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Receptor Regulation of the Volume‐Sensitive Efflux of Taurine and Iodide from Human SH‐SY5Y Neuroblastoma Cells: Differential Requirements for Ca 2+ and Protein Kinase C
Author(s) -
Cheema Tooba Alam,
Pettigrew Veryan A.,
Fisher Stephen K.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a795
Subject(s) - taurine , osmolyte , protein kinase c , chemistry , efflux , osmotic concentration , receptor , endocrinology , medicine , biochemistry , biology , kinase , amino acid
Basal‐ and receptor‐stimulated efflux of 125 I − (used to trace Cl − ) and taurine have been monitored to determine whether these two osmolytes are released under hypotonic conditions via common or distinct mechanisms. Under basal conditions, both 125 I − and taurine were released in a volume‐dependent manner. Thrombin, mediated via the PAR‐1 subtype, significantly enhanced the release of both 125 I − and taurine (3–6‐fold) increasing the threshold osmolarity for efflux from 200 to 290 mOsM. Inclusion of anion channel blockers attenuated the release of both 125 I − and taurine under basal‐ and receptor‐stimulated conditions. Basal release of 125 I − and taurine was independent of Ca 2+ or the activity of protein kinase C (PKC). However, although PAR‐1‐stimulated taurine efflux was attenuated by either a depletion of intracellular Ca 2+ or inhibition of PKC, the enhanced release of 125 I − was independent of both parameters. Stimulated efflux of 125 I − following activation of muscarinic cholinergic receptors was also markedly less dependent on Ca 2+ availability and PKC activity than that observed for taurine release. These results indicate that the release of these two osmolytes from SH‐SY5Y cells may occur via pharmacologically similar membrane channels, but that the receptor‐mediated release of 125 I − and taurine is differentially regulated by PKC activity and Ca 2+ availability. NIH NS23831(SKF) and F31 NS053020 (TAC)