Steady-state coupling of plasma membrane calcium entry to extrusion revealed by novel L-type calcium channel block

William C. Lester, Elizabeth A. Schroder, Don E. Burgess, Doug Yozwiak, Douglas A. Andres, Jonathan Satin

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The L-type Ca2+ channel (CaV1.2) is the main pathway for trans-sarcolemmal (SL) Ca2+ influx in cardiac myocytes. To maintain Ca2+ homeostasis, chronic SL Ca2+-influx must be matched by chronic SL efflux. In this study we tested the hypothesis that chronic down-regulation of SL Ca2+ entry regulates SL extrusion. We studied mRNA and Ca2+ handling responses to chronic down-regulation of Ca2+ channel current induced by over-expression of the small GTPase Rem. Rem lowered net SL diastolic Ca2+ entry, and reduced the twitch Ca2+ amplitude. Rem also significantly slowed Ca2+ transient decay kinetics (p < 10-3). Rem reduced NCX1.1 protein level and function. To measure Na-Ca2+ exchange (NCX) function and sarcoplasmic reticulum (SR) store load we perfused Ca2+-free bath for 25 s followed by rapid application of 50 mM caffeine. In control, caffeine transient relaxations were described by a bi-exponential decay with a fast phase that was 10 mM Ni2+-senstive. Rem significantly slowed caffeine-induced relaxation time course (Rem versus control, p < 10-6). To test whether extrusion slowing was mediated by insufficient basal Ca2+ for allosteric NCX activation we measured the effect of increasing bath Ca2+ from 1.8 to 6 mM on caffeine-induced relaxation kinetics. 6 mM Ca2+ did not alter kinetics of control cells, but in Rem-over-expressed cells 6 mM Ca2+ sped kinetics. We conclude that chronic block of CaV1.2 channel-mediated SL entry alters NCX expression, and coincidentally controls SR Ca loading and SL Ca2+ efflux.

Original languageEnglish
Pages (from-to)353-362
Number of pages10
JournalCell Calcium
Issue number4
StatePublished - Oct 2008

Bibliographical note

Funding Information:
We acknowledge Paul Cornelius and Ken Campbell for statistical and programming consultation, and Miranda Byse for constructive comments. We also are grateful to Zachary Fulkerson and Kristen Edenfield for support. Supported by NIH (HL074091 and HL072936). JS is an Established Investigator of the American Heart Association.


  • Ca channel
  • Calcium (cellular)
  • G-proteins
  • Na/Ca exchanger
  • Sarcolemma

ASJC Scopus subject areas

  • Physiology
  • Molecular Biology
  • Cell Biology


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