The L-type voltage-dependent Ca2+ channel EGL-19 controls body wall muscle function in Caenorhabditis elegans

Abstract

Caenorhabditis elegans is a powerful model system widely used to investigate the relationships between genes and complex behaviors like locomotion. However, physiological studies at the cellular level have been restricted by the difficulty to dissect this microscopic animal. Thus, little is known about the properties of body wall muscle cells used for locomotion. Using in situ patch clamp technique, we show that body wall muscle cells generate spontaneous spike potentials and develop graded action potentials in response to injection of positive current of increasing amplitude. In the presence of K+ channel blockers, membrane depolarization elicited Ca2+ currents inhibited by nifedipine and exhibiting Ca2+-dependent inactivation. Our results give evidence that the Ca2+ channel involved belongs to the L-type class and corresponds to EGL-19, a putative Ca2+ channel originally thought to be a member of this class on the basis of genomic data. Using Ca2+ fluorescence imaging on patch-clamped muscle cells, we demonstrate that the Ca2+ transients elicited by membrane depolarization are under the control of Ca2+ entry through L-type Ca2+ channels. In reduction of function egl-19 mutant muscle cells, Ca2+ currents displayed slower activation kinetics and provided a significantly smaller Ca2+ entry, whereas the threshold for Ca2+ transients was shifted toward positive membrane potentials.

Scalable electrophysiology in intact small animals with nanoscale suspended electrode arrays

“…As further confirmation that nano-SPEARs record electrophysiological activity from the body-wall muscles we found that egl-19(n582) and shk-1(ok1581) loss-of-function (lf) mutant worms show longer putative spike waveforms as compared to WT worms, which is consistent with previously reported patch-clamp electrophysiology data for body-wall muscle APs 7,33,34 (Fig. 3d–f, Supplementary Fig.…”

“…egl-19(lf) encodes L-type voltage-gated Ca 2+ channels 1,2 and shk-1(lf) encodes voltage-gated K + channels expressed in muscles 3,1 . The strain YX9 [ myo-3p∷NpHR∷ECFP;lin-15(+) ], 3X outcrossed was obtained from Anthony Fouad.…”

“…5). In addition, egl-19(lf) have been shown to have a longer inter-spike-interval (ISI) as compared to WT animals 33,34 . When we analyzed our nano-SPEARs recordings from egl-19(lf) animals we found that the mean spike width is more than 2 times longer than the mean WT width and the inter-spike interval is 50% greater than WT animals (p < 0.001, Fig.…”

Gap Junctions Synchronize Action Potentials and Ca2+ Transients in Caenorhabditis elegans Body Wall Muscle

“…Current models regarding C. elegans locomotion mostly focus on the roles of neurons in locomotion with relatively little mention of the body wall muscle (1, 2, 13, 30 -32), which was partly due to the lack of knowledge on the electrical properties of C. elegans body wall muscle. Earlier electrophysiological data and mathematical modeling led to the conclusion that C. elegans body wall muscle cells function as simple actuators and generate only graded membrane potential changes (14,53). However, more recent studies show that C. elegans body wall muscle cells actually fire all-ornone APs (28,29).…”

In vivo identification of genes that modify ether-a-go-go-related gene activity in Caenorhabditis elegans may also affect human cardiac arrhythmia

“…We found that this channel is activated at hyperpolarized potentials at which the wild-type channel is normally closed. In work from other laboratories, recordings from C. elegans muscle yield resting-membrane potentials ranging from Ϫ20 to Ϫ80 mV (13)(14)(15). In this voltage range, UNC-103 (n500) (if analogous in behavior to HERG A653T) could abnormally hyperpolarize the muscle (Fig.…”