%0 Journal Article
%T Ca2+/Calmodulin and Presynaptic Short-Term Plasticity
%A Sumiko Mochida
%J ISRN Neurology
%D 2011
%R 10.5402/2011/919043
%X Synaptic efficacy is remodeled by neuronal firing activity at the presynaptic terminal. Presynaptic activity-dependent changes in transmitter release induce postsynaptic plasticity, including morphological change in spine, gene transcription, and protein synthesis and trafficking. The presynaptic transmitter release is triggered and regulated by Ca2+, which enters through voltage-gated Ca2+ (CaV) channels and diffuses into the presynaptic terminal accompanying action potential firings. Residual Ca2+ is sensed by Ca2+-binding proteins, among other potential actions, it mediates time- and space-dependent synaptic facilitation and depression via effects on CaV2 channel gating and vesicle replenishment in the readily releasable pool (RRP). Calmodulin, a Ca2+-sensor protein with an EF-hand motif that binds Ca2+, interacts with CaV2 channels and autoreceptors in modulation of SNARE-mediated exocytosis. 1. Introduction For memory formation in a neuronal circuit, the primary function of presynaptic terminals is the firing activity-dependent release of neurotransmitters and subsequent recycling of their carrier synaptic vesicles, processes which critically depend on ATP and Ca2+. Presynaptic firing of action potentials activates voltage-gated Ca2+£¿£¿(CaV) channels, and Ca2+ entry initiates release of neurotransmitters. Ca2+£¿£¿dependence on fast neurotransmitter release is thought to be conferred by the synaptotagmin, a family of Ca2+ sensors that interact with SNAREs [1]. Synaptotagmin 1 and 2 are synaptic vesicle proteins with tandem C2 domains that bind Ca2+ and ensure the synchronization of Ca2+-dependent exocytosis with the presynaptic action potential [2¨C5]. Neuronal firing activity also controls other protein functions and dynamically remodels synaptic efficacy. Ca2+-binding proteins sensing residual Ca2+, which accumulates locally in the presynaptic terminal during trains of action potentials, may act as potential effectors for these reactions. Considerable evidence supports a role for calmodulin (CaM), another family of Ca2+ sensors with an EF hand motif that binds Ca2+, in modulation of SNARE-mediated exocytosis [6, 7] and endocytosis [8, 9]. Targets of CaM include multiple proteins implicated in exocytosis (e.g., Ca2+ channels [10], Ca2+/ CaM kinase II [11], rab3 [12], and Munc13 [13]), and endocytosis (e.g., calcinulin [14]). Another Ca2+-binding protein with an EF hand motif, parvalbumin, acts as a mobile presynaptic Ca2+ buffer that accelerates withdrawal of residual Ca2+ and decay of short-term facilitation in the calyx of held [15] and GABAergic
%U http://www.hindawi.com/journals/isrn.neurology/2011/919043/