The action of v-src on gap junctional permeability is modulated by pH.
The product of the viral src gene (v-src) is the protein tyrosine kinase pp60v-src. Among the known consequences of pp60v-src activity is the reduction in permeability of gap junctions, an effect that is counteracted by the calcium antagonist TMB-8 (8-N,N-[diethylamino]octyl-3,4,5-trimethoxybenzoate). We show here that a decrease in intracellular pH (pHi) also counteracts the v-src effect: junctional permeability of cells containing active v-src kinase rose with decreasing pHi in the range 7.15 to 6.75, whereas junctional permeability of cells containing inactive v-src kinase or no v-src at all was insensitive to pH in that range. Low pH also counteracted the known action of diacylglycerol on junction, but only when pp60v-src kinase was inactive. Immunoblots of whole-cell lysates using an antibody against phosphotyrosine show that phosphorylation on tyrosine of at least one cellular protein, specific for pp60v-src kinase activity, was reduced by low pH but not by TMB-8. These results suggest that TMB-8 does not inhibit v-src action on junctional permeability by interfering with tyrosine phosphorylation of a protein crucial for closure of gap junction channels, but that the inhibition by low pH may be via this mechanism.
Hyrc
K
K
Department of Physiology and Biophysics, University of Miami School of Medicine, Florida 33101.
Rose
B
B
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D002463:Cell Membrane Permeability; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D007365:Intercellular Junctions / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014443:Tyrosine
D002121:Calcium Channel Blockers; D004075:Diglycerides; C044295:1,2-dioctanoylglycerol; D014443:Tyrosine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src)