title: The active zone protein family ELKS supports Ca2+ influx at nerve terminals of inhibitory hippocampal neurons.
abstract: In a presynaptic nerve terminal, synaptic vesicle exocytosis is restricted to specialized sites called active zones. At these sites, neurotransmitter release is determined by the number of releasable vesicles and their probability of release. Proteins at the active zone set these parameters by controlling the presynaptic Ca(2+) signal, and through docking and priming of synaptic vesicles. Vertebrate ELKS proteins are enriched at presynaptic active zones, but their functions are not well understood. ELKS proteins are produced by two genes in vertebrates, and each gene contributes ∼50% to total brain ELKS. We generated knock-out mice for ELKS1 and found that its constitutive removal causes lethality. To bypass lethality, and to circumvent redundancy between ELKS1 and ELKS2 in synaptic transmission, we used a conditional genetic approach to remove both genes in cultured hippocampal neurons after synapses are established. Simultaneous removal of ELKS1 and ELKS2 resulted in a 50% decrease of neurotransmitter release at inhibitory synapses, paralleled by a reduction in release probability. Removal of ELKS did not affect synapse numbers or their electron microscopic appearance. Using Ca(2+) imaging, we found that loss of ELKS caused a 30% reduction in single action potential-triggered Ca(2+) influx in inhibitory nerve terminals, consistent with the deficits in synaptic transmission and release probability. Unlike deletion of the active zone proteins RIM, RIM-BP, or bruchpilot, ELKS removal did not lead to a measurable reduction in presynaptic Ca(2+) channel levels. Our results reveal that ELKS is required for normal Ca(2+) influx at nerve terminals of inhibitory hippocampal neurons.
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and.
authors.forename: Changliang
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and.
authors.forename: Lydia S
authors.initials: LS
authors.lastname: Bickford
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Held
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and.
authors.forename: Hajnalka
authors.initials: H
authors.lastname: Nyitrai
authors.affiliation: Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California 94305 tcs1@stanford.edu kaeser@hms.harvard.edu.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Südhof
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and Department of Molecular and Cellular Physiology and tcs1@stanford.edu kaeser@hms.harvard.edu.
authors.forename: Pascal S
authors.initials: PS
authors.lastname: Kaeser
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D005260:Female; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D020691:rab GTP-Binding Proteins
chemical_list: D002352:Carrier Proteins; C486769:Erc1 protein, mouse; D009419:Nerve Tissue Proteins; D020691:rab GTP-Binding Proteins; D002118:Calcium
keywords: ELKS; active zone; calcium; knock-out; priming