scholarly journals Mutations in Tyr808 reveal a potential auto-inhibitory mechanism of guanylate cyclase-B regulation

2013 ◽  
Vol 33 (3) ◽  
Author(s):  
Takeshi Katafuchi
Keyword(s):  
Guanylate Cyclase ◽  
Sequence Similarity ◽  
Activation Mechanism ◽  
Phosphorylation Sites ◽  
Wild Type ◽  
Tyrosine Residues ◽  
Sphingosine 1 Phosphate ◽  
Membrane Bound ◽  
Partial Fragment ◽  
Insight Into

In this study, Tyr808 in GC-B (guanylate cyclase-B), a receptor of the CNP (C-type natriuretic peptide), has been shown to be a critical regulator of GC-B activity. In searching for phosphorylation sites that could account for suppression of GC-B activity by S1P (sphingosine-1-phosphate), mutations were introduced into several candidate serine/threonine and tyrosine residues. Although no novel phosphorylation sites that influenced the suppression of GC-B were identified, experiments revealed that mutations in Tyr808 markedly enhanced GC-B activity. CNP-stimulated activities of the Y808F and Y808A mutants were greater than 30-fold and 70-fold higher, respectively, than that of WT (wild-type) GC-B. The Y808E and Y808S mutants were constitutively active, expressing 270-fold higher activity without CNP stimulation than WT GC-B. Those mutations also influenced the sensitivity of GC-B to a variety of inhibitors, including S1P, Na3VO4 and PMA. Y808A, Y808E and Y808S mutations markedly weakened S1P- and Na3VO4-dependent suppression of GC-B activity, whereas Y808E and Y808S mutations rather elevated cGMP production. Tyr808 is conserved in all membrane-bound GCs and located in the niche domain showing sequence similarity to a partial fragment of the HNOBA (haem nitric oxide binding associated) domain, which is found in soluble GC and in bacterial haem-binding kinases. This finding provides new insight into the activation mechanism of GCs.

Identification of Tyrosine Residues of Importance for Survival Signaling through the Scaffolding Protein Gab2 in Both Wild-Type FLT3 and the FLT3-ITD.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1622-1622
Author(s):  
Kristina Masson ◽  
Tao Liu ◽  
Jianmin Sun ◽  
Lars Ronnstrand
Keyword(s):  
Scaffolding Protein ◽  
Phosphorylation Sites ◽  
Wild Type ◽  
Internal Tandem Duplication ◽  
Tyrosine Residues ◽  
Downstream Signaling ◽  
Juxtamembrane Region ◽  
Future Potential ◽  
Survival Signaling

Abstract The receptor tyrosine kinase FLT3 is normally expressed in hematopoietic progenitor cells and has been implicated as a major cause of transformation in acute myeloid leukemia, where it in approximately 30% of cases is mutated and constitutively active. This is in most cases due to duplication of a DNA sequence coding for amino acids in the juxtamembrane region of FLT3, commonly referred to as ITD (Internal Tandem Duplication). In this study we have identified several novel in vivo tyrosine phosphorylation sites that are phosphorylated in wild-type FLT3 upon ligand stimulation and that are constitutively phosphorylated in the FLT3-ITD. We were able to demonstrate that these phosphorylation sites are critical for full phosphorylation of the scaffolding protein Gab2 both in wild-type FLT3 and FLT3-ITD. Y-to-F mutants of either wild-type FLT3 or FLT3-ITD, lacking these tyrosine residues, fail to phosphorylate Gab2 and demonstrate a considerable reduction in phosphorylation of Akt and Erk. Furthermore, FL-dependent survival and proliferation of wild-type FLT3 expressing Ba/F3 cells as well as FL-independent survival and proliferation of Ba/F3 cells transfected with FLT3-ITD was dramatically reduced by mutation of these tyrosine residues. In the case of the FLT3-ITD, this was shown to correlate with strongly reduced STAT5 phosphorylation. To verify the importance of Gab2 in FLT3-ITD signaling, we used siRNA technology to knock down the expression of Gab2 in the human AML cell line MV4-11 that is known to express FLT3-ITD. Knockdown of Gab2 expression led to a dramatic reduction in the phosphorylation of Akt, Erk and Stat5. To summarize, we have identified novel phosphorylation sites in FLT3 and how they link to downstream signaling of survival and proliferation. These findings not only reveal novel phosphorylation sites in FLT3 but also contribute to the understanding of the molecular mechanism by which FLT3-ITD functions in pathological conditions. Future studies are aiming at elucidating the mechanism by which Gab2 mediates phosphorylation and activation of STAT5, which could be a future potential target for therapy in AML with FLT3-ITD.

scholarly journals Structural Insight into the Activation Mechanism of Human Pancreatic Prophospholipase A2

