CD82 Protects Against Glaucomatous Axonal Transport Deficits via mTORC1 Activation in Mice

Abstract

Background: Glaucoma is a leading cause of irreversible blindness worldwide characterized by progressive optic nerve degeneration and retinal ganglion cell (RGC) loss. Axonal transport deficits have been demonstrated to be the earliest crucial pathophysiological changes underlying axonal degeneration in glaucoma. The critical feature of this pathological process and the significance of early intervention remain to be further explored. Here, we explore the role of a tetraspanin superfamily member CD82 in protection of glaucomatous neurodegeneration in an acute ocular hypertension mouse model. Methods:Expression level of CD82 in retina was examined before and after an acute ocular hypertension (AOHT) model in mouse. Overexpression of CD82 was achieved by intraocular injection of adeno-associated virus vector expressing CD82. Axonal transport deficits were evaluated by intravitreally injected Cholera toxin B (CTB) from eyes to superior colliculus and the distribution of endogenous synaptophysin. Subsequent optic nerve (ON) degeneration phenotypes were also examined including axon loss, myelin damage, and Aβ accumulation. In vitro neurite outgrowth assay was performed in SH-SY5Y cells with Cd82-plasmid transfection. Another optic nerve crush (ONC) model was taken to further validate the neuroprotective effects of CD82 by evaluation of axonal regeneration, RGC survival, and visual function of mice. Downstream pathway of CD82 was analyzed by qPCR examination and western blotting analysis as well as phenotype detection.Results:We found a transient downregulation of CD82 after acute IOP elevation, with parallel emergence of axonal transport deficits. Overexpression of CD82 with AAV2/9 vector in mouse retina improved optic nerve (ON) axonal transport and ameliorated subsequent axon degeneration. In vitro neurite outgrowth assay displayed longer neurite length of SH-SY5Y cells with transfection of Cd82-plasmid. Moreover, CD82 overexpression could stimulate ON regeneration and restore mouse vision after an optic nerve crush model. CD82 exerted protective effect through upregulation of TRAF2, which was an E3 ubiquitin ligase and activated mTORC1 through K63-linked ubiquitylation and intracellular repositioning of Raptor. Conclusions:These findings indicate that CD82 overexpression protects against glaucomatous axonal transport deficits through TRAF2-dependent activation of mTORC1 pathway, which offers deeper insights into tetraspanins superfamily and demonstrated potential neuroprotective strategy in glaucoma treatments.