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Rab3a interacting molecule (RIM) and the tethering of pre‐synaptic transmitter release site‐associated CaV2.2 calcium channels
Author(s) -
Wong Fiona K.,
Stanley Elise F.
Publication year - 2010
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2009.06466.x
Subject(s) - immunoprecipitation , synaptic vesicle , voltage dependent calcium channel , microbiology and biotechnology , neurotransmission , biophysics , calcium , chemistry , biology , synaptosome , vesicle , biochemistry , antibody , membrane , receptor , immunology , organic chemistry
Biochemical and physiological evidence suggest that pre‐synaptic calcium channels are attached to the transmitter release site within the active zone by a molecular tether. A recent study has proposed that ‘Rab3a Interacting Molecule’ (RIM) serves as the tether for CaV2.1 channels in mouse brain, based in part on biochemical co‐immunoprecipitation (co‐IP) using a monoclonal antibody, mRIM . We previously argued against this idea for CaV2.2 calcium channel at chick synapses based on experiments using a different anti‐RIM antibody, pRIM1,2 : while staining for the two proteins co‐localized and co‐varied at the transmitter release face, consistent with an association, they failed to co‐IP from a synaptosome membrane lysate. RIM is, however, a family of proteins and we tested the possibility that the mRIM antibody used in the more recent study identifies a particular channel‐tethering variant. We find that co‐immunostaining with mRIM and anti‐CaV2.2 antibody neither co‐localized nor co‐varied at the transmitter release face and the two proteins did not co‐IP, arguing against a common protein complex and a key CaV2.2 scaffolding role for RIM at the active zone. The differing results might be reconciled, however, in a model where a RIM family member contributes to a protein bridge that anchors the pre‐fusion secretory vesicle to the calcium channel protein complex.