Slc13a5, also known as NaCT or mINDY, is a Na⁺ -coupled citrate co-transporter. It mediates the entry of extracellular citrate into the cytosol, playing a crucial role in cellular metabolic homeostasis [2,3,4,5,7,8]. In the liver, it affects fatty acid and cholesterol synthesis, fatty acid oxidation, glycolysis, and gluconeogenesis; in neurons, it is essential for the synthesis of neurotransmitters like glutamate, GABA, and acetylcholine [5]. Perturbations in its expression are linked to non-alcoholic fatty liver disease, obesity, insulin resistance, cell proliferation, and early infantile epileptic encephalopathy [3]. Genetically modified mouse models, such as Slc13a5-knockout mice, have been instrumental in studying its functions [8].

Deletion of Slc13a5 in mice leads to a phenotype that protects against diet-induced obesity and diabetes [5]. However, loss-of-function mutations in humans cause severe early infantile epileptic encephalopathy-25/developmental epileptic encephalopathy-25 (EIEE25/DEE25) [5]. The difference might be due to species-specific functional features, as mouse Slc13a5 is a low-capacity transporter while human SLC13A5 is high-capacity [5]. In addition, SLC13A5-deficient Huh7 cells show compromised citrate uptake and catabolism, and exogenous citrate contributes to intermediary metabolism mainly under hypoxic conditions in SLC13A5-deficient hepatocellular carcinoma cells and primary rat cortical neurons [7].

In conclusion, Slc13a5 is vital for maintaining metabolic homeostasis and neurotransmitter synthesis. The study of Slc13a5-knockout mouse models has revealed its dual-sided role in metabolism-related protection and neurological disorders. Understanding its function can provide insights into the mechanisms of metabolic diseases and epileptic encephalopathies, potentially guiding the development of targeted therapies [1,2,3,5,6,7,8].

References:

1. Goodspeed, Kimberly, Liu, Judy S, Nye, Kimberly L, Minassian, Berge A, Bailey, Rachel M. 2022. SLC13A5 Deficiency Disorder: From Genetics to Gene Therapy. In Genes, 13, . doi:10.3390/genes13091655. https://pubmed.ncbi.nlm.nih.gov/36140822/

2. Gill, Dipender, Zagkos, Loukas, Gill, Rubinder, Burgess, Stephen, Zahn, Grit. 2023. The citrate transporter SLC13A5 as a therapeutic target for kidney disease: evidence from Mendelian randomization to inform drug development. In BMC medicine, 21, 504. doi:10.1186/s12916-023-03227-5. https://pubmed.ncbi.nlm.nih.gov/38110950/

3. Li, Zhihui, Wang, Hongbing. 2021. Molecular Mechanisms of the SLC13A5 Gene Transcription. In Metabolites, 11, . doi:10.3390/metabo11100706. https://pubmed.ncbi.nlm.nih.gov/34677420/

4. Chen, Fangfang, Willenbockel, Hanna Friederike, Cordes, Thekla. 2023. Mapping the Metabolic Niche of Citrate Metabolism and SLC13A5. In Metabolites, 13, . doi:10.3390/metabo13030331. https://pubmed.ncbi.nlm.nih.gov/36984771/

5. Kopel, Jonathan J, Bhutia, Yangzom D, Sivaprakasam, Sathish, Ganapathy, Vadivel. . Consequences of NaCT/SLC13A5/mINDY deficiency: good versus evil, separated only by the blood-brain barrier. In The Biochemical journal, 478, 463-486. doi:10.1042/BCJ20200877. https://pubmed.ncbi.nlm.nih.gov/33544126/

6. Beltran, Adriana S. 2024. Novel Approaches to Studying SLC13A5 Disease. In Metabolites, 14, . doi:10.3390/metabo14020084. https://pubmed.ncbi.nlm.nih.gov/38392976/

7. Kumar, Avi, Cordes, Thekla, Thalacker-Mercer, Anna E, Murphy, Anne N, Metallo, Christian M. . NaCT/SLC13A5 facilitates citrate import and metabolism under nutrient-limited conditions. In Cell reports, 36, 109701. doi:10.1016/j.celrep.2021.109701. https://pubmed.ncbi.nlm.nih.gov/34525352/

8. Bhutia, Yangzom D, Kopel, Jonathan J, Lawrence, John J, Neugebauer, Volker, Ganapathy, Vadivel. 2017. Plasma Membrane Na⁺-Coupled Citrate Transporter (SLC13A5) and Neonatal Epileptic Encephalopathy. In Molecules (Basel, Switzerland), 22, . doi:10.3390/molecules22030378. https://pubmed.ncbi.nlm.nih.gov/28264506/