Molecular Phenotypes Segregate Missense Mutations in SLC13A5 Epilepsy.

Area of Science:

• Molecular Biology
• Neuroscience
• Genetics

Background:

• The sodium-coupled citrate transporter (NaCT, SLC13A5) is crucial for citrate uptake, driven by sodium gradients.
• Mutations in SLC13A5 lead to early infantile epileptic encephalopathy type-25 (EIEE25, SLC13A5 Epilepsy) due to impaired neuronal and astrocyte citrate transport.
• Understanding the molecular mechanisms of these mutations is vital for developing effective treatments.

Purpose of the Study:

• To mechanistically classify six frequent SLC13A5 mutations.
• To investigate the impact of these mutations on protein cell surface expression and citrate transport function.
• To provide insights into the molecular defects underlying SLC13A5 Epilepsy.

Main Methods:

• Phenotyping of six frequent SLC13A5 mutations.
• Assessment of protein cell surface expression and citrate transport activity.
• Analysis of protein glycosylation, cellular localization, and half-life.

Main Results:

• Mutations were classified into Class I (impaired transport, normal expression) and Class II (low expression, ER retention, impaired transport).
• Class I mutants include C50R, T142M, and T227M; Class II mutants include G219R, S427L, and L488P.
• Post-translational defects, including protein folding and glycosylation issues in Class II mutants, were identified, with mRNA levels remaining similar to wild-type.

Conclusions:

• This classification provides a mechanistic understanding of SLC13A5 mutations in epilepsy.
• Class I and Class II mutations necessitate distinct therapeutic strategies.
• Findings illuminate NaCT trafficking pathways and offer a foundation for targeted treatments for SLC13A5 Epilepsy.