title: Structural elements that underlie Doc2β function during asynchronous synaptic transmission.
abstract: Double C2-like domain-containing proteins alpha and beta (Doc2α and Doc2β) are tandem C2-domain proteins proposed to function as Ca(2+) sensors for asynchronous neurotransmitter release. Here, we systematically analyze each of the negatively charged residues that mediate binding of Ca(2+) to the β isoform. The Ca(2+) ligands in the C2A domain were dispensable for Ca(2+)-dependent translocation to the plasma membrane, with one exception: neutralization of D220 resulted in constitutive translocation. In contrast, three of the five Ca(2+) ligands in the C2B domain are required for translocation. Importantly, translocation was correlated with the ability of the mutants to enhance asynchronous release when overexpressed in neurons. Finally, replacement of specific Ca(2+)/lipid-binding loops of synaptotagmin 1, a Ca(2+) sensor for synchronous release, with corresponding loops from Doc2β, resulted in chimeras that yielded slower kinetics in vitro and slower excitatory postsynaptic current decays in neurons. Together, these data reveal the key determinants of Doc2β that underlie its function during the slow phase of synaptic transmission.
authors.affiliation: Department of Neuroscience, University of Wisconsin, Madison, WI 53706; and Howard Hughes Medical Institute, University of Wisconsin, Madison, WI 53706.
authors.forename: Renhao
authors.initials: R
authors.lastname: Xue
authors.affiliation: Department of Neuroscience, University of Wisconsin, Madison, WI 53706; and Howard Hughes Medical Institute, University of Wisconsin, Madison, WI 53706.
authors.forename: Jon D
authors.initials: JD
authors.lastname: Gaffaney
authors.affiliation: Department of Neuroscience, University of Wisconsin, Madison, WI 53706; and Howard Hughes Medical Institute, University of Wisconsin, Madison, WI 53706 chapman@wisc.edu.
authors.forename: Edwin R
authors.initials: ER
authors.lastname: Chapman
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D019706:Excitatory Postsynaptic Potentials; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008561:Membrane Fusion; D018345:Mice, Knockout; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009500:Neutralization Tests; D016716:PC12 Cells; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D050600:SNARE Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000378:metabolism; D050863:Synaptotagmin I / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; C490422:Doc2b protein, rat; D008024:Ligands; D050505:Mutant Proteins; D009419:Nerve Tissue Proteins; D050600:SNARE Proteins; D050863:Synaptotagmin I; D049452:Green Fluorescent Proteins; D002118:Calcium
keywords: C2-domain; Ca2+ sensor; Doc2β; asynchronous synaptic transmission; synaptotagmin 1