Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.2 (focal adhesion kinase)
 44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated mechanisms involved in integrin-mediated signal transduction in platelets by examining integrin-dependent phosphorylation and activation of a newly identified protein tyrosine kinase, pp125FAK (FAK, focal adhesion kinase). This kinase was previously shown to be localized in focal adhesions in fibroblasts, and to be phosphorylated on tyrosine in normal and Src-transformed fibroblasts. We show that thrombin and collagen activation of platelets causes an induction of tyrosine phosphorylation of pp125FAK and that pp125FAK molecules isolated from activated platelets display enhanced levels of phosphorylation in immune-complex kinase assays. pp125FAK was not phosphorylated on tyrosine after thrombin or collagen treatment of Glanzmann's thrombasthenic platelets deficient in the fibrinogen receptor GPIIb-IIIa, or of platelets pretreated with an inhibitory monoclonal antibody to GP IIb-IIIa. Fibrinogen binding to GP IIb-IIIa was not sufficient to induce pp125FAK phosphorylation because pp125FAK was not phosphorylated on tyrosine in thrombin-treated platelets that were not allowed to aggregate. These results indicate that tyrosine phosphorylation of pp125FAK is dependent on platelet aggregation mediated by fibrinogen binding to the integrin receptor GP IIb-IIIa. The induction of tyrosine phosphorylation of pp125FAK was inhibited in thrombin- and collagen-treated platelets preincubated with cytochalasin D, which prevents actin polymerization following activation. Under all of these conditions, there was a strong correlation between the induction of tyrosine phosphorylation of pp125FAK in vivo and stimulation of the phosphorylation of pp125FAK in vitro in immune-complex kinase assays. This study provides the first genetic evidence that tyrosine phosphorylation of pp125FAK is dependent on integrin-mediated events, and demonstrates that there is a strong correlation between tyrosine phosphorylation of pp125FAK in platelets, and the activation of pp125FAK-associated phosphorylating activity in vitro.
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PMID:Integrin-dependent phosphorylation and activation of the protein tyrosine kinase pp125FAK in platelets. 138 45

The platelet aggregatory effect of heparin was investigated with whole blood aggregometry in blood from healthy volunteers with collagen as activator. Tests were performed before and 3 hours after 0.5 g acetylsalicylic acid given perorally. Three protocols were tested. In the first experiment and before acetylsalicylic acid low doses (2.5 and 5 IU/ml) of heparin and low molecular weight heparin (LMW-heparin) did not affect aggregation while higher doses (25 and 250 IU/ml) had an antiaggregatory effect (p less than 0.0001). After acetylsalicylic acid, and with the same amount of collagen as before acetylsalicylic acid, aggregation decreased by 82 +/- 4%. Both heparin and LMW-heparin increased the aggregation (p less than 0.05). In the second experiment the collagen dose was titrated to give a similar light to moderate degree of aggregation before as compared to after acetylsalicylic acid. Low doses of heparin (p less than 0.01) but not hirudin increased the aggregation to the same degree before and after acetylsalicylic acid. In the third experiment the RGDS peptide (ARG-GLY-ASP-SER), a blocker of GPIIb/IIIa platelet receptor dose dependently inhibited platelet aggregation by 93 +/- 17%. With added RGDS peptide heparin still increased aggregation (p less than 0.001). In conclusion, with whole blood aggregometry both heparin and LMW-heparin but not the specific thrombin inhibitor hirudin stimulated platelet aggregation before and after acetylsalicylic acid ingestion. The heparin aggregatory effect was not inhibited by the RGDS peptide implying platelet activation via non specific mechanisms. These heparin effects could be of clinical importance for the treatment of arterial thromboembolic disease.
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PMID:Heparin and low molecular weight heparin but not hirudin stimulate platelet aggregation in whole blood from acetylsalicylic acid treated healthy volunteers. 165 47

