Biology subjects

Moran, N.

Publications and source records attributed to Moran, N..

8 recordsLinked to original sources

bioRxiv2026

Ontological Analysis of Brain Proteostasis Highlights the Sex-Dependent Trajectory of ApoE Isoform-Specific Regulation

Apolipoprotein E (ApoE) is the strongest genetic predictor of Alzheimers disease (AD) risk, with ApoE4 increasing and ApoE2 decreasing risk relative to ApoE3. Using a global LC-MS proteomic approach, we integrated protein abundance and kinetics in Human-APOE knock-in mice for young (3-month) and aged (18-month) cohorts to quantify the changes in steady-state proteostasis. By mapping 6,052 identified proteins and 3,986 associated turnover rates into ontological groups, we observed that vesicle trafficking and mitochondrial dysregulation occur as early as 3 months in ApoE4 mice accompanied by hyperactive metabolism that eventually reduces with age. In contrast, young and old ApoE2 mice retain similar signatures to ApoE3 mice in metabolic, mitochondrial, cellular regulation, and membrane trafficking ontologies. We found that females had more isoform-induced ontological changes relative to ApoE3, providing insight into sex-dependent vulnerabilities. Our global proteomic approach for ApoE proteostasis crucially unifies independent literature observations while providing turnover kinetics to uncover the underlying mechanism behind abundance changes. Data are available via ProteomeXchange with identifier PXD079261. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=189 SRC="FIGDIR/small/735293v1_ufig2.gif" ALT="Figure 1000"> View larger version (45K): org.highwire.dtl.DTLVardef@28ebfforg.highwire.dtl.DTLVardef@9dc6f2org.highwire.dtl.DTLVardef@704577org.highwire.dtl.DTLVardef@e0b0e2_HPS_FORMAT_FIGEXP M_FIG C_FIG O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/735293v1_ufig1.gif" ALT="Figure 1001"> View larger version (48K): org.highwire.dtl.DTLVardef@17d0474org.highwire.dtl.DTLVardef@af771borg.highwire.dtl.DTLVardef@1b49f67org.highwire.dtl.DTLVardef@14d3aa2_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Quantitative and Kinetic Proteomics Reveal ApoE Isoform-dependent Proteostasis Adaptations in Mouse Brain

Apolipoprotein E (ApoE) polymorphisms modify the risk of neurodegenerative disease with the ApoE4 isoform increasing and ApoE2 isoform decreasing risk relative to the wild-type control ApoE3 isoform. To elucidate how ApoE isoforms alter the proteome, we measured relative protein abundance and turnover in transgenic mice expressing a human ApoE gene (isoform 2, 3, or 4). This data provides insight into how ApoE isoforms affect the in vivo synthesis and degradation of a wide variety of proteins. We identified 4849 proteins and tested for ApoE isoform-dependent changes in the homeostatic regulation of [~]2700 ontologies. In the brain, we found that ApoE4 and ApoE2 both lead to modified regulation of mitochondrial membrane proteins relative to the wild-type control ApoE3. In ApoE4 mice, this regulation is not cohesive suggesting that aerobic respiration is impacted by proteasomal and autophagic dysregulation. ApoE2 mice exhibited a matching change in mitochondrial matrix proteins and the membrane which suggests coordinated maintenance of the entire organelle. In the liver, we did not observe these changes suggesting that the ApoE-effect on proteostasis is amplified in the brain relative to other tissues. Our findings underscore the utility of combining protein abundance and turnover rates to decipher proteome regulatory mechanisms and their potential role in biology.

biochemistry↗

bioRxiv2023

Rice OsHAK18 mediates shoot-to-root circulation of potassium and sodium and source-to-sink transport of soluble sugar

High-affinity potassium (K+) transporters HAK/KUP/KT have been identified in all genome-sequenced terrestrial plants. They play important role in K+ acquisition, translocation and enhancing salt tolerance. Here we report that the plasma-membrane-located OsHAK18 functions in K+ and sodium (Na+) circulation and sugar translocation in rice. OsHAK18 is expressed mainly, though not exclusively, in vascular tissues and particularly in the phloem. Knockout (KO) of OsHAK18 reduced K+ concentration in phloem sap and in the root but increased K+ accumulation in the shoot of both Nipponbare and Zhonghua11 cultivars, while overexpression (OX) of OsHAK18 driven by its endogenous promoter increased K+ concentration in phloem sap and in roots, and promoted Na+ retrieval from shoot to root under salt stress. Split-root experimental analysis of rubidium (Rb+) uptake and circulation indicated that OsHAK18-OX promoted Rb+ translocation from shoot to root. In addition, OsHAK18-KO increased while OsHAK18-OX reduced soluble sugar content in the shoot and affected oppositely the sugar concentration in the phloem and its content in the root. Moreover, OsHAK18-OX increased dramatically grain yield and physiological K+ utilization efficiency. Taken together, our results suggest that - unlike other OsHAKs analyzed heretofore - OsHAK18 is critical to K+ and Na+ re-circulation from shoot to root and enhances the source-to-sink translocation of a photo-assimilate. One sentence summaryRice potassium transporter OsHAK18 mediates shoot-to-root circulation of potassium and sodium and source-to-sink translocation of soluble sugar which improves potassium use efficiency and grain yield.

