Deciphering the Role of miR-30a-5p and DLGAP1 Gene in Non-small Cell Lung Cancer.

BACKGROUND/AIM: Non-small cell lung cancer (NSCLC) is the deadliest form of cancer worldwide. Understanding the mechanisms of lung cancer development is vital for targeted therapy advancements. This article explores the little-known role of the guanylate kinase-associated protein (GKAP), encoded by the Disks large-associated protein 1 (DLGAP1) gene, in NSCLC along with assessing microRNA-30a-5p's influence on DLGAP1 gene expression in the A549 cell line. MATERIALS AND METHODS: Experiments were conducted on A549 cells transfected with synthetic oligonucleotides. The luciferase assay was employed to confirm the binding site of miR-30a-5p to the 3'UTR of DLGAP1 mRNA. The role of miRNA-30a-5p mimic in regulating potential target gene expression at the protein and mRNA levels was studied by performing RT-qPCR and western blot analyses. The effects of DLGAP1 knockdown and miRNA-30a-5p mimic on cell viability and the cell cycle were evaluated using the MTT test and flow cytometry with annexin/iodide cell staining. RESULTS: The luciferase assay indicated that miR-30a-5p has the ability to bind to the 3'UTR of DLGAP1 mRNA. RT-qPCR revealed that the overexpression of miR-30a-5p down-regulates DLGAP1 mRNA. Western blot analysis indicated that miR-30a-5p slightly reduces the level of the GKAP protein. Knockdown of DLGAP1 with synthetic oligonucleotides, as well as transfection with a miR-30a-5p mimic, significantly attenuates cell proliferation and increases the number of cells in the early and late stages of apoptosis. CONCLUSION: Our findings reveal the antiproliferative effect of miR-30a-5p and DLGAP1 gene knockdown on A549 cancer cells, implying that these elements could be considered as therapeutic targets for personalized medicine in NSCLC patients.

DLGAP1-AS2 promotes estrogen receptor signalling and confers tamoxifen resistance in breast cancer.

BACKGROUND: Tamoxifen is a first-line endocrine agent and is often used to treat estrogen receptor-positive (ER+) breast cancer. Unfortunately, approximately 30-40% of patients who received tamoxifen therapy experience recurrence or progression to a fatal advanced stage due to tamoxifen resistance. However, the mechanisms of tamoxifen resistance remain unclear. METHODS: The expression of lncRNA DLGAP1 antisense RNA 2 (DLGAP1-AS2) was detected by qPCR. The effect of DLGAP1-AS2 on tamoxifen resistance was evaluated by MTT, colony formation, TUNEL and flow cytometric assays. The mechanisms by which DLGAP1-AS2 regulates tamoxifen resistance were investigated through qPCR, RNA pull-down assays and RNA immunoprecipitation (RIP) assays. RESULTS: Our results showed that DLGAP1-AS2 is significantly upregulated in breast cancer and that tamoxifen can induce DLGAP1-AS2 expression. Further investigation suggested that upregulation of DLGAP1-AS2 can increase cell viability and inhibit apoptosis, while downregulation of DLGAP1-AS2 results in the opposite effects. Mechanistically, DLGAP1-AS2 can bind to the AFF3 protein to inhibit its degradation, which further promotes ER signalling. CONCLUSIONS: Our research clarified that DLGAP1-AS2 promotes ER signalling to induce tamoxifen resistance and that targeting DLGAP1-AS2 might be a promising strategy to overcome tamoxifen resistance in breast cancer.

N6-methyladenosine (m6A)-mediated lncRNA DLGAP1-AS1enhances breast canceradriamycin resistance through miR-299-3p/WTAP feedback loop.

Chemotherapy resistance is identified as an obstacle for breast cancer (BC) therapy, and, besides, increasing evidence indicates that long-noncoding RNAs (lncRNAs) participate in the regulation of BC adriamycin (ADR) resistance. Here, our work shows that lncRNA DLGAP1 antisense RNA 1 (DLGAP1-AS1) is up-regulated in ADR-resistant BC cells (MCF-7/ADR). Clinically, higher DLGAP1-AS1 expression was closely correlated to poorer clinical prognosis. Results showed that DLGAP1-AS1 promoted the ADR IC50 and proliferation of ADR-resistant cells. Moreover, N6-methyladenosine (m6A) methyltransferase WT1 associated protein (WTAP) binds to the m6A modified site of DLGAP1-AS1 and motivates its stability. Mechanistically, DLGAP1-AS1 sponged miR-299-3p through 3'-untranslated region (3'-UTR) binding, which in turn relieved the repression of WTAP and thus upregulated WTAP expression. In conclusion, above findings conclude that lncRNA DLGAP1-AS1 promotes BC ADR-resistance through WTAP/DLGAP1-AS1/miR-299-3p feedback loop.

