Gene/Protein Disease Symptom Drug Enzyme Compound
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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Semaphorin 3A (Sema3A) is a secreted disulfide-bound homodimeric molecule that induces growth cone collapse and repulsion of axon growth in the nervous system. Recently, it has been demonstrated that Sema3A is produced by endothelial cells and inhibits integrin function in an autocrine fashion. In this study, we investigated the effects of Sema3A on platelet function by using 2 distinct human Sema3A chimera proteins. We detected expression of functional Sema3A receptors in platelets and dose-dependent and saturable binding of Sema3A to platelets. Sema3A dose-dependently inhibited activation of integrin alphaIIbbeta3 by all agonists examined including adenosine diphosphate (ADP), thrombin, convulxin, phorbol 12-myristate 13-acetate, and A23187. Sema3A inhibited not only platelet aggregation induced by thrombin or collagen but also platelet adhesion and spreading on immobilized fibrinogen. Moreover, Sema3A impaired alphaIIbbeta3-independent spreading on glass coverslips and aggregation-independent granular secretion. Sema3A inhibited agonist-induced elevation of filamentous action (F-actin) contents, phosphorylation of cofilin, and Rac1 activation. In contrast, Sema3A did not affect the levels of cyclic nucleotides or agonist-induced increase of intracellular Ca2+ concentrations. Thus, the extensive inhibition of platelet function by Sema3A appears to be mediated, at least in part, through impairment of agonist-induced Rac1-dependent actin rearrangement.
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PMID:Negative regulation of platelet function by a secreted cell repulsive protein, semaphorin 3A. 1583 6

We established a phosphatidylserine (PS)/phosphatidylcholine (PC) microvesicles-induced preeclampsia-like model in mice. PS/PC were prepared by mixing 80% PC and 20% PS, and suspended in 0.05 M Tris-HCl at a concentration of 10 mg/mL. One hundred microliters of PS/PC (n = 6) and saline as a control (n = 10) were injected in tail veins of Institute of Cancer Research (ICR) mice every day from days 5.5 to 16.5 of pregnancy. Systolic blood pressure (SBP) was measured by means of the tail-cuff method. On day 17.5, the mice were anesthetized by diethyl ether and euthanized with the collapse of the circulation by drawing blood from the heart. The animals were dissected and the fetuses and placentas removed. Fetal weight and placental weight were evaluated. Plasma antithrombin activity (AT), thrombin-antithrombin complex (TAT), platelet counts, and proteinuria were measured on day 17.5. Placentas were fixed in 4% paraformaldehyde for histologic studies. Statistical analysis was evaluated by analysis of variance and Welch's t-test. Mice injected with PS/PC showed a significant elevation in SBP (124 versus 101 mm Hg; p < 0.001), a significant increase in TAT levels (23 versus 6.6 mug/L; p < 0.05), a significant decrease in platelet counts (88 versus 102 x 10 (10)/L; p < 0.05), a decrease in AT, an increase in proteinuria, and a significant reduction in fetal weight (1.2 versus 1.3 g; p < 0.0001) and placental weight (0.13 versus 0.15 g; p < 0.001), compared with controls. Placentas of mice injected with PS/PC showed diffuse fibrin depositions in the labyrinth layer. We have demonstrated that the artificial PS/PC vesicles induce intrauterine growth restriction with elevations of SBP. The elevation of plasma TAT and the diffuse fibrin depositions in the placentas indicate enhanced thrombin formation, and the significant elevations of SBP indicate preeclampsia-like changes that can be induced by hypercoagulation in the placenta.
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PMID:Phosphatidylserine/phosphatidylcholine microvesicles can induce preeclampsia-like changes in pregnant mice. 1605 3

Allostery is a common mechanism of regulation of enzyme activity and specificity, and its signatures are readily identified from functional studies. For many allosteric systems, structural evidence exists of long-range communication among protein domains, but rarely has this communication been traced to a detailed pathway. The thrombin mutant D102N is stabilized in a self-inhibited conformation where access to the active site is occluded by a collapse of the entire 215-219 beta-strand. Binding of a fragment of the protease activated receptor PAR1 to exosite I, 30-A away from the active site region, causes a large conformational change that corrects the position of the 215-219 beta-strand and restores access to the active site. The crystal structure of the thrombin-PAR1 complex, solved at 2.2-A resolution, reveals the details of this long-range allosteric communication in terms of a network of polar interactions.
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PMID:Structural identification of the pathway of long-range communication in an allosteric enzyme. 1825 Mar 35

