Search results for "Phosphor"

Glycogen phosphorylase from flight muscle of the hawk moth, Manduca sexta: purification and properties of three interconvertible forms and the effect…

1994

Glycogen phosphorylase (EC 2.4.1.1) of Manduca sexta flight muscle was separated into three distinct peaks of activity on diethylaminoethyl-Sephacel. The three fractions of phosphorylase activity were further purified by affinity chromatography on AMP-Sepharose and shown to have the same relative molecular mass (=178000) on polyacrylamide gradient gel electrophoresis under non-denaturating conditions and to produce subunits of molecular mass =92000 on SDS gelelectrophoresis. On the basis of their kinetic properties with respect to the activator AMP and the inhibitor caffeine, the three fractions of phosphorylase activity were assigned as follows: peak 1=phosphorylase b (unphosphorylated for…

Determination of phosphorylation degrees in caseins by on-line gel electrophoresis coupled to ICP-SFMS

2007

The determination of the phosphorylation degree of proteins is essential in many biochemical fields. Besides mass spectrometric techniques elucidating the protein structure, ICP-MS has entered this research area as it provides excellent quantification capabilities. In this work the separation of the proteins has been carried out by gel electrophoresis on-line coupled to an ICP equipped with a double-focusing sector field-MS (ELEMENT 2). Based on the simultaneous detection of 32S+ and 31P+, this work presents an alternative approach to determining the phosphorylation degree of caseins. For the example of α- and β-casein the results obtained were in excellent agreement with the expected value…

Oxidative stress inhibits IFN-α-induced antiviral gene expression by blocking the JAK–STAT pathway

2006

Abstract BACKGROUND/AIMS: Unresponsiveness to IFN-alpha is common in chronic hepatitis C. Since conditions associated with an increased oxidative stress (advanced age, steatosis, fibrosis, iron overload, and alcohol consumption) reduce the likelihood of response, we hypothesized that oxidative stress may affect the antiviral actions of IFN-alpha. METHODS: We examined in a human hepatocellular carcinoma cell line (Huh-7) the effect of hydrogen peroxide (H2O2), as a generator of oxidative stress, on the IFN-alpha signaling pathway. RESULTS: Pretreatment of Huh-7 cells with 0.5-1 mM H2O2 resulted in the suppression of the IFN-alpha-induced antiviral protein MxA and of IRF-9 mRNA expression. Th…

Akt induces enhanced myocardial contractility and cell size in vivo in transgenic mice

2002

The serine-threonine kinase Akt seems to be central in mediating stimuli from different classes of receptors. In fact, both IGF-1 and IL6-like cytokines induce hypertrophic and antiapoptotic signals in cardiomyocytes through PI3K-dependent Akt activation. More recently, it was shown that Akt is involved also in the hypertrophic and antiapoptotic effects of β-adrenergic stimulation. Thus, to determine the effects of Akt on cardiac function in vivo, we generated a model of cardiac-specific Akt overexpression in mice. Transgenic mice were generated by using the E40K, constitutively active mutant of Akt linked to the rat α-myosin heavy chain promoter. The effects of cardiac-selective Akt overex…

Oxidative inactivation of mitochondrial creatine kinase: Differential sensitivity of isoforms

2010

Expression analysis and functional activity of interleukin-7 splice variants.

2008

Alternative splicing results in multiple protein isoforms derived from a single gene. The magnitude of this process ranges from a complete loss of function to gain of new function. We examined, as a paradigm, alternative splicing of the non-redundant human cytokine, interleukin-7 (IL-7). We show that extensive IL-7 splicing in human tissues of different histology, including MTB+ granuloma lesions, transformed tissue and tumor cell lines. IL-7 splice variants were expressed as recombinant proteins. A differentially spliced IL-7 isoform, lacking exon 5, leads to STAT-5 phosphorylation in CD4+ and CD8+ T cells, promotes thymocyte maturation and T-cell survival. Human tumor lesions show aberran…

Goodpasture antigen-binding protein, the kinase that phosphorylates the goodpasture antigen, is an alternatively spliced variant implicated in autoim…

2000

The non-collagenous C-terminal domain of the alpha(3) chain of collagen IV is the autoantigen in Goodpasture disease, an autoimmune disorder described only in humans. Specific N-terminal phosphorylation is a biological feature unique to the human domain when compared with other homologous domains lacking immunopathogenic potential. We have recently cloned from a HeLa-derived cDNA library a novel serine/threonine kinase (Goodpasture antigen-binding protein (GPBP)) that phosphorylates the N-terminal region of the human domain (Raya, A. Revert, F, Navarro, S. and Saus J. (1999) J. Biol. Chem. 274, 12642-12649). We show here that the pre-mRNA of GPBP is alternatively spliced in human tissues an…

Interaction mechanism of endogenous PP2A inhibitor protein ENSA with PP2A

2022

The vast diversity of protein phosphatase 2A (PP2A) holoenzyme composition ensures its multifaceted role in the regulation of cellular growth and signal transduction. In several pathological conditions, such as cancer, PP2A is inhibited by endogenous inhibitor proteins. Several PP2A inhibitor proteins have been identified, one of which is α-endosulfine (ENSA). ENSA inhibits PP2A activity when it is phosphorylated at Ser67 by Greatwall (Gwl) kinase. The role of ENSA in PP2A inhibition is rather well characterized, but knowledge of the mechanism of inhibition is scarce. In this study, we have performed comprehensive structural characterization of ENSA, and its interaction with PP2A A- and var…

Centrins, gatekeepers for the light-dependent translocation of transducin through the photoreceptor cell connecting cilium

2006

Centrins are members of a highly conserved subgroup of the EF-hand superfamily of Ca(2+)-binding proteins commonly associated with centrosome-related structures. In the retina, centrins are also prominent components of the photoreceptor cell ciliary apparatus. Centrin isoforms are differentially localized at the basal body and in the lumen of the connecting cilium. All molecular exchanges between the inner and outer segments occur through this narrow connecting cilium. Ca(2+)-activated centrin isoforms bind to the visual heterotrimeric G-protein transducin via an interaction with the betagamma-subunit. Ca(2+)-dependent assemblies of centrin/G-protein complexes may regulate the transducin mo…

β1-Integrin Cytoplasmic Subdomains Involved in Dominant Negative Function

1998

The beta1-integrin cytoplasmic domain consists of a membrane proximal subdomain common to the four known isoforms ("common" region) and a distal subdomain specific for each isoform ("variable" region). To investigate in detail the role of these subdomains in integrin-dependent cellular functions, we used beta1A and beta1B isoforms as well as four mutants lacking the entire cytoplasmic domain (beta1TR), the variable region (beta1COM), or the common region (beta1 deltaCOM-B and beta1 deltaCOM-A). By expressing these constructs in Chinese hamster ovary and beta1 integrin-deficient GD25 cells (Wennerberg et al., J Cell Biol 132, 227-238, 1996), we show that beta1B, beta1COM, beta1 deltaCOM-B, a…