title: Calyculin-A disrupts subplasmalemmal junction and recurring Ca2+ waves in vascular smooth muscle.
abstract: Excitation-contraction coupling (E-C coupling) in phenylephrine(PE)-stimulated rabbit inferior vena cava (IVC) depends on the generation of asynchronous recurring Ca2+ waves in the in situ vascular smooth muscle cells (VSMC). Previous studies by our group have implicated a putative non-selective cationic store-operated channel and the reverse-mode Na+-Ca2+ exchange in refilling of the intracellular Ca2+ store via the sarco/endoplasmic reticulum ATPase (SERCA) and the maintenance of the recurring Ca2+ waves. We hypothesize that for the proper functioning of these three Ca2+ translocators in the process of SR refilling, the plasma membrane (PM) and the underlying superficial sarcoplasmic reticulum (SR) form specialized PM-SR junctions, which are essential for the maintenance of the recurring Ca2+ waves. In order to test this hypothesis, calyculin-A, a serine/threonine phosphatase inhibitor that has been demonstrated to result in the disruption of the PM-SR junctions was used. In the control rabbit IVC, electron microscopy of the in situ VSMC indicates that 14.2+/-0.7% of the PM is closely apposed by the prominent superficial SR network, forming numerous flattened PM-SR junctional cytoplasmic spaces. In the control IVC stimulation with 5 microM PE resulted in sustained recurring Ca2+ waves with a frequency of 0.42+/-0.02 Hz. In calyculin-A treated rabbit IVC, a concentration-dependent dissociation of the superficial SR and loss of PM-SR junctions was observed. This progressive loss of the PM-SR junctions occurs over the same concentration range as the inhibition of PE-induced recurring Ca2+ waves. These findings offer support for the hypothesis that the presence of the PM-SR junctions is required for the generation of asynchronous recurring Ca2+ waves, which underlie excitation-contraction coupling in the VSMC of the rabbit IVC.
authors.affiliation: The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, University of British Columbia, St. Paul's Hospital, Room 166-1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6.
authors.forename: Cheng-Han
authors.initials: CH
authors.lastname: Lee
authors.forename: Kuo-Hsing
authors.initials: KH
authors.lastname: Kuo
authors.forename: Jiazhen
authors.initials: J
authors.lastname: Dai
authors.forename: Joyce M
authors.initials: JM
authors.lastname: Leo
authors.forename: Chun Yong
authors.initials: CY
authors.lastname: Seow
authors.forename: Cornelis van
authors.initials: Cv
authors.lastname: Breemen
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D008387:Marine Toxins; D046529:Microscopy, Electron, Transmission; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009924:Organ Culture Techniques; D010080:Oxazoles / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014682:Vena Cava, Inferior / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; C059041:calyculin A; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium