The Glycosaminoglycan-Dependent Interactome of Neurexin-1 in Human Fetal Glial Cells.

Neurexins are synaptic adhesion molecules best characterized in neurons, where they regulate synapse assembly and function, with emerging evidence indicating they are also abundantly expressed by astrocytes. To elucidate the interactome of NRXN1α, we employed a proximity labeling strategy in cultured human fetal glial cells (SVG p12 cells). This approach enables the identification of transient and spatially restricted protein interactions, offering insights into the molecular environment of NRXN1α in glia. Further, we investigated how the presence and number of glycosaminoglycan (GAG) chains present on NRXN1α influence these interactions by generating glycosylation-deficient mutants at previously characterized GAG glycosites. Here, we show that the astrocytic NRXN1α interactome in SVG p12 cells consists of over 400 proteins, half of which are likely modulated by GAGs. Our findings provide a systems-level view of NRXN1α-associated proteins in fetal glia cultured in the absence of neurons and highlight the role of GAG valency in modulating its interactome.