Targeting the cis ‐dimerization of LINGO ‐1 with low MW compounds affects its downstream signalling

Background and Purpose The transmembrane protein LINGO ‐1 is a negative regulator in the nervous system mainly affecting axonal regeneration, neuronal survival, oligodendrocyte differentiation and myelination. However, the molecular mechanisms regulating its functions are poorly understood. In the present study, we investigated the formation and the role of LINGO ‐1 cis ‐dimers in the regulation of its biological activity. Experimental Approach LINGO ‐1 homodimers were identified in both HEK 293 and SH ‐ SY 5 Y cells using co‐immunoprecipitation experiments and BRET saturation analysis. We performed a hypothesis‐driven screen for identification of small‐molecule protein–protein interaction modulators of LINGO ‐1 using a BRET ‐based assay, adapted for screening. The compound identified was further assessed for effects on LINGO ‐1 downstream signalling pathways using Western blotting analysis and A lpha S creen technology. Key Results LINGO ‐1 was present as homodimers in primary neuronal cultures. LINGO ‐1 interacted homotypically in cis ‐orientation and LINGO ‐1 cis‐ dimers were formed early during LINGO ‐1 biosynthesis. A BRET ‐based assay allowed us to identify phenoxybenzamine as the first conformational modulator of LINGO ‐1 dimers. In HEK ‐293 cells, phenoxybenzamine was a positive modulator of LINGO ‐1 function, increasing the LINGO ‐1‐mediated inhibition of EGF receptor signalling and E rk phosphorylation. Conclusions and Implications Our data suggest that LINGO ‐1 forms constitutive cis ‐dimers at the plasma membrane and that low MW compounds affecting the conformational state of these dimers can regulate LINGO ‐1 downstream signalling pathways. We propose that targeting the LINGO ‐1 dimerization interface opens a new pharmacological approach to the modulation of its function and provides a new strategy for drug discovery.