GALECTIN-1/NRP1 INTERACTION VIA CARBOHYDRATE BINDING PRODUCES REGENERATIVE RESPONSE AND FUNCTIONAL RECOVERY AFTER SPINAL CORD INJURY BY BLOCKING THE SEMAPHORINE 3A PATHWAY

L.A. PASQUINI, H.R. QUINTA, G.A. RABINOVICH, J.M. PASQUINI

Berlin

Congreso; XI European Meeting on Glial Cells in Health and Disease.; 2013

Glia meeting

Galectins (Gals) are a family of soluble lectins that, when binding to b- Galactosides, form multivalent complexes with glycoconjugates of the cellular surface and induce a modulation of intracellular signaling pathways for differentiation and survival. Recently, Galectin-1 has been described as a microglial deactivator which prevents neurodegeneration and promotes neuroprotection in an EAE model. However, its action at neuronal level is poorly understood. Spinal cord injury (SCI) also remains a major challenge to neurological research, as severalfactors such as extracellular matrix molecules inhibit axonal regeneration. Among them, Semaphorine 3A (Sema3A) contributes to the inhibition of axonal regeneration by acting on microtubules and actin cytoskeleton. Neuropilin-1 (Nrp-1) is a neuronal receptor whose binding of Sema3A generates repulsion of axonal growth. In addition, Nrp-1 has been described as a target of Gal-1 in non-neuronal systems. The aim of this work was to study the role of Gal-1 intraumatic SCI, considering that Sema3A expression is ?turned on? in SCI and prevents axonal regeneration via Nrp-1. Gal-1 knockout mice (Lgals1-/-) were submitted to a full traumatic SCI at thoracic level (T9-T10) and treated with different concentrations of recombinant Gal-1. We demonstrated that Lgals1-/- mice treated with Gal-1 have a dose-dependent functional recovery of motility as early as 6 days post-treatment, which is structurally associated to neuronal repopulation and high axonal regeneration. These effects were only observed in animals treated with Gal-1 with dimerizing capacity, but not in mice treated with a mutant Gal-1, only present in a monomeric form. In addition, we observed that microglial response was ?turned off? in Gal-1-treated mice. Moreover, exogenous dimeric Gal-1 bound to the surface of injured motoneurons and promoted the spread of Nrp-1. 3D confocal microscopy reconstruction showed Gal-1 and Nrp-1 spatial proximity. To confirm this result, we carried out immunoprecipitation assays, which allowed us to determine that only the dimeric form of Gal-1 interacted with Nrp-1 and induced a decrease in the levels of Sema-3A bound to Nrp-1. Our results show that Gal-1-based treatments combine its neuronal effect on Nrp-1 with its deactivating effect on microglia, which leads to a better restorative process after medullar lesion. The findings presented here support the potential of dimeric Gal-1 as a therapeutic agent for human SCI patients.