2009 ◽  
Vol 284 (24) ◽  
pp. 16659-16666 ◽  
Author(s):  
Wei Xu ◽  
Lina Yi ◽  
Yumei Feng ◽  
Ling Chen ◽  
Jinsong Liu
Keyword(s):  
Phospholipase A2 ◽  
Catalytic Triad ◽  
Activation Mechanism ◽  
X Ray ◽  
Pancreatic Phospholipase ◽  
Pancreatic Phospholipase A2 ◽  
Obesity And Diabetes ◽  
Membrane Bound ◽  
Structural Insight ◽  
Insight Into

Pancreatic phospholipase A2 (phospholipase A2 group 1B, G1B) belongs to the superfamily of secreted phospholipase A2 (PLA2) enzymes. G1B has been proposed to be a potential target for diseases such as hypertension, obesity, and diabetes. Human pancreatic prophospholipase A2 (pro-hG1B) is activated by cleavage of the first seven-residue propeptide (phospholipase A2 propeptide, PROP). However, questions still remain on the mode of action for pro-hG1B. In this work, we expressed pro-hG1B in Pichia pastoris and determined the crystal structure at 1.55-Å resolution. The x-ray structure demonstrates that pro-hG1B forms a trimer. In addition, PROP occupies the catalytic cavity and can be self-cleaved at 37 °C. A new membrane-bound surface and activation mechanism are proposed based on the trimeric model of pro-hG1B. We also propose a new autoproteolytic mechanism for pro-hG1B by the reaction triad Asp49-Arg0-Ser(-2) that is similar to the serine protease catalytic triad.

scholarly journals The soluble ectodomain of RetC634Y inhibits both the wild-type and the constitutively active Ret

2003 ◽  
Vol 372 (3) ◽  
pp. 897-903 ◽  
Author(s):  
Laura CERCHIA ◽  
Domenico LIBRI ◽  
Maria Stella CARLOMAGNO ◽  
Vittorio de FRANCISCIS
Keyword(s):  
Molecular Basis ◽  
Multiple Endocrine Neoplasia Type ◽  
Cell System ◽  
Biologically Active ◽  
Tyrosine Kinase Receptor ◽  
Wild Type ◽  
Membrane Bound ◽  
Ret Oncogene ◽  
Insight Into

Substitution of Cys-634 in the extracellular domain of the Ret tyrosine kinase receptor causes its dimerization and activation of its transforming potential. To gain further insight into the molecular basis leading to Ret activation we purified a mutant protein consisting of the entire ectodomain of the Ret carrying a Cys-634→Tyr substitution (EC-RetC634Y). The protein is glycosylated, like the native one, and is biologically active. By using an in vitro cell system we show that EC-RetC634Y inhibits the membrane-bound receptor RetC634Y, interfering with its dimerization. Furthermore, we demonstrate that EC-RetC634Y competes with the wild-type Ret receptor for ligand binding. The results presented support the notion of the possible involvment of glial cell line-derived neurotrophic factor (GDNF) with multiple endocrine neoplasia type 2A (MEN2A) tumours, and describe a useful tool for generating molecular mimetics directed towards specific mutations of the ret oncogene.

Molecular and genetic characterization of natural variants of HIV-1 Nef gene from North India and its functional implication in down-regulation of MHC-I and CD-4

2020 ◽  
Vol 18 ◽  
Author(s):  
J. Singh ◽  
L. Ronsard ◽  
M. Pandey ◽  
R. Kapoor ◽  
V.G. Ramachandran ◽  
...  
Keyword(s):  
Biological Activities ◽  
Sequence Similarity ◽  
Eukaryotic Expression ◽  
North India ◽  
Cell Surface Expression ◽  
Functional Domains ◽  
Wild Type ◽  
Down Regulation ◽  
Subtype B ◽  
Hiv 1

Background: HIV-1 Nef is an important accessory protein with multiple effector functions. Genetic studies of HIV-1 Nef gene shows extensive genetic diversity and the functional studies have been carried out mostly with Nef derived from regions dominated by subtype B (North America & Europe). Objective: This study was carried out to characterize genetic variations of the Nef gene from HIV-1 infected individuals from North-India and to find out their functional implications. Methods: The unique representative variants were sub-cloned in eukaryotic expression vector and further characterized with respect to their ability to down regulate cell surface expression of CD4 and MHC-1molecules. Results: The phylogenetic analysis of Nef variants revealed sequence similarity with either consensus subtype B or B/C recombinants. Boot scan analysis of some of our variants showed homology to B/C recombinant and some to wild type Nef B. Extensive variations were observed in most of the variants. The dN/dS ratio revealed 80% purifying selection and 20% diversifying selection implying the importance of mutations in Nef variants. Intracellular stability of Nef variants differed greatly when compared with wild type Nef B and C. There were some variants that possessed mutations in the functional domains of Nef and responsible for its differential CD4 and MHC-1 down regulation activity. Conclusion: We observed enhanced biological activities in some of the variants, perhaps arising out of amino acid substitutions in their functional domains. The CD4 and MHC-1 down-regulation activity of Nef is likely to confer immense survival advantage allowing the most rare genotype in a population to become the most abundant after a single selection event.

