Functional expression of V-ATPases in the plasma membrane of glial cells.
Vacuolar H(+) ATPase (V-ATPase) activity is essential for many cellular processes, including intracellular membrane traffic, protein processing and degradation, and receptor-mediated endocytosis. Proton transport by V-ATPases could also play a role during cell transformation, tumorigenesis, and cell metastasis, and V-ATPase c-subunit overexpression was reported to be correlated with invasiveness of pancreatic tumors (Ohta et al., 1996). In the present work, we found that mRNAs encoding V-ATPase subunits are not overexpressed in C6 tumoral glioma cells when compared with immortalized astrocytes DI TNC1 and astrocytes in primary cultures. Accordingly, V-ATPase subunit mRNA levels are similar in human gliomas (grade II or IV) and in peritumoral tissues. A significant proportion (25%) of V-ATPase is present in the plasma membrane of both the C6 and the DI TNC1 astrocytic cells in culture. A bafilomycin-sensitive hyperpolarizing pump current through the plasma membrane was detected and measured after ionic channel inhibition, which corresponds most probably to an electrogenic transport of protons. This suggests that the plasma membrane V-ATPase is active. It could contribute to cytoplasmic pH regulation in astrocytic cells.
Philippe
Jean-Marc
JM
Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, Gif sur Yvette, France.
Dubois
Jean-Marc
JM
Rouzaire-Dubois
Beatrice
B
Cartron
Pierre-François
PF
Vallette
François
F
Morel
Nicolas
N
D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000201:enzymology*; D001932:Brain Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002462:Cell Membrane / Q000201:enzymology* / Q000648:ultrastructure; D002490:Central Nervous System / Q000166:cytology / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D005910:Glioma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D009579:Nitrobenzoates / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D019789:Tetraethylammonium / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism
D020533:Angiogenesis Inhibitors; D007473:Ion Channels; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers; D012333:RNA, Messenger; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D019789:Tetraethylammonium; D025262:Vacuolar Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase