Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.2.2.7 (heparinase)
 1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rab proteins are ras-like low molecular mass GTP-binding proteins, which are postulated to act as specific regulators of membrane trafficking in exocytosis and endocytosis. We have previously shown that synthetic peptides, corresponding to the effector domain of Rab3 proteins, stimulate a complete exocytotic response in mast cells. We have used a PCR-cloning strategy to investigate the presence of mRNA encoding Rab3 in mast cells. RNA based PCR was then performed on mast cell RNA using degenerate oligonucleotide primers based on two conserved sequences among Rab3 proteins. However, no PCR products were obtained, even for proteins known to be expressed in high copy numbers in mast cells (beta-actin and Fc receptor). We have found that the problem resides in the presence of mast cell secretory granule derived heparin, that copurifies with the RNA; heparin has been shown to inhibit the activity of reverse transcriptase and Taq polymerase in PCR. After treating the RNA (obtained from about 500 mast cells) with heparinase, several PCR products of varying size were obtained using primers specific for Rab3 proteins. These products were cloned and sequenced. We have found clones containing sequences that had a 100% homology at the deduced amino acid level to a portion of Rab3B and Rab3D (amino acids 16 to 83).
 ...
PMID:RT-PCR cloning of Rab3 isoforms expressed in peritoneal mast cells. 750 66

Heparin-induced thrombocytopenia represents one of the most severe drug-induced disorders of platelets. This syndrome is believed to be mediated through antibodies generated against a heparin-platelet factor 4 complex. Complexation of a sulfated mucopolysaccharide chain of heparin with a platelet granular protein (platelet factor 4) produces an allosteric modification of platelet factor 4 resulting in neoepitope formation and the generation of antiheparin-platelet factor 4 antibodies. These antibodies are capable of activating platelets by binding to heparin, platelet factor 4 and the Fc receptor on platelets, resulting in a complex pathophysiology involving ischemic, thrombotic, and inflammatory processes. To characterize this antibody, IgG fractions were obtained from the serum of patients with heparin-induced thrombocytopenia using ammonium sulphate precipitation and heparin-platelet factor 4-sepharose 4B affinity chromatography methods. With the affinity purification, two major components, peaks I and II, with high antiheparin-platelet factor 4 antibody titers were eluted. The purity of all the fractionated immunoglobulins was established by sodium dodecylsulphate-polyacrylamide gel electrophoretic analyses. While peak I did not induce 14C-serotonin release from platelets in the heparin-dependent assay for heparin-induced thrombocytopenia antibodies (14C-serotonin release assay), peak II and the IgGs obtained with the ammonium sulphate precipitation method exhibited a strong and concentration-dependent activation in the presence and absence of heparin and low molecular weight heparin. These immunoglobulins were treated with heparinase, a cationic ion-exchange resin (Heparsorb), or dialyzed to remove traces of heparin, and when tested in the 14C-serotonin release assay, showed the same high degree of activity. These data are suggestive of the generation of heparin-induced thrombocytopenia antibodies capable of activating platelets directly in a nonheparin-dependent manner. These observations underscore the complex pathophysiology of heparin-induced thrombocytopenia syndrome and suggest that the severity of this syndrome in some patients may be due to the generation of "super-active" heparin-induced thrombocytopenia antibodies capable of activating platelets without the requirement of heparin. This could explain why the cessation of heparin in patients does not necessarily correct the symptoms of heparin-induced thrombocytopenia or associated thrombosis.
 ...
PMID:Functional heterogeneity of antiheparin-platelet factor 4 antibodies: implications in the pathogenesis of the HIT syndrome. 1072 34