Crucial role of type 2 inositol 1,4,5-trisphosphate receptors for acetylcholine-induced Ca2+ oscillations in vascular myocytes.
OBJECTIVE
The aim of this study was to correlate the expression of InsP3R subtypes in native vascular and visceral myocytes with specific Ca2+-signaling patterns.


RESULTS
By Western blot and immunostaining, we showed that rat portal vein expressed InsP3R1 and InsP3R2 but not InsP3R3, whereas rat ureter expressed InsP3R1 and InsP3R3 but not InsP3R2. Acetylcholine induced single Ca2+ responses in all ureteric myocytes but only in 50% of vascular myocytes. In the remaining vascular myocytes, the first transient peak was followed by Ca2+ oscillations. By correlating Ca2+ signals and immunostaining, we revealed that oscillating vascular cells expressed both InsP3R1 and InsP3R2 whereas nonoscillating vascular cells expressed only InsP3R1. Acetylcholine-induced oscillations were not affected by inhibitors of ryanodine receptors, Ca2+-ATPases, Ca2+ influx, and mitochondrial Ca2+ uniporter but were inhibited by intracellular infusion of heparin. Using specific antibodies against InsP3R subtypes, we showed that acetylcholine-induced Ca2+ oscillations were specifically blocked by the anti-InsP3R antibody. These data were supported by antisense oligonucleotides targeting InsP3R2, which selectively inhibited Ca2+ oscillations.


CONCLUSIONS
Our results suggest that in native smooth muscle cells, a differential expression of InsP3R subtypes encodes specific InsP3-mediated Ca2+ responses and that the presence of the InsP3R2 subtype is required for acetylcholine-induced Ca2+ oscillations in vascular myocytes.
Morel
Jean-Luc
JL
Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017, Université Bordeaux 2, Bordeaux, France.
Fritz
Nicolas
N
Lavie
Jean-Louis
JL
Mironneau
Jean
J
D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000096:biosynthesis / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D032342:Muscle Cells / Q000737:chemistry / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D020033:Protein Isoforms / Q000096:biosynthesis / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000502:physiology*
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D000109:Acetylcholine; D002118:Calcium