title: Altered short-term synaptic plasticity and reduced muscle strength in mice with impaired regulation of presynaptic CaV2.1 Ca2+ channels.
abstract: Facilitation and inactivation of P/Q-type calcium (Ca(2+)) currents through the regulation of voltage-gated Ca(2+) (CaV) 2.1 channels by Ca(2+) sensor (CaS) proteins contributes to the facilitation and rapid depression of synaptic transmission in cultured neurons that transiently express CaV2.1 channels. To examine the modulation of endogenous CaV2.1 channels by CaS proteins in native synapses, we introduced a mutation (IM-AA) into the CaS protein-binding site in the C-terminal domain of CaV2.1 channels in mice, and tested synaptic facilitation and depression in neuromuscular junction synapses that use exclusively CaV2.1 channels for Ca(2+) entry that triggers synaptic transmission. Even though basal synaptic transmission was unaltered in the neuromuscular synapses in IM-AA mice, we found reduced short-term facilitation in response to paired stimuli at short interstimulus intervals in IM-AA synapses. In response to trains of action potentials, we found increased facilitation at lower frequencies (10-30 Hz) in IM-AA synapses accompanied by slowed synaptic depression, whereas synaptic facilitation was reduced at high stimulus frequencies (50-100 Hz) that would induce strong muscle contraction. As a consequence of altered regulation of CaV2.1 channels, the hindlimb tibialis anterior muscle in IM-AA mice exhibited reduced peak force in response to 50 Hz stimulation and increased muscle fatigue. The IM-AA mice also had impaired motor control, exercise capacity, and grip strength. Taken together, our results indicate that regulation of CaV2.1 channels by CaS proteins is essential for normal synaptic plasticity at the neuromuscular junction and for muscle strength, endurance, and motor coordination in mice in vivo.
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195-7280;
authors.forename: Evanthia
authors.initials: E
authors.lastname: Nanou
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195-7280;
authors.forename: Jin
authors.initials: J
authors.lastname: Yan
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195-7290.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Whitehead
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195-7290.
authors.forename: Min Jeong
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195-7290.
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Froehner
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195-7280;
authors.forename: Todd
authors.initials: T
authors.lastname: Scheuer
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195-7280; wcatt@uw.edu.
authors.forename: William A
authors.initials: WA
authors.lastname: Catterall
mesh_terms: D000818:Animals; D020864:Calcium Channels, N-Type / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D053580:Muscle Strength; D009469:Neuromuscular Junction / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D010805:Physical Conditioning, Animal; D009435:Synaptic Transmission
chemical_list: D020864:Calcium Channels, N-Type
keywords: calcium channels; calcium sensor proteins; calmodulin; synaptic facilitation; synaptic plasticity