P2Y2 receptor-mediated Ca2+ signaling and spontaneous Ca2+ releases in human valvular myofibroblasts.
Valvular myofibroblasts (VMFs), being the most predominant cells in the cardiac valve, perform a variety of functions to maintain normal valvular physiology. These functions, such as contraction, proliferation, and wound repair, are all directly or indirectly mediated by intracellular Ca(2+) concentrations ([Ca (2+)](i)). Knowing how [Ca(2+)](i) is regulated by vasoactive agents in VMFs enriches the understanding of valvular biology in both health and diseases. In this study we examined the characteristics of purinergic agonist-induced [Ca(2+)] (i) responses and observed spontaneous Ca(2+) releases in cultured human VMFs. Secondary cultures of human mitral VMFs were incubated with the Ca(2+)-sensitive fluorescent indicator fura-2 or fluo-4 and visualized with fluorescence microscopy. Both ATP and UTP activated P(2Y2) receptors and induced endoplasmic reticulum (ER) Ca(2+) release and Ca(2+) influx. The lack of [Ca(2+)](i) responses in VMFs challenged with the selective P(2Y1) agonists ADPbetaS and 2-Me-S-ATP further supported that functional P(2Y2) receptors are responsible for the Ca(2+) signals. Finally, in a small number of VMFs spontaneous Ca(2+) releases in localized areas were observed. Blockade of the RyR elongated the latency period between each Ca(2+) releasing event, demonstrating the presence of functional RyRs in VMFs.
Liang
Willmann
W
School of Biological Sciences, Nanyang Technological University, Singapore.
McDonald
Paul
P
McManus
Bruce
B
van Breemen
Cornelis
C
Wang
Xiaodong
X
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D006351:Heart Valves / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007477:Ions; D008297:Male; D008875:Middle Aged; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058473:Receptors, Purinergic P2Y2
D007477:Ions; C546385:P2RY2 protein, human; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D002118:Calcium