A genome-wide association study identifies a novel candidate locus at the DLGAP1 gene with susceptibility to resistant hypertension in the Japanese population.

Numerous genetic variants associated with hypertension and blood pressure are known, but there is a paucity of evidence from genetic studies of resistant hypertension, especially in Asian populations. To identify novel genetic loci associated with resistant hypertension in the Japanese population, we conducted a genome-wide association study with 2705 resistant hypertension cases and 21,296 mild hypertension controls, all from BioBank Japan. We identified one novel susceptibility candidate locus, rs1442386 on chromosome 18p11.3 (DLGAP1), achieving genome-wide significance (odds ratio (95% CI) = 0.85 (0.81-0.90), P = 3.75 × 10-8) and 18 loci showing suggestive association, including rs62525059 of 8q24.3 (CYP11B2) and rs3774427 of 3p21.1 (CACNA1D). We further detected biological processes associated with resistant hypertension, including chemical synaptic transmission, regulation of transmembrane transport, neuron development and neurological system processes, highlighting the importance of the nervous system. This study provides insights into the etiology of resistant hypertension in the Japanese population.

LncRNA DLGAP1-AS2 regulates miR-503/cyclin D1 to promote cell proliferation in non-small cell lung cancer.

BACKGROUND: LncRNA DLGAP1-AS2 plays an oncogenic role in glioma, while its role in other cancers is unknown. This study aimed to study the role of DLGAP1-AS2 in non-small cell lung cancer (NSCLC). METHODS: Expression of DLGAP1-AS2 in NSCLC and paired non-tumor tissues from 64 NSCLC patients and the prognostic value of DLGAP1-AS2 for NSCLC were analyzed by performing a 5-year follow-up study. The interaction between DLGAP1-AS2 and miR-503 was confirmed by dual luciferase reporter assay, and their relationship was explored in NSCLC cells transfected with DLGAP1-AS2 expression vector or miR-503 mimic. The roles of DLGAP1-AS2 and miR-503 in regulating cyclin D1 expression were analyzed by RT-qPCR and Western blot. Cell proliferation was analyzed by CCK-8 assay. RESULTS: DLGAP1-AS2 was upregulated in NSCLC and predicted poor survival. Interaction between DLGAP1-AS2 and miR-503 was confirmed by dual luciferase activity assay. Overexpression experiments showed that DLGAP1-AS2 and miR-503 overexpression failed to significantly affect the expression of each other. Interestingly, DLGAP1-AS2 overexpression upregulated cyclin D1, a target of miR-503, increased cell proliferation and reduced the effects of miR-503 overexpression on cyclin D1 expression and cell proliferation. CONCLUSIONS: DLGAP1-AS2 may regulate miR-503/cyclin D1 to promote cell proliferation in NSCLC.

Inflammation-Related circRNA Polymorphism and Ischemic Stroke Prognosis.

CircRNAs belong to a novel class of noncoding RNAs that are generated by exons of genes by alternative mRNA splicing and involved in pathophysiological processes of ischemic stroke by regulating neuro-inflammation. A total of 982 patients were enrolled in our study for stroke recovery analysis. The aim of our study was to first explore the association between the inflammation-related circRNA polymorphism and functional outcome 3 months after ischemic stroke by using multivariate logistic regression model. Next, we further investigated the role of circRNA polymorphism in predicting stroke recurrence by using Cox proportional hazard regression model. Five circRNA polymorphisms were genotyped by using polymerase chain reaction and ligation detection reaction method. We identified circ-STAT3 (signal transducer and activator of transcription) rs2293152 GG genotype to be associated with poorer recovery 90 days after stroke (OR = 1.452, 95% CI: 1.165-4.362, p = 0.016). After adjusting for confound factors, the association for rs2293152 with 3 months outcome after IS was stronger, suggesting a mechanism that rs2293152 is an independent risk factor for stroke recovery (OR = 2.255, 95% CI: 1.034-2.038, p = 0.031). However, no other circRNA polymorphisms (circ-DLGAP4 rs41274714, circ-TRAF2 rs10870141, circ-ITCH rs10485505, rs4911154) were associated with functional outcome 3 months after stroke in any genetic models. Subgroup analysis revealed that the negative effect of rs2293152 GG genotype was greater in female and older patients, subjects with history of hypertension. Additionally, all the circRNA polymorphisms were not correlated with recurrent risk of ischemic stroke. Our results indicated that circ-STAT3 might be a novel biomarker for predicting functional outcome after stroke and an important contributor to the ischemic stroke recovery.

