Ca2+ uptake and release properties of a thapsigargin-insensitive nonmitochondrial Ca2+ store in A7r5 and 16HBE14o- cells.
In a previous study we overexpressed the thapsigargin (tg)-insensitive Pmr1 Ca(2+) pump of the Golgi apparatus of Caenorhabditis elegans in COS-1 cells and studied the properties of the Ca(2+) store into which it was integrated. Here we assessed the properties of an endogenous tg-insensitive nonmitochondrial Ca(2+) store in A7r5 and 16HBE14o- cells, which express a mammalian homologue of Pmr1. The tg-insensitive Ca(2+) store was considerably less leaky for Ca(2+) than the sarco(endo)plasmic-reticulum Ca(2+)-ATPase (SERCA)-containing Ca(2+) store. Moreover like for the worm Pmr1 Ca(2+) pump expressed in COS-1 cells, Ca(2+) accumulation into the endogenous tg-insensitive store showed a 2 orders of magnitude lower sensitivity to cyclopiazonic acid than the SERCA-mediated transport. 2,5-Di-(tert-butyl)-1,4-benzohydroquinone was only a very weak inhibitor of the tg-insensitive Ca(2+) uptake in A7r5 and 16HBE14o- cells and in COS-1 cells overexpressing the worm Pmr1. Inositol 1,4,5-trisphosphate released 11% of the Ca(2+) accumulated in permeabilized A7r5 cells pretreated with tg with an EC(50) that was 5 times higher than for the SERCA-containing Ca(2+) store but failed to release Ca(2+) in 16HBE14o- cells. In the presence of tg, 15% of intact A7r5 cells responded to 10 microm arginine-vasopressin with a small rise in cytosolic Ca(2+) concentration after a long latency. In conclusion, A7r5 and 16HBE14o- cells express a Pmr1-containing Ca(2+) store with properties that differ substantially from the SERCA-containing Ca(2+) store.
Missiaen
Ludwig
L
Laboratorium voor Fysiologie, K.U.Leuven Campus Gasthuisberg O/N, Herestraat 49, B-3000 Leuven, Belgium. Ludwig.Missiaen@med.kuleuven@ac.be
Vanoevelen
Jo
J
Parys
Jan B
JB
Raeymaekers
Luc
L
De Smedt
Humbert
H
Callewaert
Geert
G
Erneux
Christophe
C
Wuytack
Frank
F
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001980:Bronchi / Q000166:cytology; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D008928:Mitochondria / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection; D014667:Vasopressins / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D004791:Enzyme Inhibitors; D006873:Hydroquinones; D007211:Indoles; D014667:Vasopressins; C019359:2,5-di-tert-butylhydroquinone; D019284:Thapsigargin; D001120:Arginine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid