scholarly journals Higher order Rab programming in phagolysosome biogenesis

2006 ◽  
Vol 174 (7) ◽  
pp. 923-929 ◽  
Author(s):  
Esteban A. Roberts ◽  
Jennifer Chua ◽  
George B. Kyei ◽  
Vojo Deretic
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Higher Order ◽  
Intracellular Pathogen ◽  
Control Mechanisms ◽  
Rab Gtpases ◽  
Endosomal Compartment ◽  
Phagosomal Maturation ◽  
Naturally Occurring ◽  
Latex Beads

Phagosomes offer kinetically and morphologically tractable organelles to dissect the control of phagolysosome biogenesis by Rab GTPases. Model phagosomes harboring latex beads undergo a coordinated Rab5–Rab7 exchange, which is akin to the process of endosomal Rab conversion, the control mechanisms of which are unknown. In the process of blocking phagosomal maturation, the intracellular pathogen Mycobacterium tuberculosis prevents Rab7 acquisition, thus, providing a naturally occurring tool to study Rab conversion. We show that M. tuberculosis inhibition of Rab7 acquisition and arrest of phagosomal maturation depends on Rab22a. Four-dimensional microscopy revealed that phagosomes harboring live mycobacteria recruited and retained increasing amounts of Rab22a. Rab22a knockdown in macrophages via siRNA enhanced the maturation of phagosomes with live mycobacteria. Conversely, overexpression of the GTP-locked mutant Rab22aQ64L prevented maturation of phagosomes containing heat-killed mycobacteria, which normally progress into phagolysosomes. Moreover, Rab22a knockdown led to Rab7 acquisition by phagosomes harboring live mycobacteria. Our findings show that Rab22a defines the critical checkpoint for Rab7 conversion on phagosomes, allowing or disallowing organellar transition into a late endosomal compartment. M. tuberculosis parasitizes this process by actively recruiting and maintaining Rab22a on its phagosome, thus, preventing Rab7 acquisition and blocking phagolysosomal biogenesis.

Exploration of Ion Channels in Mycobacterium tuberculosis: Implication on Drug Discovery and Potent Drug Targets Against Tuberculosis

2020 ◽  
Vol 14 (1) ◽  
pp. 14-29
Author(s):  
Manish Dwivedi
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Drug Targets ◽  
Cell Envelope ◽  
Intracellular Pathogen ◽  
Host Immune System ◽  
Transporter Proteins ◽  
Channel Proteins ◽  
Medical Importance ◽  
Potent Drug ◽  
Emergence Of Resistance

Scientific interest in mycobacteria has been sparked by the medical importance of Mycobacterium tuberculosis (Mtb) that is known to cause severe diseases in mammals, i.e. tuberculosis and by properties that distinguish them from other microorganisms which are notoriously difficult to treat. The treatment of their infections is difficult because mycobacteria fortify themselves with a thick impermeable cell envelope. Channel and transporter proteins are among the crucial adaptations of Mycobacterium that facilitate their strength to combat against host immune system and anti-tuberculosis drugs. In previous studies, it was investigated that some of the channel proteins contribute to the overall antibiotic resistance in Mtb. Moreover, in some of the cases, membrane proteins were found responsible for virulence of these pathogens. Given the ability of M. tuberculosis to survive as an intracellular pathogen and its inclination to develop resistance to the prevailing anti-tuberculosis drugs, its treatment requires new approaches and optimization of anti-TB drugs and investigation of new targets are needed for their potential in clinical usage. Therefore, it is imperative to investigate the survival of Mtb. in stressed conditions with different behavior of particular channel/ transporter proteins. Comprehensive understanding of channel proteins and their mechanism will provide us direction to find out preventive measures against the emergence of resistance and reduce the duration of the treatment, eventually leading to plausible eradication of tuberculosis.

