γ2 GABAAR Trafficking and the Consequences of Human Genetic Variation

GABA type A receptors (GABA(A)Rs) mediate the majority of fast inhibitory neurotransmission in the central nervous system (CNS). Most prevalent as heteropentamers composed of two alpha, two beta, and a gamma 2 subunit, these ligand-gated ionotropic chloride channels are capable of extensive genetic diversity (alpha 1-6, beta 1-3, gamma 1-3, delta, epsilon, theta, pi, rho 1-3). Part of this selective GABA(A)R assembly arises from the critical role for gamma 2 in maintaining synaptic receptor localization and function. Accordingly, mutations in this subunit account for over half of the known epilepsy-associated genetic anomalies identified in GABA(A)Rs. Fundamental structure-function studies and cellular pathology investigations have revealed dynamic GABA(A)R trafficking and synaptic scaffolding as critical regulators of GABAergic inhibition. Here, we introduce in vitro and in vivo findings regarding the specific role of the gamma 2 subunit in receptor trafficking. We then examine gamma 2 subunit human genetic variation and assess disease related phenotypes and the potential role of altered GABA(A)R trafficking. Finally, we discuss new-age imaging techniques and their potential to provide novel insight into critical regulatory mechanisms of GABA(A)R function.