GABRA1 frameshift variants impair GABA_A receptor proteostasis

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Gamma-aminobutyric acid type A receptors (GABA_ARs) are crucial inhibitory ion channels in the central nervous system.
• Genetic variants in GABA_AR subunit genes are linked to epilepsy.
• Frameshift variants can lead to truncated subunits, but their pathogenic mechanisms are unclear.

Purpose of the Study:

• To investigate the molecular mechanisms and functional consequences of four clinical frameshift variants in the GABA_AR α₁ subunit (GABRA1 gene).
• To evaluate how these variants affect GABA_AR biogenesis, trafficking, and proteostasis.
• To understand the role of these variants in the pathogenesis of GABA_AR-associated epilepsy.

Main Methods:

• Generated and analyzed four frameshift variants (K401fs, S326fs, V290fs, F272fs) in the GABRA1 gene.
• Utilized HEK293T cells to assess cell surface trafficking and ion channel function.
• Investigated endoplasmic reticulum (ER) retention and the unfolded protein response (UPR) activation.

Main Results:

• All four variants showed significantly reduced cell surface expression, leading to non-functional ion channels.
• The severity of proteostasis deficiency varied among variants, correlating with transmembrane domain deletions.
• Variants exhibited ER retention and differentially activated the UPR.

Conclusions:

• Frameshift variants in GABRA1 impair GABA_AR function through distinct yet overlapping proteostasisdeficiency mechanisms.
• These findings provide insights into the molecular basis of genetic epilepsy caused by GABRA1 variants.
• The study highlights the importance of proper protein biogenesis and trafficking for GABA_AR function.