Presence of functional endothelin-1 receptors in nuclear membranes of human aortic vascular smooth muscle cells.
Our previous work showed that the nucleus plays a role in excitation-contraction coupling and that the channels and receptors could be present at the nuclear membrane. In the study reported here, the objective was to test the hypothesis that endothelin-1 (ET-1) receptors are functional at the level of the nuclear membranes and that their stimulation importantly regulates free nucleoplasmic Ca2+ level. Using a Fluo-3 Ca2+ measurement technique in human vascular smooth muscle cells (HVSMC), superfusion with increasing concentrations of extracellular ET-1 induced a dose-dependent sustained increase of free cytosolic ([Ca]c), nuclear ([Ca]n) Ca2+ and contraction with an EC50 near 3 x 10(-10) M. Like the extracellular ET-1, the cytosolic application of ET-1 using the perforated sarcolemma membrane technique, induced a dose-dependent increase of nuclear free calcium of HVSMC with an EC50 of 2 x 10(-11) M. These results strongly suggest that ET-1 receptors are functional at the level of the nuclear membranes. Furthermore, the sensitivity of ET-1 receptors at the nuclear membrane level seems to be higher than that of the receptors at the sarcolemma membrane. Finally, our results suggest that cytosolic ET-1 may play a role in preventing HVSMC nuclear calcium overload, thus protecting the cells from apoptosis.
Bkaily
G
G
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Québec, Canada. gbkail01@courrier.usherb.ca
Choufani
S
S
Hassan
G
G
El-Bizri
N
N
Jacques
D
D
D'Orléans-Juste
P
P
D000328:Adult; D001011:Aorta / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000032:analysis / Q000502:physiology*
D019332:Endothelin-1; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D002118:Calcium