Down-regulation of Voltage-gated Ca2+ Channels by Neuronal Calcium Sensor-1 Is β Subunit-specific

Matthieu Rousset,Thierry Cens,Sophie Gavarini,Andreas Jeromin,Pierre Charnet

doi:10.1074/jbc.m209537200

Abstract

Neuronal Ca(2+) sensor protein-1 (NCS-1) is a member of the Ca(2+) binding protein family, with three functional Ca(2+) binding EF-hands and an N-terminal myristoylation site. NCS-1 is expressed in brain and heart during embryonic and postnatal development. In neurons, NCS-1 facilitates neurotransmitter release, but both inhibition and facilitation of the Ca(2+) current amplitude have been reported. In heart, NCS-1 co-immunoprecipitates with K(+) channels and modulates their activity, but the potential effects of NCS-1 on cardiac Ca(2+) channels have not been investigated. To directly assess the effect of NCS-1 on the various types of Ca(2+) channels we have co-expressed NCS-1 in Xenopus oocytes, with Ca(V)1.2, Ca(V)2.1, and Ca(V)2.2 Ca(2+) channels, using various subunit combinations. The major effect of NCS-1 was to decrease Ca(2+) current amplitude, recorded with the three different types of alpha(1) subunit. When expressed with Ca(V)2.1, the depression of Ca(2+) current amplitude induced by NCS-1 was dependent upon the identity of the beta subunit expressed, with no block recorded without beta subunit or with the beta(3) subunit. Current-voltage and inactivation curves were also slightly modified and displayed a different specificity toward the beta subunits. Taken together, these data suggest that NCS-1 is able to modulate cardiac and neuronal voltage-gated Ca(2+) channels in a beta subunit specific manner.

Highlights

Neuronal Ca2؉ sensor protein-1 (NCS-1) is a member of the Ca2؉ binding protein family, with three functional Ca2؉ binding EF-hands and an N-terminal myristoylation site
Our results show that NCS-1 down-regulates expression of L, N, and P/Q-type Ca2ϩ channels in a ␤ subunit-specific manner and induces minor modifications of the electrophysiological properties of the channel
X. laevis oocytes are a system of choice to study the functional effect of NCS-1 on voltage-gated Ca2ϩ channels

Summary

Introduction

Neuronal Ca2؉ sensor protein-1 (NCS-1) is a member of the Ca2؉ binding protein family, with three functional Ca2؉ binding EF-hands and an N-terminal myristoylation site. Current-voltage and inactivation curves were slightly modified and displayed a different specificity toward the ␤ subunits Taken together, these data suggest that NCS-1 is able to modulate cardiac and neuronal voltage-gated Ca2؉ channels in a ␤ subunit specific manner. Several types of Ca2ϩ channels have been characterized (T, L, N, P/Q, and R) that appear to play a specific role in each of these functions These channels share a common architecture composed of a major ␣1 subunit (for which ten genes are known) tightly associated with regulatory subunits ␣2-␦ (four different genes), ␤ (four genes), and possibly ␥ (eight genes) in a functional multimeric complex [1,2,3,4]. Effects on N-type Ca2ϩ channel (CaV2.2) properties have been reported [20], and the expression of NCS-1 in mammalian cardiac myocytes and subsequent effect on Kϩ channel expression [26] gave rise to the possibility that NCS-1 may regulate multiple types of Ca2ϩ channels and other voltage-dependent ion channels, in neurons [27]

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Conclusion