Scientific publications

Exogenous aralar/slc25a12 can replace citrin/slc25a13 as malate aspartate shuttle component in liver

Mar 16, 2023 | Magazine: Molecular Genetics and Metabolism Reports

Luis González-Moreno 1 2 3, Andrea Santamaría-Cano 1 2 3, Alberto Paradela 4, María Luz Martínez-Chantar 5 6, Miguel Á Martín 7 8 9, Mercedes Pérez-Carreras 10, Alberto García-Picazo 11, Jesús Vázquez 12 13, Enrique Calvo 12 13, Gloria González-Aseguinolaza 14 15, Takeyori Saheki 16, Araceli Del Arco 2 3 17 18, Jorgina Satrústegui 1 2 3, Laura Contreras 1 2 3


The deficiency of CITRIN, the liver mitochondrial aspartate-glutamate carrier (AGC), is the cause of four human clinical phenotypes, neonatal intrahepatic cholestasis caused by CITRIN deficiency (NICCD), silent period, failure to thrive and dyslipidemia caused by CITRIN deficiency (FTTDCD), and citrullinemia type II (CTLN2). Clinical symptoms can be traced back to disruption of the malate-aspartate shuttle due to the lack of citrin. A potential therapy for this condition is the expression of aralar, the AGC present in brain, to replace citrin. To explore this possibility we have first verified that the NADH/NAD+ ratio increases in hepatocytes from citrin(-/-) mice, and then found that exogenous aralar expression reversed the increase in NADH/NAD+ observed in these cells. Liver mitochondria from citrin (-/-) mice expressing liver specific transgenic aralar had a small (~ 4-6 nmoles x mg prot-1 x min-1) but consistent increase in malate aspartate shuttle (MAS) activity over that of citrin(-/-) mice.

These results support the functional replacement between AGCs in the liver. To explore the significance of AGC replacement in human therapy we studied the relative levels of citrin and aralar in mouse and human liver through absolute quantification proteomics. We report that mouse liver has relatively high aralar levels (citrin/aralar molar ratio of 7.8), whereas human liver is virtually devoid of aralar (CITRIN/ARALAR ratio of 397). This large difference in endogenous aralar levels partly explains the high residual MAS activity in liver of citrin(-/-) mice and why they fail to recapitulate the human disease, but supports the benefit of increasing aralar expression to improve the redox balance capacity of human liver, as an effective therapy for CITRIN deficiency.

CITA DEL ARTÍCULO Mol Genet Metab Rep. 2023 Mar 16:35:100967. doi: 10.1016/j.ymgmr.2023.100967. eCollection 2023 Jun.