Identification of Climate-Smart Bread Wheat Germplasm Lines with Enhanced Adaptation to Global Warming

Bread wheat (Triticum aestivum L.) is widely grown in sub-tropical and tropical areas and, as such, it is exposed to heatstress especially during the grain filling period (GFP). Global warming has further affected its production and productivity in these heat-stressed environments. We examined the effects of heatstress on 18 morpho-physiological and yield-related traits in 96 bread wheat accessions. Heat stress decreased crop growth and GFP, and consequently reduced morphological and yield-related traits in the delayed sown crop. A low heat susceptibility index and high yield stability were used for selecting tolerant accessions. Under heatstress, the days to 50% anthesis, flag-leaf area, chlorophyll content, normalized difference vegetation index (NDVI), thousand grain weight (TGW), harvest index and grain yield were significantly reduced both in tolerant and susceptible accessions. The reduction was severe in susceptible accessions (48.2% grain yield reduction in IC277741). The plant height, peduncle length and spike length showeda significant reduction in susceptible accessions, but a non-significant reduction in the tolerant accessions under the heatstress. The physiological traits like the canopy temperature depression (CTD), plant waxiness and leaf rolling were increased in tolerant accessions under heatstress. Scanning electron microscopy of matured wheat grains revealed ultrastructural changes in endosperm and aleurone cells due to heat stress. The reduction in size and density of large starch granules is the major cause of the yield and TGW decrease in the heat-stress-susceptible accessions. The most stable and high-yielding accessions, namely, IC566223, IC128454, IC335792, EC576707, IC535176, IC529207, IC446713 and IC416019 were identified as the climate-smart germplasm lines. We selected germplasm lines possessing desirable traits as potential parents for the development of bi-parent and multi-parent mapping populations.

Regulation of Macrophage Cell Surface GAPDH Alters LL-37 Internalization and Downstream Effects in the Cell

Mycobacterium tuberculosis (M.tb), the major causative agent of tuberculosis, has evolved mechanisms to evade host defenses and persist within host cells. Host-directed therapies against infected cells are emerging as an effective option. Cationic host defense peptide LL-37 is known to internalize into cells and induce autophagy resulting in intracellular killing of M.tb. This peptide also regulates the immune system and interacts with the multifunctional protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) inside macrophages. Our investigations revealed that GAPDH moonlights as a mononuclear cell surface receptor that internalizes LL-37. We confirmed that the surface levels of purinergic receptor 7, the receptor previously reported for this peptide, remained unaltered on M.tb infected macrophages. Upon infection or cellular activation with IFNγ, surface recruited GAPDH bound to and internalized LL-37 into endocytic compartments via a lipid raft-dependent process. We also discovered a role for GAPDH in LL-37-mediated autophagy induction and clearance of intracellular pathogens. In infected macrophages wherein GAPDH had been knocked down, we observed an inhibition of LL-37-mediated autophagy which was rescued by GAPDH overexpression. This process was dependent on intracellular calcium and p38 MAPK pathways. Our findings reveal a previously unknown process by which macrophages internalize an antimicrobial peptide via cell surface GAPDH and suggest a moonlighting role of GAPDH in regulating cellular phenotypic responses of LL-37 resulting in reduction of M.tb burden.

Host glyceraldehyde-3-phosphate dehydrogenase-mediated iron acquisition is hijacked by intraphagosomal Mycobacterium tuberculosis

Availability of iron is a key factor in the survival and multiplication of Mycobacterium tuberculosis (M.tb) within host macrophage phagosomes. Despite host cell iron regulatory machineries attempts to deny supply of this essential micronutrient, intraphagosomal M.tb continues to access extracellular iron. In the current study, we report that intracellular M.tb exploits mammalian secreted Glyceraldehyde 3-phosphate dehydrogenase (sGAPDH) for the delivery of host iron carrier proteins lactoferrin (Lf) and transferrin (Tf). Studying the trafficking of iron carriers in infected cells we observed that sGAPDH along with the iron carrier proteins are preferentially internalized into infected cells and trafficked to M.tb containing phagosomes where they are internalized by resident mycobacteria resulting in iron delivery. Collectively our findings provide a new mechanism of iron acquisition by M.tb involving the hijack of host sGAPDH. This may contribute to its successful pathogenesis and provide an option for targeted therapeutic intervention.

