Biology subjects

Yee, E.

Publications and source records attributed to Yee, E..

5 recordsLinked to original sources

bioRxiv2026

Aerobic Exercise Preserves Capillary Oxygen Homeostasis and Neurovascular Function in a Mouse Model of Alzheimer's Disease

Age-related cerebrovascular dysfunction is increasingly recognized as a critical contributor to cognitive decline and Alzheimers disease (AD) progression. Aerobic physical activity (PA) and other modifiable lifestyle interventions can substantially reduce the likelihood of dementia; however, their ability to mitigate cerebrovascular alterations remains poorly defined. PA reportedly improves systemic vascular health and cognitive function in aging humans, but its impact on cerebrovascular function during aging and amyloid {beta} (A{beta}) pathology is unclear. Here, we longitudinally quantified microvascular oxygen tension and stimulus-evoked oxygen dynamics in awake APP/PS1dE9 mice and wild-type littermates using two-photon phosphorescence lifetime microscopy. Routine aerobic PA initiated in early adulthood preserved basal arteriolar, capillary, and venular oxygenation, prevented age-dependent increases in microvascular heterogeneity, and mitigated excessive oxygen extraction in preclinical AD mice. While amyloid pathology impaired stimulus-evoked oxygen responses across vascular compartments, PA selectively enhanced capillary dilation and accelerated hyperemic kinetics without altering vascular density or architecture. Notably, sedentary AD mice developed lower, widely-dispersed distributions in capillary oxygenation, hallmarks of malignant microvascular dysfunction, which were largely absent in physically active animals. These findings demonstrate that routine aerobic PA preserves basal capillary oxygenation and stimulus-evoked hyperemia during aging and A{beta}, supporting a capillary-centric mechanism through which exercise confers neurovascular resilience in preclinical AD.

neuroscience↗

bioRxiv2025

Rational design of tertiary coordination sphere of a heme-based sensor for two-orders enhanced oxygen affinity

Biological O2 sensing is crucial for diverse physiological functions across all forms of life. Heme-containing proteins achieve this by binding O2 to their iron center and have been found to display O2 affinities spanning several orders of magnitude. Despite decades of investigation into the structure and function of heme-based O2 sensors, the molecular mechanisms that enable the tuning of O2 affinity to match specific physiological roles remain unclear. Here, we utilize the O2 sensing mycobacterial DosS protein as a model system to explore the role of heme irons tertiary coordination sphere in controlling its O2 affinity. By rationally and systematically modifying the tertiary coordination sphere to promote the formation of a Trp-Tyr-Asn H-bond triad within the hemes distal pocket, we have enhanced the O2 affinity of WT DosS by over 150-fold. The rationally designed DosS exhibited a Kd value of 3 {+/-} 1 nM, compared to 460 {+/-} 80 nM for WT DosS. Employing a combination of structural, biochemical, spectroscopic, and computational studies, our analysis of WT and designed DosS variants highlights how the interplay between distal H-bond networks and heme-pocket electrostatics drives large differences in their O2 sensing capabilities. Ultimately, our work shows how metalloenzymes can dramatically alter their sensitivity to diatomic signaling molecules by tuning the tertiary coordination sphere, broadly impacting how we understand related biological sensing and signaling.

biochemistry↗

bioRxiv2024

IL15/IL15Rα complex induces an anti-tumor immune response following radiation therapy only in the absence of Tregs and fails to induce expansion of progenitor TCF1+ CD8 T cells

