In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 42 ( 2009-10-20), p. 18028-18033
Abstract:
As the most prototypical G protein-coupled receptor, β-adrenergic receptor (βAR) regulates the pace and strength of heart beating by enhancing and synchronizing L-type channel (LCC) Ca 2+ influx, which in turn elicits greater sarcoplasmic reticulum (SR) Ca 2+ release flux via ryanodine receptors (RyRs). However, whether and how βAR-protein kinase A (PKA) signaling directly modulates RyR function remains elusive and highly controversial. By using unique single-channel Ca 2+ imaging technology, we measured the response of a single RyR Ca 2+ release unit, in the form of a Ca 2+ spark, to its native trigger, the Ca 2+ sparklet from a single LCC. We found that acute application of the selective βAR agonist isoproterenol (1 μM, ≤20 min) increased triggered spark amplitude in an LCC unitary current-independent manner. The increased ratio of Ca 2+ release flux underlying a Ca 2+ spark to SR Ca 2+ content indicated that βAR stimulation helps to recruit additional RyRs in synchrony. Quantification of sparklet-spark kinetics showed that βAR stimulation synchronized the stochastic latency and increased the fidelity (i.e., chance of hit) of LCC-RyR intermolecular signaling. The RyR modulation was independent of the increased SR Ca 2+ content. The PKA antagonists Rp-8-CPT-cAMP (100 μM) and H89 (10 μM) both eliminated these effects, indicating that βAR acutely modulates RyR activation via the PKA pathway. These results demonstrate unequivocally that RyR activation by a single LCC is accelerated and synchronized during βAR stimulation. This molecular mechanism of sympathetic regulation will permit more fundamental studies of altered βAR effects in cardiovascular diseases.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0906560106
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2009
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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