Exposure of a specific pleioform of multifunctional glyceraldehyde 3-phosphate dehydrogenase initiates CD14-dependent clearance of apoptotic cells

Rapid clearance of apoptotic cells by phagocytes is crucial for organogenesis, tissue homeostasis, and resolution of inflammation. This process is initiated by surface exposure of various 'eat me' ligands. Though phosphatidylserine (PS) is the best recognized general recognition ligand till date, recent studies have shown that PS by itself is not sufficient for clearance of apoptotic cells. In this study, we have identified a specific pleioform of GAPDH (Glyceraldehyde 3-phosphate dehydrogenase) that functions as an 'eat me' signal on apoptotic cell surface. This specific form of GAPDH which is exposed on surface of apoptotic cells was found to interact with CD14 present on plasma membrane of phagocytes leading to their engulfment. This is the first study demonstrating the novel interaction between multifunctional GAPDH and the phagocytic receptor CD14 resulting in apoptotic cell clearance (efferocytosis).

Glyceraldehyde-3-Phosphate Dehydrogenase Facilitates Macroautophagic Degradation of Mutant Huntingtin Protein Aggregates

Protein aggregate accumulation is a pathological hallmark of several neurodegenerative disorders. Autophagy is critical for clearance of aggregate-prone proteins. In this study, we identify a novel role of the multifunctional glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in clearance of intracellular protein aggregates. Previously, it has been reported that though clearance of wild-type huntingtin protein is mediated by chaperone-mediated autophagy (CMA), however, degradation of mutant huntingtin (mHtt with numerous poly Q repeats) remains impaired by this route as mutant Htt binds with high affinity to Hsc70 and LAMP-2A. This delays delivery of misfolded protein to lysosomes and results in accumulation of intracellular aggregates which are degraded only by macroautophagy. Earlier investigations also suggest that mHtt causes inactivation of mTOR signaling, causing upregulation of autophagy. GAPDH had earlier been reported to interact with mHtt resulting in cellular toxicity. Utilizing a cell culture model of mHtt aggregates coupled with modulation of GAPDH expression, we analyzed the formation of intracellular aggregates and correlated this with autophagy induction. We observed that GAPDH knockdown cells transfected with N-terminal mutant huntingtin (103 poly Q residues) aggregate-prone protein exhibit diminished autophagy. GAPDH was found to regulate autophagy via the mTOR pathway. Significantly more and larger-sized huntingtin protein aggregates were observed in GAPDH knockdown cells compared to empty vector-transfected control cells. This correlated with the observed decrease in autophagy. Overexpression of GAPDH had a protective effect on cells resulting in a decreased load of aggregates. Our results demonstrate that GAPDH assists in the clearance of protein aggregates by autophagy induction. These findings provide a new insight in understanding the mechanism of mutant huntingtin aggregate clearance. By studying the molecular mechanism of protein aggregate clearance via GAPDH, we hope to provide a new approach in targeting and understanding several neurodegenerative disorders.

Moonlighting glyceraldehyde-3-phosphate dehydrogenase (GAPDH) modulates protein aggregation

Onset of protein aggregation reflects failure of the cellular folding machinery to keep aggregation-prone protein from misfolding and accumulating into a non-degradable state. FRET based analysis and biochemical data reveal that cytosolic prion (cyPrP) and httQ-103 interact with the multifunctional protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) leading to few detectable aggregates in GAPDH-over expressing cells.The preventive effect of GAPDH suggests that this abundant and long-lived cytoplasmic protein has an active role in the shielding and maintenance, in soluble form of proteins as heterogeneous as huntingtin and cyPrP.

