Biology subjects

Tejero, J.

Publications and source records attributed to Tejero, J..

4 recordsLinked to original sources

bioRxiv2025

Cytochrome b5 reductase 4 efficiently reduces Neuroglobin and Cytoglobin

Cytoglobin and Neuroglobin are heme-containing proteins expressed in most vertebrates, including mammals, with still not completely defined physiological roles. Most of the putative functions of cytoglobin/neuroglobin, such as oxygen binding or nitric oxide dioxygenation, rely on the heme iron being in the ferrous (Fe2+) oxidation state. Therefore, it is very possible that reducing systems are active in the cell to maintain both proteins in the ferrous state. We have previously shown that the cytochrome b5 reductase isoform 3/ cytochrome b5 system, the canonical reductase of hemoglobin and myoglobin, can reduce cytoglobin at very fast rates, consistent with a possible physiological role. However this reducing system is unable to reduce neuroglobin, which to date lacks a validated, physiologically feasible reducing system. Here we have studied the interaction of cytochrome b5 reductase isoform 4 with cytoglobin and neuroglobin and found that cytochrome b5 reductase 4 can reduce cytoglobin at rates comparable to those observed with cytochrome b5 reductase 3/ cytochrome b5. Remarkably, it can also reduce neuroglobin efficiently. Studying different surface mutations of cytoglobin and neuroglobin we note that some cytoglobin mutations, in particular R84E and K116E decrease reduction rates by more than 10-fold, whereas surface mutations in neuroglobin that were shown to impair the interaction of neuroglobin with cytochrome c (E60K/D73K/E87K) show little effect on the reduction rates. We conclude that cytochrome b5 reductase 4 can supplement cytochrome b5 reductase 3/ cytochrome b5 roles for cytoglobin reduction in vivo and is a strong candidate for a physiological role as neuroglobin reductase.

biochemistry↗

bioRxiv2025

Engineering a highly selective, hemoprotein-based scavenger as a carbon monoxide poisoning antidote with no hypertensive effect

Carbon monoxide (CO) poisoning causes 50,000-100,000 emergency department visits and [~]1,500 deaths in the United States annually. Current treatments are limited to supplemental and/or hyperbaric oxygen to accelerate CO elimination. Even with oxygen therapy, nearly half of CO poisoning survivors suffer long-term cardiac and neurocognitive deficits related to slow CO clearance, highlighting a need for point of care antidotal therapies. Given the natural interaction between CO and ferrous heme, we hypothesized that the hemoprotein RcoM, a transcriptional regulator of microbial CO metabolism, would make an ideal platform for CO-selective scavenging from endogenous hemoproteins. We engineered an RcoM truncate (RcoM-HBD-CCC) that exhibits high CO affinity (Ka,CO = 2.8x1010 M-1), remarkable selectivity for CO over oxygen (Ka,O2 = 1.4x105 M-1; Ka,CO/Ka,O2 = 1.9x105), thermal stability (Tm = 72{degrees}C), slow autoxidation rate (kox = 1.1 h-1). In a murine model of acute CO poisoning, infused RcoM-HBD-CCC accelerated CO clearance from hemoglobin in red blood cells and was rapidly excreted in urine. Moreover, infused RcoM-HBD-CCC elicited minimal hypertension in mice compared to infused hemoglobin, attributed to a comparatively limited reactivity toward nitric oxide (NO) via dioxygenation (kNOD(RcoM) = 6-8x106 M-1s-1 vs kNOD(Hb) = 6-8x107 M-1s-1). These data suggest that RcoM-HBD-CCC is a safe, selective, and efficacious CO scavenger. Additionally, by limiting hypertension RcoM-HBD-CCC improves end-organ adverse effects compared with hemoglobin-based therapeutics.

biochemistry↗

bioRxiv2024

Myoglobin Inhibits Breast Cancer Cell Fatty Acid Oxidation and Migration via Heme-Dependent Oxidant Production and Not Fatty Acid Binding

