The Biomedical Importance of the Missing Pathway for Farnesol and Geranylgeraniol Salvage

Mononuclear phagocyte morphological response to chemoattractants is dependent on geranylgeranyl pyrophosphate

Statins are used to treat hypercholesterolemia and function by inhibiting the production of the rate-limiting metabolite mevalonate. As such, statin treatment not only inhibits de novo synthesis of cholesterol but also isoprenoids that are involved in prenylation, the posttranslational lipid modification of proteins. The immunomodulatory effects of statins are broad and often conflicting. Previous work demonstrated that statins increased survival and inhibited myeloid cell trafficking in a murine model of sepsis, but the exact mechanisms underlying this phenomenon were unclear. Herein, we investigated the role of prenylation in chemoattractant responses. We found that simvastatin treatment abolished chemoattractant responses induced by stimulation by C5a and FMLP. The inhibitory effect of simvastatin treatment was unaffected by the addition of either farnesyl pyrophosphate (FPP) or squalene but was reversed by restoring geranylgeranyl pyrophosphate (GGPP). Treatment with prenyltransferase inhibitors showed that the chemoattractant response to both chemoattractants was dependent on geranylgeranylation. Proteomic analysis of C15AlkOPP-prenylated proteins identified several geranylgeranylated proteins involved in chemoattractant responses, including RHOA, RAC1, CDC42, and GNG2. Chemoattractant responses in THP-1 human macrophages were also geranylgeranylation dependent. These studies provide data that help clarify paradoxical findings on the immunomodulatory effects of statins. Furthermore, they establish the role of geranylgeranylation in mediating the morphological response to chemoattractant C5a.NEW & NOTEWORTHY The immunomodulatory effect of prenylation is ill-defined. We investigated the role of prenylation on the chemoattractant response to C5a. Simvastatin treatment inhibits the cytoskeletal remodeling associated with a chemotactic response. We showed that the chemoattractant response to C5a was dependent on geranylgeranylation, and proteomic analysis identified several geranylgeranylated proteins that are involved in C5a receptor signaling and cytoskeletal remodeling. Furthermore, they establish the role of geranylgeranylation in mediating the response to chemoattractant C5a.

Absence of farnesol salvage in Candida albicans and probably in other fungi

Farnesol salvage, a two-step pathway converting farnesol to farnesyl pyrophosphate (FPP), occurs in bacteria, plants, and animals. This paper investigates the presence of this pathway in fungi. Through bioinformatics, biochemistry, and physiological analyses, we demonstrate its absence in the yeasts Saccharomyces cerevisiae and Candida albicans, suggesting a likely absence across fungi. We screened 1,053 fungal genomes, including 34 from C. albicans, for potential homologs to four genes (Arabidopsis thaliana AtFOLK, AtVTE5, AtVTE6, and Plasmodium falciparum PfPOLK) known to accomplish farnesol/prenol salvage in other organisms. Additionally, we showed that 3H-farnesol was not converted to FPP or any other phosphorylated prenol, and exogenous farnesol was not metabolized within 90 minutes at any phase of growth and did not rescue cells from the toxic effects of atorvastatin, but it did elevate the levels of intracellular farnesol (Fi). All these experiments were conducted with C. albicans. In sum, we found no evidence for farnesol salvage in fungi.

IMPORTANCE

The absence of farnesol salvage constitutes a major difference in the metabolic capabilities of fungi. In terms of fungal physiology, the lack of farnesol salvage pathways relates to how farnesol acts as a quorum-sensing molecule in Candida albicans and why farnesol should be investigated for use in combination with other known antifungal antibiotics. Its absence is essential for a model (K. W. Nickerson et al., Microbiol Mol Biol Rev 88:e00081-22, 2024), wherein protein farnesylation, protein chaperones, and the unfolded protein response are combined under the unifying umbrella of a cell's intracellular farnesol (Fi). In terms of human health, farnesol should have at least two different modes of action depending on whether those cells have farnesol salvage. Because animals have farnesol salvage, we can now see the importance of dietary prenols as well as the potential importance of farnesol in treating neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, and multiple sclerosis.

LC-MS metabolomics analysis of serum metabolites during neoadjuvant chemoradiotherapy in locally advanced rectal cancer

BACKGROUND

This study aimed to investigate the serum metabolite profiles during neoadjuvant chemoradiotherapy (NCRT) in locally advanced rectal cancer (LARC) using liquid chromatography-mass spectrometry (LC-MS) metabolomics analysis.

METHODS

60 serum samples were collected from 20 patients with LARC before, during, and after radiotherapy. LC-MS metabolomics analysis was performed to identify the metabolite variations. Functional annotation was applied to discover altered metabolic pathways. The key metabolites were screened and their ability to predict sensitivity to radiotherapy was calculated using random forests and ROC curves.