Mycobacterium tuberculosis glyceraldehyde-3-phosphate dehydrogenase plays a dual role-As an adhesin and as a receptor for plasmin(ogen)

The spread of infection is directly determined by the ability of a pathogen to invade and infect host tissues. The process involves adherence due to host-pathogen interactions and traversal into deeper tissues. Mycobacterium tuberculosis (Mtb) primarily infects the lung but is unique in its ability to infect almost any other organ of the human host including immune privileged sites such as the central nervous system (CNS). The extreme invasiveness of this bacterium is not fully understood. In the current study, we report that cell surface Mtb glyceraldehyde-3-phosphate dehydrogenase (GAPDH) functions as a virulence factor by multiple mechanisms. Firstly, it serves as a dual receptor for both plasminogen (Plg) and plasmin (Plm). CRISPRi-mediated silencing of this essential enzyme confirmed its role in the recruitment of Plg/Plm. Our studies further demonstrate that soluble GAPDH can re-associate on Mtb bacilli to promote plasmin(ogen) recruitment. The direct association of plasmin(ogen) via cell surface GAPDH or by the re-association of soluble GAPDH enhanced bacterial adherence to and traversal across lung epithelial cells. Furthermore, the association of GAPDH with host extracellular matrix (ECM) proteins coupled with its ability to recruit plasmin(ogen) may endow cells with the ability of directed proteolytic activity vital for tissue invasion.

Repurposing ethyl bromopyruvate as a broad-spectrum antibacterial

BACKGROUND

The emergence of drug-resistant bacteria is a major hurdle for effective treatment of infections caused by Mycobacterium tuberculosis and ESKAPE pathogens. In comparison with conventional drug discovery, drug repurposing offers an effective yet rapid approach to identifying novel antibiotics.

METHODS

Ethyl bromopyruvate was evaluated for its ability to inhibit M. tuberculosis and ESKAPE pathogens using growth inhibition assays. The selectivity index of ethyl bromopyruvate was determined, followed by time-kill kinetics against M. tuberculosis and Staphylococcus aureus. We first tested its ability to synergize with approved drugs and then tested its ability to decimate bacterial biofilm. Intracellular killing of M. tuberculosis was determined and in vivo potential was determined in a neutropenic murine model of S. aureus infection.

RESULTS

We identified ethyl bromopyruvate as an equipotent broad-spectrum antibacterial agent targeting drug-susceptible and -resistant M. tuberculosis and ESKAPE pathogens. Ethyl bromopyruvate exhibited concentration-dependent bactericidal activity. In M. tuberculosis, ethyl bromopyruvate inhibited GAPDH with a concomitant reduction in ATP levels and transferrin-mediated iron uptake. Apart from GAPDH, this compound inhibited pyruvate kinase, isocitrate lyase and malate synthase to varying extents. Ethyl bromopyruvate did not negatively interact with any drug and significantly reduced biofilm at a 64-fold lower concentration than vancomycin. When tested in an S. aureus neutropenic thigh infection model, ethyl bromopyruvate exhibited efficacy equal to that of vancomycin in reducing bacterial counts in thigh, and at 1/25th of the dosage.

CONCLUSIONS

Ethyl bromopyruvate exhibits all the characteristics required to be positioned as a potential broad-spectrum antibacterial agent.

Peptidoglycan-treated tumor antigen-pulsed dendritic cells impart complete resistance against tumor rechallenge

