Cytosolic chloride ion is a key factor in lysosomal acidification and function of autophagy in human gastric cancer cell |
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Authors: | Shigekuni Hosogi Katsuyuki Kusuzaki Toshio Inui Xiangdong Wang Yoshinori Marunaka |
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Affiliation: | 1. Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, , Kyoto, Japan;2. Japan Institute for Food Education and Health, Heian Jogakuin (St. Agnes') University, , Kyoto, Japan;3. Department of Orthopaedic Surgery, Kyoto Kujo Hospital, , Kyoto, Japan;4. Department of Bio‐Ionomics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, , Kyoto, Japan;5. Saisei Mirai Clinics, , Moriguchi, Japan;6. Department of Respiratory Medicine, Shanghai Respiratory Research Institute, Fudan University Zhongshan Hospital, , Shanghai, China |
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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. |
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Keywords: | autophagy chloride ion lysosome pH apoptosis |
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