RESULTS

The results showed that NCRT led to significant changes in the serum metabolite profiles. The serum metabolic profiles showed an apparent separation between different time points and different sensitivity groups. Moreover, the functional annotation showed that the differential metabolites were associated with a series of important metabolic pathways. Pre-radiotherapy (3Z,6Z)-3,6-Nonadiena and pro-radiotherapy 1-Hydroxyibuprofen showed good predictive performance in discriminating the sensitive and non-sensitive group to NCRT, with an AUC of 0.812 and 0.75, respectively. Importantly, the combination of different metabolites significantly increased the predictive ability.

CONCLUSION

This study demonstrated the potential of LC-MS metabolomics for revealing the serum metabolite profiles during NCRT in LARC. The identified metabolites may serve as potential biomarkers and therapeutic targets for the management of this disease. Furthermore, the understanding of the affected metabolic pathways may help design more personalized therapeutic strategies for LARC patients.

Physiological adventures in Candida albicans: farnesol and ubiquinones

SUMMARYFarnesol was first identified as a quorum-sensing molecule, which blocked the yeast to hyphal transition in Candida albicans, 22 years ago. However, its interactions with Candida biology are surprisingly complex. Exogenous (secreted or supplied) farnesol can also act as a virulence factor during pathogenesis and as a fungicidal agent triggering apoptosis in other competing fungi. Farnesol synthesis is turned off both during anaerobic growth and in opaque cells. Distinctly different cellular responses are observed as exogenous farnesol levels are increased from 0.1 to 100 µM. Reported changes include altered morphology, stress response, pathogenicity, antibiotic sensitivity/resistance, and even cell lysis. Throughout, there has been a dearth of mechanisms associated with these observations, in part due to the absence of accurate measurement of intracellular farnesol levels (Fi). This obstacle has recently been overcome, and the above phenomena can now be viewed in terms of changing Fi levels and the percentage of farnesol secreted. Critically, two aspects of isoprenoid metabolism present in higher organisms are absent in C. albicans and likely in other yeasts. These are pathways for farnesol salvage (converting farnesol to farnesyl pyrophosphate) and farnesylcysteine cleavage, a necessary step in the turnover of farnesylated proteins. Together, these developments suggest a unifying model, whereby high, threshold levels of Fi regulate which target proteins are farnesylated or the extent to which they are farnesylated. Thus, we suggest that the diversity of cellular responses to farnesol reflects the diversity of the proteins that are or are not farnesylated.

Beyond the MEP Pathway: A novel kinase required for prenol utilization by malaria parasites

A proposed treatment for malaria is a combination of fosmidomycin and clindamycin. Both compounds inhibit the methylerythritol 4-phosphate (MEP) pathway, the parasitic source of farnesyl and geranylgeranyl pyrophosphate (FPP and GGPP, respectively). Both FPP and GGPP are crucial for the biosynthesis of several essential metabolites such as ubiquinone and dolichol, as well as for protein prenylation. Dietary prenols, such as farnesol (FOH) and geranylgeraniol (GGOH), can rescue parasites from MEP inhibitors, suggesting the existence of a missing pathway for prenol salvage via phosphorylation. In this study, we identified a gene in the genome of P. falciparum, encoding a transmembrane prenol kinase (PolK) involved in the salvage of FOH and GGOH. The enzyme was expressed in Saccharomyces cerevisiae, and its FOH/GGOH kinase activities were experimentally validated. Furthermore, conditional knockout parasites (Δ-PolK) were created to investigate the biological importance of the FOH/GGOH salvage pathway. Δ-PolK parasites were viable but displayed increased susceptibility to fosmidomycin. Their sensitivity to MEP inhibitors could not be rescued by adding prenols. Additionally, Δ-PolK parasites lost their capability to utilize prenols for protein prenylation. Experiments using culture medium supplemented with whole/delipidated human plasma in transgenic parasites revealed that human plasma has components that can diminish the effectiveness of fosmidomycin. Mass spectrometry tests indicated that both bovine supplements used in culture and human plasma contain GGOH. These findings suggest that the FOH/GGOH salvage pathway might offer an alternate source of isoprenoids for malaria parasites when de novo biosynthesis is inhibited. This study also identifies a novel kind of enzyme related to isoprenoid metabolism.

