Combined Targeted and Untargeted Profiling of HeLa Cells Deficient in Purine De Novo Synthesis

Wide metabolite coverage LC-MS/MS assay for the diagnosis of inherited metabolic disorders in urine

OBJECTIVE

The laboratory diagnosis of inherited metabolic disorders (IMD) has undergone significant development in recent decades, mainly due to the use of mass spectrometry, which allows rapid multicomponent analysis of a wide range of metabolites. Combined with advanced software tools, the diagnosis becomes more efficient as a benefit for both physicians and patients.

METHODS

A hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry assay for determination of urinary purines, pyrimidines, N-acylglycines, N-acetylated amino acids, sugars, sugar alcohols and other diagnostically important biomarkers was developed and validated. Evaluation of the results consisting of utilisation of robust scaling and advanced visualization tools is simple and even suitable for urgent requirements.

RESULTS

The developed method, covering 65 biomarkers, provides a comprehensive diagnostic platform for 51 IMD. For most analytes, linearity with R2 > 0.99, intra and inter-day accuracy between 80 and 120 % and precision lower than 20 % were achieved. Diagnostic workflow was evaluated on 47 patients and External Quality Assurance samples involving a total of 24 different IMD. Over seven years, more than 2300 urine samples from patients suspected for IMD have been routinely analysed.

CONCLUSIONS

This method offers the advantage of a broad coverage of intermediate metabolites of interest and therefore may be a potential alternative and simplification for clinical laboratories that use multiple methods for screening these markers.

Cytoophidia: a conserved yet promising mode of enzyme regulation in nucleotide metabolism

Nucleotide biosynthesis encompasses both de novo and salvage synthesis pathways, each characterized by significant material and procedural distinctions. Despite these differences, cells with elevated nucleotide demands exhibit a preference for the more intricate de novo synthesis pathway, intricately linked to modes of enzyme regulation. In this study, we primarily scrutinize the biological importance of a conserved yet promising mode of enzyme regulation in nucleotide metabolism-cytoophidia. Cytoophidia, comprising cytidine triphosphate synthase or inosine monophosphate dehydrogenase, is explored across diverse biological models, including yeasts, Drosophila, mice, and human cancer cell lines. Additionally, we delineate potential biomedical applications of cytoophidia. As our understanding of cytoophidia deepens, the roles of enzyme compartmentalization and polymerization in various biochemical processes will unveil, promising profound impacts on both research and the treatment of metabolism-related diseases.

PAICS as a potential target for cancer therapy linking purine biosynthesis to cancer progression

Tumor cells are required to undergo metabolic reprogramming for rapid development and progression, and one of the metabolic characteristics of cancer cells is the excessive synthesis and utilization of nucleotides. Abnormally increased nucleotides and their metabolites not only directly accelerate tumor cell progression but also indirectly act on stromal cells in the tumor microenvironment (TME) via a paracrine manner to regulate tumor progression. Purine nucleotides are mainly produced via de novo nucleotide synthesis in tumor cells; therefore, intervening in their synthesis has emerged as a promising strategy in anti-tumor therapy. De novo purine synthesis is a 10-step reaction catalyzed by six enzymes to synthesize inosine 5-monophosphate (IMP) and subsequently synthesize AMP and GMP. Phosphoribosylaminoimidazole carboxylase/phosphori-bosylaminoimidazole succinocarboxamide synthetase (PAICS) is a bifunctional enzyme that catalyzes de novo purine synthesis. Aberrantly elevated PAICS expression in various tumors is associated with poor prognosis. Evidence suggests that PAICS and its catalytic product, N-succinylcarboxamide-5-aminoimidazole ribonucleotide (SAICAR), could inhibit tumor cell apoptosis and promote the growth, epithelial-mesenchymal transition (EMT), invasion, and metastasis by regulating signaling pathways such as pyruvate kinase M2 (PKM2), extracellular signal-related kinases 1 and 2 (ERK1/2), focal adhesion kinase (FAK) and so on. This review summarizes the structure, biological functions and the molecular mechanisms of PAICS in cancer development and discusses its potential to be a target for tumor therapy.