Molecular basis of calmodulin tethering and Ca2+-dependent inactivation of L-type Ca2+ channels.

Published

Journal Article

Ca(2+)-dependent inactivation (CDI) of L-type Ca(2+) channels plays a critical role in controlling Ca(2+) entry and downstream signal transduction in excitable cells. Ca(2+)-insensitive forms of calmodulin (CaM) act as dominant negatives to prevent CDI, suggesting that CaM acts as a resident Ca(2+) sensor. However, it is not known how the Ca(2+) sensor is constitutively tethered. We have found that the tethering of Ca(2+)-insensitive CaM was localized to the C-terminal tail of alpha(1C), close to the CDI effector motif, and that it depended on nanomolar Ca(2+) concentrations, likely attained in quiescent cells. Two stretches of amino acids were found to support the tethering and to contain putative CaM-binding sequences close to or overlapping residues previously shown to affect CDI and Ca(2+)-independent inactivation. Synthetic peptides containing these sequences displayed differences in CaM-binding properties, both in affinity and Ca(2+) dependence, leading us to propose a novel mechanism for CDI. In contrast to a traditional disinhibitory scenario, we suggest that apoCaM is tethered at two sites and signals actively to slow inactivation. When the C-terminal lobe of CaM binds to the nearby CaM effector sequence (IQ motif), the braking effect is relieved, and CDI is accelerated.

Full Text

Duke Authors

Cited Authors

  • Pitt, GS; Zühlke, RD; Hudmon, A; Schulman, H; Reuter, H; Tsien, RW

Published Date

  • August 17, 2001

Published In

Volume / Issue

  • 276 / 33

Start / End Page

  • 30794 - 30802

PubMed ID

  • 11408490

Pubmed Central ID

  • 11408490

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M104959200

Language

  • eng

Conference Location

  • United States