Learning and reaction times in mouse touchscreen tests are differentially impacted by mutations in genes encoding postsynaptic interacting proteins SYNGAP1, NLGN3, DLGAP1, DLGAP2 and SHANK2.

The postsynaptic terminal of vertebrate excitatory synapses contains a highly conserved multiprotein complex that comprises neurotransmitter receptors, cell-adhesion molecules, scaffold proteins and enzymes, which are essential for brain signalling and plasticity underlying behaviour. Increasingly, mutations in genes that encode postsynaptic proteins belonging to the PSD-95 protein complex, continue to be identified in neurodevelopmental disorders (NDDs) such as autism spectrum disorder, intellectual disability and epilepsy. These disorders are highly heterogeneous, sharing genetic aetiology and comorbid cognitive and behavioural symptoms. Here, by using genetically engineered mice and innovative touchscreen-based cognitive testing, we sought to investigate whether loss-of-function mutations in genes encoding key interactors of the PSD-95 protein complex display shared phenotypes in associative learning, updating of learned associations and reaction times. Our genetic dissection of mice with loss-of-function mutations in Syngap1, Nlgn3, Dlgap1, Dlgap2 and Shank2 showed that distinct components of the PSD-95 protein complex differentially regulate learning, cognitive flexibility and reaction times in cognitive processing. These data provide insights for understanding how human mutations in these genes lead to the manifestation of diverse and complex phenotypes in NDDs.

Exosomal circ_DLGAP4 promotes diabetic kidney disease progression by sponging miR-143 and targeting ERBB3/NF-κB/MMP-2 axis.

Diabetic kidney disease (DKD) is closely associated with the high risk of cardiovascular disease and mortality. Exosomal circRNAs can exert significant roles in the pathology of various diseases. Nevertheless, the role of exosomal circRNAs in DKD progression remains barely known. Circular RNA DLGAP4 has been reported to be in involved in acute ischemic stroke. In our study, we found exosomal circ_DLGAP4 was increased in the exosomes isolated from HG-treated mesangial cells (MCs), DKD patients, and DKD rat models compared with the corresponding normal subjects. Then, we observed that exo-circ_DLGAP4 significantly promoted proliferation and fibrosis of MCs cells. Moreover, to study the underlying mechanism of circ_DLGAP4 in regulating DKD, bioinformatics method was consulted and miR-143 was predicted as its target. The direct correlation between miR-143 and circ_DLGAP4 was validated in MCs. MCs proliferation and fibrosis were increased by circ_DLGAP4, which could be decreased by mimic-miR-143. Next, elevated expression of Erb-b2 receptor tyrosine kinase 3 (ERBB3) is involved in various diseases. However, the function of ERBB3 in DKD development remains poorly known. Next, ERBB3 was predicted as the downstream target for miR-143. It was displayed that circ_DLGAP4 promoted proliferation and fibrosis of MCs by sponging miR-143 and regulating ERBB3/NF-κB/MMP-2 axis. Meanwhile, the loss of exo-circ_DLGAP4 induced miR-143 and repressed ERBB3/NF-κB/MMP-2 expression in MCs. Subsequently, in vivo assays were performed and it was proved that overexpression of circ_DLGAP4 markedly promoted DKD progression in vivo via modulating miR-143/ERBB3/NF-κB/MMP-2. In conclusion, we indicated that exosomal circ_DLGAP4 could prove a novel insight for DKD development.

Dlgap1 negatively regulates browning of white fat cells through effects on cell proliferation and apoptosis.

