Plexin-B3 interacts with EB-family proteins through a conserved motif

Plexins are transmembrane receptors that are highly expressed in the central nervous system. They participate in the patterning of neural connections and regulation of cell adhesion and motility in many cell types. The aim of this study was to characterize novel protein-protein interactions of plexin-B3 intracellular portion.

To identify new interactors of plexin-B3 yeast two-hybrid screen was performed. We used GST pull-down and co-immunoprecipitation to verify those results. Deletion mutants were used to map the interacting regions. The physiological relevance of this interaction was assessed with neurite outgrowth assay in Neuro2A cell line.

We show that the N-terminal segment of intracellular domain of plexin-B3 interacts with microtubule plus end-binding proteins EB1, EB2 and EB3. The corresponding region in human plexin-A2, B1 and B3 contains the conserved EB-binding motif SxIP and these plexins also associate with EBs indicating the specificity of plexin-EB binding. As to the EB proteins, their N-terminal microtubule-binding domain is dispensable for plexin interaction. Plexin-EB interaction is involved in neurite growth as the synthetic peptide corresponding to the EB-binding region of plexin-B1 increases significantly the number of neurite tips in Neuro2A cells.

Microtubule end-binding proteins EB1, EB2 and EB3 interact with plexin-A2, B1 and B3 through a conserved EB-binding motif, which is located in their intracellular domain N-terminal segment.

The observed interaction between plexin intracellular domain and EBs suggests a novel function for plexins in regulating EB-mediated changes in microtubule dynamics and neurite growth.