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© The Rockefeller University Press,
0021-9525/2000//53 $5.00
The Journal of Cell Biology, Volume 151, Number 1,
, 2000 53-68
Original Article |
Synbindin, a Novel Syndecan-2–Binding Protein in Neuronal Dendritic Spines
Dendritic spines are small protrusions on the surface of dendrites that receive the vast majority of excitatory synapses. We previously showed that the cell-surface heparan sulfate proteoglycan syndecan-2 induces spine formation upon transfection into hippocampal neurons. This effect requires the COOH-terminal EFYA sequence of syndecan-2, suggesting that cytoplasmic molecules interacting with this sequence play a critical role in spine morphogenesis. Here, we report a novel protein that binds to the EFYA motif of syndecan-2. This protein, named synbindin, is expressed by neurons in a pattern similar to that of syndecan-2, and colocalizes with syndecan-2 in the spines of cultured hippocampal neurons. In transfected hippocampal neurons, synbindin undergoes syndecan-2–dependent clustering. Synbindin is structurally related to yeast proteins known to be involved in vesicle transport. Immunoelectron microscopy localized synbindin on postsynaptic membranes and intracellular vesicles within dendrites, suggesting a role in postsynaptic membrane trafficking. Synbindin coimmunoprecipitates with syndecan-2 from synaptic membrane fractions. Our results show that synbindin is a physiological syndecan-2 ligand on dendritic spines. We suggest that syndecan-2 induces spine formation by recruiting intracellular vesicles toward postsynaptic sites through the interaction with synbindin.
Key Words: heparan sulfate proteoglycan dendritic spines spine apparatus synapse vesicle transport
© 2000 The Rockefeller University Press
Abbreviations used in this paper: CNS, central nervous system; DIV, days in vitro; E, embryonic day; GFP, green fluorescent protein; GRIP, glutamate receptor–interacting protein; GST, glutathione-S-transferase; His, hexahistidine; HSPG, heparan sulfate proteoglycan; PSD, postsynaptic density; RT, reverse transcriptase; RyR-2, ryanodine receptor; SNARE, soluble NSF attachment protein receptor; TRAPP, transport protein particle.
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