Skip to main content
NUTRITION 2023 Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Topical Area: Vitamins and Minerals

Vitamins and Minerals (Poster Session)

(P11-010-23) Increased Mitochondrial TYMS Localization Improves Mitochondrial Function

Saturday, July 22, 2023
12:00 PM – 1:00 PM ET
Location: Poster Board 233
Disclosure(s):
Luisa F. Castillo, BS: No relevant financial relationship(s) with ineligible companies to disclose.


Objectives: Maintenance of cellular thymidylate (dTMP, or the “T” base in DNA) pools is essential for accurate nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) replication and integrity. The enzymes required for de novo dTMP synthesis translocate to the nucleus and form a multi-enzyme complex that localizes to sites of DNA replication and repair; translocation and comlex formation is essential to support dTMP synthesis within the nuclear compartment. dTMP synthesis is compartmentalized within the cell, occurring with unique isozymes within the nuclear, mitochondrial, and cytosolic compartments. However, one of these enzymes, thymidylate synthase (TYMS), is shared between all three cellular compartments. The aim of these studies was to elucidate the role of TYMS mitochondrial partitioning in supporting mitochondrial dTMP synthesis and supporting mtDNA integrity.

Methods: Stable HeLa cell lines were created with plasmids conferring TYMS over-expression localized specifically to the mitochondria (mito-TYMS), then cultured in defined medium containing “control” levels of folate (25 nM (6S)5-formyltetrahydrofolate) or “folate-deficient” medium (2 nM (6S)5-formyltetrahydrofolate).

Results: In the control medium, over-expression of mito-TYMS led to a 4-fold increase in mtDNA copy number, and mitochondrial membrane potential was increased by 3-fold. Importantly, there was also a 2-fold increase in mitochondrial oxygen consumption (OCR) in mito-TYMS expressing cells. There was no difference in mitochondrial mass based on TYMS overexpression or folate exposure.

Conclusions: These data suggest that mitochondrial TYMS localization may be a key modifier of mitochondrial dTMP synthesis capacity. These findings may have therapeutic implications, as TYMS is targeted by the chemotherapeutic agent 5-fluorouracil, and changes in mtDNA copy number and mitochondrial membrane potential are associated with various cancers and disease states.

Funding Sources: N/A