Structural and functional characterization of the IgSF21-neurexin2α complex and its related signaling pathways in the regulation of inhibitory synapse organization

Nicolas Chofflet; Yusuke Naito; Anthony John Pastore; Nirmala Padmanabhan; Phuong Trang Nguyen; Christian Poitras; Benjamin Feller; Nayoung Yi; Jeremie Van Prooijen; Husam Khaled; Benoit Coulombe; Steven J Clapcote; Steve Bourgault; Tabrez J Siddiqui; Gabby Rudenko; Hideto Takahashi

doi:10.3389/fnmol.2024.1371145

Structural and functional characterization of the IgSF21-neurexin2α complex and its related signaling pathways in the regulation of inhibitory synapse organization

Front Mol Neurosci. 2024 Mar 20:17:1371145. doi: 10.3389/fnmol.2024.1371145. eCollection 2024.

Authors

Nicolas Chofflet^{1

2}, Yusuke Naito^{1

2}, Anthony John Pastore³, Nirmala Padmanabhan^{4

5}, Phuong Trang Nguyen⁶, Christian Poitras⁷, Benjamin Feller^{1

8}, Nayoung Yi^{1

8}, Jeremie Van Prooijen¹, Husam Khaled^{1

8}, Benoit Coulombe^{7

9}, Steven J Clapcote¹⁰, Steve Bourgault⁶, Tabrez J Siddiqui^{4

5

11

12}, Gabby Rudenko³, Hideto Takahashi^{1

2

8

13}

Affiliations

¹ Synapse Development and Plasticity Research Unit, Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada.
² Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.
³ Department of Pharmacology and Toxicology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States.
⁴ PrairieNeuro Research Centre, Health Sciences Centre, Kleysen Institute for Advanced Medicine, Winnipeg, MB, Canada.
⁵ Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB, Canada.
⁶ Quebec Network for Research on Protein Function, Engineering and Applications (PROTEO), Department of Chemistry, Université du Québec à Montréal, Montreal, QC, Canada.
⁷ Department of Translational Proteomics, Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada.
⁸ Department of Medicine, Université de Montréal, Montreal, QC, Canada.
⁹ Department of Biochemistry and Molecular Medicine, Université de Montréal, Montreal, QC, Canada.
¹⁰ School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom.
¹¹ The Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada.
¹² Program in Biomedical Engineering, University of Manitoba, Winnipeg, MB, Canada.
¹³ Division of Experimental Medicine, McGill University, Montreal, QC, Canada.

Abstract

The prevailing model behind synapse development and specificity is that a multitude of adhesion molecules engage in transsynaptic interactions to induce pre- and postsynaptic assembly. How these extracellular interactions translate into intracellular signal transduction for synaptic assembly remains unclear. Here, we focus on a synapse organizing complex formed by immunoglobulin superfamily member 21 (IgSF21) and neurexin2α (Nrxn2α) that regulates GABAergic synapse development in the mouse brain. We reveal that the interaction between presynaptic Nrxn2α and postsynaptic IgSF21 is a high-affinity receptor-ligand interaction and identify a binding interface in the IgSF21-Nrxn2α complex. Despite being expressed in both dendritic and somatic regions, IgSF21 preferentially regulates dendritic GABAergic presynaptic differentiation whereas another canonical Nrxn ligand, neuroligin2 (Nlgn2), primarily regulates perisomatic presynaptic differentiation. To explore mechanisms that could underlie this compartment specificity, we targeted multiple signaling pathways pharmacologically while monitoring the synaptogenic activity of IgSF21 and Nlgn2. Interestingly, both IgSF21 and Nlgn2 require c-jun N-terminal kinase (JNK)-mediated signaling, whereas Nlgn2, but not IgSF21, additionally requires CaMKII and Src kinase activity. JNK inhibition diminished de novo presynaptic differentiation without affecting the maintenance of formed synapses. We further found that Nrxn2α knockout brains exhibit altered synaptic JNK activity in a sex-specific fashion, suggesting functional linkage between Nrxns and JNK. Thus, our study elucidates the structural and functional relationship of IgSF21 with Nrxn2α and distinct signaling pathways for IgSF21-Nrxn2α and Nlgn2-Nrxn synaptic organizing complexes in vitro. We therefore propose a revised hypothesis that Nrxns act as molecular hubs to specify synaptic properties not only through their multiple extracellular ligands but also through distinct intracellular signaling pathways of these ligands.

Keywords: CaMKII kinase; GABAergic synapse; IgSF21; Src kinase; c-jun N-terminal kinase; neurexin2α; neuroligin2; signal transduction.

Grants and funding

The authors declare that financial support was received for the research, authorship, and/or publication of this article. This work was supported by a Canadian Institutes of Health Research (CIHR) grant (MOP-133517), a Natural Science and Engineering Research Council Discovery (NSERC) grant (RGPIN-2017-04753) and Fonds de la Recherche du Québec Research Scholars (FRQS Junior 2, 29106, and Senior, 251655) grants to HT, support from National Institutes of Health (NIH) (NIMH R01MH077303) to GR, support from NIH (NIA T32AG067952) to AJP, an NSERC grant (RGPIN-2022-04134) and a CIHR grant (PJT-463249) to TS, an NSERC grant (RGPIN-2018-06209) to SB, a Medical Research Council (UK) grant (G0900625) to SC, a strategic development grant from the Ministère de l’économie, de l’innovation et de l’énergie (Government of Québec) and the IRCM to BC, an IRCM doctoral scholarship to NC, an Iizuka Takeshi Scholarship Foundation award to YN, an FRQS doctoral scholarship (303256) and an Alzheimer Society Research Program doctoral award to NY, and IRCM doctoral and Emmanuel-Triassi scholarships to HK. The operation of this supercomputer was funded by the Canada Foundation for Innovation (CFI), Ministère de l’Économie et de l’Innovation du Québec (MEI), and Fonds de recherche du Québec (FRQ).