BACKGROUND: Obesity is a metabolic imbalance characterized by excessive deposition of white fat. The browning of white fat can effectively treat obesity and related diseases. Although Dlgap1 (Discs, Large (Drosophila) Homolog-Associated Protein 1) is suspected to have an effect on this process, no empirical evidence is available. METHODS: To understand the role of Dlgap1, we cultured white and brown fat cells, then performed overexpression and knockout experiments. RESULTS: We found that Dlgap1 overexpression in brown adipocytes inhibits brown-fat-related gene expression, promotes white-fat-related genes, while also increasing brown-adipocyte proliferation and apoptosis. However, the gene overexpression has no effect on brown adipocyte maturation. Knocking out Dlgap1 in white fat cells promotes the expression and inhibition of brown-fat-related and white-fat-related genes, respectively. Additionally, the knockout inhibits white fat cell proliferation and apoptosis, while also promoting their maturation. CONCLUSIONS: Dlgap1 negatively regulates the browning of white adipocytes by influencing cell proliferation and apoptosis.

LncRNA DLGAP1-AS2 modulates glioma development by up-regulating YAP1 expression.

LncRNA DLGAP1 antisense RNA 2 (DLGAP1-AS2) is one kind cytoplasmic long non-coding RNA; however, there is rarely little information about its function in physiological process. Here, we demonstrated that LncRNA DLGAP1-AS2 was up-regulated in glioma and was quite correlated with poor prognosis of glioma patients. Depletion of DLGAP1-AS2 in glioma cells could inhibit cell proliferation and cell migration, and induce cell apoptosis, resulting in the suppression of the progression of glioma consequently. Furthermore, knockdown of DLGAP1-AS2 inhibited the growth of xenograft glioma tumour in vivo as well. Finally, we verified Yes Associated Protein 1 (YAP1) was the downstream target of DLGAP1-AS2 and DLGAP1-AS2 modulated glioma cell proliferation, migration and apoptosis via regulating YAP1. Our study revealed novel mechanism about how did lncRNA DLGAP1-AS2 execute function in glioma and thus provided potential therapeutic interventions for the treatment of glioma.

Long noncoding RNA DLGAP1-AS1 promotes cell proliferation in hepatocellular carcinoma via sequestering miR-486-5p.

Hepatocellular carcinoma (HCC) is most prevalent tumor in liver and one of the most fatal cancers in the world. Long noncoding RNAs (lncRNAs) have been accepted as important regulators in carcinomas. But there are still many lncRNAs including DLGAP1-AS1 unannotated in HCC. First of all, GEPIA suggested that DLGAP1-AS1 presented high expression in HCC tissue samples relative to the normal tissues. Besides, overexpression of DLGAP1-AS1 was also proved in HCC cell lines. Moreover, DLGAP1-AS1 knockdown efficiently suppressed cell proliferation in HCC. Interestingly, miR-486-5p was predicted and validated to interact with DLGAP1-AS1, while the level of miR-486-5p was significantly increased In HCC after DLGAP1-AS1 knockdown. Moreover, we uncovered that ectopic expression of miR-486-5p induced suppression on HCC cell proliferation and that miR-486-5p inhibition offset the effect of DLGAP1-AS1 silence on HCC cell proliferation and apoptosis. Furthermore, H3F3B was identified as target of miR-486-5p and was therefore positively regulated by DLGAP1-AS1 in HCC. Of note, H3F3B upregulation partly revived the declined cell proliferative capacity in response to DLGAP1-AS1 knockdown. To conclude, DLGAP1-AS1 exerted its oncogenic role in HCC via miR-486-5p/H3F3B axis. Our new findings provided novel theoretical basis for discovery of therapeutic targets of HCC.

Cognitive impairment and autistic-like behaviour in SAPAP4-deficient mice.

In humans, genetic variants of DLGAP1-4 have been linked with neuropsychiatric conditions, including autism spectrum disorder (ASD). While these findings implicate the encoded postsynaptic proteins, SAPAP1-4, in the etiology of neuropsychiatric conditions, underlying neurobiological mechanisms are unknown. To assess the contribution of SAPAP4 to these disorders, we characterized SAPAP4-deficient mice. Our study reveals that the loss of SAPAP4 triggers profound behavioural abnormalities, including cognitive deficits combined with impaired vocal communication and social interaction, phenotypes reminiscent of ASD in humans. These behavioural alterations of SAPAP4-deficient mice are associated with dramatic changes in synapse morphology, function and plasticity, indicating that SAPAP4 is critical for the development of functional neuronal networks and that mutations in the corresponding human gene, DLGAP4, may cause deficits in social and cognitive functioning relevant to ASD-like neurodevelopmental disorders.

