LRFN2 binding to NMDAR inhibits the progress of ESCC via regulating the Wnt/β-Catenin and NF-κB signaling pathway

As a neuronal transmembrane protein, leucine-rich repeat and fibronectin type-III domain-containing protein 2 (LRFN2) can recruit and combine with N-methyl-D-aspartic acid receptors (NMDARs) to promote nerve growth. Genetic studies suggest that mutations in LRFN2 are associated with various cancers. However, the role and mechanism of LRFN2 in the progression of esophageal squamous cell carcinoma (ESCC) have not been elucidated. In this study, we demonstrated that LRFN2 was significantly downregulated in ESCC tissues by qRT-PCR and immunohistochemistry. Low LRFN2 expression was an adverse prognostic factor in patients with ESCC. Overexpression of LRFN2 effectively suppressed the proliferation, migration, invasion and epithelial-to-mesenchymal transition in vitro and tumor growth in vivo. Bioinformatics analysis indicated that Wnt/β-catenin signaling regulation was one of the most potential mechanisms and studies confirmed that overexpression of LFRN2 obviously downregulated the expression of β-catenin, c-Myc and cyclin D1 in ESCC cells and tumor tissues. Further studies revealed that LRFN2 plays anti-ESCC role by binding with NMDAR-GRIN2B and this effect can be weakened by NR2B-selective NMDA antagonist-NMDA-IN-1. Moreover, the bioinformatics analysis showed that the interaction of GRIN2B and GSK3β affects the NF-κB pathway, which was demonstrated by western blot experiments. Collectively, our results indicate that LRFN2 binding to NMDARs inhibits the progression of ESCC by regulating the Wnt/β-catenin and NF-κB pathway, which provides a new therapeutic target for improving the prognosis of patients with ESCC.

Sorting nexin-27 regulates AMPA receptor trafficking through the synaptic adhesion protein LRFN2

The endosome-associated cargo adaptor sorting nexin-27 (SNX27) is linked to various neuropathologies through sorting of integral proteins to the synaptic surface, most notably AMPA receptors. To provide a broader view of SNX27-associated pathologies, we performed proteomics in rat primary neurons to identify SNX27-dependent cargoes, and identified proteins linked to excitotoxicity, epilepsy, intellectual disabilities, and working memory deficits. Focusing on the synaptic adhesion molecule LRFN2, we established that SNX27 binds to LRFN2 and regulates its endosomal sorting. Furthermore, LRFN2 associates with AMPA receptors and knockdown of LRFN2 results in decreased surface AMPA receptor expression, reduced synaptic activity, and attenuated hippocampal long-term potentiation. Overall, our study provides an additional mechanism by which SNX27 can control AMPA receptor-mediated synaptic transmission and plasticity indirectly through the sorting of LRFN2 and offers molecular insight into the perturbed function of SNX27 and LRFN2 in a range of neurological conditions.