plant biology↗

bioRxiv2023

A tale of two pumps: Blue light and ABA alter Arabidopsis leaf hydraulics via bundle sheath cells H+-pumps and channels

This study focuses on the cellular mechanism underlying the co-regulation of the leaf hydraulic conductance (Kleaf) by blue light (BL) and the stress hormone ABA in Arabidopsis thaliana. Our previous work has demonstrated that (1) Kleaf increased by BL signaling within the leaf bundle sheath cells (BSCs), which activated their plasmalemma (PM) H+-ATPase (AHA2), acidifying the xylem sap; (2) external acidification enhanced the BSCs Kleaf and their osmotic water permeability (Pf); (3) ABA decreased both Kleaf and Pf by reducing the BSCs PM aquaporins activity. We now show, using pH and EM (membrane potential) probes combined with H+-pumps inhibitors and manipulations of cytosolic and external Ca2+ concentrations ([Ca2+]CYT, [Ca2+]EXT, respectively), that, in the BSCs: (a) under BL, ABA inhibits AHA2, depolarizing the BSCs and alkalinizing the xylem sap, (b) ABA stimulates the BSCs vacuolar H+-ATPase (VHA), alkalinizing their cytosol; (c) each pump stimulation, AHA2 by BL and VHA by ABA, requires [Ca2+]CYT elevation. ABA-effect-mimicking conditions in patch-clamp experiments activate the BSCs K+-release channels (SKOR and/or GORK). ABA decreased the Kleaf of skor mutants less than WTs, while during water deprivation stress, skor plants transpired more and their leaves lost relatively less K+ than WT. This suggests a role for SKOR in water conservation under drought.

plant biology↗

bioRxiv2022

Cooperative host-microbe metabolism of a plant toxin in bees

During pollination, bees are exposed to a myriad of xenobiotics, including plant metabolites, which may exert a wide range of effects on their health. Although bees encode enzymes that help in the metabolism of xenobiotics, they still have reduced detoxification gene diversity when compared to other insects, and may rely on other components of their physiology, such as the microbiota, to degrade potentially toxic molecules. In this study, we show that amygdalin, a cyanogenic glycoside found in honey bee-pollinated almond trees, can be metabolized by both bees and members of the gut microbiota. In microbiota-deprived bees, amygdalin is degraded into prunasin, leading to prunasin accumulation in the midgut and hindgut. In microbiota-colonized bees, on the other hand, amygdalin is degraded even further, and prunasin does not accumulate in the gut, suggesting that the microbiota contribute to the full degradation of amygdalin into hydrogen cyanide. In vitro experiments demonstrated that amygdalin degradation by bee gut bacteria is strain-specific and not characteristic of a particular genus or species. We found strains of Bifidobacterium, Bombilactobacillus and Gilliamella that can degrade amygdalin, and the degradation mechanism appears to vary since only some strains produce prunasin as an intermediate. Finally, we investigated the basis of degradation in Bifidobacterium wkB204, a strain that fully degrades amygdalin. We found overexpression and secretion of several carbohydrate-degrading enzymes, including one in glycoside hydrolase family 3 (GH3). We expressed this GH3 in Escherichia coli and detected prunasin as a byproduct when cell lysates were cultured with amygdalin, supporting its contribution to amygdalin degradation. These findings demonstrate that both host and microbiota can act together to metabolize dietary plant metabolites. How amygdalin degradation into hydrogen cyanide affects bee health remains to be elucidated.

ecology↗

bioRxiv2021

Stress is basic: ABA alkalinizes both the xylem sap and the cytosol of Arabidopsis vascular bundle sheath cellsby inhibiting their P-type H+-ATPaseand stimulating their V-type H+-ATPase

