Role for human arylamine N-acetyltransferase 1 in the methionine salvage pathway

Area of Science:

• Biochemistry
• Cancer Biology
• Metabolomics

Background:

• Arylamine N-acetyltransferase 1 (NAT1) is a Phase II drug metabolizing enzyme linked to cancer cell growth and survival.
• The precise mechanisms by which NAT1 influences cancer remain largely unknown.

Purpose of the Study:

• To investigate the role of NAT1 in cancer cell metabolism, focusing on folate catabolism and the S-adenosylmethionine (SAM) cycle.
• To identify specific metabolic pathways affected by NAT1 knockdown in cancer cells.

Main Methods:

• Utilized a focused metabolomics approach to analyze changes in cellular metabolites after NAT1 knockdown using shRNA.
• Assessed cancer cell growth in supplemented media and measured enzyme expression levels.
• Employed siRNA to investigate the interplay between NAT1 and isomerase MRI-1.

Main Results:

• NAT1 knockdown led to decreased acetylation of p-aminobenzoylglutamate (pABG) but did not alter intracellular pABG levels or SAM cycle components.
• Homocysteine flux in the medium changed post-NAT1 knockdown, suggesting a role in methionine synthesis.
• NAT1 knockdown inhibited the methionine salvage pathway in HT-29 cells, attributed to low MRI-1 expression, indicating enzyme redundancy.

Conclusions:

• Human NAT1 plays a novel endogenous role in regulating the methionine salvage pathway, potentially explaining its influence on cancer cell growth and survival.
• A functional redundancy exists between NAT1 and MRI-1 in certain cancer cell lines.
• The findings provide new insights into the metabolic underpinnings of NAT1's role in cancer.