266 Effects of Inflammatory States on Ovarian Biology and Oocyte Competence

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 134-135
Author(s):  
Jennifer A Hernandez Gifford ◽  
Emily Ferranti ◽  
Kylee Forrest ◽  
Craig A Gifford
Keyword(s):  
Granulosa Cell ◽  
Oocyte Maturation ◽  
Beta Catenin ◽  
Control Mechanisms ◽  
Steroid Production ◽  
Oocyte Competence ◽  
Nuclear Maturation ◽  
Naturally Occurring ◽  
Hormonal Milieu

Abstract Female fertility is dependent on estradiol concentrations which regulate a multitude of ovarian functions including follicle development and oocyte maturation leading to ovulation of a viable oocyte. Estradiol biosynthesis is regulated by coordinated actions of follicle-stimulating hormone and intra-ovarian control mechanisms including the co-transcription factor beta-catenin. Beta-catenin is a multi-faceted protein recognized for its role in granulosa cell steroid production and is shown to be modulated by lipopolysaccharide (LPS), the endotoxin responsible for stimulation of the immune system in infections caused by Gram-negative bacteria. Beef heifers treated with subacute concentrations of LPS during a synchronized follicular wave demonstrate a decline in serum estradiol concentrations 50 h after CIDR withdrawal, corresponding with dominant follicle maturation and preceding ovulation. The endotoxin exposure also resulted in increased LPS concentration and E2:P4 ratios in follicular fluid suggesting that low dose LPS modulates the intra-follicular hormonal milieu. Additionally, in a granulosa cell line, LPS treatment decreased mRNA expression of aromatase and beta-catenin. These data indicate that LPS alters E2 synthesis by modulating beta-catenin and subsequent steroidogenic enzyme expression. To further explore the contribution of naturally occurring LPS exposure on follicular steroid production and developing oocytes, bovine ovary pairs were collected from local abattoirs. Oocytes were aspirated from small follicles and matured in vitro to evaluate meiotic events related to nuclear maturation and spindle morphology. Small follicles from ovarian pairs were separated by the detectable LPS concentrations into high and low LPS groups. Oocytes matured from low LPS follicles demonstrated an increase in the percent of abnormal maturation events. Data indicate that induced or naturally occurring low doses of LPS can alter circulating and follicular estradiol concentrations impairing oocyte maturation. Perturbation to local ovarian signaling cascades from subclinical inflammatory disease may be an unappreciated factor altering fertility and leading to decreased cow retention.

Stimulation of steroidogenesis in cultured rat adrenocortical cells by unsaturated fatty acids

1995 ◽  
Vol 268 (6) ◽  
pp. R1484-R1490 ◽  
Author(s):  
I. Sarel ◽  
E. P. Widmaier
Keyword(s):  
Fatty Acids ◽  
Unsaturated Fatty Acids ◽  
Lipid Homeostasis ◽  
Control Mechanisms ◽  
Adrenocortical Cells ◽  
Stimulatory Action ◽  
Apparent Lack ◽  
Naturally Occurring ◽  
Oleic And Linoleic Acids ◽  
Stimulation Of

The hypothesis that the stimulatory action of free fatty acids (FFA) in the hypothalamic-pituitary-adrenocortical (HPA) axis occurs in part at the adrenal cortex was evaluated. Pathophysiological concentrations of oleic and linoleic acids, but not stearic or caprylic acid, stimulated steroidogenesis from cultured rat adrenocortical cells (concentrations eliciting 50% of maximal responses, approximately 60 and 120 microM, respectively), with a latency of 90 min. Maximal stimulation of steroidogenesis by both acids was < 50% of that produced by adrenocorticotropic hormone (ACTH) and was blocked by cycloheximide. The maximal steroidogenic response to ACTH was inhibited approximately 50% by oleic acid. The actions of oleic and linoleic acids were not associated with an increase in adenosine 3',5'-cyclic monophosphate (cAMP) secretion but appeared to require intracellular oxidation. None of the lipids influenced cell viability or corticosterone radioimmunoassay. The latency of the steroidogenic response, the putative requirement for intracellular oxidation, and the apparent lack of involvement of cAMP suggest a mechanism of action of FFA distinct from that of ACTH, yet still requiring protein synthesis. It is concluded that the modulation of steroidogenesis by these abundant naturally occurring lipids may be an important component of the control mechanisms within the HPA pathway in disorders of lipid homeostasis (e.g., obesity, starvation, or diabetes).

