Glycosaminoglycan modification of NRP1 exon 4-skipping variant drives colorectal cancer metastasis via endosomal-exosomal trafficking.

Neuropilin-1 (NRP1) is a transmembrane glycoprotein that functions as a co-receptor with various cellular functions. Our previous studies identified the NRP1 exon 4-skipping (NRP1-ΔE4) splice variant as an aggressive metastasis driver by activating endosomal signals. Here, we demonstrate the critical role of glycosaminoglycan (GAG) modification in regulating NRP1-ΔE4's cellular trafficking and oncogenic activity. NRP1-ΔE4 undergoes constitutive internalization into endosomes and subsequent exosomal release from colorectal cancer (CRC) cells. Exosomal NRP1-ΔE4 enhances the migration and invasion of both donor and recipient CRC cells. Genetic or pharmacological inhibition of exosome secretion, or immunodepletion of exosomal NRP1-ΔE4, markedly reduces its metastatic potential. Notably, GAG modification at the O-glycosylation site Ser612 is essential for NRP1-ΔE4's endosomal trafficking and exosomal release. This modification also promotes the formation of a trimeric complex with Met and β1-integrin, leading to their co-internalization and accumulation in endosomes, which activates FAK signaling and drives CRC metastasis. These findings reveal GAG modification as a key regulatory process that governs the endosomal-exosomal trafficking of NRP1-ΔE4 to facilitate CRC cell dissemination.