title: Enhancement of lysosomal osmotic sensitivity induced by the photooxidation of membrane thiol groups.
abstract: The osmotic lysis of photodamaged lysosomes is a critical event for killing tumor cells. How the photodamage increases lysosomal osmotic sensitivity is still unclear. In this work, the effect of the photooxidation of membrane thiol groups on the lysosomal osmotic sensitivity was studied by measuring the thiol groups with 5,5'-dithiobis(2-nitrobenzoic acid) and examining the lysosomal beta-hexosaminidase latency loss in a hypotonic sucrose medium. The results show that methylene blue-mediated photooxidation of lysosomes decreased their membrane thiol groups and produced cross-linkage of membrane proteins (molecular weight ranging from 75000 to 125000), which was visualized by sodium dodecyl sulfatepolyacrylamide gel electrophoresis. Simultaneously, the lysosomal osmotic sensitivity increased. These photoinduced alterations of the lysosomes could be recovered by reducing the oxidized thiol groups with dithiothreitol. It indicates that the photooxidation of membrane thiol groups can increase the lysosomal osmotic sensitivity and therefore provides a new explanation for the photoinduced lysosomal lysis.
authors.affiliation: Department of Cellular Biophysics, Institute of Biophysics, Academia Sinica, Beijing, People's Republic of China.
authors.forename: Feng-Yi
authors.initials: FY
authors.lastname: Wan
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.forename: Yi-Gang
authors.initials: YG
authors.lastname: Zhong
authors.forename: Wen
authors.initials: W
authors.lastname: Zhu
authors.forename: Yi-Nan
authors.initials: YN
authors.lastname: Wang
authors.forename: Guo-Jiang
authors.initials: GJ
authors.lastname: Zhang
mesh_terms: D000818:Animals; D019281:Dimerization; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D008099:Liver; D008247:Lysosomes / Q000378:metabolism / Q000528:radiation effects*; D008565:Membrane Proteins / Q000378:metabolism / Q000528:radiation effects*; D009995:Osmosis / Q000528:radiation effects; D010084:Oxidation-Reduction; D010777:Photochemistry; D051381:Rats; D013438:Sulfhydryl Compounds / Q000378:metabolism / Q000528:radiation effects
chemical_list: D008565:Membrane Proteins; D013438:Sulfhydryl Compounds