In pulmonary fibrosis the connective tissue framework and the mechanical properties of the lung are profoundly altered. Changes in amounts or distributions of each component of lung tissue (collagen, elastin, and ground substance such as glycosaminoglycans) might be expected to produce changes in viscoelastic properties of lung parenchyma and lead to mechanical inefficiency of the lungs. In order to evaluate the viscoelastic properties of the alveolar wall of fibrotic lungs, we analysed stress relaxation curves (SRL) of lung tissue in hamsters. Golden hamsters were divided into two groups: control (group C) and a group treated intratracheally with bleomycin (group B). Small piece of the alveolar wall tissue (80 x 80 x 1000 microns) was extended, and SRC was recorded for 3 minutes at the fixed extended length. Relaxation times (Tm) were used as indices of tissue viscoelastic properties. Three different Tm (Tm1: short, Tm2: moderate, and Tm3: long relaxation times) were obtained using the method of residuals. In group B, Tm3 (long relaxation time) was significantly larger than Tm3 in the other. Our results in relaxation time suggested that alveolar walls become more viscous with fibrosis. This rise in tissue viscosity with fibrosis may have been due to altered properties of the increased elastic fibers.
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PMID:[Viscoelastic properties of the alveolar wall in experimental pulmonary fibrosis]. 258 99

The effect of photodynamic therapy on the tumor microvasculature in the first few hours after treatment was studied at the light and electron microscopy levels. BALB/c mice with EMT-6 tumor received ip injections of hematoporphyrin derivative, chlorin, or phthalocyanine, and 24 hours later, the tumors were treated with light at 100 J/cm2 at the appropriate therapeutic wavelength for each photosensitizer. Animals were killed and their tumors removed at time 0, 30 minutes, 1 hour, and 2, 4, 6, 8, 12, 16, and 24 hours after treatment. The results indicate that for all three sensitizers the effects of photodynamic therapy leading to rapid necrosis of tumor tissue are not the result of direct tumor cell kill but are secondary to destruction of the tumor microvasculature. The first observable signs of destruction occur in the subendothelial zone of the tumor capillary wall. This zone, composed of dense collagen fibers and other connective tissue elements, is destroyed in the first few hours after phototherapy. However, the ultrastructural changes seen in this zone are different for the hematoporphyrin derivative, compared with chlorin and phthalocyanine. Binding of photosensitizers to the elements in this zone as well as altered permeability and transport through the endothelial cell layer because of the increased intraluminal pressure may be key features of tumor destruction.
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PMID:Mechanism of tumor destruction following photodynamic therapy with hematoporphyrin derivative, chlorin, and phthalocyanine. 297 28

Von Willebrand's disease (vWD), one of the most frequent hereditary bleeding disorders, is associated with a deficiency or a defective structure of von Willebrand factor (vWF). The defect is transmitted by autosomal inheritance. vWF is a plasma glycoprotein which mediates platelet adherence to the subendothelium of the injured blood vessel and is thus indispensable for primary hemostasis. vWF is composed of identical subunits linked together by disulfide bridges. Each subunit contains binding site(s) for factor VIII, collagen and platelets. The highly polymeric vWF factor is the largest known plasma protein. Functional activity is preferentially associated with the largest multimeric forms of vWF. Binding of vWF onto collagen fibrils activates its platelet binding sites, which are apparently not accessible in circulating vWF. Aggregation of washed fixed platelets in the presence of ristocetin or collagen is used for assessment of vWF's biological activity. Important additional information for the diagnosis of vWD is provided by the antigen assay and by electrophoretic analysis of the multimeric pattern of vWF. In type I vWD, all polymeric forms of vWF are reduced in the same proportion, while only the largest, i.e. the most active, multimers are deficient in type II vWD. The most severe type III vWD is characterized by an undetectable concentration of vWF. DDAVP corrects the prolonged bleeding time in patients with mild forms of vWD. Cryoprecipitate or "virus inactivated" factor VIII concentrates are employed for substitution therapy. Our results suggest that the newly introduced "virus inactivated" factor VIII concentrate from SRK is likewise suitable for this purpose.
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PMID:[Von Willebrand's disease]. 312 18

