The Molecular Architecture of Ribbon Presynaptic Terminals |
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Authors: | George Zanazzi Gary Matthews |
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Institution: | (1) Department of Neurobiology & Behavior, State University of New York, Stony Brook, NY 11794-5230, USA;(2) Department of Neurobiology & Behavior, Graduate Program in Neuroscience, State Universtiy of New York, Stony Brook, NY 11794-5230, USA |
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Abstract: | The primary receptor neurons of the auditory, vestibular, and visual systems encode a broad range of sensory information by
modulating the tonic release of the neurotransmitter glutamate in response to graded changes in membrane potential. The output
synapses of these neurons are marked by structures called synaptic ribbons, which tether a pool of releasable synaptic vesicles
at the active zone where glutamate release occurs in response to calcium influx through L-type channels. Ribbons are composed
primarily of the protein, RIBEYE, which is unique to ribbon synapses, but cytomatrix proteins that regulate the vesicle cycle
in conventional terminals, such as Piccolo and Bassoon, also are found at ribbons. Conventional and ribbon terminals differ,
however, in the size, molecular composition, and mobilization of their synaptic vesicle pools. Calcium-binding proteins and
plasma membrane calcium pumps, together with endomembrane pumps and channels, play important roles in calcium handling at
ribbon synapses. Taken together, emerging evidence suggests that several molecular and cellular specializations work in concert
to support the sustained exocytosis of glutamate that is a hallmark of ribbon synapses. Consistent with its functional importance,
abnormalities in a variety of functional aspects of the ribbon presynaptic terminal underlie several forms of auditory neuropathy
and retinopathy. |
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Keywords: | Sensory Hair cell Retina Pinealocyte RIBEYE L-type calcium channel Glutamate Synaptic vesicle Exocytosis Endocytosis |
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