scholarly journals Salicylic Acid Accumulation Controlled by LSD1 Is Essential in Triggering Cell Death in Response to Abiotic Stress

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 962
Author(s):  
Maciej Jerzy Bernacki ◽  
Anna Rusaczonek ◽  
Weronika Czarnocka ◽  
Stanisław Karpiński
Keyword(s):  
Cell Death ◽  
Salicylic Acid ◽  
Abiotic Stress ◽  
Wild Type ◽  
Pr Genes ◽  
Genes Expression ◽  
Salicylic Acid Accumulation ◽  
Cell Death Phenotype ◽  
Insight Into

Salicylic acid (SA) is well known hormonal molecule involved in cell death regulation. In response to a broad range of environmental factors (e.g., high light, UV, pathogens attack), plants accumulate SA, which participates in cell death induction and spread in some foliar cells. LESION SIMULATING DISEASE 1 (LSD1) is one of the best-known cell death regulators in Arabidopsis thaliana. The lsd1 mutant, lacking functional LSD1 protein, accumulates SA and is conditionally susceptible to many biotic and abiotic stresses. In order to get more insight into the role of LSD1-dependent regulation of SA accumulation during cell death, we crossed the lsd1 with the sid2 mutant, caring mutation in ISOCHORISMATE SYNTHASE 1(ICS1) gene and having deregulated SA synthesis, and with plants expressing the bacterial nahG gene and thus decomposing SA to catechol. In response to UV A+B irradiation, the lsd1 mutant exhibited clear cell death phenotype, which was reversed in lsd1/sid2 and lsd1/NahG plants. The expression of PR-genes and the H2O2 content in UV-treated lsd1 were significantly higher when compared with the wild type. In contrast, lsd1/sid2 and lsd1/NahG plants demonstrated comparability with the wild-type level of PR-genes expression and H2O2. Our results demonstrate that SA accumulation is crucial for triggering cell death in lsd1, while the reduction of excessive SA accumulation may lead to a greater tolerance toward abiotic stress.

Volatile Anesthetics Affect Nutrient Availability in Yeast

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 563-574
Author(s):  
Laura K Palmer ◽  
Darren Wolfe ◽  
Jessica L Keeley ◽  
Ralph L Keil
Keyword(s):  
Amino Acids ◽  
Nutrient Availability ◽  
Wild Type Strain ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Wild Type ◽  
Anesthetic Exposure ◽  
Sites Of Action ◽  
Insight Into ◽  
Lines Of Evidence

Abstract Volatile anesthetics affect all cells and tissues tested, but their mechanisms and sites of action remain unknown. To gain insight into the cellular activities of anesthetics, we have isolated genes that, when overexpressed, render Saccharomyces cerevisiae resistant to the volatile anesthetic isoflurane. One of these genes, WAK3/TAT1, encodes a permease that transports amino acids including leucine and tryptophan, for which our wild-type strain is auxotrophic. This suggests that availability of amino acids may play a key role in anesthetic response. Multiple lines of evidence support this proposal: (i) Deletion or overexpression of permeases that transport leucine and/or tryptophan alters anesthetic response; (ii) prototrophic strains are anesthetic resistant; (iii) altered concentrations of leucine and tryptophan in the medium affect anesthetic response; and (iv) uptake of leucine and tryptophan is inhibited during anesthetic exposure. Not all amino acids are critical for this response since we find that overexpression of the lysine permease does not affect anesthetic sensitivity. These findings are consistent with models in which anesthetics have a physiologically important effect on availability of specific amino acids by altering function of their permeases. In addition, we show that there is a relationship between nutrient availability and ubiquitin metabolism in this response.

scholarly journals NMR and LC-MS-Based Metabolomics to Study Osmotic Stress in Lignan-Deficient Flax

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 767
Author(s):  
Kamar Hamade ◽  
Ophélie Fliniaux ◽  
Jean-Xavier Fontaine ◽  
Roland Molinié ◽  
Elvis Otogo Nnang ◽  
...  
Keyword(s):  
Stress Response ◽  
Osmotic Stress ◽  
Biosynthetic Pathway ◽  
Potential Role ◽  
Plant Secondary Metabolites ◽  
Wild Type ◽  
Osmotic Stress Response ◽  
Transgenic Flax ◽  
Insight Into

