Biology subjects

Mai, Z.

Publications and source records attributed to Mai, Z..

8 recordsLinked to original sources

bioRxiv2026

Pharmacological activation of mitophagy prevents calcific aortic valve disease by targeting dysregulated mitochondrial-to-nuclear communication

Abstract Background and Aims: Calcific aortic valve disease (CAVD) lacks pharmacologic therapy. Mitophagy impairment contributes to various degenerative diseases, but whether it occurs in calcified aortic valves and during human valvular interstitial cell (hVIC) osteogenic differentiation remains unknown. We therefore investigated the role of mitophagy in CAVD and whether its pharmacological treatment prevents disease progression. Methods: Single-cell RNA sequencing (scRNA-seq) was performed on human aortic valves and hVICs. TJ0113, a novel orally available mitophagy activator from our previous screening, was tested in two CAVD mouse models. Multi-omics analyses and functional rescue experiments were performed to elucidate the mechanism. Results: Mitophagy was impaired in calcified human aortic valves and during hVIC osteogenic differentiation. TJ0113 activated MCL1-mediated mitophagy and attenuated disease progression in vitro and in vivo. Mechanistically, the mitophagy receptor MCL1 anchors a fraction of PRMT3 on mitochondria. During osteogenic differentiation, a dysregulated mitochondrial-to-nuclear communication is initiated by the increased release of PRMT3 into the cytosol, where it interacts with BACH1 and impairs BACH1 nuclear translocation. This leads to a widespread loss of BACH1 genomic occupancy, relieving BACH1-mediated transcriptional repression of the pro-osteogenic factor PARM1 and promoting hVIC osteogenic differentiation. Mitophagy activation by TJ0113 restored MCL1-PRMT3 binding and reversed these alterations. Conclusions: Mitophagy impairment drives CAVD through dysregulated mitochondrial-to-nuclear communication mediated by the MCL1-PRMT3-BACH1-PARM1 axis. Pharmacological mitophagy activation by TJ0113 corrects this communication and attenuates disease progression, representing a promising therapeutic strategy for CAVD.

pathology↗

bioRxiv2026

Beyond Respiration: Heme A Synthase (CtaA) Orchestrates Hydrogen Sulfide Production and Virulence via Metabolic Reprogramming in Staphylococcus aureus

Endogenous hydrogen sulfide (H2S) serves as a pivotal gasotransmitter conferring antimicrobial resistance and shielding bacteria from oxidative stress. While cystathionine {gamma}-lyase (CSE)-dependent H2S production is critical for Staphylococcus aureus survival, the upstream regulatory nodes linking metabolic status to H2S-mediated redox defense remain elusive. Here, we identify heme A synthase (CtaA) as a master regulator that couples respiratory metabolism with H2S biosynthesis, specifically under glucose-depleted conditions mimicking host niches such as abscesses and phagosomes. Using a Himar1 transposon screen followed by a high efficiency detection method, we demonstrate that CtaA deficiency precipitates a catastrophic collapse in H2S levels (<10% of wild-type), leading to severe virulence and antimicrobial resistance changes. Specifically, the {Delta}ctaA mutant exhibits attenuated hemolytic activity and significantly reduced virulence in a Galleria mellonella model, despite displaying paradoxical resistance to specific antimicrobials. Mechanistically, CtaA deletion triggers a maladaptive metabolic reprogramming characterized by the downregulation of the L-cysteine transporter TcyP and dysregulation of arginine metabolism, which collectively impair the bacteriums capacity to produce endogenous H2S to defense oxidative stress. Notably, this redox vulnerability is linked to altered endogenous nitric oxide (NO) dynamics, suggesting a disrupted H2S-NO crosstalk essential for stress adaptation. Our findings elucidate a novel metabolic-redox axis where CtaA governs H2S homeostasis to counteract host-imposed oxidative stress. Targeting the CtaA-H2S axis represents a promising therapeutic strategy to sensitize S. aureus to host immune clearance by dismantling its critical redox shield.

microbiology↗

bioRxiv2025

Ancient gene clusters initiate monoterpene indole alkaloid biosynthesis and C-3 stereochemistry inversion

