GAG-binding sites of Sema2b. Ribbon representation of Sema2bΔC in complex with SOS, the sema domain is shown in orange, the PSI domain in blue, the Ig-like domain in red, and SOS is shown in stick representation. A 66-residue long C-terminal tail, which was omitted from the construct used for crystallization, is represented by a dashed gray line. The C-terminal central helix predicted by AlphaFold is shown in green. Schematic domain organization of Sema2b is shown below the ribbon representation, highlighting the locations of SOS binding sites with yellow stars. The high-affinity binding site is indicated by a violet star.
Daniel Rozbesky Research Group
Significance
The development of the nervous system relies on precise axon guidance, orchestrated by cues like semaphorins. These cues not only engage their cognate receptors but also interact with extracellular matrix components like proteoglycans, whose role remains poorly understood. Our study reveals that secreted semaphorins bind specifically to proteoglycan glycosaminoglycan chains via multiple sites, with an essential high-affinity site located at the C-terminal tail. Deleting this site disrupts semaphorin activity in guiding olfactory receptor neuron axons in vivo. We propose that secreted semaphorins attach to cell surfaces via proteoglycan interactions, aiding their recognition by axon receptors.
NOURISANAMI, Farahdokht; SOBOL, Margarita; LI, Zhuoran; HORVATH, Matej; KOWALSKA, Karolina et al. Molecular mechanisms of proteoglycan-mediated semaphorin signaling in axon guidance.
Proceedings of the National Academy of Sciences of the United States of America, 2024, e24202755121, https://doi.org/10.1073/pnas.2402755121