Lignans, phenolic plant secondary metabolites, are derived from the phenylpropanoid biosynthetic pathway. Although, being investigated for their health benefits in terms of antioxidant, antitumor, anti-inflammatory and antiviral properties, the role of these molecules in plants remains incompletely elucidated; a potential role in stress response mechanisms has been, however, proposed. In this study, a non-targeted metabolomic analysis of the roots, stems, and leaves of wild-type and PLR1-RNAi transgenic flax, devoid of (+) secoisolariciresinol diglucoside ((+) SDG)—the main flaxseed lignan, was performed using 1H-NMR and LC-MS, in order to obtain further insight into the involvement of lignan in the response of plant to osmotic stress. Results showed that wild-type and lignan-deficient flax plants have different metabolic responses after being exposed to osmotic stress conditions, but they both showed the capacity to induce an adaptive response to osmotic stress. These findings suggest the indirect involvement of lignans in osmotic stress response.

scholarly journals Overexpression of the pitaya phosphoethanolamine N-methyltransferase gene (HpPEAMT) enhanced simulated drought stress in tobacco

2021 ◽  
Author(s):  
Ai-Hua Wang ◽  
Lan Yang ◽  
Xin-Zhuan Yao ◽  
Xiao-Peng Wen
Keyword(s):  
Drought Stress ◽  
Stress Response ◽  
Transgenic Plants ◽  
Drought Tolerance ◽  
Transgenic Tobacco ◽  
Sequence Similarity ◽  
Amino Acid Sequence Similarity ◽  
Transgenic Tobacco Plants ◽  
Wild Type ◽  
Tobacco Plants

AbstractPhosphoethanolamine N-methyltransferase (PEAMTase) catalyzes the methylation of phosphoethanolamine to produce phosphocholine and plays an important role in the abiotic stress response. Although the PEAMT genes has been isolated from many species other than pitaya, its role in the drought stress response has not yet been fully elucidated. In the present study, we isolated a 1485 bp cDNA fragment of HpPEAMT from pitaya (Hylocereus polyrhizus). Phylogenetic analysis showed that, during its evolution, HpPEAMT has shown a high degree of amino acid sequence similarity with the orthologous genes in Chenopodiaceae species. To further investigate the function of HpPEAMT, we generated transgenic tobacco plants overexpressing HpPEAMT, and the transgenic plants accumulated significantly more glycine betaine (GB) than did the wild type (WT). Drought tolerance trials indicated that, compared with those of the wild-type (WT) plants, the roots of the transgenic plants showed higher drought tolerance ability and exhibited improved drought tolerance. Further analysis revealed that overexpression of HpPEAM in Nicotiana tabacum resulted in upregulation of transcript levels of GB biosynthesis-related genes (NiBADH, NiCMO and NiSDC) in the leaves. Furthermore, compared with the wild-type plants, the transgenic tobacco plants displayed a significantly lower malondialdehyde (MDA) accumulation and higher activities of the superoxide dismutase (SOD) and peroxidase (POD) antioxidant enzymes under drought stress. Taken together, our results suggested that HpPEAMT enhanced the drought tolerance of transgenic tobacco.

scholarly journals Cloning and Characterization of theFlavobacterium johnsoniae Gliding Motility GenesgldD and gldE

2001 ◽  
Vol 183 (14) ◽  
pp. 4167-4175 ◽  
Author(s):  
David W. Hunnicutt ◽  
Mark J. McBride
Keyword(s):  
Membrane Protein ◽  
Cytoplasmic Membrane ◽  
Sequence Similarity ◽  
Gliding Motility ◽  
Wild Type ◽  
Bacteriophage Infection ◽  
Flavobacterium Johnsoniae ◽  
Latex Spheres ◽  
Serovar Typhimurium

ABSTRACT Cells of Flavobacterium johnsoniae move over surfaces by a process known as gliding motility. The mechanism of this form of motility is not known. Cells of F. johnsoniaepropel latex spheres along their surfaces, which is thought to be a manifestation of the motility machinery. Three of the genes that are required for F. johnsoniae gliding motility,gldA, gldB, and ftsX, have recently been described. Tn4351 mutagenesis was used to identify another gene, gldD, that is needed for gliding. Tn4351-induced gldD mutants formed nonspreading colonies, and cells failed to glide. They also lacked the ability to propel latex spheres and were resistant to bacteriophages that infect wild-type cells. Introduction of wild-type gldD into the mutants restored motility, ability to propel latex spheres, and sensitivity to bacteriophage infection. gldD codes for a cytoplasmic membrane protein that does not exhibit strong sequence similarity to proteins of known function. gldE, which lies immediately upstream ofgldD, encodes another cytoplasmic membrane protein that may be involved in gliding motility. Overexpression ofgldE partially suppressed the motility defects of agldB point mutant, suggesting that GldB and GldE may interact. GldE exhibits sequence similarity to Borrelia burgdorferi TlyC and Salmonella enterica serovar Typhimurium CorC.

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