TY - JOUR T1 - Critical Residues of the <em>Caenorhabditis elegans unc-2</em> Voltage-Gated Calcium Channel That Affect Behavioral and Physiological Properties JF - The Journal of Neuroscience JO - J. Neurosci. SP - 6537 LP - 6545 DO - 10.1523/JNEUROSCI.23-16-06537.2003 VL - 23 IS - 16 AU - Eleanor A. Mathews AU - Esperanza García AU - Celia M. Santi AU - Gregory P. Mullen AU - Colin Thacker AU - Donald G. Moerman AU - Terrance P. Snutch Y1 - 2003/07/23 UR - http://www.jneurosci.org/content/23/16/6537.abstract N2 - The Caenorhabditis elegans unc-2 gene encodes a voltage-gated calcium channel α1 subunit structurally related to mammalian dihydropyridine-insensitive high-threshold channels. In the present paper we describe the characterization of seven alleles of unc-2. Using an unc-2 promoter-tagged green fluorescent protein construct, we show that unc-2 is primarily expressed in motor neurons, several subsets of sensory neurons, and the HSN and VC neurons that control egg laying. Examination of behavioral phenotypes, including defecation, thrashing, and sensitivities to aldicarb and nicotine suggests that UNC-2 acts presynaptically to mediate both cholinergic and GABAergic neurotransmission. Sequence analysis of the unc-2 alleles shows that e55, ra605, ra606, ra609, and ra610 all are predicted to prematurely terminate and greatly reduce or eliminate unc-2 function. In contrast, the ra612 and ra614 alleles are missense mutations resulting in the substitution of highly conserved residues in the C terminus and the domain IVS4-IVS5 linker, respectively. Heterologous expression of a rat brain P/Q-type channel containing the ra612 mutation shows that the glycine to arginine substitution affects a variety of channel characteristics, including the voltage dependence of activation, steady-state inactivation, as well as channel kinetics. Overall, our findings suggest that UNC-2 plays a pivotal role in mediating a number of physiological processes in the nematode and also defines a number of critical residues important for calcium channel function in vivo. ER -