The inversion of C3 stereochemistry in monoterpenoid indole alkaloids (MIAs), derived from the central precursor strictosidine (3S), is a critical step for the biosynthesis of numerous 3R MIAs and spirooxindoles, including the antihypertensive drug reserpine. While early MIA biosynthesis preserves the 3S configuration, the mechanism underlying C3 inversion has remained unresolved. Here, we identify and biochemically characterize a conserved oxidase-reductase pair in the Gentianales order: the heteroyohimbine/yohimbine/corynanthe C3-oxidase (HYC3O) and C3-reductase (HYC3R), which together invert the 3S stereochemistry to 3R across diverse substrates. Notably, HYC3O and HYC3R reside in gene clusters in Rauvolfia tetraphylla and Catharanthus roseus, homologous to an elusive geissoschizine synthase (GS) cluster we also uncovered. In R. tetraphylla, these clusters are in tandem on a single chromosome, likely derived from segmental duplication, whereas in C. roseus they reside on separate chromosomes due to translocation. Comparative genomics indicate the GS cluster originated at the base of Gentianales ([~]135 Mya), coinciding with the evolution of the strictosidine synthase cluster, while the reserpine cluster arose later in rauvolfioid Apocynaceae. Together, these findings uncover the genomic and biochemical basis for key events in MIA evolution and diversification, providing insights beyond the canonical vinblastine and ajmaline biosynthetic pathways.

biochemistry↗

bioRxiv2024

Parallel evolution of methyltransferases leads to vobasine biosynthesis in Tabernaemontana elegans and Catharanthus roseus

Monoterpenoid indole alkaloids (MIA) are one of the largest and most complex alkaloid class in nature, boasting many clinically significant drugs such as anticancer vinblastine and antiarrhythmic ajmaline. Many MIAs undergo nitrogen N-methylation, altering their reactivity and affinity to the biological targets through a straightforward reaction. Remarkably, all known MIA N-methyltransferases (NMT) originate from the neofunctionalization of ancestral {gamma}-tocopherol C-methyltransferases ({gamma}TMTs), a phenomenon seemingly unique to the Apocynaceae family. In this study, we unveil and characterize a new {gamma}TMT-like enzyme from the plant Tabernaemontana elegans (toad tree): perivine N{beta}-methyltransferase (TePeNMT). TePeNMT and other homologs form a distinct clade in our phylogenetic study, setting them apart from other {gamma}TMTs and {gamma}TMT-like NMTs discovered to date. Enzyme kinetic experiments and enzyme homology modeling studies reveal the significant differences in enzyme active sites between TePeNMT and CrPeNMT, a previously characterized perivine N{beta}-methyltransferase from Catharanthus roseus (Madagascar periwinkle). Collectively, our findings suggest that parallel evolution of ancestral {gamma}TMTs may be responsible for the occurrence of perivine N-methylation in T. elegans and C. roseus.

biochemistry↗

bioRxiv2024

Oxidation of Four Monoterpenoid Indole Alkaloid Classes by Three Cytochrome P450 Monooxygenases from Tabernaemontana litoralis

Cytochrome P450 monooxygenases (CYPs) are well known for their ability to catalyze diverse oxidation reactions, playing a significant role in the biosynthesis of various natural products. In the realm of monoterpenoid indole alkaloids (MIAs), one of the largest groups of alkaloids in nature, CYPs are integral to reactions such as hydroxylation, epoxidation, ring opening, ring rearrangement, and aromatization, contributing to the extensive diversification of these compounds. In this study, we investigate the transcriptome, metabolome, and MIA biosynthesis in Tabernaemontana litoralis (milky way tree), a prolific producer of rare pseudoaspidosperma-type MIAs. Alongside known pseudoaspidosperma biosynthetic genes, we identify and characterize three new CYPs that facilitate regio- and stereospecific oxidation of four MIA skeletons: iboga, aspidosperma, pseudoaspidosperma, and quebrachamine. Notably, the tabersonine 14,15-{beta}-epoxidase catalyzes the formation of pachysiphine, the stereoisomer of 14,15--epoxytabersonine (lochnericine) found in Catharanthus roseus (Madagascar periwinkle) roots. The pseudovincadifformine 18-hydroxylase is the first CYP identified to modify a pseudoaspidosperma skeleton. Additionally, we demonstrate that the enzyme responsible for C10-hydroxylation of the iboga MIA coronaridine also catalyzes the same reaction on voaphylline, which bears a quebrachamine skeleton. With the discovery of a new MIA, 11-hydroxypseudovincadifformine, this study provides a comprehensive understanding of MIA biosynthesis and diversification in T. litoralis, highlighting its potential for further exploration.

