Phosphorylation States (phosphorylation + states)

Distribution by Scientific Domains

Selected Abstracts

Regulation of sperm flagellar motility activation and chemotaxis caused by egg-derived substance(s) in sea cucumber

CYTOSKELETON, Issue 4 2009
Masaya Morita
Abstract The sea cucumber Holothuria atra is a broadcast spawner. Among broadcast spawners, fertilization occurs by means of an egg-derived substance(s) that induces sperm flagellar motility activation and chemotaxis. Holothuria atra sperm were quiescent in seawater, but exhibited flagellar motility activation near eggs with chorion (intact eggs). In addition, they moved in a helical motion toward intact eggs as well as a capillary filled with the water layer of the egg extracts, suggesting that an egg-derived compound(s) causes motility activation and chemotaxis. Furthermore, demembranated sperm flagella were reactivated in high pH (>7.8) solution without cAMP, and a phosphorylation assay using (,-32P)ATP showed that axonemal protein phosphorylation and dephosphorylation also occurred in a pH-dependent manner. These results suggest that the activation of sperm motility in holothurians is controlled by pH-sensitive changes in axonemal protein phosphorylation. Ca2+ concentration affected the swimming trajectory of demembranated sperm, indicating that Ca2+ -binding proteins present at the flagella may be associated with regulation of flagellar waveform. Moreover, the phosphorylation states of several axonemal proteins were Ca2+ -sensitive, indicating that Ca2+ impacts both kinase and phosphatase activities. In addition, in vivo sperm protein phosphorylation occurred after treatment with a water-soluble egg extract. Our results suggest that one or more egg-derived compounds activate motility and subsequent chemotactic behavior via Ca2+ -sensitive flagellar protein phosphorylation. Cell Motil. Cytoskeleton 2009. 2009 Wiley-Liss, Inc. [source]

Altered subcellular location of phosphorylated Smads in Alzheimer's disease

Uwe Ueberham
Abstract A number of growth factors and cytokines, such as transforming growth factor beta 1 (TGF-,1), is elevated in Alzheimer's disease (AD), giving rise to activated intracellular mitogenic signaling cascades. Activated mitogenic signaling involving the mitogen-activated protein kinases (MAPKs) and other protein kinases might alter the phosphorylation states of structural proteins such as tau, resulting in hyperphosphorylated deposits. Many intracellular signaling proteins are potential targets of misregulated phosphorylation and dephosphorylation. Recently, a crosstalk between MAPKs and Smad proteins, both involved in mediating TGF-,1 signaling, has been reported. Although TGF-,1 has previously been shown to be involved in the pathogenesis of AD, the role of Smad proteins has not been investigated. In this study we thus analysed the subcellular distribution of phosphorylated Smad2 and Smad3 in the hippocampus of both normal and AD brains. Here we report on strong nuclear detection of phosphorylated Smad2 and Smad3 in neurons of control brains. In AD brains these phosphorylated proteins were additionally found in cytoplasmic granules in hippocampal neurons, within amyloid plaques and attached to neurofibrillary tangles. Our data suggest a critical role of Smad proteins in the pathogenesis of AD. [source]

The yeast zinc finger regulators Pdr1p and Pdr3p control pleiotropic drug resistance (PDR) as homo- and heterodimers in vivo

Yasmine M. Mamnun
Summary The transcription factors Pdr1p and Pdr3p from Saccharomyces cerevisiae mediate pleiotropic drug resistance (PDR) by controlling expression of ATP-binding cassette (ABC) transporters such as Pdr5p, Snq2p and Yor1p. Previous in vitro studies demonstrated that Pdr1p and Pdr3p recognize so-called pleiotropic drug resistance elements (PDREs) in the promoters of target genes. In this study, we show that both Pdr1p and Pdr3p are phosphoproteins; Pdr3p isoforms migrate as two bands in gel electrophoresis, reflecting two distinct phosphorylation states. Most importantly, native co-immunoprecipitation experiments, using functional epitope-tagged Pdr1p/Pdr3p variants, demonstrate that Pdr1p and Pdr3p can form both homo- and heterodimers in vivo. Furthermore, in vivo footprinting of PDRE-containing promoters demonstrate that Pdr1p/Pdr3p constitutively occupy both perfect and degenerate PDREs in vivo. Thus, in addition to interaction with other regulators, differential dimerization provides a plausible explanation for the observation that Pdr3p and Pdr1p can both positively and negatively control PDR promoters with different combinations of perfect and degenerate PDREs. [source]

Germinal vesicle materials are not required for the activation of MAP kinase in porcine oocyte maturation

K. Sugiura
Abstract The requirement of the germinal vesicle (GV) for the normal kinetics of mitogen-activated protein (MAP) kinase activity during porcine oocyte maturation was investigated. Porcine follicular oocytes were enucleated, and the locations of their extracellular signal-regulated kinases 1 and 2 (ERK1/2), major MAP kinases in maturating porcine oocytes, were detected by indirect immunofluorescent microscopy. The MAP kinase activity was assayed as myelin basic protein (MBP) kinase activity, and the phosphorylation states of ERK1/2 were detected by immunoblotting analyses. Translocation of MAP kinase into the GV and association with the spindle were observed in intact oocytes, while MAP kinase in enucleated oocytes was distributed almost uniformly in cytoplasm throughout the culturing period. The phosphorylation and the activation of MAP kinase were induced, and the activity was comparable with that of control denuded oocytes. The high level of activity was maintained through maturation, even in the absence of spindle formation. These results indicate that the presence of nuclear material and translocation into the GV are dispensable for the activation of MAP kinase and that associating with the spindle is not required for maintenance of its activity though porcine oocyte maturation. Mol. Reprod. Dev. 59:215,220, 2001. 2001 Wiley-Liss, Inc. [source]

A MAS NMR Study of the Bacterial ABC Transporter ArtMP

CHEMBIOCHEM, Issue 4 2010
Vivien Lange Dr.
Abstract ATP-binding cassette (ABC) transport systems facilitate the translocation of substances, like amino acids, across cell membranes energised by ATP hydrolysis. This work describes first structural studies on the ABC transporter ArtMP from Geobacillus stearothermophilus in native lipid environment by magic-angle spinning NMR spectroscopy. The 2D crystals of ArtMP and 3D crystals of isolated ArtP were prepared in different nucleotide-bound or -unbound states. From selectively 13C,15N-labelled ArtP, several sequence-specific assignments were obtained, most of which could be transferred to spectra of ArtMP. Residues Tyr133 and Pro134 protrude directly into the ATP-binding pocket at the interface of the ArtP subunits, and hence, are sensitive monitors for structural changes during nucleotide binding and hydrolysis. Distinct sets of NMR shifts were obtained for ArtP with different phosphorylation states of the ligand. Indications were found for an asymmetric or inhomogeneous state of the ArtP dimer bound with triphosphorylated nucleotides. With this investigation, a model system was established for screening all functional states occurring in one ABC transporter in native lipid environment. [source]