Cytosolic chloride ion is a key factor in lysosomal acidification and function of autophagy in human gastric cancer cell.
Bottom Line: 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.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.
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.Show MeSH
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Mentions: The mechanism of low pHc induced by culture in low Cl− medium would be because of lowered activity of NHE and/or Na+-driven Cl−/bicarbonate (HCO3−) exchanger (NDCBE) participating in HCO3− uptake into cytosolic space caused by lowered [Cl−]c, as NHE activity is diminished by lowering [Cl−]c , and NDCBE activity also depends on [Cl−]c . The mechanism increasing pHlys observed in low Cl− medium would be because of an insufficient amount of counter anion, Cl−, in the cytosolic space (lowered [Cl−]c) co-transported into the intra-luminal space at proton moving into intra-lysosomal space disturbing proton movement into intra-lysosomal space. Thus, an insufficient amount of cytosolic Cl− would cause elevation of pHlys associated with low [Cl−]lys, and NO3− would not play an identical role to Cl− in lysosomal acidity or autophagy function (see the conclusion and Fig.9 in detail).
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.