biochemistry↗

bioRxiv2022

Sparse-spectral microendoscopy for real-time visualization of tumor cell phenotype and microenvironment spatial heterogeneity in vivo

Cancer heterogeneity and its transformation with time propels treatment resistance and confounds patient outcomes. The inability to monitor in vivo the low abundance, heterocellular phenotypes that resist treatment and ultimately lead to patient death limits the ability to design precision therapies. Here we overcome limitations in multiplexed fluorescence phenotyping to introduce real-time, cellular resolution visualization of tumor heterogeneity in vivo. This method was performed to simultaneously map for the first time 5 individual biomarkers of stemness, proliferation, metabolism, leukocytes and angiogenesis deep within the peritoneal cavities of micrometastatic cancer mouse models at 17 frames per second (fps). The newly developed imaging system revealed distinct cancer cell phenotype-immune cell spatial correlations and clearly visualized the dynamic spatial response of resistant cancer cell niches following treatment. Furthermore, wide-field datasets were generated to facilitate derivation of a mathematical framework for quantifying biomarker spatial variation and thereby overcoming the area restrictions of conventional tumor biopsy. These results pave the way for real-time identification of cancer cell phenotypes in a clinical setting, on which optimized treatment regimens can be based for personalized treatment and precision therapy e.g., tumor margin determination during surgical resection. Additionally, this modality can be used to obtain more fundamental insights into tumor heterogeneity and how treatments affect the molecular and cellular responses of patient-specific disease.

bioengineering↗

bioRxiv2022

Improved protein glycosylation enabled heterologous biosynthesis of monoterpenoid indole alkaloids and their unnatural derivatives in yeast