Solid tumors elicit suppressive T cell responses which impair antigen-presenting cell (APC) functions. Such immune suppression results in uncontrolled tumor growth and mortality. Addressing APC dysfunction, dendritic cell (DC)-mediated anti-tumor vaccination was extensively investigated in both mice and humans. These studies never achieved full resistance to tumor relapse. Herein, we describe a repetitive RM-1 murine tumor rechallenge model for recurrence in humans. Using this newly developed model, we show that priming with tumor antigen-pulsed, Toll-like receptor (TLR)2 ligand-activated DCs elicits a host-protective anti-tumor immune response in C57BL/6 mice. Upon stimulation with the TLR2 ligand peptidoglycan (PGN), the tumor antigen-pulsed DCs induce complete resistance to repetitive tumor challenges. Intra-tumoral injection of PGN reduces tumor growth. The tumor resistance is accompanied by increased expression of interleukin (IL)-27, T-box transcription factor TBX21 (T-bet), IL-12, tumor necrosis factor (TNF)-α and interferon (IFN)-γ, along with heightened cytotoxic T lymphocyte (CTL) functions. Mice primed four times with PGN-stimulated tumor antigen-pulsed DCs remain entirely resistant to repeat challenges with RM-1 tumor cells, suggesting complete prevention of relapse and recurrence of tumor. Adoptive transfer of T cells from these mice, which were fully protected from RM-1 rechallenge, confers anti-tumor immunity to syngeneic naive recipient mice upon RM-1 challenge. These observations indicate that PGN-activated DCs induce robust host-protective anti-tumor T cells that completely resist tumor growth and recurrence.

Trafficking of a multifunctional protein by endosomal microautophagy: linking two independent unconventional secretory pathways

During physiologic stresses, like micronutrient starvation, infection, and cancer, the cytosolic moonlighting protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is trafficked to the plasma membrane (PM) and extracellular milieu (ECM). Our work demonstrates that GAPDH mobilized to the PM, and the ECM does not utilize the classic endoplasmic reticulum-Golgi route of secretion; instead, it is first selectively translocated into early and late endosomes from the cytosol via microautophagy. GAPDH recruited to this common entry point is subsequently delivered into multivesicular bodies, leading to its membrane trafficking through secretion via exosomes and secretory lysosomes. We present evidence that both pathways of GAPDH membrane trafficking are up-regulated upon iron starvation, potentially by mobilization of intracellular calcium. These pathways also play a role in clearance of misfolded intracellular polypeptide aggregates. Our findings suggest that cells build in redundancy for vital cellular pathways to maintain micronutrient homeostasis and prevent buildup of toxic intracellular misfolded protein refuse.-Chauhan, A. S., Kumar, M., Chaudhary, S., Dhiman, A., Patidar, A., Jakhar, P., Jaswal, P., Sharma, K., Sheokand, N., Malhotra, H., Raje, C. I., Raje. M. Trafficking of a multifunctional protein by endosomal microautophagy: linking two independent unconventional secretory pathways.

Mycobacterium tuberculosis Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) Functions as a Receptor for Human Lactoferrin

Iron is crucial for the survival of living cells, particularly the human pathogen Mycobacterium tuberculosis (M.tb) which uses multiple strategies to acquire and store iron. M.tb synthesizes high affinity iron chelators (siderophores), these extract iron from host iron carrier proteins such as transferrin (Tf) and lactoferrin (Lf). Recent studies have revealed that M.tb may also relocate several housekeeping proteins to the cell surface for capture and internalization of host iron carrier protein transferrin. One of the identified receptors is the glycolytic enzyme Glyceraldehyde-3-phosphate dehydrogenase (GAPDH). This conserved multifunctional protein has been identified as a virulence factor in several other bacterial species. Considering the close structural and functional homology between the two major human iron carrier proteins (Tf and Lf) and the fact that Lf is abundantly present in lung fluid (unlike Tf which is present in plasma), we evaluated whether GAPDH also functions as a dual receptor for Lf. The current study demonstrates that human Lf is sequestered at the bacterial surface by GAPDH. The affinity of Lf-GAPDH (31.7 ± 1.68 nM) is higher as compared to Tf-GAPDH (160 ± 24 nM). Two GAPDH mutants were analyzed for their enzymatic activity and interaction with Lf. Lastly, the present computational studies offer the first significant insights for the 3D structure of monomers and assembled tetramer with the associated co-factor NAD⁺. Sequence analysis and structural modeling identified the surface exposed, evolutionarily conserved and functional residues and predicted the effect of mutagenesis on GAPDH.