Genetic analysis for cognitive flexibility in the trail-making test in attention deficit hyperactivity disorder patients from single nucleotide polymorphism, gene to pathway level.

Objectives: Investigation of the genetic basis of endophenotype and analysis the pathways with multiple genes of small effects might increase the understanding of the genetic basis of attention deficit hyperactivity disorder (ADHD). Here we aimed to explore the genetic basis of cognitive flexibility in ADHD at the single nucleotide polymorphism (SNP), gene and pathway levels. Methods: The trail-making test was used to test the cognitive flexibility of 788 ADHD patients. A genome-wide association analysis of cognitive flexibility was conducted for 644,166 SNPs. Results: The top SNP rs2049161 (P = 5.08e-7) involved gene DLGAP1 and the top gene CADPS2 in the gene-based analysis resulted in much literature evidence of associations with psychiatric disorders. Gene expression and network analysis showed their contribution to cognition function. The interval-enrichment analysis highlighted a potential contribution of 'adenylate cyclase activity' and ADCY2 to cognitive flexibility. Candidate pathway-based analysis for all SNPs found that glutamate system-, neurite outgrowth- and noradrenergic system-related pathways were significantly associated with cognitive flexibility (FDR <0.05), among which the neurite outgrowth pathway was also associated with ADHD symptoms. Conclusions: This study provides evidence for the genes and pathways associated with cognitive flexibility and facilitate the uncovering of the genetic basis of ADHD.

Translating Alzheimer's disease-associated polymorphisms into functional candidates: a survey of IGAP genes and SNPs.

The International Genomics of Alzheimer's Project (IGAP) is a consortium for characterizing the genetic landscape of Alzheimer's disease (AD). The identified and/or confirmed 19 single-nucleotide polymorphisms (SNPs) associated with AD are located on non-coding DNA regions, and their functional impacts on AD are as yet poorly understood. We evaluated the roles of the IGAP SNPs by integrating data from many resources, based on whether the IGAP SNP was (1) a proxy for a coding SNP or (2) associated with altered mRNA transcript levels. For (1), we confirmed that 12 AD-associated coding common SNPs and five nonsynonymous rare variants are in linkage disequilibrium with the IGAP SNPs. For (2), the IGAP SNPs in CELF1 and MS4A6A were associated with expression of their neighboring genes, MYBPC3 and MS4A6A, respectively, in blood. The IGAP SNP in DSG2 was an expression quantitative trait loci (eQTL) for DLGAP1 and NETO1 in the human frontal cortex. The IGAP SNPs in ABCA7, CD2AP, and CD33 each acted as eQTL for AD-associated genes in brain. Our approach for identifying proxies and examining eQTL highlighted potentially impactful, novel gene regulatory phenomena pertinent to the AD phenotype.

SAPAP4 Deletion Causes Synaptic Dysfunction in the nucleus accumbens.

SAP90/PSD95-associated proteins (SAPAPs) are one type of scaffold protein in the postsynaptic density (PSD). Scaffold proteins play an important role in synaptic function. Recently, many studies have shown that mutations associated with scaffold proteins cause dysfunction in neuronal circuitry and in behavior. SAPAP4, as a protein in the SAPAP family, may have an impact on synaptic functions and on behaviors. To test this hypothesis, mice with a genetic deletion of SAPAP4 were used in our study. SAPAP4-/- mice displayed decreased cocaine sensitivity behavior after an acute injection of 20 mg/kg cocaine. We also found that the spine density of medium spiny neurons (MSNs) in the nucleus accumbens (NAc) shell was reduced in SAPAP4-/- mice. Furthermore, SAPAP4-/- mice displayed altered synaptic transmission and a decreased frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) in the NAc. Our findings demonstrate that SAPAP4 plays a critical role in cocaine-related behavior and in the synaptic function of the NAc.

Examination of the expression and prognostic significance of DLGAPs in gastric cancer using the TCGA database and bioinformatic analysis.

