title: Cytosolic chloride ion is a key factor in lysosomal acidification and function of autophagy in human gastric cancer cell.
abstract: The purpose of the present study was to clarify roles of cytosolic chloride ion (Cl(-) ) in regulation of lysosomal acidification [intra-lysosomal pH (pHlys )] and autophagy function in human gastric cancer cell line (MKN28). The MKN28 cells cultured under a low Cl(-) condition elevated pHlys and reduced the intra-lysosomal Cl(-) concentration ([Cl(-) ]lys ) via reduction of cytosolic Cl(-) concentration ([Cl(-) ]c ), showing abnormal accumulation of LC3II and p62 participating in autophagy function (dysfunction of autophagy) accompanied by inhibition of cell proliferation via G0 /G1 arrest without induction of apoptosis. We also studied effects of direct modification of H(+) transport on lysosomal acidification and autophagy. Application of bafilomycin A1 (an inhibitor of V-type H(+) -ATPase) or ethyl isopropyl amiloride [EIPA; an inhibitor of Na(+) /H(+) exchanger (NHE)] elevated pHlys and decreased [Cl(-) ]lys associated with inhibition of cell proliferation via induction of G0 /G1 arrest similar to the culture under a low Cl(-) condition. However, unlike low Cl(-) condition, application of the compound, bafilomycin A1 or EIPA, induced apoptosis associated with increases in caspase 3 and 9 without large reduction in [Cl(-) ]c compared with low Cl(-) condition. These observations suggest that the lowered [Cl(-) ]c primarily causes dysfunction of autophagy without apoptosis via dysfunction of lysosome induced by disturbance of intra-lysosomal acidification. This is the first study showing that cytosolic Cl(-) is a key factor of lysosome acidification and autophagy.
authors.affiliation: Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan; Japan Institute for Food Education and Health, Heian Jogakuin (St. Agnes') University, Kyoto, Japan.
authors.forename: Shigekuni
authors.initials: S
authors.lastname: Hosogi
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kusuzaki
authors.forename: Toshio
authors.initials: T
authors.lastname: Inui
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Wang
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Marunaka
mesh_terms: D000143:Acids / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D000143:Acids; D051017:Apoptosis Regulatory Proteins; D002712:Chlorides
keywords: apoptosis; autophagy; chloride ion; lysosome; pH
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