Reverse overshot water-wheel retroendocytosis of apotransferrin extrudes cellular iron

Iron (Fe), a vital micronutrient for all organisms, must be managed judiciously because both deficiency or excess can trigger severe pathology. Although cellular Fe import is well understood, its export is thought to be limited to transmembrane extrusion through ferroportin (also known as Slc40a1), the only known mammalian Fe exporter. Utilizing primary cells and cell lines (including those with no discernible expression of ferroportin on their surface), we demonstrate that upon Fe loading, the multifunctional enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is recruited to the cell surface, 'treadmills' apotransferrin in and out of the cell. Kinetic analysis utilizing labeled ligand, GAPDH-knockdown cells, (55)Fe-labeled cells and pharmacological inhibitors of endocytosis confirmed GAPDH-dependent apotransferrin internalization as a prerequisite for cellular Fe export. These studies define an unusual rapid recycling process of retroendocytosis for cellular Fe extrusion, a process mirroring receptor mediated internalization that has never before been considered for maintenance of cellular cationic homeostasis. Modulation of this unusual pathway could provide insights for management of Fe overload disorders.

Secreted multifunctional Glyceraldehyde-3-phosphate dehydrogenase sequesters lactoferrin and iron into cells via a non-canonical pathway

Lactoferrin is a crucial nutritionally important pleiotropic molecule and iron an essential trace metal for all life. The current paradigm is that living organisms have evolved specific membrane anchored receptors along with iron carrier molecules for regulated absorption, transport, storage and mobilization of these vital nutrients. We present evidence for the existence of non-canonical pathway whereby cells actively forage these vital resources from beyond their physical boundaries, by secreting the multifunctional housekeeping enzyme Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) into the extracellular milieu. This effect’s an autocrine/paracrine acquisition of target ligand into the cell. Internalization by this route is extensively favoured even by cells that express surface receptors for lactoferrin and involves urokinase plasminogen activator receptor (uPAR). We also demonstrate the operation of this phenomenon during inflammation, as an arm of the innate immune response where lactoferrin denies iron to invading microorganisms by chelating it and then itself being sequestered into surrounding host cells by GAPDH.

Vaginal displacement during course of adjuvant radiation for cervical cancer: results from a prospective IG-IMRT study

OBJECTIVE

To compare internal target volume (ITV) generated using population-based displacements (ITV_study) with empty and full bladder scan fusion (ITV_EBFB) for organ-at-risk (OAR) doses during adjuvant intensity-modulated radiation therapy (IMRT) for cervical cancer.

METHODS

From January 2011 to October 2012, patients undergoing IMRT were included. CT simulation was carried out after inserting vault markers. Planning target volume (PTV)_EBFB received 50 Gy per 25 fractions. Pre-treatment megavoltage CT (MVCT) was performed. MVCTs were registered using bony landmarks with Day 1 MVCT. Displacement of the centre of mass of markers was measured along each axis. Directional ITV was calculated using mean ± 2 standard deviations (SDs) (ITV_study). Replanning was performed using PTV study, and OAR doses were compared with PTV_EBFB using Wilcoxon test.

RESULTS

A total of 348/386 data sets were evaluable for 16 patients. The median vaginal displacement was 1.2 mm (SD, 1.3 mm), 4.0 mm (SD, 3.5 mm) and 2.8 mm (SD, 3.3 mm) in the mediolateral, superoinferior and anteroposterior directions, respectively. The ITV margins were 4.1, 10.3 and 10.6 mm. ITV_study and ITV_EBFB were 115.2 cm(3) (87.7-152.2 cm(3)) and 151 cm(3) (95.7-277.1 cm(3)) (p < 0.0001), respectively. PTV_study and PTV_EBFB were 814 and 881 cm(3) (p < 0.0001), respectively. Median doses to the bladder were lower with the PTV_study (46.2 Gy vs 43.2 Gy; p = 0.0001), and a similar trend was observed in the volume of the small bowel receiving 40 Gy (68.2 vs 60.1 cm(3); p = 0.09).

CONCLUSION

Population-based PTV margins can lead to reduction in OAR doses.

ADVANCES IN KNOWLEDGE

Population-based ITV may reduce OAR doses while executing adjuvant IMRT for cervical cancer.