The postsynaptic scaffold proteins ProSAP1/Shank2 and Homer1 are associated with glutamate receptor complexes at rat retinal synapses.
The postsynaptic density (PSD) at glutamatergic synapses is a macromolecular complex of various molecules that organize the different glutamate receptors spatially and link them to their appropriate downstream signaling pathways and to the cytoskeleton. Recently, a new family of multidomain proteins called Shanks or ProSAPs (proline-rich synapse-associated proteins) has been identified. They are suggested to be central adaptor proteins of the PSD of glutamatergic synapses, bridging different types of glutamate receptor complexes. With immunocytochemistry and light and electron microscopy, we examined the cellular, synaptic, and postnatal developmental expression of ProSAP1/Shank2 at the synapses of rat retina. With double-labeling experiments and confocal microscopy, we analyzed the association of ProSAP1/Shank2 with proteins specific for glutamatergic, glycinergic, and gamma-aminobutyric acid (GABA)ergic synapses and with proteins known to be involved in the structural and functional organization of PSDs containing N-methyl-D-aspartate receptors [95-kDa postsynaptic density protein (PSD-95)], group I metabotropic glutamate receptors (Homer1), and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors [glutamate receptor-interacting protein (GRIP)]. ProSAP1/Shank2 was present postsynaptically at the glutamatergic ribbon synapses of photoreceptor and bipolar cells, and it was absent from glycinergic and GABAergic amacrine cell synapses. The double-labeling experiments revealed a high rate of colocalization of ProSAP1/Shank2 with Homer1 and PSD-95, and little colocalization with GRIP. These data suggest that ProSAP1/Shank2 acts as an organizer at PSDs of different glutamatergic retinal synapses.
Brandstätter
Johann Helmut
JH
Max Planck Institute for Brain Research, Department of Neuroanatomy, D-60528 Frankfurt am Main, Germany. brandstaett@mpih-frankfurt.mpg.de
Dick
Oliver
O
Boeckers
Tobias M
TM
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis*; D000076122:Disks Large Homolog 4 Protein; D000072233:Homer Scaffolding Proteins; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000648:ultrastructure; D009479:Neuropeptides / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000378:metabolism / Q000648:ultrastructure; D017470:Receptors, Glutamate / Q000378:metabolism / Q000648:ultrastructure*; D012160:Retina / Q000378:metabolism / Q000648:ultrastructure*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure*
D002352:Carrier Proteins; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D000072233:Homer Scaffolding Proteins; C000606624:Homer1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; C033652:postsynaptic density proteins