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See detailDistinct involvement of beta3 integrin cytoplasmic domain tyrosine residues 747 and 759 in integrin-mediated cytoskeletal assembly and phosphotyrosine signaling.
Schaffner-Reckinger, Elisabeth UL; Gouon, V.; Melchior, Chantal UL et al

in The Journal of biological chemistry (1998), 273(20), 12623-32

We have investigated the structural requirements of the beta3 integrin subunit cytoplasmic domain necessary for tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin during alphav beta3 ... [more ▼]

We have investigated the structural requirements of the beta3 integrin subunit cytoplasmic domain necessary for tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin during alphav beta3-mediated cell spreading. Using CHO cells transfected with various beta3 mutants, we demonstrate a close correlation between alphav beta3-mediated cell spreading and tyrosine phosphorylation of FAK and paxillin, and highlight a distinct involvement of the NPLY747 and NITY759 motifs in these signaling processes. Deletion of the NITY759 motif alone was sufficient to completely prevent alphav beta3-dependent focal contact formation, cell spreading, and FAK/paxillin phosphorylation. The single Y759A substitution induced a strong inhibitory phenotype, while the more conservative, but still phosphorylation-defective, Y759F mutation restored wild type receptor function. Alanine substitution of the highly conserved Tyr747 completely abolished alphav beta3-dependent formation of focal adhesion plaques, cell spreading, and FAK/paxillin phosphorylation, whereas a Y747F substitution only partially restored these events. As none of these mutations affected receptor-ligand interaction, our results suggest that the structural integrity of the NITY759 motif, rather than the phosphorylation status of Tyr759 is important for beta3-mediated cytoskeleton reorganization and tyrosine phosphorylation of FAK and paxillin, while the presence of Tyr at residue 747 within the NPLY747 motif is required for optimal beta3 post-ligand binding events. [less ▲]

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See detailExpression of the plasma membrane Ca2+-ATPase in myogenic cells.
Hammes, A.; Oberdorf-Maass, S.; Jenatschke, S. et al

in The Journal of biological chemistry (1996), 271(48), 30816-22

To study the physiological function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in intact cells, L6 myogenic cell lines stably overexpressing the human PMCA isoform 4CI (= human PMCA ... [more ▼]

To study the physiological function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in intact cells, L6 myogenic cell lines stably overexpressing the human PMCA isoform 4CI (= human PMCA isoform 4b) were generated. Several independent L6 clones and controls stably transfected with the empty expression vector were analyzed in detail. The resting cytosolic calcium level in hPMCA4CI-overexpressing muscle cells (measured by the Fura-2 method) was significantly reduced by 20-30% compared with controls. This was shown in a cytosolic window of 1322 single cells (p < 0.01). Furthermore, the differentiation process of these cells was remarkably accelerated compared with control myoblasts and parental nontransfected L6 cells as assessed by multinucleated myotube formation and creatine phosphokinase activity elevation. After 4 and 6 days of differentiation, PMCA-overexpressing L6 cells from four independent clones displayed a 3- and 4-fold higher creatine phosphokinase activity compared with controls (n = 5, p < 0.02). These results may extend the concept of the function of the PMCA from simple prevention of calcium overload to an active involvement in intracellular calcium regulation with potentially important consequences for cellular functions. [less ▲]

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See detailPhosphorylation of the Ca2+-pumping ATPase of heart sarcolemma and erythrocyte plasma membrane by the cAMP-dependent protein kinase.
Neyses, Ludwig UL; Reinlib, L.; Carafoli, E.

in The Journal of biological chemistry (1985), 260(18), 10283-7

The Ca2+ ATPase of heart sarcolemma was stimulated by the exposure of sarcolemma vesicles to ATP and the catalytic subunit of the cAMP-dependent protein kinase. The effect of the phosphorylation system ... [more ▼]

The Ca2+ ATPase of heart sarcolemma was stimulated by the exposure of sarcolemma vesicles to ATP and the catalytic subunit of the cAMP-dependent protein kinase. The effect of the phosphorylation system was primarily on the Km(Ca2+) of the pumping ATPase. The ATPase purified from heart sarcolemma or erythrocytes became phosphorylated under the conditions mentioned above. Hydroxylamine treatment of the labeled ATPase has shown that the phosphorylation was additive to be acylphosphate formed on the ATPase during the reaction cycle. The stoichiometry of the kinase-promoted phosphorylation (i.e. the fraction of the ATPase molecules that became labeled) approached 30% with both the heart and the erythrocyte enzyme. [less ▲]

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