Abstracts

Rationale: Integrins as membrane receptors on neurons play an important role in the development of neuroplasticity in the brain. Integrin recruitment and relocalization, and extracellular matrix (ECM) protein-integrin attachments have been reported to dynamically change their position during cell spreading and migration. We propose that ECM protein fibronectin-integrin interactions modulate epileptogenesis through alternation of inhibitory GABA-A channels, as well as changes of cell adhesion and elasticity (remodeling). Here, we tested this hypothesis in adult mouse hippocampal dentate gyrus granule cells (DGGCs) in epileptic neurons. Methods: We utilized the kindling model of epilepsy, single-cell immunocytochemistry, patch-clamp electrophysiology, and atomic force microscopy (AFM), a unique nanotechnique that allows progressive functional changes in neuronal membrane plasticity and mechanotransduction in single neurons. Results: There was marked increase in fibronectin receptor alpha5߱-integrin staining intensity in DGGCs from epilepsy mice. In electrophysiological recordings, fibronectin significantly inhibited GABA-A current, while RGD, which is known to disrupt FN-integrin-dependent cell adhesive events, strikingly enhanced GABA-A current by 400% in dissociated DGGCs and tonic currents by 190% in DGGCs from hippocampal slices, respectively. In AFM study, the unbinding force (25 pN) and binding probability between fibronectin-coated AFM probe and membrane integrins were significantly reduced in epileptic DGCs. Moreover, the cell elasticity, that partially represents changes in cytoskeletal reorganization, was strikingly increased in epilepsy. Treatment with a5߱-integrin mAb significantly reversed this membrane dysfunction. Conclusions: These results indicate that fibronectin-adhesive activities modulate development of epilepsy through modulation of inhibitory GABA current and cell membrane plasticity, and are functional dynamic and primarily bound to alpha5߱-integrins. We suggest that integrin signaling pathway may offer new targets for the prevention or treatment of epilepsy. Funding: N/A