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  • 1
    Electronic Resource
    Electronic Resource
    Platelet talin is phosphorylated by calyculin A (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 57 (1995), S. 120-126 
    Details
    ISSN: 0730-2312
    Keywords: protein phosphatase ; calyculin A ; platelet ; talin ; phosphorylation ; phosphoamino acid analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Calyculin A and okadaic acid, potent and cell permeable inhibitors of type 1 and type 2A protein phosphatases, inhibit platelet aggregation and secretion. However, the relationship between phosphatase inhibition and inhibition of platelet function is not well understood. We found that in unstimulated platelets, talin (P235) was phosphorylated at threonine residues by calyculin A. Furthermore, the extent of talin phosphorylation by calyculin A was closely correlated with its inhibition of thrombin-induced platelet aggregation. Since the binding of talin to platelet glycoprotein IIb/IIIa complex has been shown to be affected by its phosphorylation, these results suggest that type 1 and/or type 2A protein phosphatases may play a role in the regulation of membrane-cytoskeleton interaction through dephosphorylation of talin.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240570112
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  • 2
    Electronic Resource
    Electronic Resource
    Involvement of protein phsophatase-1 in cytoskeletal organization of cultured endothelial cells (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 59 (1995), S. 368-375 
    Details
    ISSN: 0730-2312
    Keywords: calcyculin A ; protein phosphatase ; cytoskeleton ; endothelial cell ; immunocytochemsitry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The phosphorylation and dephosphorylation of cytoskeletal proteins regulate the shape of eukaryotic cells. To elucidate the role of serine/threonine protein phosphatases (PP) in this process, we studied the effect of calyculin A (CLA), a potent and specific inhibitor of protein phosphatases 1 (PP-1) and 2A (PP-2A) on the cytoskeletal structure of cultured human umbilical vien endothelial cells (HUVECs). The addition of CLA (5 min) caused marked alterations in cell morphology, such as cell constriction and bleb formation. Microtubules and F-actin were reorganized, becoming markedly condensed around the nucleus. Although the fluorescence intensity of phosphoamino acids was not significantly different to immunocytochemistry between cells with and without CLA, polypeptides of 135, 140, 158, and 175 kDa were specifically phosphorylated on serine and/or threonine residues. There was no significant effect on tyrosine residues. The effects of CLA on cytoskeletal changes and protein phosphorylation were almost completely inhibited by the non-selective kinase inhibitor, K-252a. The effect of CLA on cell morphology was at least 100 times more potent than that of okadaic acid, consistent with the inhibitory potency against PP-1. The catalytic subunit of PP-1 was also identified in HUVECs by Western blotting with its monoclonal antibody. These results suggest that PP-1 is closely involved in sustaining the normal structure of the cytoskeleton. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240590308
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  • 3
    Electronic Resource
    Electronic Resource
    LFA-1/ICAM-3 mediates neutrophil homotypic aggregation under fluid shear stress (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 60 (1996), S. 550-559 
    Details
    ISSN: 0730-2312
    Keywords: shear stress ; homotypic aggregation ; LFA-1 ; ICAM-3 ; NiCl2 sensitive Ca2+ channel ; Ca2+ influx ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We found that human neutrophils undergo homotypic aggregation by loading the physiological range of fluid shear stress (12-30 dynes/cm2). Under the fluid shear stress, an increase of intracellular Ca2+ concentration of neutrophils was observed. This increase of intracellular Ca2+ concentration was caused by Ca2+ influx, and the blockage of the flux by NiCl2 suppressed the neutrophil homotypic aggregation. Furthermore, this neutrophil aggregation under fluid shear stress was completely inhibited by pretreatment with antibody against LFA-1 or ICAM-3. These results suggested that NiCl2-sensitive Ca2+ channel played an important role in LFA-1/ICAM-3-mediated neutrophil homotypic aggregation under fluid shear stress. © 1996 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    Calpain activation in shear-induced platelet aggregation (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 54-64 
    Details
    ISSN: 0730-2312
    Keywords: calpain activation ; platelet ; proteolysis of talin ; shear stress ; shear-induced platelet aggregation (SIPA) ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fluid shear stress has been known to activate platelet reaction such as aggregation, but the exact mechanism of shear-induced platelet aggregation (SIPA) has not been fully understood. Calpain, an intracellular calcium-activated cysteine protease, is abundant in platelets and is considered to be activated and involved in the proteolytic processes during platelet activation. A possible activation of calpain in SIPA was investigated, employing a newly developed aggregometer and specific monoclonal antibodies to detect activation of calpain. When a shear stress gradient varying between 6 and 108 dyn/cm2 was applied to platelets, activation of μ-calpain was observed only in high-shear-stressed platelets, resulting in the proteolysis of talin. At 1 min after the onset of constant high shear stress of 108 dyn/cm2, μ-calpain activation and proteolysis of talin were detected and increased in a time-dependent manner. Constant shear stress more than 50 dyn/cm2, applied for 5 min, caused μ-calpain activation and proteolysis of talin, which were increased in a shear-force-dependent manner. Calpeptin, a calpain-specific peptide antagonist, caused the complete inhibition of both μ-calpain activation and proteolysis of talin, while SIPA profiles with calpeptin showed almost no change compared to those without calpeptin. These results suggest the possibility of calpain involvement in late phases of shear-induced platelet activation such as cytoskeletal reorganization. J. Cell. Biochem. 