Junctional sarcoplasmic reticulum motility in adult mouse ventricular myocytes

Benjamin M. Drum, Can Yuan, Ana de la Mata, Nathan Grainger, L. Fernando Santana

Research output: Contribution to journalArticle

Abstract

Excitation-contraction (EC) coupling is the coordinated process by which an action potential triggers cardiac myocyte contraction. EC coupling is initiated in dyads where the junctional sarcoplasmic reticulum (jSR) is in tight proximity to the sarcolemma of cardiac myocytes. Existing models of EC coupling critically depend on dyad stability to ensure the fidelity and strength of EC coupling, where even small variations in ryanodine receptor channel and voltage-gated calcium channel-α 1.2 subunit separation dramatically alter EC coupling. However, dyadic motility has never been studied. Here, we developed a novel strategy to track specific jSR units in dissociated adult ventricular myocytes using photoactivatable fluorescent proteins. We found that the jSR is not static. Instead, we observed dynamic formation and dissolution of multiple dyadic junctions regulated by the microtubule-associated molecular motors kinesin-1 and dynein. Our data support a model where reproducibility of EC coupling results from the activation of a temporally averaged number of SR Ca2+ release units forming and dissolving SR-sarcolemmal junctions. These findings challenge the long-held view that the jSR is an immobile structure and provide insights into the mechanisms underlying its motility.

Original languageEnglish (US)
Pages (from-to)C598-C604
JournalAmerican journal of physiology. Cell physiology
Volume318
Issue number3
DOIs
StatePublished - Mar 1 2020

Keywords

  • cardiomyocytes
  • dyadic plasticity
  • EC coupling
  • junctional sarcoplasmic reticulum
  • live imaging

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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