Impaired formation of high-order gephyrin oligomers underlies gephyrin dysfunction-associated pathologies

Seungjoon Kim; Mooseok Kang; Dongseok Park; Ae-Ree Lee; Heinrich Betz; Jaewon Ko; Iksoo Chang; Ji Won Um

doi:10.1016/j.isci.2021.102037

Impaired formation of high-order gephyrin oligomers underlies gephyrin dysfunction-associated pathologies

iScience. 2021 Jan 7;24(2):102037. doi: 10.1016/j.isci.2021.102037. eCollection 2021 Feb 19.

Authors

Seungjoon Kim¹, Mooseok Kang^{1

2}, Dongseok Park¹, Ae-Ree Lee^{1

2}, Heinrich Betz³, Jaewon Ko¹, Iksoo Chang^{1

2

4}, Ji Won Um^{1

2}

Affiliations

¹ Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea.
² Core Protein Resources Center, DGIST, Daegu 42988, Korea.
³ Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
⁴ Supercomputing Bigdata Center, DGIST, Daegu 42988, Korea.

Abstract

Gephyrin is critical for the structure, function, and plasticity of inhibitory synapses. Gephyrin mutations have been linked to various neurological disorders; however, systematic analyses of the functional consequences of these mutations are lacking. Here, we performed molecular dynamics simulations of gephyrin to predict how six reported point mutations might change the structural stability and/or function of gephyrin. Additional in silico analyses revealed that the A91T and G375D mutations reduce the binding free energy of gephyrin oligomer formation. Gephyrin A91T and G375D displayed altered clustering patterns in COS-7 cells and nullified the inhibitory synapse-promoting effect of gephyrin in cultured neurons. However, only the G375D mutation reduced gephyrin interaction with GABA_A receptors and neuroligin-2 in mouse brain; it also failed to normalize deficits in GABAergic synapse maintenance and neuronal hyperactivity observed in hippocampal dentate gyrus-specific gephyrin-deficient mice. Our results provide insights into biochemical, cell-biological, and network-activity effects of the pathogenic G375D mutation.

Keywords: Molecular Biology; Neuroscience; Structural Biology.