Cytosolic chloride ion is a key factor in lysosomal acidification and function of autophagy in human gastric cancer cell

• Published in: Journal of cellular and molecular medicine Vol. 18; no. 6; pp. 1124 - 1133
• Main Authors: Hosogi, Shigekuni, Kusuzaki, Katsuyuki, Inui, Toshio, Wang, Xiangdong, Marunaka, Yoshinori
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.06.2014; John Wiley & Sons, Ltd
• Subjects: Acidification; Acids - metabolism; Amiloride; Amino acids; Apoptosis; Apoptosis - drug effects; Apoptosis Regulatory Proteins - metabolism; Autophagy; Autophagy - drug effects; Blotting, Western; Cancer; Caspase; Caspase-3; Cell culture; Cell Cycle - drug effects; Cell growth; Cell proliferation; Cell Proliferation - drug effects; chloride ion; Chlorides; Chlorides - pharmacology; Cytosol - metabolism; Disease; Gastric cancer; Homeostasis - drug effects; Humans; Hydrogen; lysosome; Lysosomes - metabolism; Na+/H+-exchanging ATPase; Original; Phagocytosis; Phosphorylation; Proteins; Starvation; Stomach Neoplasms - drug therapy; Stomach Neoplasms - metabolism; Stomach Neoplasms - pathology; Tumor Cells, Cultured; United States > US; Japan; pH; apoptosis; autophagy; chloride ion; lysosome
• ISSN: 1582-1838; 1582-4934; 1582-4934
• DOI: 10.1111/jcmm.12257

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.