The purpose of this study was to evaluate the effect of increased arginine levels in intravenous hyperalimentation (IVH) therapy on wound healing and thymic immune function. Groups of SD rats, 275-325 g, underwent placement of internal jugular catheter, 7-cm dorsal skin wounding, insertion of polyvinyl alcohol sponges subcutaneously, and closure of wounds with stainless-steel sutures. Twenty-four hours later, rats were started on IVH at a rate of 0.8-1 ml/100 g body wt/hr. All IVH solutions contained 20% dextrose, adequate amounts of minerals and vitamins, and two different amino acid mixtures: (A) Fre III (4.05 g ARG/liter) (n = 13); (B) experimental (7.50 g ARG/liter) (n = 11). Solutions were isonitrogenous, and contained similar amounts of essential amino acids. After 7 days of IVH, weight gain did not differ between the two groups; however, cumulative N balance was superior in group A. Wound healing was improved in group B as assessed by fresh wound strip breaking strength, fixed breaking strength, and the amount of reparative collagen deposition as assessed by the hydroxyproline content of the implanted sponges. Group B animals also had improved thymic function as assessed by thymic weight, the total number of thymic lymphocytes/gland and mitogenic reactivity of thymic lymphocytes to PHA and Con A. The experiments indicate that high arginine levels in IVH solutions improve wound healing and thymic immune function following injury.
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PMID:Intravenous hyperalimentation with high arginine levels improves wound healing and immune function. 392 66

Supplemental dietary arginine HCl (ARG-HCl) minimizes immediate post-wounding weight loss, accelerates wound healing, and is thymotropic for uninjured and wounded rats. The present experiments were to determine if arginine-pituitary interactions underlie these effects because arginine is a growth hormone secretagogue. Effects of 1% dietary ARG-HCl supplements (0.5% added to a regular commercial rat diet containing 1.8% ARG, 0.5% in drinking water) were studied in (a) hypophysectomized (hypox) rats supplemented with ACTH, L-thyroxine, testosterone propionate, (b) such hypox rats additionally supplemented with bovine growth (hypox + bGH) hormone, (c) intact rats (Int), and (d) intact rats supplemented with growth hormone (Int. bGH). Group (a) hypox rats healed their wounds as rapidly as intact rats (dorsal skin incision breaking strength, accumulation of reparative collagen in sc polyvinyl alcohol sponges). Group (b) hypox, bGH rats showed increased wound breaking strength and accumulation of reparative collagen in the sc sponges to levels significantly greater than those of intact controls; bGH given to intact controls did not affect these indices of wound healing. Supplemental ARG-HCl given intact rats significantly minimized immediate postoperative weight loss, increased wound breaking strength and sponge reparative collagen accumulation, and increased thymic weight. None of these effects of supplemental ARG-HCl were observed in group (a) hypox rats or group (b) hypox + bGH rats. We conclude that an intact hypothalamic-pituitary axis is necessary for these beneficial effects of supplemental ARG-HCl given wounded rats.
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PMID:Wound healing and thymotropic effects of arginine: a pituitary mechanism of action. 684 17

Collagen-induced polyarthritis in rats is a new experimental model that shares clinical and histologic features with adjuvant arthritis. To determine whether collagen-induced arthritis is a form of adjuvant disease and to further exclude contamination of collagen with an adjuvant substance, native type II collagen was studied for adjuvant properties. IgM and IgG PFC activity and PBMC [3H]TdR incorporation were studied in rats after injection with TNP-OA combined with IFA, IFA and CII, or CFA. In general, humoral and CMI responses to TNP-OA were lower in rats injected with IFA/CII compared with those with IFA; the presence of CII during primary immunization failed to significantly enhance PFC activity to TNP after a boost. CFA-injected rats gave maximal values in both studies. Mice pretreated with BII in the absence of oil gave PFC responses below control after sensitization with SRC. Furthermore, CII was unable to replace mycobacteria in the induction of EAE in rats and was devoid of mitogenic or polyclonal stimulatory properties. It is concluded that collagen-induced arthritis is a distinct entity from adjuvant arthritis and is dependent upon the unique immunogenicity of type II collagen in rats rather than upon an adjuvant effect.
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PMID:Collagen-induced polyarthritis in rats: a study of native type II collagen for adjuvant activity. 698 10

