism* / Q000648:ultrastructure; D014357:Trypsin / Q000235:genetics / Q000378:metabolism*
chemical_list: C483345:PSAP protein, human; C483344:Psap protein, mouse; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D049231:Saposins; C587505:saposin A, mouse; C040749:PRSS3 protein, human; D014357:Trypsin; C506446:CASP14 protein, human; C506449:Casp14 protein, mouse; D020169:Caspases
keywords: Bar; Caspase; Caspase,; Cell Differentiation; Kallikrein; Keratinocyte; Protein Processing