title: Differential regulation of protein-tyrosine phosphatases by integrin alpha IIb beta 3 through cytoskeletal reorganization and tyrosine phosphorylation in human platelets.
abstract: The major platelet integrin alpha IIb beta 3 (glycoprotein IIb-IIIa) has been implicated in the regulation of tyrosine phosphorylation and dephosphorylation in activated platelets. To investigate the mechanisms of the alpha IIb beta 3-dependent tyrosine dephosphorylation, normal platelets or thrombasthenic platelets lacking alpha IIb beta 3 were stimulated with thrombin and fractionated into Triton X-100-soluble or -insoluble subcellular matrices. We then examined the kinetics of the tyrosine-phosphorylated proteins and distribution of protein-tyrosine phosphatases in these fractions and whole cell lysates. First, alpha IIb beta 3-dependent tyrosine dephosphorylation was recovered mainly in the cytoskeleton with similar kinetics to the whole cell lysate. Second, protein-tyrosine phosphatase (PTP) 1B and its cleaved 42-kDa form were associated with the cytoskeleton in an aggregation-dependent manner, whereas association of PTP1C with the cytoskeleton was regulated differentially both by thrombin stimulation and by alpha IIb beta 3-mediated aggregation. Several calpain inhibitors did not affect either tyrosine phosphorylation and dephosphorylation or relocation of PTP1B, but they did inhibit cleavage of PTP1B. Cytochalasin D blocked relocation of both PTP1B and PTP1C but not PTP1B cleavage. SH-PTP2 was distributed in the other fractions than the cytoskeleton and showed no relocation on thrombin stimulation. Finally, the cytoskeleton-associated PTP1C became tyrosine-phosphorylated in an alpha IIb beta 3-mediated aggregation-dependent manner. Thus, integrin alpha IIb beta 3 was involved differentially in the regulation of PTP1B and PTP1C.
authors.affiliation: Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ezumi
authors.forename: H
authors.initials: H
authors.lastname: Takayama
authors.forename: M
authors.initials: M
authors.lastname: Okuma
mesh_terms: D000328:Adult; D001692:Biological Transport; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D001798:Blood Proteins / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D016023:Integrins / Q000172:deficiency / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D019000:Phosphotyrosine; D015539:Platelet Activation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D010980:Platelet Membrane Glycoproteins / Q000172:deficiency / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D013915:Thrombasthenia / Q000097:blood; D013917:Thrombin / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D016023:Integrins; D007527:Isoenzymes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D010980:Platelet Membrane Glycoproteins; D019000:Phosphotyrosine; D015638:Cytochalasin D; D014443:Tyrosine; D017027:Protein Tyrosine Phosphatases; D013917:Thrombin; D002154:Calpain