title: Delayed appearance of the scaffolding proteins PSD-95 and Homer-1 at the developing rat calyx of Held synapse.
abstract: The calyx of Held synapse is a giant axosomatic synapse that acts as a fast relay in the sound localization circuit of the brainstem. In rodents it forms within a relatively brief period starting around the second postnatal day (P2). The relative timing of the formation of its pre- and the postsynaptic compartment are not yet known. By means of fluorescent immunohistochemistry in neonatal rats we therefore compared the developmental expression patterns of the vesicular glutamate transporter (VGLUT)-1 and the postsynaptic density scaffolding proteins Homer-1 and PSD-95 in the medial nucleus of the trapezoid body (MNTB). Before its formation, colocalized punctate staining of VGLUT-1 and Homer-1 or PSD-95 was observed on principal neurons, in agreement with earlier work showing that they are already innervated by fibers from the cochlear nucleus before the calyx forms. The expression of VGLUT-1 clusters within the nascent calyx of Held synapse preceded the expression of Homer-1 and PSD-95 clusters, as indicated by the presence of principal neurons with only a large contiguous cluster (LCC) of VGLUT-1 at P2-3, whereas no neurons with only an LCC for Homer-1 or PSD-95 were seen. At P3 the first principal neurons with both a pre- and a postsynaptic LCC were observed, and at P12 all principal neurons had both a pre- and a postsynaptic LCC. The relatively late appearance of Homer-1 and PSD-95 within the developing calyx of Held synapse suggests that they play a role in its stabilization and the recruitment of additional receptors to its postsynaptic density.
authors.affiliation: Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, 3015 GE Rotterdam, The Netherlands.
authors.forename: John S
authors.initials: JS
authors.lastname: Soria Van Hoeve
authors.forename: J Gerard G
authors.initials: JG
authors.lastname: Borst
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000166:cytology* / Q000254:growth & development*; D002352:Carrier Proteins / Q000378:metabolism*; D000076122:Disks Large Homolog 4 Protein; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D000072233:Homer Scaffolding Proteins; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000378:metabolism*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D000072233:Homer Scaffolding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1