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UDP-N-acetylglucosamine (UDP-GlcNAc) is a crucial sugar nucleotide for glycan synthesis in eukaryotes. In the malaria parasite Plasmodium falciparum , UDP-GlcNAc is synthesized via the hexosamine biosynthetic pathway (HBP) and is essential for glycosylphosphatidylinositol (GPI) anchor production, the most prominent form of protein glycosylation in the parasite. In this study, we explore a conditional knockout of glucosamine-6-phosphate N-acetyltransferase ( Pf GNA1), a key HBP enzyme. Pf GNA1 depletion led to significant disruptions in HBP metabolites, impairing GPI biosynthesis and causing mislocalization of the merozoite surface protein 1 (MSP1), the most abundant GPI-anchored protein in the parasite. Furthermore, parasites were arrested at the schizont stage, exhibiting severe segmentation defects and an incomplete rupture of the parasitophorous vacuole membrane (PVM), preventing egress from host red blood cells. Our findings demonstrate the critical role of HBP and GPI biosynthesis in P. falciparum asexual blood stage development and underscore the potential of targeting these pathways as a therapeutic strategy against malaria.

The cell surface of Toxoplasma gondii is rich in glycoconjugates which hold diverse and vital functions in the lytic cycle of this obligate intracellular parasite. Additionally, the cyst wall of bradyzoites, that shields the persistent form responsible for chronic infection from the immune system, is heavily glycosylated. Formation of glycoconjugates relies on activated sugar nucleotides, such as uridine diphosphate N -acetylglucosamine (UDP-GlcNAc). The glucosamine-phosphate- N -acetyltransferase (GNA1) generates N -acetylglucosamine-6-phosphate critical to produce UDP-GlcNAc. Here, we demonstrate that downregulation of T . gondii GNA1 results in a severe reduction of UDP-GlcNAc and a concomitant drop in glycosylphosphatidylinositols (GPIs), leading to impairment of the parasite’s ability to invade and replicate in the host cell. Surprisingly, attempts to rescue this defect through exogenous GlcNAc supplementation fail to completely restore these vital functions. In depth metabolomic analyses elucidate diverse causes underlying the failed rescue: utilization of GlcNAc is inefficient under glucose-replete conditions and fails to restore UDP-GlcNAc levels in GNA1-depleted parasites. In contrast, GlcNAc-supplementation under glucose-deplete conditions fully restores UDP-GlcNAc levels but fails to rescue the defects associated with GNA1 depletion. Our results underscore the importance of glucosamine-6-phosphate acetylation in governing T . gondii replication and invasion and highlight the potential of the evolutionary divergent GNA1 in Apicomplexa as a target for the development of much-needed new therapeutic strategies.

Castration-resistant prostate cancer (CRPC) progresses despite androgen deprivation therapy, as cancer cells adapt to grow without testosterone, becoming more aggressive and prone to metastasis. CRPC biology complicates the development of effective therapies, posing challenges for patient care. Recent gene-expression and metabolomics studies highlight the Hexosamine Biosynthetic Pathway (HBP) as a critical player, with key components like GNPNAT1 (Glucosamine-phosphate N-acetyltransferase 1) being downregulated in CRPC. GNPNAT1 knockdown in pre-clinical models has been shown to increase growth and metastasis in CRPC tumors, though the mechanisms remain unclear. To investigate the cellular basis of these CRPC phenotypes, we generated a CRISPR-Cas9 knockout model of GNPNAT1 in 22Rv1 CRPC cells, analyzing its impact on transcriptomic and glycoproteomic profiles of cells. We find that HBP inhibition disrupts the cytoskeleton, altering mitotic progression and promoting uncontrolled growth. GNPNAT1 KO cells showed reduced levels of cytoskeletal filaments, such as actin and microtubules, leading to cell structure disorganization and chromosomal mis-segregation. GNPNAT1 inhibition also activated PI3K/AKT signaling, promoting cell proliferation, impaired cell adhesion by mis-localizing Eph Receptor B6, enhancing migration via the RhoA (Ras homolog family member A) pathway and promoting epithelial-to-mesenchymal transition. These findings suggest that HBP plays a critical role in regulating CRPC cell behavior, and targeting this pathway could provide a novel therapeutic approach.

