Differential vesicular sorting of AMPA and GABAA receptors

In mature neurons AMPA receptors cluster at excitatory synapses primarily on dendritic spines, whereas GABA(A) receptors cluster at inhibitory synapses mainly on the soma and dendritic shafts. The molecular mechanisms underlying the precise sorting of these receptors remain unclear. By directly studying the constitutive exocytic vesicles of AMPA and GABA(A) receptors in vitro and in vivo, we demonstrate that they are initially sorted into different vesicles in the Golgi apparatus and inserted into distinct domains of the plasma membrane. These insertions are dependent on distinct Rab GTPases and SNARE complexes. The insertion of AMPA receptors requires SNAP25-syntaxin1A/B-VAMP2 complexes, whereas insertion of GABA(A) receptors relies on SNAP23-syntaxin1A/B-VAMP2 complexes. These SNARE complexes affect surface targeting of AMPA or GABA(A) receptors and synaptic transmission. Our studies reveal vesicular sortingmechanisms controlling the constitutive exocytosis of AMPA and GABA(A) receptors, which are critical for the regulation of excitatory and inhibitory responses in neurons.