scholarly journals Myricetin, quercetin and catechin-gallate inhibit glucose uptake in isolated rat adipocytes

2005 ◽  
Vol 386 (3) ◽  
pp. 471-478 ◽  
Author(s):  
Pablo STROBEL ◽  
Claudio ALLARD ◽  
Tomás PEREZ-ACLE ◽  
Rosario CALDERON ◽  
Rebeca ALDUNATE ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Glucose Uptake ◽  
Protein Tyrosine Kinase ◽  
Glucose Transporter ◽  
Insulin Signalling ◽  
Biological Activities ◽  
Inhibition Mechanism ◽  
Protein Data Bank Code ◽  
Protein Tyrosine ◽  
Comparative Model

The facilitative glucose transporter, GLUT4, mediates insulin-stimulated glucose uptake in adipocytes and muscles, and the participation of GLUT4 in the pathogenesis of various clinical conditions associated with obesity, visceral fat accumulation and insulin resistance has been proposed. Glucose uptake by some members of the GLUT family, mainly GLUT1, is inhibited by flavonoids, the natural polyphenols present in fruits, vegetables and wine. Therefore it is of interest to establish if these polyphenolic compounds present in the diet, known to be effective antioxidants but also endowed with several other biological activities such as protein-tyrosine kinase inhibition, interfere with GLUT4 function. In the present study, we show that three flavonoids, quercetin, myricetin and catechin-gallate, inhibit the uptake of methylglucose by adipocytes over the concentration range of 10–100 μM. These three flavonoids show a competitive pattern of inhibition, with Ki=16, 33.5 and 90 μM respectively. In contrast, neither catechin nor gallic acid inhibit methylglucose uptake. To obtain a better understanding of the interaction among GLUT4 and flavonoids, we have derived a GLUT4 three-dimensional molecular comparative model, using structural co-ordinates from a GLUT3 comparative model and a mechanosensitive ion channel [PDB (Protein Data Bank) code 1MSL] solved by X-ray diffraction. On the whole, the experimental evidence and computer simulation data favour a transport inhibition mechanism in which flavonoids and GLUT4 interact directly, rather than by a mechanism related to protein-tyrosine kinase and insulin signalling inhibition. Furthermore, the results suggest that GLUT transporters are involved in flavonoid incorporation into cells.

scholarly journals Regulation of c-Fes Tyrosine Kinase and Biological Activities by N-Terminal Coiled-Coil Oligomerization Domains

1999 ◽  
Vol 19 (12) ◽  
pp. 8335-8343 ◽  
Author(s):  
Haiyun Cheng ◽  
Jim A. Rogers ◽  
Nancy A. Dunham ◽  
Thomas E. Smithgall
Keyword(s):  
Tyrosine Kinase ◽  
Mammalian Cells ◽  
Protein Tyrosine Kinase ◽  
Biological Activities ◽  
Coiled Coil ◽  
Protein Tyrosine ◽  
Coiled Coil Domain ◽  
Fibroblast Transformation

ABSTRACT The cytoplasmic protein-tyrosine kinase Fes has been implicated in cytokine signal transduction, hematopoiesis, and embryonic development. Previous work from our laboratory has shown that active Fes exists as a large oligomeric complex in vitro. However, when Fes is expressed in mammalian cells, its kinase activity is tightly repressed. The Fes unique N-terminal sequence has two regions with strong homology to coiled-coil-forming domains often found in oligomeric proteins. Here we show that disruption or deletion of the first coiled-coil domain upregulates Fes tyrosine kinase and transforming activities in Rat-2 fibroblasts and enhances Fes differentiation-inducing activity in myeloid leukemia cells. Conversely, expression of a Fes truncation mutant consisting only of the unique N-terminal domain interfered with Rat-2 fibroblast transformation by an activated Fes mutant, suggesting that oligomerization is essential for Fes activation in vivo. Coexpression with the Fes N-terminal region did not affect the transforming activity of v-Src in Rat-2 cells, arguing against a nonspecific suppressive effect. Taken together, these findings suggest a model in which Fes activation may involve coiled-coil-mediated interconversion of monomeric and oligomeric forms of the kinase. Mutation of the first coiled-coil domain may activate Fes by disturbing intramolecular coiled-coil interaction, allowing for oligomerization via the second coiled-coil domain. Deletion of the second coiled-coil domain blocks fibroblast transformation by an activated form of c-Fes, consistent with this model. These results provide the first evidence for regulation of a nonreceptor protein-tyrosine kinase by coiled-coil domains.

Protein-tyrosine Kinase p72 syk Is Activated by Platelet Activating Factor in Platelets

1994 ◽  
Vol 72 (06) ◽  
pp. 937-941 ◽  
Author(s):  
Karim Rezaul ◽  
Shigeru Yanagi ◽  
Kiyonao Sada ◽  
Takanobu Taniguchi ◽  
Hirohei Yamamura
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Platelet Activating Factor ◽  
Kinase Assay ◽  
Potential Candidate ◽  
Protein Tyrosine ◽  
Induced Aggregation

SummaryIt has been demonstrated that activation of platelets by platelet-activating factor (PAF) results in a dramatic increase in tyrosine phosphorylation of several cellular proteins. We report here that p72 syk is a potential candidate for the protein-tyrosine phosphorylation following PAF stimulation in porcine platelets. Immunoprecipitation kinase assay revealed that PAF stimulation resulted in a rapid activation of p72 syk which peaked at 10 s. The level of activation was found to be dose dependent and could be completely inhibited by the PAF receptor antagonist, CV3988. Phosphorylation at the tyrosine residues of p72 syk coincided with activation of yllsyk. Pretreatment of platelets with aspirin and apyrase did not affect PAF induced activation of p72 syk .Furthermore, genistein, a potent protein-tyrosine-kinase inhibitor, diminished PAF-induced p72 syk activation and Ca2+ mobilization as well as platelet aggregation. These results suggest that p72 syk may play a critical role in PAF-induced aggregation, possibly through regulation of Ca2+ mobilization.

scholarly journals Protein tyrosine phosphatase receptor type C (PTPRC or CD45)

2021 ◽  
pp. jclinpath-2020-206927
Author(s):  
Maryam Ahmed Al Barashdi ◽  
Ahlam Ali ◽  
Mary Frances McMullin ◽  
Ken Mills
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Protein Tyrosine Kinase ◽  
Biological Activities ◽  
Tyrosine Phosphatase ◽  
Cell Types ◽  
Receptor Type ◽  
Future Research ◽  
Protein Tyrosine ◽  
Type C ◽  
Almost All

The leucocyte common antigen, protein tyrosine phosphatase receptor type C (PTPRC), also known as CD45, is a transmembrane glycoprotein, expressed on almost all haematopoietic cells except for mature erythrocytes, and is an essential regulator of T and B cell antigen receptor-mediated activation. Disruption of the equilibrium between protein tyrosine kinase and phosphatase activity (from CD45 and others) can result in immunodeficiency, autoimmunity, or malignancy. CD45 is normally present on the cell surface, therefore it works upstream of a large signalling network which differs between cell types, and thus the effects of CD45 on these cells are also different. However, it is becoming clear that CD45 plays an essential role in the innate immune system and this is likely to be a key area for future research. In this review of PTPRC (CD45), its structure and biological activities as well as abnormal expression of CD45 in leukaemia and lymphoma will be discussed.

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