Background Glucosamine-6-phosphate N -acetyltransferase (GNA1) is the key enzyme that causes overproduction of N -acetylglucosamine in Bacillus subtilis . Previously, we increased GlcNAc production by promoting the expression of GNA1 from Caenorhabditis elegans ( Ce GNA1) in an engineered B. subtilis strain BSGN12. In this strain overflow metabolism to by-products acetoin and acetate had been blocked by mutations, however pyruvate accumulated as an overflow metabolite. Although overexpression of Ce GNA1 drove carbon flux from pyruvate to the GlcNAc synthesis pathway and decreased pyruvate accumulation, the residual pyruvate reduced the intracellular pH, resulting in inhibited Ce GNA1 activity and limited GlcNAc production. Results In this study, we attempted to further overcome pyruvate overflow by enzyme engineering and host engineering for enhanced GlcNAc production. To this end, the key enzyme Ce GNA1 was evolved through error-prone PCR under pyruvate stress to enhance its catalytic activity. Then, the urease from Bacillus paralicheniformis was expressed intracellularly to neutralize the intracellular pH, making it more robust in growth and more efficient in GlcNAc production. It was found that the activity of mutant Ce GNA1 increased by 11.5% at pH 6.5–7.5, with the catalytic efficiency increasing by 27.5% to 1.25 s −1  µM −1 . Modulated expression of urease increased the intracellular pH from 6.0 to 6.8. The final engineered strain BSGN13 overcame pyruvate overflow, produced 25.6 g/L GlcNAc with a yield of 0.43 g GlcNAc/g glucose in a shake flask fermentation and produced 82.5 g/L GlcNAc with a yield of 0.39 g GlcNAc/g glucose by fed-batch fermentation, which was 1.7- and 1.2-times, respectively, of the yield achieved previously. Conclusions This study highlights a strategy that combines pathway enzyme engineering and host engineering to resolve overflow metabolism in B. subtilis for the overproduction of GlcNAc. By means of modulated expression of urease reduced pyruvate burden, conferred bacterial survival fitness, and enhanced GlcNAc production, all of which improved our understanding of co-regulation of cell growth and metabolism to construct more efficient B. subtilis cell factories.

Apicomplexa form a phylum of obligate parasitic protozoa of great clinical and veterinary importance. These parasites synthesize glycoconjugates for their survival and infectivity, but the enzymatic steps required to generate the glycosylation precursors are not completely characterized. In particular, glucosamine-phosphate N-acetyltransferase (GNA1) activity, needed to produce the essential UDP-N-acetylglucosamine (UDP-GlcNAc) donor, has not been identified in any Apicomplexa. We scanned the genomes of Plasmodium falciparum and representatives from six additional main lineages of the phylum for proteins containing the Gcn5-related N-acetyltransferase (GNAT) domain. One family of GNAT-domain containing proteins, composed by a P. falciparum sequence and its six apicomplexan orthologs, rescued the growth of a yeast temperature-sensitive GNA1 mutant. Heterologous expression and in vitro assays confirmed the GNA1 enzymatic activity in all lineages. Sequence, phylogenetic and synteny analyses suggest an independent origin of the Apicomplexa-specific GNA1 family, parallel to the evolution of a different GNA1 family in other eukaryotes. The inability to disrupt an otherwise modifiable gene target suggests that the enzyme is essential for P. falciparum growth. The relevance of UDP-GlcNAc for parasite viability, together with the independent evolution and unique sequence features of Apicomplexa GNA1, highlights the potential of this enzyme as a selective therapeutic target against apicomplexans.

Glucosamine 6-phosphate N-acetyltransferase 1 (GNPNAT1) serves as a critical rate-limiting enzyme within the hexosamine biosynthetic pathway (HBP). However, its expression patterns, clinical significance in various cancers, and role in modulating the tumor immune microenvironment are not well understood. This study analyzed the differential expression patterns of GNPNAT1 and its potential association with patient prognosis using pan-cancer datasets. Using a multi-omics approach and multiple databases, we examined the correlations between GNPNAT1 expression and tumor stemness, mutational profiles, RNA modifications, the tumor immune microenvironment, and drug sensitivity. Additionally, we conducted enrichment analyses and functional experiments for cervical cancer (CC) to preliminarily elucidate the signaling pathways and biological processes that GNPNAT1 may regulate. GNPNAT1 exhibits aberrant expression in various tumor types, and its expression levels hold substantial prognostic implications for some cancer patients. In certain tumors, GNPNAT1 expression is associated with tumor mutational profiles, RNA modifications, and drug sensitivity. Furthermore, the study found that GNPNAT1 expression levels correlate with key molecules, including immune checkpoint genes, chemokines, and immunostimulatory factors. Enrichment analyses in CC suggests that GNPNAT1 may be involved in cell adhesion and immune-related pathways. Knockdown of GNPNAT1 was shown by functional assays, significantly attenuated CC cell proliferation and migration. GNPNAT1 may serve as a promising prognostic biomarker for certain tumors, such as CC. Its association with immune regulation and treatment resistance highlights its potential as a new target for immunotherapy interventions.

An approach for designing individual expression environments that reduce or prevent protein aggregation and precipitation is described. Inefficient folding of difficult proteins in unfavorable translation environments can cause significant losses of overexpressed proteins as precipitates or inclusion bodies. A number of chemical chaperones including alcohols, polyols, polyions or polymers are known to have positive effects on protein stability. However, conventional expression approaches can use such stabilizing agents only post-translationally during protein extraction and purification. Proteins that already precipitate inside of the producer cells cannot be addressed. The open nature of cell-free protein expression systems offers the option to include single chemicals or cocktails of stabilizing compounds already into the expression environment. We report an approach for systematic screening of stabilizers in order to improve the solubility and quality of overexpressed proteins co-translationally. A comprehensive list of representative protein stabilizers from the major groups of naturally occurring chemical chaperones has been analyzed and their concentration ranges tolerated by cell-free expression systems have been determined. As a proof of concept, we have applied the method to improve the yield of proteins showing instability and partial precipitation during cell-free synthesis. Stabilizers that co-translationally improve the solubility and functional folding of human glucosamine 6-phosphate N-acetyltransferase have been identified and cumulative effects of stabilizers have been studied.

