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Platelet adhesion to collagen under flow causes dissociation of a phosphoprotein complex of heat-shock proteins and protein phosphatase 1. 1997

R Polanowska-Grabowska, and C G Simon, and R Falchetto, and J Shabanowitz, and D F Hunt, and A R Gear
Department of Biochemistry, University of Virginia, Charlottesville 22908, USA.

Phosphorylation/dephosphorylation events in human blood platelets were investigated during their adhesion to collagen under flow conditions. Using 32P-labeled platelets and one-dimensional gel electrophoresis, we found that adhesion to collagen mediated primarily by the alpha2beta1 integrin resulted in a strong dephosphorylation of several protein bands. Neither adhesion to polylysine nor thrombin-induced aggregation caused similar protein dephosphorylation. In addition, treatment with okadaic acid (OA), an inhibitor of serine/threonine protein phosphatases type 1 (PP1) and 2A (PP2A), caused significant inhibition of adhesion, suggesting that adhesion is regulated by OA-sensitive phosphatases. Recent studies indicate that phosphatases may be associated with the heat-shock proteins. Immunoprecipitations with antibodies against either the heat-shock cognate protein 70 (hsc70) or heat-shock protein 90 (hsp90) showed the presence of a phosphoprotein complex in 32P-labeled, resting human platelets. Antibody probing of this complex detected hsc70, hsp90, two isoforms of the catalytic subunit of PP1, PP1C alpha and PP1C delta, as well as the M regulatory subunit of PP1 (PP1M). OA, at concentrations that markedly blocked platelet adhesion to collagen, caused hyperphosphorylation of the hsc70 complex. In platelets adhering to collagen, hsc70 was completely dephosphorylated and hsp90, PP1 alpha, and PP1M were dissociated from the complex, suggesting involvement of heat-shock proteins and protein phosphatases in platelet adhesion.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D008970 Molecular Weight The sum of the weight of all the atoms in a molecule. Molecular Weights,Weight, Molecular,Weights, Molecular
D010749 Phosphoprotein Phosphatases A group of enzymes removing the SERINE- or THREONINE-bound phosphate groups from a wide range of phosphoproteins, including a number of enzymes which have been phosphorylated under the action of a kinase. (Enzyme Nomenclature, 1992) Phosphoprotein Phosphatase,Phosphoprotein Phosphohydrolase,Protein Phosphatase,Protein Phosphatases,Casein Phosphatase,Ecto-Phosphoprotein Phosphatase,Nuclear Protein Phosphatase,Phosphohistone Phosphatase,Phosphoprotein Phosphatase-2C,Phosphoseryl-Protein Phosphatase,Protein Phosphatase C,Protein Phosphatase C-I,Protein Phosphatase C-II,Protein Phosphatase H-II,Protein-Serine-Threonine Phosphatase,Protein-Threonine Phosphatase,Serine-Threonine Phosphatase,Threonine Phosphatase,Ecto Phosphoprotein Phosphatase,Phosphatase C, Protein,Phosphatase C-I, Protein,Phosphatase C-II, Protein,Phosphatase H-II, Protein,Phosphatase, Casein,Phosphatase, Ecto-Phosphoprotein,Phosphatase, Nuclear Protein,Phosphatase, Phosphohistone,Phosphatase, Phosphoprotein,Phosphatase, Phosphoseryl-Protein,Phosphatase, Protein,Phosphatase, Protein-Serine-Threonine,Phosphatase, Protein-Threonine,Phosphatase, Serine-Threonine,Phosphatase, Threonine,Phosphatase-2C, Phosphoprotein,Phosphatases, Phosphoprotein,Phosphatases, Protein,Phosphohydrolase, Phosphoprotein,Phosphoprotein Phosphatase 2C,Phosphoseryl Protein Phosphatase,Protein Phosphatase C I,Protein Phosphatase C II,Protein Phosphatase H II,Protein Phosphatase, Nuclear,Protein Serine Threonine Phosphatase,Protein Threonine Phosphatase,Serine Threonine Phosphatase
D010750 Phosphoproteins Phosphoprotein
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D010973 Platelet Adhesiveness The process whereby PLATELETS adhere to something other than platelets, e.g., COLLAGEN; BASEMENT MEMBRANE; MICROFIBRILS; or other "foreign" surfaces. Adhesiveness, Platelet,Adhesivenesses, Platelet,Platelet Adhesivenesses
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D003094 Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of SKIN; CONNECTIVE TISSUE; and the organic substance of bones (BONE AND BONES) and teeth (TOOTH). Avicon,Avitene,Collagen Felt,Collagen Fleece,Collagenfleece,Collastat,Dermodress,Microfibril Collagen Hemostat,Pangen,Zyderm,alpha-Collagen,Collagen Hemostat, Microfibril,alpha Collagen
D003599 Cytoskeleton The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm. Cytoplasmic Filaments,Cytoskeletal Filaments,Microtrabecular Lattice,Cytoplasmic Filament,Cytoskeletal Filament,Cytoskeletons,Filament, Cytoplasmic,Filament, Cytoskeletal,Filaments, Cytoplasmic,Filaments, Cytoskeletal,Lattice, Microtrabecular,Lattices, Microtrabecular,Microtrabecular Lattices
D004791 Enzyme Inhibitors Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme

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