Abstract
In nerve terminals, Ca(2+)-stimulated synaptic vesicle exocytosis is rapidly followed by endocytosis. Synaptic vesicle endocytosis requires clathrin-coated pits similar to receptor-mediated endocytosis in fibroblasts. Binding of clathrin AP-2 (adaptor complex) to an unidentified high affinity membrane receptor appears to be necessary for coated pit assembly in fibroblasts. We now show that synaptic vesicles have a high affinity AP-2 site (KD, approximately 1 x 10(-10) M) similar to the one observed in fibroblasts. Using a combination of competition and direct binding assays, we demonstrate that synaptotagmin I, an intrinsic membrane protein of synaptic vesicles, has all of the properties of the AP-2 receptor and that AP-2 binds to the second C2 domain in the molecule. Thus, synaptotagmin I may be a multifunctional protein with a function in endocytosis in addition to the previously proposed role in exocytosis.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Vesicular Transport
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Adenosine Triphosphate / metabolism
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Base Sequence
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Brain / metabolism*
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Calcium-Binding Proteins*
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Cell Membrane / metabolism
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Cell Membrane / ultrastructure
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Cell Polarity
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Clathrin / metabolism*
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Cytosol / metabolism
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Endocytosis
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Exocytosis
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Membrane Glycoproteins / genetics
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Membrane Glycoproteins / metabolism*
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Models, Biological
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Molecular Sequence Data
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism*
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Phosphoproteins / metabolism*
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Protein Binding
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Recombinant Fusion Proteins / metabolism
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Structure-Activity Relationship
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Synaptic Vesicles / metabolism*
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Synaptotagmin I
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Synaptotagmins
Substances
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Adaptor Proteins, Vesicular Transport
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Calcium-Binding Proteins
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Clathrin
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Membrane Glycoproteins
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Nerve Tissue Proteins
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Phosphoproteins
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Recombinant Fusion Proteins
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Synaptotagmin I
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Synaptotagmins
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Adenosine Triphosphate