Circular dichroism of polypeptides

1967 ◽  
Vol 297 (1448) ◽  
pp. 163-170 ◽  
Keyword(s):  
Conformational Changes ◽  
Control Mechanisms ◽  
Ordered Structure ◽  
Ordered Structures ◽  
Naturally Occurring ◽  
Synthetic Polypeptides ◽  
Spectroscopic Characteristics ◽  
Physical Attributes ◽  
The Right ◽  
Polypeptide Conformation

The polypeptides, together with the polynucleotides, are polymers which possess the unique property, under the right conditions, of forming ordered structures in dilute isotropic solution. This general attribute is responsible for the precise specificity of structure, and consequently of biochemical function, of the naturally occurring proteins and nucleic acids in their most usual native environment, aqueous solution. It gives rise also to the possibility of extraordinarily delicate biological control mechanisms, based on the induction of conformational changes in the macromolecule by small alterations in the environment. The most versatile methods available for the study of polypeptide conformation in solution are without doubt the spectroscopic ones, and of these the measurement of optical activity is preeminent. The ordered structure of these molecules—and we shall consider here primarily the synthetic homopolyamino acids—makes it possible to regard them essentially as one dimensional unimolecular crystals, and indeed they possess a number of important physical attributes associated with the crystalline state. Thus the collapse of the ordered structure when the environment is changed commonly occurs in a sharp cooperative manner, recalling a crystalline phase transition (melting). More particularly the ordered system of chromophores (peptide groups) gives rise to certain of the spectroscopic characteristics of molecular crystals, and it is these phenomena which provide us with the principal means of studying synthetic polypeptides and proteins in solution. It is evident then that a better understanding of these effects will be of the greatest relevance to the study of conformations and conformational changes in these molecules.

scholarly journals Mycobacterium aviumSubsp.aviumInfection in Four Veal Calves: Differentiation from Intestinal Tuberculosis

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Christine Goepfert ◽  
Nadine Regenscheit ◽  
Vanessa Schumacher ◽  
Simone Roos ◽  
Christophe Rossier ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mycobacterium Avium ◽  
Intestinal Tuberculosis ◽  
Clinical Signs ◽  
Domestic Animals ◽  
Intracellular Pathogen ◽  
Veal Calves ◽  
Mycobacterium Avium Intracellulare ◽  
Granulomatous Enteritis ◽  
Positive Results

Mycobacterium aviumsubsp.avium(Maa) is an intracellular pathogen belonging to theMycobacterium avium-intracellularecomplex (MAC). Reservoirs of MAC are the natural environment, wildlife and domestic animals. In adult bovine, MAC infections are typically caused byMycobacterium aviumsubsp.paratuberculosis(Map). Maa infections in bovine are rarely reported but may cause clinical disease and pathological lesions similar to those observed in paratuberculosis or those induced by members of theMycobacterium tuberculosiscomplex (MTBC). Therefore, differentiation of MAC from MTBC infection should be attempted, especially if unusual mycobacterial lesions are encountered. Four veal calves from a fattening farm dying with clinical signs of otitis media, fever, and weight loss were submitted for necropsy. Samples from affected organs were taken for histologic investigation, bacteriologic culture, and bacterial specification using PCR. Macroscopic thickening of the intestinal mucosa was induced by granulomatous enteritis and colitis. Intracytoplasmic acid-fast bacteria were detected by Ziehl-Neelsen stains and PCR revealed positive results forMycobacterium aviumsubsp.avium. Clinical and pathological changes of Maa infection in veal calves had features ofMycobacterium aviumsubsp.paratuberculosisand the MTBC. Therefore,Mycobacterium tuberculosiscomplex infection should be considered in cases of granulomatous enteritis in calves.

scholarly journals Route of Injection Affects the Impact of InlB Internalin Domain Variants on Severity ofListeria monocytogenesInfection in Mice

