QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

The Journal of Neuroscience, May 9, 2007, 27(19):5236-5248; doi:10.1523/JNEUROSCI.3545-06.2007

This Article Full Text Full Text (PDF) Supplemental Data Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Wykes, R. C. E. Articles by Seward, E. P. Search for Related Content PubMed PubMed Citation Articles by Wykes, R. C. E. Articles by Seward, E. P.

 Previous Article  |  Next Article 

Cellular/Molecular
Differential Regulation of Endogenous N- and P/Q-Type Ca²⁺ Channel Inactivation by Ca²⁺/Calmodulin Impacts on Their Ability to Support Exocytosis in Chromaffin Cells

Robert C. E. Wykes, ^*  Claudia S. Bauer, ^*  Saeed U. Khan, Jamie L. Weiss, and Elizabeth P. Seward

Department of Biomedical Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom

Correspondence should be addressed to Elizabeth P. Seward, Department of Biomedical Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. Email: e.p.seward{at}sheffield.ac.uk

P/Q-type (Ca_V2.1) and N-type (Ca_V2.2) Ca²⁺ channels are critical to stimulus-secretion coupling in the nervous system; feedback regulation of these channels by Ca²⁺ is therefore predicted to profoundly influence neurotransmission. Here we report divergent regulation of Ca²⁺-dependent inactivation (CDI) of native N- and P/Q-type Ca²⁺ channels by calmodulin (CaM) in adult chromaffin cells. Robust CDI of N-type channels was observed in response to prolonged step depolarizations, as well as repetitive stimulation with either brief step depolarizations or action potential-like voltage stimuli. Adenoviral expression of Ca²⁺-insensitive calmodulin mutants eliminated CDI of N-type channels. This is the first demonstration of CaM-dependent CDI of a native N-type channel. CDI of P/Q-type channels was by comparison modest and insensitive to expression of CaM mutants. Cloning of the C terminus of the Ca_V2.1 1 subunit from chromaffin cells revealed multiple splice variants lacking structural motifs required for CaM-dependent CDI. The physiological relevance of CDI on stimulus-coupled exocytosis was revealed by combining perforated-patch voltage-clamp recordings of pharmacologically isolated Ca²⁺ currents with membrane capacitance measurements of exocytosis. Increasing stimulus intensity to invoke CDI resulted in a significant decrease in the exocytotic efficiency of N-type channels compared with P/Q-type channels. Our results reveal unexpected diversity in CaM regulation of native Ca_V2 channels and suggest that the ability of individual Ca²⁺ channel subtypes to undergo CDI may be tailored by alternative splicing to meet the specific requirements of a particular cellular function.

Key words: voltage-gated calcium channels; Ca_V2.1; Ca_V2.2; calmodulin; chromaffin cells; exocytosis

---

Received Aug. 16, 2006; revised March 26, 2007; accepted March 28, 2007.

Correspondence should be addressed to Elizabeth P. Seward, Department of Biomedical Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. Email: e.p.seward{at}sheffield.ac.uk

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help