Structural elements that underlie Doc2β function during asynchronous synaptic transmission.
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.
['Xue|Renhao|R|', 'Gaffaney|Jon D|JD|', 'Chapman|Edwin R|ER|']
D000818:Animals D002118:Calcium D002135:Calcium-Binding Proteins D002462:Cell Membrane D019706:Excitatory Postsynaptic Potentials D049452:Green Fluorescent Proteins D006624:Hippocampus D007700:Kinetics D008024:Ligands D008561:Membrane Fusion D018345:Mice, Knockout D050505:Mutant Proteins D009154:Mutation D009419:Nerve Tissue Proteins D009474:Neurons D009500:Neutralization Tests D016716:PC12 Cells D017433:Protein Structure, Secondary D017434:Protein Structure, Tertiary D021381:Protein Transport D051381:Rats D050600:SNARE Proteins D013329:Structure-Activity Relationship D009435:Synaptic Transmission D013572:Synaptic Vesicles D050863:Synaptotagmin I
Doc2β asynchronous synaptic transmission C2-domain synaptotagmin 1 Ca2+ sensor