Biology subjects

Wang, R. Z.

Publications and source records attributed to Wang, R. Z..

4 recordsLinked to original sources

bioRxiv2025

B7-H4 Binds Galectin-9 Glycosylation-Dependently and Attenuates Galectin-9-Mediated CD28/AKT Activation and T Cell Death

B7-H4, a member of the B7 family, is broadly expressed on various cancer cells and has been implicated in negative immune regulation, particularly in suppressing anti-tumor immunity. However, the receptor for B7-H4 and the molecular mechanisms underlying its immunoinhibitory effects remain poorly understood. In this study, using peritoneal immune cells from mice adoptively transferred with OVA-expressing tumor cells and OVA-specific OT-1 T cells, we identified Galectin-9 (Gal-9) as a binding partner for B7-H4 and elucidated its role in modulating T cell responses through this interaction. We demonstrated that glycosylation in the IgC domain of B7-H4 is required for its binding to Gal-9; while the N-terminal carbohydrate recognition domain (N-CRD) of Gal-9, including the R65 residue in the N-CRD, is essential for this interaction. Additionally, we found that other B7 family members (B7.1, B7.2, B7-H2, and B7-DC) and immune cell surface receptors (CD28, 2B4, CD226, and SLAMF1) also bind to Gal-9 at comparable levels to B7-H4 and T cell immunoglobulin mucin receptor 3 (TIM-3). In vitro functional assays revealed that B7-H4 inhibits Gal-9-induced activation of CD28 downstream signaling and reduces Gal-9-mediated T cell death. In vivo, Gal-9 deficiency in mice resulted in a significant reduction in the proportion of splenic CD4+ T cells, whereas B7-H4 deficiency exhibited no observable phenotype. Furthermore, B7-H4 and Gal-9 double-knockout mice displayed no additional phenotype differences compared to Gal-9 single-knockout mice. Notably, tumor growth following tumor cell challenge was unaffected in all three knockout models (Gal-9 single-, B7-H4 single-, or double-knockout). Collectively, these findings suggest that B7-H4, other B7 family members, Gal-9, and T cell surface immune receptors form a complex regulatory network that modulates T cell activity and anti-tumor responses, although no single member exerts a major effect. This study provides a detailed molecular characterization of the interaction between B7-H4 and Gal-9 and identifies other previously unknown Gal-9 binding partners, offering valuable insights into the intricate regulatory network involving these molecules.

immunology↗

bioRxiv2024

Cyanobacteria from marine oxygen deficient zones encode both form I and form II rubiscos

Cyanobacteria are highly abundant in the marine photic zone and primary drivers of the conversion of inorganic carbon to biomass. To date, all studied Cyanobacterial lineages encode carbon fixation machinery hinged upon form I rubisco enzymes within a CO2-concentrating carboxysome. Here, we report that the AMZ IB lineage of Prochlorococcus from global oxygen deficient zones (ODZs) harbor both form I and form II rubisco enzymes, the latter of which are typically non-carboxysomal and possess biochemical properties tuned towards low oxygen environments. Our analyses reveal that these cyanobacterial form II enzymes are functional in vitro and were likely acquired via lateral gene transfer from proteobacteria. Global metagenomic read recruitment demonstrates that Prochlorococcus with form II rubisco are essentially restricted to ODZs in the Eastern Tropical Pacific, suggesting that acquisition may confer an advantage specifically under low-O2 conditions. Populations of AMZ IB Prochlorococcus express both forms of rubisco in situ, with the highest form II rubisco expression at depths where both oxygen and light are particularly low, possibly as a mechanism to increase the efficiency of photoautotrophy under energy limitation. Our findings expand the diversity of carbon fixation configurations in the microbial world and may have implications for the overall capacity of ODZs to sequester carbon.

microbiology↗

bioRxiv2023

Bacterial Form I' rubisco has smaller carbon isotope fractionation than its Form I counterpart

Form I rubiscos evolved in Cyanobacteria [≥]2.5 billion years ago and are enzymatically unique due to the presence of small subunits (RbcS) that cap both ends of an octameric large subunit (RbcL) rubisco assembly to form a hexadecameric (L8S8) holoenzyme. Although RbcS was previously thought to be integral to Form I rubisco stability, the recent discovery of a closely related sister clade of octameric rubiscos (Form I; L8) demonstrates that the enzyme complex assembles without small subunits (Banda et al. 2020). Rubisco also displays a kinetic isotope effect (KIE) where the 3PG product is depleted in 13C relative to 12C. In Cyanobacteria only two Form I KIE measurements exist, making interpretation of bacterial carbon isotope data difficult. To aid comparison, we measured in vitro the KIEs of Form I (Candidatus Promineofilum breve) and Form I (Synechococcus elongatus PCC 6301) rubiscos and found the KIE to be smaller in the L8 rubisco (16.25 {+/-} 1.36{per thousand} vs. 22.42 {+/-} 2.37{per thousand} respectively). Therefore, while small subunits may not be necessary for protein stability, they may affect the KIE. Our findings may provide insight into the function of RbcS and allow more refined interpretation of environmental carbon isotope data.

evolutionary biology↗

bioRxiv2022

Evolution of Carbon Isotope Fractionation in Cyanobacteria

The history of Earths carbon cycle reflects trends in atmospheric composition convolved with the evolution of photosynthesis. Fortunately, key parts of the carbon cycle have been recorded in the carbon isotope ratios of sedimentary rocks. The dominant model used to interpret this record as a proxy for ancient atmospheric CO2 is based on carbon isotope fractionations of modern photoautotrophs, and longstanding questions remain about how their evolution might have impacted the record. We tested the intersection of environment and evolution by measuring both biomass ({varepsilon}p) and enzymatic ({varepsilon}Rubisco) carbon isotope fractionations of a cyanobacterial strain (Synechococcus elongatus PCC 7942) solely expressing a putative ancestral Form 1B rubisco dating to >>1 Ga. This strain, nicknamed ANC, grows in ambient pCO2 and displays larger {varepsilon}p values than WT, despite having a much smaller {varepsilon}Rubisco (17.23 {+/-} 0.61{per thousand} vs. 25.18 {+/-} 0.31{per thousand} respectively). Measuring both enzymatic and biomass fractionation revealed a surprising result--ANC {varepsilon}p exceeded ANC {varepsilon}Rubisco in all conditions tested, contradicting prevailing models of cyanobacterial carbon isotope fractionation. However, these models were corrected by accounting for cyanobacterial physiology, notably the CO2 concentrating mechanism (CCM). Our model suggested that additional fractionating processes like powered inorganic carbon uptake systems contribute to {varepsilon}p, and this effect is exacerbated in ANC. Understanding the evolution of rubisco and the CCM is therefore critical for interpreting the carbon isotope record. Large fluctuations in that record may reflect the evolving efficiency of carbon fixing metabolisms in addition to changes in atmospheric CO2. Significance StatementEarth scientists rely on chemical fossils like the carbon isotope record to derive ancient atmospheric CO2 concentrations, but interpretation of this record is calibrated using modern organisms. We tested this assumption by measuring the carbon isotope fractionation of a reconstructed ancestral rubisco enzyme (>1 billion years old) in vivo and in vitro. Our results contradicted prevailing models of carbon flow in Cyanobacteria, but our data could be rationalized if light-driven uptake of CO2 is taken into account. Our study showed that the carbon isotope record tracks both the evolution of photosynthesis physiology as well as changes in atmospheric CO2, highlighting the value of considering both evolution and physiology for comparative biological approaches to understanding Earths history.

evolutionary biology↗