66:54-64, 1997. © 1997 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    Involvement of protein phosphatase 2A in PKC-independent pathway of neutrophil superoxide generation by fMLP (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 60 (1996), S. 279-288 
    Details
    ISSN: 0730-2312
    Keywords: superoxide ; p47phox ; phosphorylation ; okadaic acid ; protein phosphatase 1 and 2A ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We examined the effects of okadaic acid, a protein phosphatase 1 and 2A inhibitor, on superoxide generation in human neutrophils. Superoxide generation induced by fMLP was inhibited by low-dose okadaic acid (10-100 nM), but it had no effect on superoxide synthesis by PMA, and the fMLP-induced rise of the intracellular Ca2+ concentration was not affected by low-dose okadaic acid. These findings suggested that the inhibitory mechanism of okadaic acid might involve PKC-independent and Ca2+-independent pathways in fMLP induced NADPH oxidase activation.Both fMLP-stimulated phosphorylation of serine residues in p47phox and its translocation to the plasma membrane were suppressed by low-dose okadaic acid. On the other hand, PMA-induced phosphorylation and translocation of p47phox were not affected by such a low dose of okadaic acid. These findings suggested that fMLP induced phosphorylation of serine residues in p47phox was regulated by protein phosphatase 2A, and its phosphorylation was necessary for translocation and superoxide generation in fMLP-activated human neutrophils. © 1996 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Simultaneous digital imaging analysis of cytosolic calcium and morphological change in platelets activated by surface contact (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 61 (1996), S. 292-300 
    Details
    ISSN: 0730-2312
    Keywords: platelets ; morphological change ; [Ca2+]i ; confocal laser scanning microscopy ; surface contact activation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The dynamic change of cytoplasmic Ca2+ concentration ([Ca2+]i) and morphological change were investigated simultaneously by confocal laser scanning microscopy using fluo-3 and by differential interference contrast optics in platelets activated by contact with the following types of surfaces: native glass and glass treated with poly-L-lysine (PLL), fibrinogen (Fg), or von Willebrand factor (vWF). The initial [Ca2+]i values just after the surface contact were comparable (approximately 100 nM) among platelets deposited on the four surface types. On the PLL-surface, no morphological change or [Ca2+]i elevation was observed. Glass-, Fg-, and vWF-surface adhered platelets showed pseudopod formation and spreading associated with the inhomogeneous [Ca2+]i rise. The platelets on the Fg-surface were the most active in terms of [Ca2+]i rise and morphological change. During pseudopod formation, the mean [Ca2+]i value was maximal and localized high [Ca2+]i zones were observed inside pseudopods, as well as in the center of the platelets. After spreading, high [Ca2+]i zones still remained in the center of the cell. This new technique enabled simultaneous observation of [Ca2+]i and cell shape and we clearly demonstrated a close relationship between [Ca2+]i and morphological alterations. © 1996 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    Shear stress down-regulates gene transcription and production of adrenomedullin in human aortic endothelial cells (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 109-115 
    Details
    ISSN: 0730-2312
    Keywords: fluid shear stress ; adrenomedullin ; endothelial cell ; SSRE ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vascular endothelial cells are potent modulators of vascular tone in response to shear stress. Levels of vasoactive peptides such as adrenomedullin (AM), endothelin-1 (ET-1), C-type natriuretic peptide (CNP), and nitric oxide (NO) are affected by fluid shear stress. AM, a potent vasodilator and suppressor of smooth muscle cell proliferation, contains the shear stress responsive element (SSRE) “GAGACC” in its promoter region. To examine the role of AM in the shear stress response, cultured human aortic endothelial cells (HAoECs) were exposed to fluid shear stresses of 12 and 24 dynes/cm2 in a cone-plate shear stress loading apparatus for various time periods, and the levels of AM gene expression and peptide secretion from HAoECs were measured by Northern blotting analysis and radioimmunoassay (RIA), respectively. Both AM gene transcription and AM peptide levels were down-regulated by fluid shear stress in a time- and magnitude-dependent manner. Our results demonstrate that the normal level of arterial shear stress down-regulates AM expression in HAoECs, suggesting that AM participates in the modulation of vascular tone by fluid shear stress. J. Cell. Biochem. 71:109-115, 1998. © 1998 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Separate analysis of nuclear and cytosolic Ca2+ concentrations in human umbilical vein endothelial cells (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 23-36 
