scholarly journals Markedly Reduced Expression of Platelet c-mpl Receptor in Essential Thrombocythemia

Blood ◽  
1997 ◽  
Vol 90 (10) ◽  
pp. 4031-4038 ◽  
Author(s):  
Yoko Horikawa ◽  
Itaru Matsumura ◽  
Koji Hashimoto ◽  
Masamichi Shiraga ◽  
Satoru Kosugi ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Essential Thrombocythemia ◽  
Normal Subjects ◽  
Protein Tyrosine Phosphorylation ◽  
Hematopoietic Stem ◽  
Protein Tyrosine ◽  
Flow Cytometric ◽  
Pathophysiological Role ◽  
And Function

Abstract Thrombopoietin (TPO) is implicated as a primary regulator of megakaryopoiesis and thrombopoiesis through binding to the cytokine receptor c-Mpl (the product of the c-mpl proto-oncogene). In an effort to determine the pathophysiological role of TPO-c-Mpl system in essential thrombocythemia (ET), we have examined the levels of serum TPO and the expression and function of platelet c-Mpl in 17 patients with ET. In spite of extreme thrombocytosis, serum TPO levels were slightly elevated or within normal range in most, if not all, patients with ET (mean ± SD, 1.31 ± 1.64 fmol/mL), as compared with normal subjects (0.76 ± 0.21 fmol/mL). Flow cytometric and Western blot analyses revealed that the expression of platelet c-Mpl was strikingly reduced in all patients with ET. Furthermore, the expression of platelet c-mpl mRNA was found to be significantly decreased in the ET patients tested. In contrast, almost identical levels of GPIIb/IIIa protein and mRNA were expressed in platelets from ET patients and normal controls. In addition to expression level, activation state of platelet c-Mpl was investigated in ET patients. Immunoblotting with anti-phosphotyrosine antibody showed that no aberrant protein-tyrosine phosphorylation was observed in platelets of ET patients before treatment with TPO, and the levels of TPO-induced protein-tyrosine phosphorylation, including c-Mpl-tyrosyl phosphorylation, roughly paralleled those of c-Mpl expression, suggesting that c-Mpl–mediated signaling pathway was not constitutively activated in platelets of ET patients. These results suggested that the TPO-c-Mpl system may not be directly linked to pathogenesis of ET, and that gene(s) mutated in ET may be important in regulating the levels of c-mpl gene expression in addition to the growth and differentiation of multipotential hematopoietic stem cells.

Role of Protein Tyrosine Phosphorylation in Etoposide-Induced Apoptosis and NF-κB Activation

1998 ◽  
Vol 55 (2) ◽  
pp. 185-191 ◽  
Author(s):  
Ikuya Usami ◽  
Masaru Kubota ◽  
Rikimaru Bessho ◽  
Akihiro Kataoka ◽  
Seiji Koishi ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Induced Apoptosis

scholarly journals Cholecystokinin receptors regulate sperm protein tyrosine phosphorylation via uptake of HCO3−

Reproduction ◽  
2015 ◽  
Vol 150 (4) ◽  
pp. 257-268 ◽  
Author(s):  
Yuchuan Zhou ◽  
Yanfei Ru ◽  
Huijuan Shi ◽  
Yanjiao Wang ◽  
Bin Wu ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Human Sperm ◽  
Peptide Hormone ◽  
Mature Sperm ◽  
Protein Tyrosine Phosphorylation ◽  
Sperm Capacitation ◽  
Protein Tyrosine ◽  
Cck Receptors ◽  
Cck2 Receptor

Cholecystokinin (CCK), a peptide hormone and a neurotransmitter, was detected in mature sperm two decades ago. However, the exact role of CCK and the types of CCK receptors (now termed CCK1 and CCK2) in sperm have not been identified. Here, we find that CCK1 and CCK2 receptors are immunolocalized to the acrosomal region of mature sperm. The antagonist of CCK1 or CCK2 receptor strongly activated the soluble adenylyl cyclase/cAMP/protein kinase A signaling pathway that drives sperm capacitation-associated protein tyrosine phosphorylation in dose- and time-dependent manners. But these actions of stimulation were abolished when sperm were incubated in the medium in the absence of HCO3−. Further investigation demonstrated that the inhibitor of CCK1 or CCK2 receptor could accelerate the uptake of HCO3−and significantly elevate the intracellular pH of sperm. Interestingly, the synthetic octapeptide of CCK (CCK8) showed the same action and mechanism as antagonists of CCK receptors. Moreover, CCK8 and the antagonist of CCK1 or CCK2 receptor were also able to accelerate human sperm capacitation-associated protein tyrosine phosphorylation by stimulating the influx of HCO3−. Thus, the present results suggest that CCK and its receptors may regulate sperm capacitation-associated protein tyrosine phosphorylation by modulating the uptake of HCO3−.

scholarly journals Role of the Lck Src Homology 2 and 3 Domains in Protein Tyrosine Phosphorylation

1996 ◽  
Vol 271 (40) ◽  
pp. 25003-25010 ◽  
Author(s):  
Kay K. Lee-Fruman ◽  
Tassie L. Collins ◽  
Steven J. Burakoff
Keyword(s):  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Src Homology 2 ◽  
Src Homology

scholarly journals Stimulation of Fc gamma RIIIA results in phospholipase C-gamma 1 tyrosine phosphorylation and p56lck activation.

1992 ◽  
Vol 176 (6) ◽  
pp. 1745-1750 ◽  
Author(s):  
L Azzoni ◽  
M Kamoun ◽  
T W Salcedo ◽  
P Kanakaraj ◽  
B Perussia
Keyword(s):  
T Cells ◽  
Tyrosine Kinase ◽  
Nk Cells ◽  
Phospholipase C ◽  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Tyrosine Residues ◽  
Stimulation Of

Binding of ligand to the alpha subunit of Fc gamma RIIIA(CD16), expressed at the natural killer (NK) cell membrane in association with homo or heterodimers of proteins of the zeta family, results in phosphorylation of several proteins on tyrosine residues. We have analyzed the role of protein tyrosine phosphorylation in the regulation of molecular events induced upon stimulation of Fc gamma RIIIA in NK cells and in T cells expressing the Fc gamma RIII alpha chain in association with endogenous zeta 2 homodimers and devoid of other (CD3, CD2) transducing molecules. Our data indicate that treatment of these cells with protein tyrosine kinase inhibitors prevents not only Fc gamma RIIIA-induced protein tyrosine phosphorylation but also phosphatidylinositol 4,5 diphosphate hydrolysis and increased intracellular Ca2+ concentration, indicating a primary role of tyrosine kinase(s) in the induction of these early activation events. Occupancy of Fc gamma RIIIA by ligand results in phospholipase C (PLC)-gamma 1 tyrosine phosphorylation in NK cells and in Fc gamma RIIIA-transfected CD3-/CD2- T cells, and induces functional activation of p56lck in Fc gamma RIIIA alpha/zeta 2-transfected T cells, suggesting the possibility that the receptor-induced PLC-gamma 1 activation occurs upon phosphorylation of its tyrosine residues mediated by this kinase and is, at least in part, responsible for the signal transduction mediated via CD16 upon ligand binding.

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