| Popis: |
The function of neuronal networks relies on a well-maintained balance between excitation and inhibition, disruption of which can have dramatic pathological impacts on brain function. Insights into mechanisms that can enhance neuronal inhibition are therefore highly sought as these may lead to the identification of novel strategies to treat various neurological disorders. Here, I present work exploring a novel mechanism of enhancing GABAA receptor-mediated inhibition, the major source of fast synaptic inhibition in the brain. This was achieved by potentiating the function of the major chloride transporter in the brain, KCC2. Through genetic mutation of KCC2 threonine sites 906 and 1007 to alanine residues in vivo (KCC2-T906A/T1007A knock-in mouse model), I demonstrate the powerful impact that phospho-modulation of these sites has on KCC2 function. Not only did preventing KCC2-T906/T1007 phosphorylation enhance EGABA hyperpolarization in mature neurons, it accelerated the developmental excitatory-to-inhibitory GABAergic shift, seemingly by enhancing the rate of chloride extrusion. This is evident when neurons were challenged with increased [Cl–]i, as KCC2-T906A/T1007A neurons were able to more effectively remove this excess Cl–. This is of particular interest for epilepsy-associated disorders as neurons load with chloride during seizures, a process hypothesized to contribute to seizure initiation. Indeed, loss-of-function mutations in KCC2 are a genetic cause of epilepsy, and deficits in KCC2 function are seen in patients with idiopathic and acquired epilepsy, highlighting a potential for KCC2 as a novel target for treating seizures; the KCC2-T906A/T1007A mice provided the first opportunity to assess this potential. Using several chemoconvulsant models, I have demonstrated that KCC2-T906A/T1007A mutations limit the onset and severity of seizures. Therefore, this thesis highlights KCC2 as a novel therapeutic target for seizures and suggests phospho-modulation of KCC2 may be a potential strategy for increasing KCC2 function in patients with epilepsy. |
