title: Volume sensitive efflux of taurine in HEK293 cells overexpressing phospholemman.
abstract: The role of the phospholemman (PLM) on the efflux of taurine and chloride induced by swelling was studied in HEK293 cells overexpressing stable transfected PLM. PLM, a substrate for protein kinases C and A, is a protein that induces an anion current in Xenopus oocytes and forms taurine-selective channels in lipid bilayers. Taurine contributes as an osmolyte to regulatory volume decrease (RVD) and is highly permeable through PLM channels in bilayers. In PLM-overexpressing cells the process of RVD was more rapid and efficient (75%) than in control cells (44%). Also, [(3)H]taurine and (125)I efflux induced by hyposmolarity were markedly increased (30-100%) in two subclones of cells overexpressing PLM. This increased efflux was sensitive to the Cl channel blockers DDF, NPPB and DIDS. Acute treatment of control cells with isoproterenol and norepinephrine induced a significant potentiation (50-60%) of [(3)H]taurine release induced by hyposmolarity. In PLM-overexpressing cells the potentiation by these drugs was higher (100%). Insulin induced also an increase in [(3)H]taurine release, but only in PLM-overexpressing cells (50%). These results indicate that PLM may play a role in the RVD and that its phosphorylation may have a physiological significance during this process. The mechanisms involved in this process could include the activation of PLM itself as channel or the modulation of other preexisting channels.
authors.affiliation: Department of Biophysics, National University of Mexico, Mexico, Mexico.
authors.forename: M
authors.initials: M
authors.lastname: Morales-Mulia
authors.forename: H
authors.initials: H
authors.lastname: Pasantes-Morales
authors.forename: J
authors.initials: J
authors.lastname: Morán
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D015536:Down-Regulation; D006801:Humans; D007457:Iodine Radioisotopes; D007473:Ion Channels / Q000187:drug effects*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D009579:Nitrobenzoates / Q000494:pharmacology; D009994:Osmolar Concentration; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013654:Taurine / Q000032:analysis / Q000378:metabolism*; D014162:Transfection; D014316:Tritium
chemical_list: D007457:Iodine Radioisotopes; D007473:Ion Channels; D008565:Membrane Proteins; D009579:Nitrobenzoates; D010750:Phosphoproteins; D014316:Tritium; C069141:phospholemman; D013654:Taurine; D005576:Colforsin; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C047983:1,9-dideoxyforskolin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid