QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online May 24, 2005
Journal of Experimental Biology 208, 2191-2203 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01616

This Article Figures Only Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Steger, K. A. Articles by Avery, L. Search for Related Content PubMed PubMed Citation Articles by Steger, K. A. Articles by Avery, L. Social Bookmarking                         What's this?

The C. elegans T-type calcium channel CCA-1 boosts neuromuscular transmission

Katherine A. Steger^1,*, Boris B. Shtonda^1,*, Colin Thacker², Terrance P. Snutch² and Leon Avery^1,

¹ Department of Molecular Biology, University of Texas, Southwestern Medical Center, Dallas, TX 75390, USA
² Department of Biotechnology Laboratory, University of British Columbia, Vancouver, BC, Canada

Author for correspondence (e-mail: leon{at}eatworms.swmed.edu)

Accepted 19 February 2005

Low threshold-activated or T-type calcium channels are postulated to mediate a variety of bursting and rhythmic electrical firing events. However, T-type channels' exact physiological contributions have been difficult to assess because of their incompletely defined pharmacology and the difficulty in isolating T-type currents from more robust high threshold calcium currents. A current in C. elegans pharyngeal muscle displays the kinetic features of a T-type calcium channel and is absent in animals homozygous for mutations at the cca-1 locus (see accompanying paper). cca-1 is expressed in pharyngeal muscle and encodes a protein (CCA-1) with strong homology to the ₁ subunits of vertebrate T-type channels. We show that CCA-1 plays a critical role at the pharyngeal neuromuscular junction, permitting the efficient initiation of action potentials in response to stimulation by the MC motor neuron. Loss of cca-1 function decreases the chance that excitatory input from MC will successfully trigger an action potential, and reduces the ability of an animal to take in food. Intracellular voltage recordings demonstrate that when wild-type cca-1 is absent, the depolarizing phase of the pharyngeal action potential tends to plateau or stall near -30 mV, the voltage at which the CCA-1 channel is likely to be activated. We conclude that the CCA-1 T-type calcium channel boosts the excitatory effect of synaptic input, allowing for reliable and rapid depolarization and contraction of the pharyngeal muscle. We also show that the pharyngeal muscle employs alternative strategies for initiating action potentials in certain cases of compromised MC motor neuron function.

Key words: calcium channel, T-type channel, neuromuscular junction, Caenorhabditis elegans, action potential

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				B. Shtonda and L. Avery CCA-1, EGL-19 and EXP-2 currents shape action potentials in the Caenorhabditis elegans pharynx J. Exp. Biol., June 1, 2005; 208(11): 2177 - 2190. [Abstract] [Full Text] [PDF]