The recombinant human TRPV6 channel functions as Ca2+ sensor in human embryonic kidney and rat basophilic leukemia cells.
The activation mechanism of the recently cloned human transient receptor potential vanilloid type 6 (TRPV6) channel, originally termed Ca(2+) transporter-like protein and Ca(2+) transporter type 1, was investigated in whole-cell patch-clamp experiments using transiently transfected human embryonic kidney and rat basophilic leukemia cells. The TRPV6-mediated currents are highly Ca(2+)-selective, show a strong inward rectification, and reverse at positive potentials, which is similar to store-operated Ca(2+) entry in electrically nonexcitable cells. The gating of TRPV6 channels is strongly dependent on the cytosolic free Ca(2+) concentration; lowering the intracellular free Ca(2+) concentration results in Ca(2+) influx, and current amplitude correlates with the intracellular EGTA or BAPTA concentration. This is also the case for TRPV6-mediated currents in the absence of extracellular divalent cations; compared with endogenous currents in nontransfected rat basophilic leukemia cells, these TRPV6-mediated monovalent currents reveal differences in reversal potential, inward rectification, and slope at very negative potentials. Release of stored Ca(2+) by inositol 1,4,5-trisphosphate and/or the sarco/endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin appears not to be involved in TRPV6 channel gating in both cell lines but, in rat basophilic leukemia cells, readily activates the endogenous Ca(2+) release-activated Ca(2+) current. In conclusion, TRPV6, expressed in human embryonic kidney cells and in rat basophilic leukemia cells, functions as a Ca(2+)-sensing Ca(2+) channel independently of procedures known to deplete Ca(2+) stores.
Institut für Pharmakologie und Toxikologie, Universität des Saarlandes, D-66421 Homburg, Germany. matthias.boedding@uniklinik-saarland.de
Matthias
M
Bödding
Ulrich
U
Wissenbach
Veit
V
Flockerzi
D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism* / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002412:Cations; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007938:Leukemia / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D050916:TRPV Cation Channels; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D002412:Cations; D002614:Chelating Agents; D018076:DNA, Complementary; D011994:Recombinant Proteins; D050916:TRPV Cation Channels; C120776:TRPV6 channel; D004533:Egtazic Acid; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium