To establish links between physiological regulation of the LCR period and kinetics of SR Ca2+ refilling we employed, as indexes of SR pumping rate and LCR period, phosphorylation of phospholamban (PLB) and the time to 90% decay of the AP-initiated global cytosolic Ca2+ transient (T-90). Graded PLB phosphorylation by -AR stimulation (ISO), a broad-spectrum phosphodiesterase inhibitor (IBMX), specific phosphodiesterase-3 inhibitor (milrinone), or by specific PKA inhibitor peptide (PKI) were paralleled by proportional changes in T-90. Concurrent changes in T-90 and LCR period were highly correlated with concurrent changes in the spontaneous cycle length. The comparison of SR Ca loading in permeabilized SANC and VM demonstrated that it is similar or larger in VM than in SANC over a wide range of free Ca2+: 50 - 250 nmol/L. However, SANC, compared to VM, spontaneously released 2-3 fold more Ca2+, suggesting that at a given SR Ca load, SR Ca2+ cycling in skinned SANC is more robust than in skinned VM. Elevation of cytosolic Ca2+ from 0 to 150 nmol/L increased PLB phosphorylation 80% at PKA-dependent site and 37% at CaMKII-dependent site in SANC, but not in VM. While phosphorylation of the CaMKII-dependent site in SANC is Ca2+-dependent, the phosphorylation of PKA-dependent site is due to an increase in Ca2+-activated adenylyl cyclase activity which is also activated by an increase in Ca2+. It is known that RyR Ca release is dependent not only from SR Ca2+ content but also from RyR Ca2+ release, and increase in RyR phosphorylation at 2809 site makes RyR more leaky elevating RyR Ca2+ release. Increase in cytosolic Ca2+ increased RyR phosphorylation at 2809 site and this effect is reversed by either inhibition of PKA or CaMKII. Thus, a unique combination of PKA-and CaMKII-dependent phosphorylation of Ca2+ cycling proteins, responsible for release and reuptake in SANC, sustain robust basal SR Ca cycling in SANC to drive primary pacemaker cell automaticity.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
1ZIAAG000260-02
Application #
7963904
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
2
Fiscal Year
2009
Total Cost
$304,949
Indirect Cost
Name
National Institute on Aging
Department
Type
DUNS #
City
State
Country
Zip Code
Vinogradova, Tatiana M; Tagirova Sirenko, Syevda; Lakatta, Edward G (2018) Unique Ca2+-Cycling Protein Abundance and Regulation Sustains Local Ca2+ Releases and Spontaneous Firing of Rabbit Sinoatrial Node Cells. Int J Mol Sci 19:
Sirenko, Syevda G; Maltsev, Victor A; Yaniv, Yael et al. (2016) Electrochemical Na+ and Ca2+ gradients drive coupled-clock regulation of automaticity of isolated rabbit sinoatrial nodal pacemaker cells. Am J Physiol Heart Circ Physiol 311:H251-67
Li, Yue; Sirenko, Syevda; Riordon, Daniel R et al. (2016) CaMKII-dependent phosphorylation regulates basal cardiac pacemaker function via modulation of local Ca2+ releases. Am J Physiol Heart Circ Physiol 311:H532-44
Sirenko, Syevda; Maltsev, Victor A; Maltseva, Larissa A et al. (2014) Sarcoplasmic reticulum Ca2+ cycling protein phosphorylation in a physiologic Ca2+ milieu unleashes a high-power, rhythmic Ca2+ clock in ventricular myocytes: relevance to arrhythmias and bio-pacemaker design. J Mol Cell Cardiol 66:106-15
Sirenko, Syevda; Yang, Dongmei; Li, Yue et al. (2013) Ca²?-dependent phosphorylation of Ca²? cycling proteins generates robust rhythmic local Ca²? releases in cardiac pacemaker cells. Sci Signal 6:ra6
Lakatta, Edward G; Maltsev, Victor A (2012) Rebuttal: what I(f) the shoe doesn't fit? ""The funny current has a major pacemaking role in the sinus node"". Heart Rhythm 9:459-60
Zahanich, Ihor; Sirenko, Syevda G; Maltseva, Larissa A et al. (2011) Rhythmic beating of stem cell-derived cardiac cells requires dynamic coupling of electrophysiology and Ca cycling. J Mol Cell Cardiol 50:66-76
Vinogradova, Tatiana M; Brochet, Didier X P; Sirenko, Syevda et al. (2010) Sarcoplasmic reticulum Ca2+ pumping kinetics regulates timing of local Ca2+ releases and spontaneous beating rate of rabbit sinoatrial node pacemaker cells. Circ Res 107:767-75
Vinogradova, Tatiana M; Lakatta, Edward G (2009) Regulation of basal and reserve cardiac pacemaker function by interactions of cAMP-mediated PKA-dependent Ca2+ cycling with surface membrane channels. J Mol Cell Cardiol 47:456-74
Lyashkov, Alexey E; Vinogradova, Tatiana M; Zahanich, Ihor et al. (2009) Cholinergic receptor signaling modulates spontaneous firing of sinoatrial nodal cells via integrated effects on PKA-dependent Ca(2+) cycling and I(KACh). Am J Physiol Heart Circ Physiol 297:H949-59

Showing the most recent 10 out of 11 publications