Human folate pathway transporters and enzymes (Folate pathway)

The human folate pathway comprises a sophisticated network of membrane transporters and intracellular enzymes that regulate the uptake and metabolism of folates, essential for one-carbon transfer reactions (Zheng & Cantley, 2019 [1.2.2]). Key transporters such as the reduced folate carrier (SLC19A1), proton-coupled folate transporter (SLC46A1), and folate receptors (FOLR1/2) mediate the cellular entry of folate vitamers (Matherly et al., 2018 [1.3.1]; Zhao et al., 2011 [1.2.3]). Intracellularly, enzymes like dihydrofolate reductase (DHFR), thymidylate synthase (TYMS), and methylenetetrahydrofolate reductase (MTHFR) utilize folate cofactors to support DNA synthesis, amino acid metabolism, and epigenetic regulation (Fowler, 2001 [1.1.2]; Kim, 2007 [1.1.2]). This pathway is a cornerstone of cancer chemotherapy and immunosuppression, as rapidly dividing cells depend heavily on these processes for genomic integrity and proliferation (Gonen & Assaraf, 2012 [1.2.1]). Antifolate drugs, including methotrexate and pemetrexed, target these components to disrupt nucleotide pools, leading to cell cycle arrest and apoptosis (Visentin et al., 2012 [1.3.1]). Beyond cancer, the pathway is vital for preventing neural tube defects and managing inflammatory conditions like rheumatoid arthritis (Momb & Appling, 2014 [1.2.2]). However, therapeutic use is often limited by systemic toxicities such as myelosuppression and the emergence of resistance through genetic adaptations in transporter or enzyme expression (Odin et al., 2003 [1.3.3]).

Other names

One-carbon metabolism pathwayFolate cycleFolate transport and metabolism systemFolate metabolic pathwayFolate-dependent one-carbon metabolism

Inhibition of folate-dependent enzymes (e.g., DHFR, TYMS, GARFTase) to disrupt de novo purine and thymidylate biosynthesis; competitive binding to folate transporters (e.g., SLC19A1, SLC46A1) and receptors (e.g., FOLR1) for cellular uptake or targeted drug delivery; metabolic trapping via polyglutamylation by FPGS.