| Annotated protein: | Signal-induced proliferation-associated 1-like protein 1 (SIPA1-like protein 1) (SPA-1-like protein p1294) (Spine-associated Rap GTPase-activating protein) (SPAR). Gene symbol: SIPA1L1. Taxonomy: Rattus norvegicus (Rat). Uniprot ID: O35412 |
| antibody wiki: | |
| SynGO gene info: | SynGO data @ SIPA1L1 |
| Ontology domain: | Cellular Component |
| SynGO term: | postsynapse (GO:0098794) |
| Synapse type(s): | hippocampus, glutamatergic |
| Annotated paper: | Pak DT, et al. "Regulation of dendritic spine morphology by SPAR, a PSD-95-associated RapGAP" Neuron. 2001 Aug 2;31(2):289-303 PMID:11502259 |
| Figure(s): | Fig 5, 6 |
| Annotation description: | Fig 5, SIPA1L1/SPAR is localized in the postsynaptic density of the majority of the excitatory synapses in cultured hippocampal neurons Literal: "SPAR immunoreactivity was present in all spiny neurons, concentrated in dendritic clusters that colocalized with PSD-95 (Figure 5A; Figure 5B1, arrowheads) and with α-actinin, a spine-enriched actin binding protein (Figure 5B2). SPAR clusters were apposed to, rather than precisely overlapping with, the synaptic vesicle protein synaptophysin (Figure 5B3), suggesting that SPAR is predominantly postsynaptic in distribution. The numerous SPAR clusters showed no colocalization with GAD puncta (Figure 5B4), indicating that SPAR is absent from inhibitory synapses present on the dendritic shafts of spiny neurons. The SPARn staining was eliminated by excess of the immunogen N-terminal peptide, but not by the C-terminal peptide (data not shown). Taken together, the above results indicate that SPAR is specifically concentrated in excitatory synapses/spines of pyramidal neurons in hippocampal culture. However, a significant fraction of PSD-95 puncta did not costain for SPAR (Figure 5B1, arrows). SPAR was present in only 68.9% ± 4.0% of excitatory synapses on spiny neurons, based on colocalization with PSD-95 clusters. As comparison, GKAP was present at 90.6% ± 1.0% of PSD-95-positive synapses. We measured the integrated staining intensity of PSD-95 clusters, and divided them into two groups with intensity above, or below, the mean. Only 8.8% ± 2.9% of the PSD-95 clusters with above-average staining intensity lacked associated SPAR staining, whereas 44.8% ± 4.5% of PSD-95 clusters with below-average intensity lacked SPAR (Figure 5C, inset). In keeping with the finding that SPAR is not present at all PSD-95-positive synapses, SPAR immunoreactivity was detected in only 65.6% ± 1.1% of dendritic spines (which were "filled" by cotransfected GFP) (Figure 5C). The presence of SPAR correlated with larger spines; only 7.7% ± 1.1% of spines with head width larger than the mean (>0.67 μm) did not stain for SPAR, whereas 45.4% ± 1.3% of spines below the mean size lacked SPAR (Figure 5C, inset). Thus, the presence of SPAR correlates with large spine head size as well as abundance of PSD-95." |
| Evidence tracking, Biological System: | Cultured neurons |
| Evidence tracking, Protein Targeting: | Antibody (detection) |
| Evidence tracking, Experiment Assay: | Confocal |
| Annotator(s): | Chiara Verpelli (ORCID:0000-0003-2949-9725) Carlo Sala (ORCID:0000-0003-0662-9523) |
| Lab: | CNR Neuroscience Institute Milan and Dept. of Biotechnology and Translational Medicine, University of Milan, 20129 Milan, Italy |
| SynGO annotation ID: | 1814 |
| Dataset release (version): | 20231201 |
| View annotation as GO-CAM model: |  |