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Konstantin A. Sobyanin ◽  
Elena V. Sysolyatina ◽  
Yaroslava M. Chalenko ◽  
Egor V. Kalinin ◽  
Svetlana A. Ermolaeva
Keyword(s):  
Human Kidney ◽  
Mortality Rates ◽  
Intracellular Pathogen ◽  
Invasion Assay ◽  
Internal Organs ◽  
Severity Of Disease ◽  
Kinase C ◽  
Naturally Occurring ◽  
Food Borne ◽  
The Impact

The facultative intracellular pathogenListeria monocytogenescauses a severe food-borne infection in humans and animals.L. monocytogenesinvasion factor InlB interacts with the tyrosine kinase c-Met via the N-terminal internalin domain. Previously, distinct variants of the InlB internalin domain (idInlB) have been described inL. monocytogenesfield isolates. Three variants were used to restore full-length InlB expression in theL. monocytogenesstrain EGDeΔinlB. Obtained isogenicL. monocytogenesstrains were tested in the invasion assay and intravenous, intraperitoneal, and intragastric models of infection in mice. All idInlBs were functional, restored InlB activity as an invasion factor, and improved invasion of the parental strain EGDeΔinlB into human kidney HEK23 cells. Meanwhile, distinct idInlBs provided different mortality rates and bacterial loads in internal organs. When recombinant strains were compared, the variant designated idInlB14 decreased severity of disease caused by intravenous and intraperitoneal bacterial administration, whereas this variant improved intestine colonization and stimulated intragastric infection. Obtained results demonstrated that naturally occurring idInlBs differed in their impact on severity ofL. monocytogenesinfection in mice in dependence on the infection route.

scholarly journals Structural and Functional Basis for an EBNA1 Hexameric Ring in Epstein-Barr Virus Episome Maintenance

2017 ◽  
Vol 91 (19) ◽  
Author(s):  
Julianna S. Deakyne ◽  
Kimberly A. Malecka ◽  
Troy E. Messick ◽  
Paul M. Lieberman
Keyword(s):  
Crystal Structure ◽  
Dna Binding ◽  
Complex Formation ◽  
Epstein Barr Virus ◽  
Higher Order ◽  
Order Complex ◽  
Barr Virus ◽  
Naturally Occurring ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) establishes a stable latent infection that can persist for the life of the host. EBNA1 is required for the replication, maintenance, and segregation of the latent episome, but the structural features of EBNA1 that confer each of these functions are not completely understood. Here, we have solved the X-ray crystal structure of an EBNA1 DNA-binding domain (DBD) and discovered a novel hexameric ring oligomeric form. The oligomeric interface pivoted around residue T585 as a joint that links and stabilizes higher-order EBNA1 complexes. Substitution mutations around the interface destabilized higher-order complex formation and altered the cooperative DNA-binding properties of EBNA1. Mutations had both positive and negative effects on EBNA1-dependent DNA replication and episome maintenance with OriP. We found that one naturally occurring polymorphism in the oligomer interface (T585P) had greater cooperative DNA binding in vitro, minor defects in DNA replication, and pronounced defects in episome maintenance. The T585P mutant was compromised for binding to OriP in vivo as well as for assembling the origin recognition complex subunit 2 (ORC2) and trimethylated histone 3 lysine 4 (H3K4me3) at OriP. The T585P mutant was also compromised for forming stable subnuclear foci in living cells. These findings reveal a novel oligomeric structure of EBNA1 with an interface subject to naturally occurring polymorphisms that modulate EBNA1 functional properties. We propose that EBNA1 dimers can assemble into higher-order oligomeric structures important for diverse functions of EBNA1. IMPORTANCE Epstein-Barr virus is a human gammaherpesvirus that is causally associated with various cancers. Carcinogenic properties are linked to the ability of the virus to persist in the latent form for the lifetime of the host. EBNA1 is a sequence-specific DNA-binding protein that is consistently expressed in EBV tumors and is the only viral protein required to maintain the viral episome during latency. The structural and biochemical mechanisms by which EBNA1 allows the long-term persistence of the EBV genome are currently unclear. Here, we have solved the crystal structure of an EBNA1 hexameric ring and characterized key residues in the interface required for higher-order complex formation and long-term plasmid maintenance.

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