title: UVA causes dual inactivation of cathepsin B and L underlying lysosomal dysfunction in human dermal fibroblasts.
abstract: Cutaneous exposure to chronic solar UVA-radiation is a causative factor in photocarcinogenesis and photoaging. Recently, we have identified the thiol-dependent cysteine-protease cathepsin B as a novel UVA-target undergoing photo-oxidative inactivation upstream of autophagic-lysosomal dysfunction in fibroblasts. In this study, we examined UVA effects on a wider range of cathepsins and explored the occurrence of UVA-induced cathepsin inactivation in other cultured skin cell types. In dermal fibroblasts, chronic exposure to non-cytotoxic doses of UVA caused pronounced inactivation of the lysosomal cysteine-proteases cathepsin B and L, effects not observed in primary keratinocytes and occurring only to a minor extent in primary melanocytes. In order to determine if UVA-induced lysosomal impairment requires single or dual inactivation of cathepsin B and/or L, we used a genetic approach (siRNA) to selectively downregulate enzymatic activity of these target cathepsins. Monitoring an established set of protein markers (including LAMP1, LC3-II, and p62) and cell ultrastructural changes detected by electron microscopy, we observed that only dual genetic antagonism (targeting both CTSB and CTSL expression) could mimic UVA-induced autophagic-lysosomal alterations, whereas single knockdown (targeting CTSB or CTSL only) did not display 'UVA-mimetic' effects failing to reproduce the UVA-induced phenotype. Taken together, our data demonstrate that chronic UVA inhibits both cathepsin B and L enzymatic activity and that dual inactivation of both enzymes is a causative factor underlying UVA-induced impairment of lysosomal function in dermal fibroblasts.
authors.affiliation: Department of Pharmacology and Toxicology, College of Pharmacy & Arizona Cancer Center, University of Arizona, Tucson, AZ 85724, USA.
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Lamore
authors.forename: Georg T
authors.initials: GT
authors.lastname: Wondrak
mesh_terms: D001343:Autophagy; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000528:radiation effects*; D056668:Cathepsin L / Q000037:antagonists & inhibitors / Q000528:radiation effects*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects*; D006801:Humans; D015603:Keratinocytes / Q000201:enzymology / Q000528:radiation effects; D008247:Lysosomes / Q000528:radiation effects*; D008544:Melanocytes / Q000201:enzymology / Q000528:radiation effects; D018384:Oxidative Stress; D034741:RNA, Small Interfering / Q000494:pharmacology; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D034741:RNA, Small Interfering; D002401:Cathepsin B; D056668:Cathepsin L