BACKGROUND AND HYPOTHESIS* Under water deprivation, in many perennial species, the stress hormone, ABA, appears in the xylem sap in the shoot (including leaf) veins and the xylem sap pH (pHEXT) increases. This study aimed to test the hypothesis that ABA is the signal for an altered proton balance of the leaf-vein-enwrapping bundle sheath cells (BSCs). METHODS* Plant Material. We used a few Arabidopsis thaliana (L.) Heynh. genotypes: wildtype (WT) of two accessions, Landsberg erecta (Ler) and Columbia (Col), and a few mutants and transformants in these backgrounds. * H+-Pumps activities. We monitored ABA effects on the H+-pump activities in the BSCs cytosol-delimiting membranes (plasma membrane and tonoplast) by monitoring the cytosol and the xylem pH, and the membrane potential (EM), by imaging the fluorescence of pH- and membrane potential (EM)-reporting probes: (a) the BSCs pHEXT - with the ratiometric fluorescent dye FITC-dextran petiole-fed into detached leaves in unbuffered xylem perfusion solution (XPS), (b) the BSCs pHCYT - with the ratiometric dye SNARF1 loaded into BSCs isolated protoplasts, and (c) the BSCs EM - with the ratiometric dye di- 8-ANEPPS. RESULTS* ABA increased the pHEXT; this response was abolished in an abi1-1 mutant with impaired signaling via a PP2C (ABI1) and in an aha2-4 mutant with knocked-down AHA2; * ABA depolarized the WT BSCs; * ABA increased pHCYT irrespective of AHA2 activity (i.e., whether or not AHA was inhibited by vanadate, or in the aha2-4 mutant); * The ABA-induced cytosol alkalinization was abolished in the absence of VHA activity (i.e., when VHA was inhibited by bafilomycin A1, or in the vha-a2 vha-a3 double mutant with inactive VHA); * All these results resemble the ABA effect on GCs; * In contrast to GCs, AHA2 and not AHA1 is the ABA major target in BSCs; * Blue light (BL) enabled the response of the BSCs VHA to ABA; * The ABA- and BL-signaling pathways acting on both BSCs pumps, AHA2 and VHA, are likely to be BSCs autonomous, based on (a) the presence in the BSCs of many genes of the ABA- and BL-signaling pathways and (b) ABA responses (depolarization and pHCYT elevation) demonstrated under BL in isolated protoplasts. SIGNIFICANCE STATEMENTWe reveal here an alkalinizing effect of the plant drought-stress hormone ABA on the pH on both sides of the plasmalemma of the vein-enwrapping bundle sheath cells (BSCs), due to ABA inhibition of the BSCs AHA2, the plasmalemma H+- ATPase and stimulation of VHA, their vacuolar H+-ATPase. Since pH affects the BSCs selective regulation of solute and water fluxes into the leaf, these H+- pumps may be attractive targets for manipulations aiming to improve plant drought response.

plant biology↗

bioRxiv2019

Out of the blue; Phototropins of the leaf vascular bundle sheath mediate the blue light regulation of the leaf hydraulic conductance

The Arabidopsis leaf veins bundle sheath cells (BSCs) - a selective barrier to water and solutes entering the mesophyll - increase the leaf radial hydraulic conductance (Kleaf) by acidifying the xylem sap by their plasma membrane H+-ATPase, AHA2. Based on this and on the BSCs expression of PHOT1 and PHOT2, and the known blue-light (BL)-induced Kleaf increase, we hypothesized that, resembling the guard cells, BL perception by the BSCs phots activates its H+-ATPase, which, consequently, upregulates Kleaf. Indeed, under BL, the Kleaf of the knockout mutant lines phot1-5, phot2-1, phot1-5phot2-1, and aha2-4 was lower than that of the WT. BSC-only-directed complementation of phot1-5 or aha2-4 by PHOT1 or AHA2, respectively, restored the BL-induced Kleaf increase. BSC-specific silencing of PHOT1 or PHOT2 prevented such Kleaf increase. A xylem-fed kinase inhibitor (tyrphostin 9) replicated this also in WT plants. White light - ineffective in the phot1-5 mutant - acidified the xylem sap (relative to darkness) in WT and in the PHOT1-complemented phot1-5. These results, supported by BL increase of BSC protoplasts water permeability and cytosolic pH and their hyperpolarization by BL, identify the BSCs as a second phot-controlled water conductance element in leaves, in series with stomatal conductance. Through both, BL regulates the leaf water balance. One-Sentence summaryBlue light regulates the leaf hydraulic conductance via the bundle-sheath cells blue light PHOT receptors which, via an autonomous signaling pathway, activate the BSCs AHA2 H+-pump.

plant biology↗

bioRxiv2017

Bundle-sheath cells are internal leaf "water valves" controlled via xylem acidification by H+-ATPase

O_LIThe leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem-sap pH of <6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates this pH and leaf radial water fluxes. C_LIO_LIWe monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts. C_LIO_LIOur results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf. C_LIO_LIAll these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance. C_LI One-sentence summaryBundle-sheath cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH

plant biology↗