Impairments in SHMT2 expression or cellular folate availability reduce oxidative phosphorylation and pyruvate kinase...

Area of Science:

• Mitochondrial biology
• Metabolic pathways
• Cellular energy production

Background:

• Serine hydroxymethyltransferase 2 (SHMT2) is crucial for mitochondrial folate metabolism.
• SHMT2 variants and decreased expression are linked to impaired mitochondrial function and aging.
• Folate-mediated one-carbon metabolism (FOCM) is functionally coordinated with the oxidative phosphorylation system.

Purpose of the Study:

• To investigate the role of SHMT2 and folate availability in mitochondrial function, energy metabolism, and proliferation.
• To examine heterozygous and homozygous cell models of reduced SHMT2 expression.
• To assess the impact of SHMT2 loss on cellular energy production and metabolic pathways.

Main Methods:

• Primary mouse embryonic fibroblasts (MEF) and HAP1 cells with altered SHMT2 expression were used.
• Cells were cultured in folate-sufficient or low-folate media.
• Assessed proliferation, folate levels, mtDNA content, protein levels, enzyme activity, membrane potential, and mitochondrial function.

Main Results:

• SHMT2 loss impaired folate accumulation, mitochondrial DNA content, formate production, membrane potential, and respiration.
• Formate supplementation rescued proliferation in folate-deficient HAP1 cells but not in SHMT2-deficient cells.
• Pyruvate kinase activity and protein levels were reduced, while mitochondrial mass and biogenesis markers were increased.

Conclusions:

• Disrupted mitochondrial FOCM impairs mitochondrial folate accumulation, respiration, formate production, and glycolysis.
• Reduced SHMT2 levels negatively impact cellular proliferation.
• Compensatory increases in mitochondrial biogenesis do not fully restore function in SHMT2-deficient cells.