Thesis (Ph.D.)--Virginia Commonwealth University, 2008. / Prepared for: Dept. of Anatomy and Neurobiology. Title from title-page of electronic thesis. Bibliography: leaves 181 - 202. Available online via the Internet.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed Feb. 19, 2008). Includes bibliographical references.

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No description available.

The predicted protein product of open reading frame slr0328 from Synechocystis sp. PCC 6803, SynPTP, possesses significant amino acid sequence similarity with known low molecular weight protein tyrosine phosphatases (PTPs). To determine the gross functional properties of this hypothetical protein, open reading frame slr0328 was cloned, and its predicted protein product was expressed in E. coli. The recombinant protein, SynPTP, was purified by metal ion column chromatography. The catalytic activity of SynPTP was examined toward several exogenous protein substrates that had been phosphorylated on either tyrosine residues or serine residues. SynPTP exhibited phosphatase activity toward tyrosine phosphorylated protein substrates (Vmax toward phosphotyrosyl 32P-casein was 1.5 nmol/min/mg). However, no phosphatase activity was detected toward serine phosphorylated protein substrates. SynPTP displayed phosphohydrolase activity toward several organophosphoesters including para-nitrophenyl phosphate (p-NPP), beta-napthyl phosphate and phosphotyrosine but not toward alpha-napthyl phosphate, phosphoserine, or phosphothreonine. Kinetic analysis indicated that the Km (0.6 mM) and Vmax (3.2 mmole/min/mg) values for SynPTP toward pNPP are similar to those of other known bacterial low molecular weight PTPs. The protein phosphatase activity of SynPTP was inhibited by sodium orthovanadate, a known inhibitor for tyrosine phosphatases, but not by okadaic acid, an inhibitor for many serine/threonine phosphatases. Mutagenic alteration of the predicted catalytic cysteine, Cys7, to serine abolished enzyme activity. Several phosphotyrosine containing proteins were detected from the whole cell extracts of Synechocystis sp. PCC 6803 through immunoreactions using anti-phosphotyrosine antibody. SynPTP was observed to dephosphorylate three of these proteins in vitro. Two of these proteins were identified by peptide-mass fingerprinting analysis, as PsaD (photosystem I subunit II) and CpcD (phycocyanin rod linker protein). In addition, several phosphotyrosine proteins were detected from the soluble and membrane fractions of Synechocystis sp. PCC 6803 cell extracts by in vitro substrate trapping as potential endogenous substrates of SynPTP. Two of these proteins were identified as the alpha and beta subunits of phycocyanin. We therefore speculate that SynPTP might be involved in the regulation of photosynthesis in Synechocystis sp. PCC 6803. / Ph. D.

Diss. (sammanfattning) Umeå : Umeå universitet, 2010. / Härtill 5 uppsatser.

Il a été montré que les fonctions et la prolongation de la survie cellulaire des neutrophiles humains par les médiateurs de l'inflammation tendent à diminuer avec le vieillissement. Les protéines tyrosines phosphatase (PTPs), comme SHP-1, sont un des mécanismes qui permettent de moduler à la baisse et de terminer ces fonctions inflammatoires qui sont modulées par l'action des cytokines. Nous avons étudié le rôle des PTPs dans l'altération due au vieillissement des fonctions des neutrophiles humains. L'utilisation d'un inhibiteur pharmacologique des PTPs a suggéré une dérégulation de l'activité phosphatasique avec le vieillissement. Cette dérégulation était confirmée aussi dans le cas de l'apoptose mesurée après 18 heures d'incubation. L'activité phosphatasique de SHP-1 purifiée par immunoprécipitation de neutrophiles de sujets jeunes ou âgés stimulés par le GM-CSF est altérée de façon significative après une minute de stimulation chez les sujets âgés. Dans les sujets jeunes SHP-1 est déplacée des radeaux lipidiques après 1 minute de stimulation par le GM-CSF alors que chez les sujets âgés, SHP-1 est présente à tous les temps de stimulation utilisés. Des immunoblots faits avec des anticorps anti-phosphotyrosine et anti-phosphosérine ont montré une augmentation de la phosphorylation en sérine dans les neutrophiles des sujets jeunes après une stimulation au GM-CSF alors que ce n'était pas le cas chez les sujets âgés. Nous avons aussi trouvé des altérations dans l'activation et le recrutement aux radeaux lipidiques de la Src kinase Lyn chez les neutrophiles des sujets âgés. De plus, nous avons démontré que SHP-1 est continuellement recrutée à Lyn chez les sujets âgés alors que cette interaction, qui est observée dans des cellules non stimulées chez les sujets jeunes, est défaite par la stimulation au GM-CSF. En conclusion, les altérations observées dans la modulation de l'activité de SHP-1 par le GM-CSF dans les radeaux lipidiques sont un des facteurs qui contribuent à la diminution des effets du GM-CSF sur les neutrophiles humains avec le vieillissement.

Tyrosyl phosphorylation plays an important role in many fundamental cellular processes, including cell growth, differentiation and proliferation. The levels of phosphotyrosine (pY) are regulated by the opposing actions of protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs). A limitation to understanding the roles of PTPs in physiological and pathological cell signaling has been the absence of global proteomic approaches that enable the systematic and comprehensive analysis of PTP expression, regulation and function. This dissertation describes the development and application of novel proteomic methodologies that permit the global analysis of PTP expression (qPTPome), regulation (by oxidation and nitrosylation; q-oxPTPome) and substrates/binding proteins. These methods provide a workflow to begin assessing PTP function at a systems level, rather than its current targeted format. Application of these techniques will provide invaluable information to begin bridging the gap in our understanding of PTP and PTK function in normal and malignant cell signaling.

Tyrosyl phosphorylation plays an important role in many fundamental cellular processes, including cell growth, differentiation and proliferation. The levels of phosphotyrosine (pY) are regulated by the opposing actions of protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs). A limitation to understanding the roles of PTPs in physiological and pathological cell signaling has been the absence of global proteomic approaches that enable the systematic and comprehensive analysis of PTP expression, regulation and function. This dissertation describes the development and application of novel proteomic methodologies that permit the global analysis of PTP expression (qPTPome), regulation (by oxidation and nitrosylation; q-oxPTPome) and substrates/binding proteins. These methods provide a workflow to begin assessing PTP function at a systems level, rather than its current targeted format. Application of these techniques will provide invaluable information to begin bridging the gap in our understanding of PTP and PTK function in normal and malignant cell signaling.

Thesis (Ph.D. in Cell Biology, Stem Cells, & Development) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 138-155). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;