    Details
    ISSN: 0730-2312
    Keywords: [Ca2+]i and [Ca2+]n ; Ca2+ gradients ; confocal laser scanning microscopy ; Fluo-3 ; heterogeneity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Ca2+ concentration inside human umbilical vein endothelial cells was studied separately in cytosol and nucleus by a confocal laser scanning microscopy using fluo-3. The in vivo calibration curve for cytosol and nucleus showed good linearity between fluorescence intensity and Ca2+ concentration in cytosol ([Ca2+]i) and nuclei ([Ca2+]n). After calibration, [Ca2+]n was constantly higher than [Ca2+]i before and after the chelation of extracellular Ca2+ suggesting an active Ca2+ accumulation system on nuclear membrane. [Ca2+]n was also constantly higher than [Ca2+]i after the stimulation of thrombin (0.05 U/ml), FCS (10%), and thapsigargin (Tsg, 1μM). The temporal change of [Ca2+]n and [Ca2+]i was identical, and [Ca2+]i gradient towards the nucleus and peripheral or central [Ca2+]n rise was observed after these stimulations. From these results, [Ca2+]n is not only regulated by the active Ca2+ accumulation system on nuclear membrane at rest but also the generation of Inositol-triphosphate. FCS caused heterogeneous [Ca2+]n or [Ca2+]i rise from cell to cell; single spike or oscillatory change of [Ca2+]n and [Ca2+]i was observed in about 56% of cells, which were completely abolished by the chelation of extracellular Ca2+, suggesting that FCS stimulated [Ca2+]n and [Ca2+]i rise solely depending on Ca2+ influx from extracellular medium. The higher concentration of [Ca2+]n and heterogeneous [Ca2+]n rise may have important roles in nuclear-specific cellular responses. © 1996 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    Fluid shear stress induces actin polymerization in human neutrophils (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 432-441 
    Details
    ISSN: 0730-2312
    Keywords: shear stress ; actin polymerization ; LFA-1 ; ICAM-3 ; homotypic aggregation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have previously reported that a physiological range of shear stress induces neutrophil homotypic aggregation mediated by lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-3 (ICAM-3) interactions. To further characterize the homotypic aggregation, actin polymerization was investigated in neutrophils stimulated by shear stress in comparison with formyl-methionyl-leucyl-phenylalanine (fMLP). In fMLP-stimulated neutrophils, actin polymerization was localized in the pseudopods, and this reaction was not mediated by a cytosolic level of Ca2+. In contrast to fMLP stimulation, the actin polymerization induced by shear stress in a cone-plate viscometer was localized in cell-cell contact regions, and this polymerization required the increase of intracellular Ca2+. This shear stress-induced actin polymerization was not observed when neutrophils were pretreated with anti-LFA-1 or anti-ICAM-3 antibody. In conclusion, LFA-1 and ICAM-3 interaction mediated by the increase of [Ca2+]i generated the intercellular signal in order to accumulate F-actin in the cell-cell contact regions. © 1996 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    Identification of μ-, m-calpains and calpastatin and capture of μ-calpain activation in endothelial cells (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 197-209 
    Details
    ISSN: 0730-2312
    Keywords: μ-calpain ; m-calpain ; calpastatin; μ-calpain activation in endothelial cells ; autolytic intermediate form of μ-calpain ; fully autolyzed postautolysis form of μ-calpain ; calpeptin ; talin ; filamin ; cytoskeletal proteolysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The presence of the calpain-calpastatin system in human umbilical vein endothelial cells (HUVEC) was investigated by means of ion exchange chromatography, Western blot analysis, and Northern blot analysis. On DEAE anion exchange chromatography, calpain and calpastatin activities were eluted at approximately 0.30 M and 0.15-0.25 M NaCl, respectively. For half-maximal activity, the protease required 800 μM Ca2+, comparable to the Ca2+ requirement of m-calpain. By Western blot analysis, the large subunit of μ-calpain (80 kDa) was found to be eluted with calpastatin (110 kDa). Both the large subunit of m-calpain (80 kDa) and calpastatin were detected in the respective active fractions. By Northern blot analysis, mRNAs for large subunits of μ- and m-calpains were detected in single bands, each corresponding to approximately 3.5 Kb. Calpastatin mRNA was observed in two bands corresponding to approximately 3.8 and 2.6 Kb. Furthermore, the activation of μ-calpain in HUVEC by a calcium ionophore was examined, using an antibody specifically recognizing an autolytic intermediate form of μ-calpain large subunit (78 kDa). Both talin and filamin of HUVEC were proteolyzed in a calcium-dependent manner, and the reactions were inhibited by calpeptin, a cell-permeable calpain specific inhibitor. Proteolysis of the cytoskeleton was preceded by the appearance of the autolytic intermediate form of μ-calpain, while the fully autolyzed postautolysis form of μ-calpain (76 kDa) remained below detectable levels at all time points examined. These results indicate that the calpain-calpastatin system is present in human endothelial cells and that μ-calpain may be involved in endothelial cell function mediated by Ca2+ via the limited proteolysis of various proteins. J. Cell. Biochem. 66:197-209, 1997. © 1997 Wiley-Liss, Inc.
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