The discs large­associated protein (DLGAP) family has been implicated in psychological and neurological diseases. However, few studies have explored the association between the expression of DLGAPs and different types of cancer. Therefore, the present study analyzed the status of DLGAPs in gastric cancer (GC) using bioinformatic tools. Analyses of data obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases revealed that there was selective upregulation of DLGAP4 and DLGAP5 expression in GC tissues when compared with normal gastric tissues. In addition, survival analysis using OncoLnc indicated that high expression of DLGAP4 was significantly correlated with shorter overall survival for all GC patients. However, Kaplan­Meier plots demonstrated that the expression of all DLGAPs, except for DLGAP3, was correlated with patient prognosis; DLGAP4 was consistently associated with GC. DLGAP4 mRNA and protein distributions were examined by reverse transcription­quantitative polymerase chain reaction and immunohistochemsitry. Furthermore, its mutation rate and associated biological processes and signaling pathways were assessed in GC with cBioPortal and FunRich analyses. Taken together, these results indicated that DLGAP4 may serve an oncogenic role in GC development and may be a monitoring target for GC prognosis.

GKAP Acts as a Genetic Modulator of NMDAR Signaling to Govern Invasive Tumor Growth.

Genetic linkage analysis previously suggested that GKAP, a scaffold protein of the N-methyl-D-aspartate receptor (NMDAR), was a potential modifier of invasion in a mouse model of pancreatic neuroendocrine tumor (PanNET). Here, we establish that GKAP governs invasive growth and treatment response to NMDAR inhibitors of PanNET via its pivotal role in regulating NMDAR pathway activity. Combining genetic knockdown of GKAP and pharmacological inhibition of NMDAR, we implicate as downstream effectors FMRP and HSF1, which along with GKAP demonstrably support invasiveness of PanNET and pancreatic ductal adenocarcinoma cancer cells. Furthermore, we distilled genome-wide expression profiles orchestrated by the NMDAR-GKAP signaling axis, identifying transcriptome signatures in tumors with low/inhibited NMDAR activity that significantly associate with favorable patient prognosis in several cancer types.

DLGAP1 and NMDA receptor-associated postsynaptic density protein genes influence executive function in attention deficit hyperactivity disorder.

Objective: To explore the association of DLGAP1 gene with executive function (EF) in attention deficit hyperactivity disorder (ADHD) children. Method: A total of 763 ADHD children and 140 healthy controls were enrolled. The difference of EF between ADHD and controls was analyzed using the analysis of covariance (ANCOVA), with IQ, sex, and age as covariates. Both the associations of SNPs with EF and three symptom traits of ADHD were conducted using an additive linear regression model by PLINK with the same covariates as ANCOVA. Results: Compared with controls, children with ADHD showed poorer cognitive flexibility and inhibition. Two SNPs (rs2049161, p-value = 5.08e-7, adjusted p-value = 1.63e-4, rs16946051, p-value = 5.18e-7, adjusted p-value = 1.66e-4) survived multiple tests in Trail Making Test. Both SNPs also showed association with TOH (rs2049161, p = 6.82e-4, rs16946051, p = 7.91e-4). Set-based analysis for gene DLGAP1 and its functional pathway DLGAP1-DLG4-NMDA showed they were associated with cognitive flexibility at both gene (p = .0057) and pathway level (p = .0321). Furthermore, the gene and pathway also showed association with ADHD symptom score. The associated SNPs and their LD proxies were related to the expression of DLGAP1 in medulla and frontal cortex. Conclusion: Children with ADHD showed deficit in EF, especially, cognitive flexibility and inhibition. DLGAP1 was associated with cognitive flexibility and plan, and the role of DLGAP1 might be implemented through the complex of DLGAP1-DLG4-NMDA.

MPP2 is a postsynaptic MAGUK scaffold protein that links SynCAM1 cell adhesion molecules to core components of the postsynaptic density.

At neuronal synapses, multiprotein complexes of trans-synaptic adhesion molecules, scaffold proteins and neurotransmitter receptors assemble to essential building blocks required for synapse formation and maintenance. Here we describe a novel role for the membrane-associated guanylate kinase (MAGUK) protein MPP2 (MAGUK p55 subfamily member 2) at synapses of rat central neurons. Through interactions mediated by its C-terminal SH3-GK domain module, MPP2 binds to the abundant postsynaptic scaffold proteins PSD-95 and GKAP and localises to postsynaptic sites in hippocampal neurons. MPP2 also colocalises with the synaptic adhesion molecule SynCAM1. We demonstrate that the SynCAM1 C-terminus interacts directly with the MPP2 PDZ domain and that MPP2 does not interact in this manner with other highly abundant postsynaptic transmembrane proteins. Our results highlight a previously unexplored role for MPP2 at postsynaptic sites as a scaffold that links SynCAM1 cell adhesion molecules to core proteins of the postsynaptic density.