Platelet glycoprotein (GP) VI is a so-far uncharacterized 62-kDa membrane protein, whose deficiency results in selective impairment in collagen-induced platelet aggregation. Our group previously reported a human polyclonal antibody (anti-p62 IgG) that induces activation of normal, but not of GPVI-deficient, platelets in an Fc-independent manner. The F(ab')2 fragments of this antibody (F(ab')2-anti-p62) stimulated tyrosine phosphorylation of numerous proteins, which was not prevented even in the presence of cAMP-increasing agents such as prostacyclin. Pretreatment of platelets with the protein-tyrosine kinase (PTK) inhibitor tyrphostin A47 completely abolished F(ab')2-anti-p62-induced platelet aggregation in parallel with dose-dependent inhibition of protein-tyrosine phosphorylation, indicating an essential requirement of PTK activity for generating GPVI-mediated signaling. We found that two cytosolic PTKs, c-Src and Syk, became rapidly activated in response to F(ab')2-anti-p62 in a way insensitive to elevation of cAMP. In contrast, in the presence of prostacyclin, F(ab')2-anti-p62 did not stimulate tyrosine phosphorylation of the focal adhesion kinase. cAMP-insensitive activation of c-Src and Syk was also observed in collagen but not thrombin-stimulated platelets. Moreover, either F(ab')2-anti-p62 or collagen stimulated cAMP-insensitive tyrosine phosphorylation of phospholipase C-gamma 2. These results indicate that the receptor-mediated activation of several PTKs in platelets is regulated through a cAMP-sensitive or -insensitive mechanism depending on the nature of each stimulus, and also suggest that GPVI engagement is coupled to cAMP-insensitive activation of c-Src and Syk accompanied by tyrosine phosphorylation of numerous substrates including phospholipase C-gamma 2 in a manner similar to collagen stimulation.
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PMID:Cyclic AMP-insensitive activation of c-Src and Syk protein-tyrosine kinases through platelet membrane glycoprotein VI. 749 87

Both genetic and descriptive studies have implicated the c-kit receptor and its ligand, KL, in the process of oocyte growth in the postnatal mouse ovary. In order to test the hypothesis that KL is an oocyte growth factor, we used an oocyte culture system to study its effects in vitro. Initial experiments established that both ovarian c-kit and KL are biologically active. An immune complex kinase assay demonstrated that ovarian c-kit, found primarily on oocytes, has autophosphorylation activity, and a bone marrow-derived mast cell coculture assay indicated that granulosa cells produce functional KL. The addition of 10 ng/ml KL to growing follicles cultured in collagen gels resulted in a 67% increase in the rate of oocyte growth, and a doubling of the rate was achieved at around 50 ng/ml. ACK2, a monoclonal antibody against c-kit, severely inhibited the growth of late fetal and neonatal oocytes in coculture with ovarian cells and had less effect on growing oocytes cultured in follicles from 10- to 11-day-old mice. Genistein, an inhibitor of tyrosine kinases, including c-kit, blocked oocyte growth and disrupted follicle morphology. In initial studies on the regulation of KL production in granulosa cells, we found that both dibutyryl cyclic AMP and growing oocytes were able to induce increased KL mRNA accumulation in granulosa cell monolayers as assessed by Northern analysis. These studies demonstrate that c-kit and KL are required for maintenance of oocyte growth in vitro.
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PMID:The ligand of the c-kit receptor promotes oocyte growth. 750 47


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