Modulation of CaV2.1 channels by the neuronal calcium-binding protein visinin-like protein-2.
CaV2.1 channels conduct P/Q-type Ca2+ currents that are modulated by calmodulin (CaM) and the structurally related Ca2+-binding protein 1 (CaBP1). Visinin-like protein-2 (VILIP-2) is a CaM-related Ca2+-binding protein expressed in the neocortex and hippocampus. Coexpression of CaV2.1 and VILIP-2 in tsA-201 cells resulted in Ca2+ channel modulation distinct from CaM and CaBP1. CaV2.1 channels with beta2a subunits undergo Ca2+-dependent facilitation and inactivation attributable to association of endogenous Ca2+/CaM. VILIP-2 coexpression does not alter facilitation measured in paired-pulse experiments but slows the rate of inactivation to that seen without Ca2+/CaM binding and reduces inactivation of Ca2+ currents during trains of repetitive depolarizations. CaV2.1 channels with beta1b subunits have rapid voltage-dependent inactivation, and VILIP-2 has no effect on the rate of inactivation or facilitation of the Ca2+ current. In contrast, when Ba2+ replaces Ca2+ as the charge carrier, VILIP-2 slows inactivation. The effects of VILIP-2 are prevented by deletion of the CaM-binding domain (CBD) in the C terminus of CaV2.1 channels. However, both the CBD and an upstream IQ-like domain must be deleted to prevent VILIP-2 binding. Our results indicate that VILIP-2 binds to the CBD and IQ-like domains of CaV2.1 channels like CaM but slows inactivation, which enhances facilitation of CaV2.1 channels during extended trains of stimuli. Comparison of VILIP-2 effects with those of CaBP1 indicates striking differences in modulation of both facilitation and inactivation. Differential regulation of CaV2.1 channels by CaM, VILIP-2, CaBP1, and other neurospecific Ca2+-binding proteins is a potentially important determinant of Ca2+ entry in neurotransmission.
Lautermilch
Nathan J
NJ
Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA.
Few
Alexandra P
AP
Scheuer
Todd
T
Catterall
William A
WA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000166:cytology; D008564:Membrane Potentials / Q000502:physiology; D051596:Neurocalcin / Q000235:genetics / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology; D014162:Transfection
D002118:Calcium; D020864:Calcium Channels, N-Type; D051596:Neurocalcin; D018377:Neurotransmitter Agents; C496687:NVP2 protein, rat