title: Increased levels of UV-induced protease activity in human UVAP-1 cells exposed to gravity-changing stress: involvement of E-64-sensitive proteases in suppression of UV mutagenicity.
abstract: Under the 1G condition, the increase in antipain-sensitive protease activity promptly after UV (mainly 254 nm wavelength) irradiation in cultured human cells is detected and found to be one of the intriguing events involved in suppression of cell mutability. It was found that two cell lines, RSa and its variant UVAP-1 cells are applicable; the former is hypermutable and not susceptible to protease activation, while the latter is hypomutable and susceptible. In the present study it was investigated whether the increase in protease activity by UV irradiation is also observed in hypomutable human UVAP-1 cells exposed to gravity-changing stress and whether the increase is involved in suppression of UV mutagenicity. Exposure of human UVAP-1 cells to gravity-changing stress such as free-fall and parabolic flight prior to UV irradiation resulted in a pronounced increase in protease activity, but not to hypergravity conditions (2 and 10G) prior to UV irradiation. To characterize the proteases, components of lysates from the cells exposed to free-fall prior to UV irradiation were fractionated by high performance liquid chromatography, indicating two separate fractions with highly increased levels of E-64-sensitive protease activity. In the cells treated with E-64 during their exposure to free-fall, K-ras codon 12 base substitution mutation was detected after UV irradiation, although the mutation was not detected after UV irradiation alone. Thus, the increase in E-64-sensitive protease activity may be involved in the suppression of UV mutagenicity in UVAP-1 cells exposed to free-fall.
authors.affiliation: Department of Environmental Biochemistry, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuoku, Chiba 260-8670, Japan.
authors.forename: Shunji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Hong-Chang
authors.initials: HC
authors.lastname: Zhang
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Hasegawa
authors.forename: Kiyonobu
authors.initials: K
authors.lastname: Karata
authors.forename: Kazuko
authors.initials: K
authors.lastname: Kita
authors.forename: Chieko
authors.initials: C
authors.lastname: Wano
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sugaya
authors.forename: Jun
authors.initials: J
authors.lastname: Nomura
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ichinose
authors.forename: Nobuo
authors.initials: N
authors.lastname: Suzuki
mesh_terms: D000976:Antipain / Q000494:pharmacology; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D010450:Endopeptidases / Q000032:analysis / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D011905:Genes, ras / Q000528:radiation effects; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D009154:Mutation / Q000528:radiation effects*; D011480:Protease Inhibitors / Q000494:pharmacology; D011836:Radiation Tolerance; D014466:Ultraviolet Rays / Q000009:adverse effects*; D018474:Weightlessness Simulation
chemical_list: D011480:Protease Inhibitors; D000976:Antipain; D010450:Endopeptidases