The monomeric heme protein myoglobin (Mb), traditionally thought to be expressed exclusively in cardiac and skeletal muscle, is now known to be expressed in approximately 40% of breast tumors. While Mb expression is associated with better patient prognosis, the molecular mechanisms by which Mb limits cancer progression are unclear. In muscle, Mbs predominant function is oxygen storage and delivery, which is dependent on the proteins heme moiety. However, prior studies demonstrate that the low levels of Mb expressed in cancer cells preclude this function. Recent studies propose a novel fatty acid binding function for Mb via a lysine residue (K46) in the heme pocket. Given that cancer cells can upregulate fatty acid oxidation (FAO) to maintain energy production for cytoskeletal remodeling during cell migration, we tested whether Mb-mediated fatty acid binding modulates FAO to decrease breast cancer cell migration. We demonstrate that the stable expression of human Mb in MDA-MB-231 breast cancer cells decreases cell migration and FAO. Site-directed mutagenesis of Mb to disrupt Mb fatty acid binding did not reverse Mb-mediated attenuation of FAO or cell migration in these cells. In contrast, cells expressing Apo-Mb, in which heme incorporation was disrupted, showed a reversal of Mb-mediated attenuation of FAO and cell migration, suggesting that Mb attenuates FAO and migration via a heme-dependent mechanism rather than through fatty acid binding. To this end, we show that Mbs heme-dependent oxidant generation propagates dysregulated gene expression of migratory genes, and this is reversed by catalase treatment. Collectively, these data demonstrate that Mb decreases breast cancer cell migration, and this effect is due to heme-mediated oxidant production rather than fatty acid binding. The implication of these results will be discussed in the context of therapeutic strategies to modulate oxidant production and Mb in tumors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=137 HEIGHT=200 SRC="FIGDIR/small/591659v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@84f5f9org.highwire.dtl.DTLVardef@130b7eeorg.highwire.dtl.DTLVardef@17b96faorg.highwire.dtl.DTLVardef@f517a5_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical Abstract:C_FLOATNO Mb-dependent oxidant generation (but not fatty acid binding) dysregulates mitochondrial respiration and migratory gene expression, leading to decreased cell migration. Created with BioRender. C_FIG HighlightsO_LIMyoglobin (Mb) expression in MDA-MB-231 breast cancer cells slows migration. C_LIO_LIMb expression decreases mitochondrial respiration and fatty acid oxidation. C_LIO_LIMb-dependent fatty acid binding does not regulate cell migration or respiration. C_LIO_LIMb-dependent oxidant generation decreases mitochondrial metabolism and migration. C_LIO_LIMb-derived oxidants dysregulate migratory gene expression. C_LI

cancer biology↗

bioRxiv2024

Methylmalonic acid induces metabolic abnormalities and exhaustion in CD8+ T cells to suppress anti-tumor immunity

Systemic levels of methylmalonic acid (MMA), a byproduct of propionate metabolism, increase with age and MMA promotes tumor progression via its direct effects in tumor cells. However, the tumorigenic role of MMA in modulating the tumor ecosystem remains to be investigated. The proliferation and function of CD8+ T cells, key anti-tumor immune cells, declines with age and in conditions of vitamin B12 deficiency, the two most well-established conditions that lead to increased systemic levels of MMA. Thus, we hypothesized that increased circulatory levels of MMA leads to suppression of CD8+ T cell immunity. Treatment of primary CD8+ T cells with MMA induced a dysfunctional phenotype characterized by a robust immunosuppressive transcriptional reprogramming and marked increases in the expression of the exhaustion regulator, TOX. Accordingly, MMA treatment upregulated exhaustion markers in CD8+ T cells and decreased their effector functions, which drove the suppression of anti-tumor immunity in vitro and in vivo. Mechanistically, MMA-induced CD8+ T cell exhaustion was associated with a suppression of NADH-regenerating reactions in the TCA cycle and concomitant defects in mitochondrial function. Thus, MMA has immunomodulatory roles, thereby highlighting MMA as an important link between aging, immune dysfunction, and cancer.

immunology↗