With over 3,000 reported structures, monoterpenoid indole alkaloids (MIAs) constitute one of the largest alkaloid groups in nature, including the clinically important anticancer drug vinblastine and its semi-synthetic derivatives from Catharanthus roseus (Madagascars periwinkle). With the elucidation of the complete 28-step biosynthesis for anhydrovinblastine, it is possible to investigate the heterologous production of vinblastine and other medicinal MIAs. In this study, we successfully expressed the flavoenzyme O-acetylstemmadenine oxidase in Saccharomyces cerevisiae (bakers yeast) by signal peptide modification, which is a vinblastine biosynthetic gene that has not been functionally expressed in this system. We also report the simultaneous genomic integration of [~]18 kb MIA biosynthetic gene cassettes as single copies by CRISPR-Cas9 in bakers yeast, which enabled the biosynthesis of vinblastine precursors catharanthine and tabersonine from the feedstocks secologanin and tryptamine. We further demonstrated the biosynthesis of fluorinated and hydroxylated catharanthine and tabersonine derivatives using our yeasts, which showed that the MIA biosynthesis accommodates unnatural substrates, and the system can be further explored to produce other complex MIAs. With over 3,000 members, monoterpenoid indole alkaloids (MIA) are one of the largest and most diverse alkaloids in nature including many human medicines, such as chemotherapeutics vinblastine from Catharanthus roseus (Madagascars periwinkle) and camptothecin from Camptotheca accuminata (happy tree), and antiarrhythmic ajmaline from Rauwolfia serpentina (Indian snakeroot).1 Recent studies have elucidated the complete 28-step biosynthetic pathway for anhydrovinblastine in C. roseus, which involves diverting a primary monoterpene geranyl pyrophosphate into the biosynthesis of secologanin via the iridoid pathway (9 steps), genesis of the first MIA strictosidine that is the universal precursor to almost all MIAs (2 steps), conversion of strictosidine to iboga type MIA catharanthine and aspidosperma type tabersonine (9 steps), decorating tabersonine to vindoline (7 steps), and the final step that couples vindoline and catharanthine to make anhydrovinblastine (Fig. 1). 2-12 These studies not only revealed the remarkable complexity of MIA formations but also enabled the exploration in heterologous production of bioactive MIAs and intermediates that are usually found in low quantities in their natural sources. Notably, strictosidine and a related corynanthe type MIA ajmalicine have been produced de novo in Saccharomyces cerevisiae (bakers yeast), 13,14 while vindoline has been produced in bakers yeast from tabersonine feedstock. 3,15,16 For strictosidine production in yeast, the challenges lie in the generally low monoterpene biosynthesis output and the intermediates consumption by yeast native metabolism.13,14,17 While studies did not report rapid MIA consumption by yeast, vindoline yields were improved by optimizing the stoichiometry of cytochrome P450 monooxygenase (CYP), CYP redox partner CYP reductase (CPR), and other factors related with CYP activities such as endoplasmic reticulum (ER) homeostasis and NADPH co-factor regeneration that are commonly exploited.15,16 In this study, we constructed yeast strains containing the remaining vinblastine biosynthetic segment and produced catharanthine and tabersonine by feeding precursors, secologanin and tryptamine, as well as their unnatural derivatives by feeding substituted tryptamine. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=96 SRC="FIGDIR/small/495323v1_fig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@52eda3org.highwire.dtl.DTLVardef@6f8d6dorg.highwire.dtl.DTLVardef@1ae0e1aorg.highwire.dtl.DTLVardef@1fed9f_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO The biosynthetic pathway for monoterpenoid indole alkaloids (MIAs) catharanthine and vindoline in C. roseus, which couple to form the anticancer anhydrovinblastine and other derivatives. TDC: tryptophan decarboxylase (Genbank P17770); STR: strictosidine synthase (Genbank CAA43936); SGD: strictosidine -glucosidase (Genbank AAF28800); GS: geissoschizine synthase (Genbank MF770507); GO: geissoschizine oxidase (Genbank MF770508); Redox1/2: oxidized geissoschizine reductase 1/2 (Genbank MF770509, MF770510); SAT: stemmadenine O-acetyltransferase (Genbank MF770511); ASO: O-acetylstemmadenine oxidase (Genbank MH136588); DPAS: dihydroprecondylocarpine synthase (Genbank A0A1B1FHP3); HL1: hydrolase 1/catharanthine synthase (Genbank MF770512); HL2: hydrolase 2/tabersonine synthase (Genbank MF770513). C_FIG

synthetic biology↗

bioRxiv2021

Landscape of microenvironment in Randall's plaque by single-cell sequencing

Randalls plaque is significantly associated with the occurrence of nephrolithiasis. However, the microenvironment of Randalls plaque is poorly characterized. To investigate the microenvironment of Randalls plaque, we analyzed single-cell RNA data of 3 Randalls plaque and 3 normal renal papillae tissue and identified 11 different cell types. We screened differentially expressed genes among all cell types between Randalls plaque and normal renal papillae. The microenvironment showed two cell types with multiple stone formation-associated transcriptomic programs. Contrary to previous studies, we did not observe macrophage M1/M2 imbalance. Notably, we detected ossification-associated macrophage is enriched in Randalls plaque and validated GPNMB and ACP5 were potential biomarkers on the ossification-associated macrophage. We also identified an endothelial subset harboring active communication (COL15A1+ PCDH17+ endothelial, DPECs) with other cells. Together with Immunofluorescence, we validated ossification-associated macrophage and DPECs are enriched in Randalls plaque tissue. Finally, cell-to-cell communication revealed that Loop of Henle, DPECs, and osteoblasts-associated macrophages was the main source of SPP1 signaling. Our work will further the understanding of the microenvironment among Randalls plaque tissues and provide deep insight into immune modulation.

bioinformatics↗