Annotated protein:MAGUK p55 subfamily member 2 (Protein MPP2). Gene symbol: MPP2. Taxonomy: Rattus norvegicus (Rat). Uniprot ID: D3ZAA9
antibody wiki:
SynGO gene info:SynGO data @ MPP2
Ontology domain:Biological Process
SynGO term:structural constituent of postsynaptic density (GO:0098919)
Synapse type(s):hippocampus, glutamatergic
Annotated paper:Rademacher N, et al. "MPP2 is a postsynaptic MAGUK scaffold protein that links SynCAM1 cell adhesion molecules to core components of the postsynaptic density" Sci Rep. 2016 Oct 19;6:35283 PMID:27756895
Figure(s):Fig. 1, 2, 3
Annotation description:MPP2 is a member of the p55 Stardust subfamily of MAGUK scaffold proteins.
MPP2 is expressed in the postsynaptic density of hippocampal neurons and displays a unique PDZ ligand specificity for SynCAM1.

Fig 1. "MPP2 is a component of postsynaptic receptor complexes." Immunoprecipitation of TARP γ-2 from crude synaptosomal fractions showed MPP2 is present in AMPAR complexes containing GluA2, PSD-95 and TARP γ-2 (Fig.2A).
MPP2 localizes to excitatory synapses (Fig. 1B). Immunostaining of cultured hippocampal neurons showed endogenous MPP2 is exclusively found in neurons (MAP2 positive cells) and MPP2 puncta along dendrites colocalized with with PSD-95 and vGlut1.

Fig. 2. "MPP2 interacts with the postsynaptic density proteins PSD-95 and GKAP." The interaction between MPP2 with PSD-95 was demonstrated immunoprecipitation of endogenous MPP2 from crude synaptosomes isolated from adult rat brain tissue. In heterologous cells, MPP2 was capable of binding PSD-95 independent of its PDZ and L27 domains. In a yeast two-hybrid screen of a rat hippocampus cDNA library that used the MPP2 PSG deletion construct (see Fig. 2A, missing L27 domains), the authors identified GKAP, an established synaptic structural protein, as another MPP2 interacting protein (Supplementary table S1). The interaction was confirmed in heterologous cells using immunoprecipitation and showed the SH3-GK domains of MPP2 mediate its interaction with GKAP (Fig. 2D).

MPP2 homomultimerises in heterologous cells (Fig. 2E). Pull-down assays using a α-Myc antibody shows Myc-MPP2 interacts with Flag-MPP2 in COS7 cells (Fig. 2e), "suggesting that MPP2 proteins are capable of intermolecular
interactions to form dimers or oligomers."

Fig. 3: "MPP2 binds directly to the synaptic adhesion molecule SynCAM1."
Co-immunoprecipitation experiments in heterologous cells show Myc-MPP2 interacts with the mCherry-tagged, 10 C-terminal amino acids of SynCAM1. This interaction was also observed in the Y2H screen (Supplemental Table S1). Point mutations occurring within this region of SynCAM1 were sufficient to disrupt the interaction with Myc-MPP2. A direct and robust interaction between MPP2 PDZ-SH3-GK domains and the SynCAM1 C-terminus was confirmed by isothermal titration calorimetry (ITC) using used bacterially produced proteins (Kd of 3.1 μM). Pull-down experiments from crude synaptosomes and immunostaining of cultured hippocampal neurons confirmed the endogenous interaction between MPP2 and SynCAM1.

Supplementary Fig. 1: The specificity of the polyclonal rabbit α-MPP2 antibody used in this paper was demonstrated by western blot analysis (Fig. S1A) and immunostaining (Fig. S1B) of COS7 cells transfected with Myc-, Flag- and GFP-tagged MPP2.
Evidence tracking, Biological System:Intact tissue
Cultured neurons
Non-neuronal tissue
Cell-free system
Evidence tracking, Protein Targeting:Over-expression
Antibody (detection)
Evidence tracking, Experiment Assay:Confocal
Western blot
Biochemical fractionation (generic)
Y2H
Protein-protein interaction (generic)
Annotator(s):Hana Goldschmidt (ORCID:0000-0002-5676-366X)
Richard Huganir (ORCID:0000-0001-9783-5183)
Lab:Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA and Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21205, USA
SynGO annotation ID:2583
Dataset release (version):20231201
View annotation as GO-CAM model:Gene Ontology