Alterations in GABA _A-Receptor Trafficking and Synaptic Dysfunction in Brain Disorders

GABA _A receptors (GABA _AR) are the major players in fast inhibitory neurotransmission in the central nervous system (CNS). Regulation of GABA _AR trafficking and the control of their surface expression play important roles in the modulation of the strength of synaptic inhibition. Different pieces of evidence show that alterations in the surface distribution of GABA _AR and dysregulation of their turnover impair the activity of inhibitory synapses. A diminished efficacy of inhibitory neurotransmission affects the excitatory/inhibitory balance and is a common feature of various disorders of the CNS characterized by an increased excitability of neuronal networks. The synaptic pool of GABA _AR is mainly controlled through regulation of internalization, recycling and lateral diffusion of the receptors. Under physiological condition these mechanisms are finely coordinated to define the strength of GABAergic synapses. In this review article, we focus on the alteration in GABA _AR trafficking with an impact on the function of inhibitory synapses in various disorders of the CNS. In particular we discuss how similar molecular mechanisms affecting the synaptic distribution of GABA _AR and consequently the excitatory/inhibitory balance may be associated with a wide diversity of pathologies of the CNS, from psychiatric disorders to acute alterations leading to neuronal death. A better understanding of the cellular and molecular mechanisms that contribute to the impairment of GABAergic neurotransmission in these disorders, in particular the alterations in GABA _AR trafficking and surface distribution, may lead to the identification of new pharmacological targets and to the development of novel therapeutic strategies.