Background. Glucosamine-Phosphate N-Acetyltransferase 1 (GNPNAT1) is a critical enzyme in the biosynthesis of uridine diphosphate-N-acetylglucosamine. It has many important functions, such as protein binding, monosaccharide binding, and embryonic development and growth. However, the role of GNPNAT1 in lung adenocarcinoma (LUAD) remains unclear. Methods. In this study, we explored the expression pattern and prognostic value of GNPNAT1 in LUAD across TCGA and GEO databases and assessed its independent prognostic value via Cox analysis. LinkedOmics and GEPIA2 were applied to investigate coexpression and functional networks associated with GNPNAT1. The TIMER web tool was deployed to assess the correlation between GNPNAT1 and the main six types of tumor-infiltrating immune cells. Besides, the correlations between GNPNAT1 and the LUAD common genetic mutations, TMB, and immune signatures were examined. Results. GNPNAT1 was validated upregulated in tumor tissues in TCGA-LUAD and GEO cohorts. Moreover, in both TCGA and GEO cohorts, high GNPNAT1 expression was found to be associated with poor overall survival. Cox analysis showed that high GNPNAT1 expression was an independent risk factor for LUAD. Functional network analysis suggested that GNPNAT1 regulates cell cycle, ribosome, proteasome, RNA transport, and spliceosome signaling through pathways involving multiple cancer-related kinases and E2F family. In addition, GNPNAT1 correlated with infiltrating levels of B cells, CD4+ T cells, and dendritic cells. B cells and dendritic cells could predict the outcome of LUAD, and B cells and CD4+ T cells were significant independent risk factors. The TMB and mutations of KRAS, EGFR, STK11, and TP53 were correlated with GNPNAT1. At last, the correlation analysis showed GNPNAT1 correlated with most of the immune signatures we performed. Conclusion. Our findings showed that GNPNAT1 was correlated to the prognosis and immune infiltration of LUAD. In particular, the tight relationship between GNPNAT1 and B cell marker genes may be the epicenter of the immune response and one of the key factors affecting the prognosis. Our findings laid the foundation for further research on the immunomodulatory role of GNPNAT1 in LUAD.

To study the regulatory mechanisms underlying lignin biosynthesis, we isolated and characterized lignescens (lig), a previously undescribed temperature-sensitive mutant of Arabidopsis thaliana that exhibits ectopic lignin deposition and growth defects under high-temperature conditions. The lig mutation was identified as a single base transition in GNA1 encoding glucosamine-6-phosphate N-acetyltransferase (GNA), a critical enzyme of UDP-AZ-acetylglucosamine (UDP-GlcNAc) biosynthesis, lig harbors a glycine-to-serine substitution at residue 68 (G68S) of GNA1. Enzyme activity assays of the mutant protein (GNA1 G68S ) showed its thermolability relative to the wild-type protein. The lig mutant exposed to the restrictive temperature contained a significantly smaller amount of UDP-GlcNAc than did the wild type. The growth defects and ectopic lignification of lig were suppressed by the addition of UDP-GlcNAc. Since UDP-GlcNAc is an initial sugar donor of N-glycan synthesis and impaired N-glycan synthesis is known to induce the unfolded protein response (UPR), we examined possible relationships between N-glycan synthesis, UPR, and the lig phenotype. N-glycans were reduced and LUMINAL BINDING PROTEIN3, a typical UPR gene, was expressed in lig at the restrictive temperature. Furthermore, treatment with UPR-inducing reagents phenocopied the lig mutant. Our data collectively suggest that impairment of N-glycan synthesis due to a shortage of UDP-GlcNAc leads to ectopic lignin accumulation, mostly through the UPR.

Abraxane (Abr), a US Food and Drug Administration-approved albumin-bound nanoparticle applied for the treatment of non-small-cell lung cancer, has been reported to be more effective than paclitaxel (PTX). To further understand the molecular mechanisms that produce this superior drug efficacy of Abr, a quantitative proteomic approach has been applied to investigate the global protein expression profiles of lung cancer cell A549 treated with Abr and PTX. Only one protein, namely, glucosamine 6-phosphate N-acetyltransferase 1 (GNA1), showed significant differential expression ( <0.05) in the cutoff of 2.0 fold, suggesting that Abr can be used safely as a substitute for PTX. GNA1 is a key enzyme in the biosynthesis of uridine diphosphate-N-acetylglucosamine, which is an important donor substrate for N-linked glycosylation and has several important functions such as embryonic development and growth. Albumin plays a major role in the regulation of this protein. In summary, this study first shows that the superior drug effect of Abr is mainly due to the downregulation of GNA1, which causes proliferative delay and cell adhesion defect. It is also noteworthy that the deficiency of GNA1 might reduce insulin secretion which correlates with type 2 diabetes.