BackgroundThis work seeks to understand whether IL15-incorporating treatments improve response to radiotherapy and uncover mechanistic rationale for overcoming resistance to IL15 agonism using novel therapeutic combinations. Experimental DesignOrthotopic tumor models of PDAC were used to determine response to treatment. IL15-/- and Rag1-/- mouse models were employed to determine dependence on IL15 and CTLs, respectively. Flow cytometry was used to assess immune cell frequency and activation state. Phospho-proteomic analyses were used to characterize intracellular signaling pathways. ResultsWe show that the combination of radiation therapy (RT) and an IL15/IL15Ra fusion complex (denoted IL15c) fails to confer anti-tumor efficacy; however, a CD8-driven anti-tumor immune response is elicited with the concurrent administration of an aCD25 Treg-depleting antibody. Using IL15-/- and Rag1-/- mice, we demonstrate that response to RT + IL15c + aCD25 is dependent on both IL15 and CTLs. Furthermore, despite an equivalent survival benefit following treatment with RT + IL15c + aCD25 and combination RT + PD1-IL2v, a novel immunocytokine with PD-1 and IL2R{beta}{gamma} binding domains, CTL immunophenotyping and phospho-proteomic analysis of intracellular metabolites showed significant upregulation of activation and functionality in CD8 T cells treated with RT + PD1-IL2v. Finally, we show the immunostimulatory response to RT + PD1-IL2v is significantly diminished with a concurrent lack of TCF+ CD8 T cell generation in the absence of functional IL15 signaling. ConclusionsOur results are illustrative of a mechanism wherein unimpeded effector T cell activation through IL2R{beta} signaling and Treg inhibition are necessary in mediating an anti-tumor immune response.

cancer biology↗

bioRxiv2024

Oxygen affinities of DosT and DosS sensor kinases with implications for hypoxia adaptation in Mycobacterium tuberculosis

DosT and DosS are heme-based kinases involved in sensing and signaling O2 tension in the microenvironment of Mycobacterium tuberculosis (Mtb). Under conditions of low O2, they activate >50 dormancy-related genes and play a pivotal role in the induction of dormancy and associated drug resistance during tuberculosis infection. In this work, we reexamine the O2 binding affinities of DosT and DosS to show that their equilibrium dissociation constants are 3.3{+/-}1 M and 0.46{+/-}0.08 M respectively, which are six to eight-fold stronger than what has been widely referred to in literature. Furthermore, stopped-flow kinetic studies reveal association and dissociation rate constants of 0.84 M-1s-1 and 2.8 s-1, respectively for DosT, and 7.2 M-1s-1 and 3.3 s-1, respectively for DosS. Remarkably, these tighter O2 binding constants correlate with distinct stages of hypoxia-induced non-replicating persistence in the Wayne model of Mtb. This knowledge opens doors to deconvoluting the intricate interplay between hypoxia adaptation stages and the signal transduction capabilities of these important heme-based O2 sensors.

biochemistry↗

bioRxiv2020

Epithelial cell biomarkers are predictive of response to biologic agents in Crohn's disease

ObjectiveTherapeutic efficacy of biologics has remained at about 50% for 2 decades. In Crohns disease (CD) patients, we examined the predictive value of an epithelial cell biomarker, ileal microvillar length (MVL), for clinical response to ustekinumab (UST) and vedolizumab (VDZ), and its relationship to another biomarker, intestinal epithelial cell (IEC) pyroptosis with respect to response to VDZ. DesignIleal biopsies from the UNITI-2 randomized controlled trial were analyzed for MVL as a predictor of clinical response to UST. In a 5-center academic retrospective cohort of CD patients, ileal MVL was analyzed to determine its predictive value for response to VDZ. Correlation between ileal MVL and IEC pyroptosis was determined, and the discriminant ability of the combination of two biomarkers to VDZ was examined. ResultsClinical response in UST was significantly higher than placebo (65% vs. 39%, p=0.03), with patients with normal MVL (>1.7 {micro}m) having the greatest therapeutic effect: 85% vs. 20% (p=0.02). For VDZ, clinical response with MVL of 1.35-1.55 {micro}m was 82% vs. 44% (<1.35 {micro}m) and 40% (>1.55 {micro}m) (p=0.038). There was no correlation between ileal MVL and IEC pyroptosis. The combination criteria of ileal pyroptosis < 14 positive cells/1000 IECs or MVL of 1.35-1.55 {micro}m could identify 84% of responders and 67% of non-responders (p=0.001). ConclusionsIleal MVL was predictive of response to UST and VDZ in prospective and retrospective CD cohorts. It was independent of ileal IEC pyroptosis, combination of the two biomarkers enhanced the discriminate ability of responders from non-responders to VDZ.

cell biology↗