Proline-Rich Synapse-Associated Protein-1/Cortactin Binding Protein 1 (ProSAP1/CortBP1) Is a PDZ-Domain Protein Highly Enriched in the Postsynaptic Density

Abstract

The postsynaptic density (PSD) is crucially involved in the structural and functional organization of the postsynaptic neurotransmitter reception apparatus. Using antisera against rat brain synaptic junctional protein preparations, we isolated cDNAs coding for proline-rich synapse-associated protein-1 (ProSAP1), a PDZ-domain protein. This protein was found to be identical to the recently described cortactin-binding protein-1 (CortBP1). Homology screening identified a related protein, ProSAP2. Specific antisera raised against a C-terminal fusion construct and a central part of ProSAP1 detect a cluster of immunoreactive bands of 180 kDa in the particulate fraction of rat brain homogenates that copurify with the PSD fraction. Transcripts and immunoreactivity are widely distributed in the brain and are upregulated during the period of synapse formation in the brain. In addition, two short N-terminal insertions are detected; they are differentially regulated during brain development. Confocal microscopy of hippocampal neurons showed that ProSAP1 is predominantly localized in synapses, and immunoelectron microscopy in situ revealed a strong association with PSDs of hippocampal excitatory synapses. The accumulation of ProSAP1 at synaptic structures was analyzed in the developing cerebral cortex. During early postnatal development, strong immunoreactivity is detectable in neurites and somata, whereas from postnatal day 10 (P10) onward a punctate staining is observed. At the ultrastructural level, the immunoreactivity accumulates at developing PSDs starting from P8. Both interaction with the actin-binding protein cortactin and early appearance at postsynaptic sites suggest that ProSAP1/ CortBP1 may be involved in the assembly of the PSD during neuronal differentiation.

The synaptic glycoprotein neuroplastin is involved in long-term potentiation at hippocampal CA1 synapses

“…Immunohistochemical experiments were performed as described (34). Np65 was detected in 7-m frontal and sagittal sections by using AS Ig1 (1:300) as primary antibody (22 h), followed by incubation with porcine anti-rabbit IgG (Dako) diluted 1:50 (30 min) and rabbit peroxidaseantiperoxidase complex (Dako) diluted 1:100 (30 min).…”

Cortactin: coupling membrane dynamics to cortical actin assembly

“…Yeast two hybrid screening of brain libraries with the cortactin SH3 domain led to the identi®cation of ®rst cortactin SH3 domain-binding protein, termed cortactin binding protein 1 (CortBP1) . Subsequent studies determined that CortBP1 is identical ProSAP1 (Boeckers et al, 1999a) and to a splice variant of Shank2 , which is a member of the Shank family of sca olding proteins (Sheng and Kim, 2000). Abundantly expressed in neurons, CortBP1 and the related protein Shank3 contain a canonical cortactin SH3 domain-binding sequence (KPPVPPKP) (Figure 2d) which mediates binding to cortactin .…”

The G Protein-coupled Receptor CL1 Interacts Directly with Proteins of the Shank Family

“…Shank (ProSAP) proteins are believed to function in the early development of the nervous system, based on the time course of Shank expression and its interaction with the actin-binding protein cortactin (19). The existence of an SAM domain identified in Shank proteins further underlines their potential roles in developmental regulation and/or synaptogenesis.…”

“…At present, the Shank family comprises three members: Shank1, Shank2, and Shank3. The Shank genes were independently cloned by several investigators and are hence known under different names, such as Shank (13), Synamon (16), ProSAP (19), CortBP (17), SSTRIP (18), and Spank (GenBank accession numbers AF159046, AF159047, and AF159048). Here, we use the name Shank to refer to the family as a whole.…”