The interplay between plasma membrane and endoplasmic reticulum Ca^sup 2+^ATPases in agonist-induced temporal Ca^sup 2+^ dynamics

• Published in: Journal of bioenergetics and biomembranes Vol. 46; no. 6; p. 503
• Main Authors: Cicek, Figen Amber, Ozgur, Ekin Ozge, Ozgur, Erol, Ugur, Mehmet
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.12.2014
• Subjects: Adenosine triphosphatase; Membranes; Plasma
• ISSN: 0145-479X; 1573-6881
• DOI: 10.1007/s10863-014-9587-3

A change in the intracellular free Ca^sup 2+^ concentration ([Ca^sup 2+^]^sub i^) functions as a transmitter for signal transduction and shows a broad temporal pattern. Even genetically homogeneous cell types show different Ca^sup 2+^ response patterns under permanent agonist stimulation. In Ca^sup 2+^ signaling, the dynamics of the Ca^sup 2+^ release from the Ca^sup 2+^ channels during continuous agonist stimulation and the simultaneous effect of the pumps are unclear. In this study, the dynamic interaction of the Ca^sup 2+^ ATPases in the plasma membrane (PMCA) and the endoplasmic reticulum membrane (SERCA) during continuous ACh stimulation is monitored using Fluo-3 and Fura-2 loaded HEK 293 cells. We characterize Ca^sup 2+^ release patterns at the sub-maximal and maximal stimulation doses in the absence of extracellular Ca^sup 2+^. We analyze the responses regarding their types, oscillation frequency and response times. La^sup 3+^ (PMCA blocker) do not change the frequency and time courses in sub-maximal ACh treatment, while with the maximal stimulation oscillation frequency increase as oscillations superimpose on robust release, and response time of [Ca^sup 2+^]^sub i^ is elongated. A similar effect of La^sup 3+^ is observed in quantal Ca^sup 2+^ release phenomenon. In the presence of CPA, a SERCA blocker, oscillations are completely abolished, but response time does not change. We also observe that during continuous receptor stimulation, Ca^sup 2+^ release do not cease. These data may suggest that Ca^sup 2+^ release continues during agonist stimulation, but SERCA and PMCA form a new steady state and return [Ca^sup 2+^]^sub i^ to its physiological concentration.[PUBLICATION ABSTRACT]