Farnesol as an antifungal agent: comparisons among MTL and MTLα haploid and diploid Candida albicans and Saccharomyces cerevisiae

Aims: Farnesol was identified 20 years ago in a search for Candida albicans quorum sensing molecules (QSM), but there is still uncertainty regarding many aspects of its mode of action including whether it employs farnesol transport mechanisms other than diffusion. Based on the structural similarity between farnesol and the farnesylated portion of the MTL a pheromone, we explored the effects of ploidy and mating type locus (MTL) on the antifungal activity of exogenous farnesol. Methods and results: We approached this question by examining five MTL a and five MTLα haploid strains with regard to their farnesol sensitivity in comparison to six heterozygous MTL a/ α diploids. We examined the haploid and diploid strains for percent cell death after exposure of exponentially growing cells to 0-200 µM farnesol. The heterozygous (MTL a/α) diploids were tolerant of exogenous farnesol whereas the MTL a and MTLα haploids were on average 2- and 4-times more sensitive, respectively. In the critical range from 10-40 µM farnesol their cell death values were in the ratio of 1:2:4. Very similar results were obtained with two matched sets of MAT a, MATα, and MAT a/α Saccharomyces cerevisiae strains. Conclusion: We propose that the observed MTL dependence of farnesol is based on differentially regulated mechanisms of entry and efflux which determine the actual cellular concentration of farnesol. The mechanisms by which pathogens such as C. albicans tolerate the otherwise lethal effects of farnesol embrace a wide range of physiological functions, including MTL type, ubiquinone type (UQ6-UQ9), energy availability, and aerobic/anaerobic status.

Potential role of geranylgeraniol in managing statin-associated muscle symptoms: a COVID-19 related perspective

Myopathy is the most common side effect of statins, but it has not been addressed effectively. In anticipation of its wider use as a small molecule to complement the current COVID-19 management, a pharmacological solution to statin-associated muscle symptoms (SAMS) is warranted. Statins act by suppressing the mevalonate pathway, which in turn affects the downstream synthesis of isoprenoids required for normal physiological functions. CoQ10 and geranylgeraniol (GG) syntheses are reduced by statin use. However, CoQ10 supplementation has not been shown to reverse SAMS. GG is an obligatory substrate for CoQ10 synthesis, an endogenous nutrient critical for skeletal muscle protein synthesis. Multiple studies showed GG supplementation is effective in reversing SAMS. This opinion paper proposes employing GG to prevent SAMS in pleiotropic statin use, including usage in the post-COVID-19 pandemic era.

Pterodon emarginatus Seed Preparations: Antiradical Activity, Chemical Characterization, and In Silico ADMET Parameters of β-caryophyllene and Farnesol

The study of medicinal plants and their active compounds is relevant to maintaining knowledge of traditional medicine and to the development of new drugs of natural origin with lower environmental impact. From the seeds of the Brazilian plant Pterodon emarginatus, six different preparations were obtained: essential oil (EO), ethanol extract (EthE) prepared using the traditional method, and four extracts using solvents at different polarities, such as n-hexane, chloroform, ethyl acetate, and methanol (HexE, ChlE, EtAE, and MetE). Chemical characterization was carried out with gas chromatography, allowing the identification of several terpenoids as characteristic components. The two sesquiterpenes β-caryophyllene and farnesol were identified in all preparations of Pterodon emarginatus, and their amounts were also evaluated. Furthermore, the total flavonoid and phenolic contents of the extracts were assessed. Successively, the antiradical activity with DPPH and ORAC assays and the influence on cell proliferation by the MTT test on the human colorectal adenocarcinoma (HT-29) cell line of the preparations and the two compounds were evaluated. Lastly, an in silico study of adsorption, distribution, metabolism, excretion, and toxicity (ADMET) showed that β-caryophyllene and farnesol could be suitable candidates for development as drugs. The set of data obtained highlights the potential medicinal use of Pterodon emarginatus seeds and supports further studies of both plant preparations and isolated compounds, β-caryophyllene and farnesol, for their potential use in disease with free radical involvement as age-related chronic disorders.

Engineering Saccharomyces cerevisiae YPH499 for Overproduction of Geranylgeraniol

Optimization of supply and conversion efficiency of geranylgeranyl diphosphate (GGPP) is important for enhancing geranylgeraniol (GGOH) production in Saccharomyces cerevisiae. In this study, first, a strain producing 26.92 ± 1.59 mg/g of dry cell weight squalene was constructed with overexpression of all genes of the mevalonate (MVA) pathway, and an engineered strain producing 597.12 mg/L GGOH at the shake flask level was obtained. Second, through additional expression of PaGGPPs-ERG20 and PaGGPPs-DPP1, and downregulating expression of ERG9, the GGOH titer was increased to 1221.96 mg/L. Then, a NADH HMG-CoA reductase from Silicibacter pomeroyi (SpHMGR) was introduced to alleviate the high dependence of the strain upon NADPH, and the GGOH production was further increased to 1271.14 mg/L. Finally, the GGOH titer reached 6.33 g/L after optimizing the fed-batch fermentation method in a 5 L bioreactor, with a 24.9% improvement from the previous report. This study might accelerate the process of developing S. cerevisiae cell factories for diterpenoid and tetraterpenoid production.