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.

Basal phosphorylation of sarcoplasmic reticulum (SR) Ca(2+) proteins is high in sinoatrial nodal cells (SANC), which generate partially synchronized, spontaneous, rhythmic, diastolic local Ca(2+) releases (LCRs), but low in ventricular myocytes (VM), which exhibit rare diastolic, stochastic SR-generated Ca(2+) sparks. We tested the hypothesis that in a physiologic Ca(2+) milieu, and independent of increased Ca(2+) influx, an increase in basal phosphorylation of SR Ca(2+) cycling proteins will convert stochastic Ca(2+) sparks into periodic, high-power Ca(2+) signals of the type that drives SANC normal automaticity. We measured phosphorylation of SR-associated proteins, phospholamban (PLB) and ryanodine receptors (RyR), and spontaneous local Ca(2+) release characteristics (LCR) in permeabilized single, rabbit VM in physiologic [Ca(2+)], prior to and during inhibition of protein phosphatase (PP) and phosphodiesterase (PDE), or addition of exogenous cAMP, or in the presence of an antibody (2D12), that specifically inhibits binding of the PLB to SERCA-2. In the absence of the aforementioned perturbations, VM could only generate stochastic local Ca(2+) releases of low power and low amplitude, as assessed by confocal Ca(2+) imaging and spectral analysis. When the kinetics of Ca(2+) pumping into the SR were increased by an increase in PLB phosphorylation (via PDE and PP inhibition or addition of cAMP) or by 2D12, self-organized, "clock-like" local Ca(2+) releases, partially synchronized in space and time (Ca(2+) wavelets), emerged, and the ensemble of these rhythmic local Ca(2+) wavelets generated a periodic high-amplitude Ca(2+) signal. Thus, a Ca(2+) clock is not specific to pacemaker cells, but can also be unleashed in VM when SR Ca(2+) cycling increases and spontaneous local Ca(2+) release becomes partially synchronized. This unleashed Ca(2+) clock that emerges in a physiological Ca(2+) milieu in VM has two faces, however: it can provoke ventricular arrhythmias; or if harnessed, can be an important feature of novel bio-pacemaker designs.

Sirenko S ，Maltsev VA ，Maltseva LA ，Yang D ，Lukyanenko Y ，Vinogradova TM ，Jones LR ，Lakatta EG ... -  《-》

Unique Ca(2+)-Cycling Protein Abundance and Regulation Sustains Local Ca(2+) Releases and Spontaneous Firing of Rabbit Sinoatrial Node Cells.

Vinogradova TM ，Tagirova Sirenko S ，Lakatta EG 《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

Ca²⁺-dependent phosphorylation of Ca²⁺ cycling proteins generates robust rhythmic local Ca²⁺ releases in cardiac pacemaker cells.

Sirenko S ，Yang D ，Li Y ，Lyashkov AE ，Lukyanenko YO ，Lakatta EG ，Vinogradova TM ... -  《-》

Phosphoprotein Phosphatase 1 but Not 2A Activity Modulates Coupled-Clock Mechanisms to Impact on Intrinsic Automaticity of Sinoatrial Nodal Pacemaker Cells.

Sirenko ST ，Zahanich I ，Li Y ，Lukyanenko YO ，Lyashkov AE ，Ziman BD ，Tarasov KV ，Younes A ，Riordon DR ，Tarasova YS ，Yang D ，Vinogradova TM ，Maltsev VA ，Lakatta EG ... -  《Cells》

CaMKII-dependent phosphorylation regulates basal cardiac pacemaker function via modulation of local Ca2+ releases.

Li Y ，Sirenko S ，Riordon DR ，Yang D ，Spurgeon H ，Lakatta EG ，Vinogradova TM ... -  《-》