Various haemostasis disorders can occur following snakebite. Almost all ophidian species that are responsible for serious, even lethal, human envenomations are concerned. Venoms of these snakes are rich in proteins interfering with haemostasis, including many enzymes. These proteins can be classified in four groups according to their action. The haemorrhagins induce capillary permeability disorders. The proteins disturbing the primary haemostasis can activate as well as inhibit platelets: phospholipases A2, serine proteases and metalloproteinases, L-amino-acido-oxydases, phosphoesterases, disintegrins, C-type lectins, dendropeptin, agregoserpentin, thrombolectin. The proteins interfering with coagulation are separated into procoagulant proteases (prothrombin activator, thrombin-like enzymes, factor X and factor V activators) and anticoagulant proteases (factor IX and X inhibitors, protein C activator, anticoagulant phospholipases A2). The venom components acting on fibrinolysis are the fibrinolytic enzymes and the plasminogene activators. The clinical consequence of these mechanisms is a local as well as diffuse haemorrhagic syndrome. A hypofibrinogenemy, even an afibrinogenemy is frequently noted. Other haemostasis parameters are disturbed: PT collapse, a patient's ACT several times higher than the control and non-systematic thrombopenia. Ophidian venoms take part in many medical, diagnostic or therapeutic, applications in medicine. Currently, the antivenomous immunotherapy is the only efficient treatment in these haemorrhagic disorders.
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PMID:[Haemostasis disorders caused by snake venoms]. 1842 Mar 71

The induction of neurite retraction and growth cone collapse via G-protein-coupled receptors is involved in developmental as well as regenerative processes. The role of individual G-protein-mediated signaling processes in the regulation of neurite morphology is still incompletely understood. Using primary neurons from brains lacking Galpha(q)/Galpha(11) or Galpha(12)/Galpha(13), we show here that G(12)/G(13)-mediated signaling is absolutely required for neurite retraction and growth cone collapse induced by the blood-borne factors lysophosphatidic acid and thrombin. Interestingly, the effects of lysophosphatidic acid were mediated mainly by G(13), whereas thrombin effects required G(12). Surprisingly, lack of Galpha(q)/Galpha(11) resulted in overshooting responses to both stimuli, indicating that G(q)/G(11)-mediated signaling most likely via activation of Rac antagonizes the effects of G(12)/G(13).
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PMID:Antagonistic regulation of neurite morphology through Gq/G11 and G12/G13. 1885 20

The G alpha subunits of the G(12) family of heterotrimeric guanine nucleotide-binding proteins (G proteins), defined by G alpha(12) and G alpha(13), have many cellular functions in common, including stimulation of stress fiber formation and focal adhesion assembly via the small GTPase RhoA activation. We and others previously showed that G alpha(12) and G alpha(13) mediate neurite retraction in neuronal cell lines, but their roles in primary cultured neurons have not been adequately understood. Here, we found that expression of constitutively active mutants of G alpha(12) or G alpha(13) caused growth cone collapse dependent on Rho-kinase activity in hippocampal neurons. The stimulation of thrombin and lysophosphatidic acid (LPA) receptors, which have been thought to selectively couple to G alpha(12) and G alpha(13), respectively, caused growth cone collapse and suppressed axon branching dependent on Rho-kinase activity in hippocampal neurons. Thrombin- and LPA-induced growth cone collapse was suppressed by both single knockdown of G alpha(12) and G alpha(13) with short hairpin RNAs and this suppression was augmented by double knockdown of both G alpha(12) and G alpha(13). These results suggest that thrombin and LPA receptors couple to both G alpha(12) and G alpha(13) for growth cone collapse.
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PMID:Lysophosphatidic acid and thrombin receptors require both G alpha12 and G alpha13 to regulate axonal morphology in hippocampal neurons. 1904 2

Obstetric crisis includes hemorrhagic shock, embolisms and difficult airway. Life will be rapidly threatened with disseminated intravascular coagulation, multiple organ failure or systemic inflammatory response syndrome in these crises. In the face of the crisis, repeated evaluation of parturients and differential diagnosis are necessary along with fetal heart monitoring. For evaluation of bleeding, one should notice that the visual estimation of vaginal bleeding does not reflect the extent of intravascular volume deficit. Treatments for hemorrhagic shock include fluid replacement, blood transfusion as well as fresh frozen plasma, platelet, anticoagulants, anti-thrombin III, and protease inhibitors. When bleeding is still uncontrollable, arterial embolization or hysterectomy will be considered. Embolic disorders are another cause of maternal mortality. The signs and symptoms are all similar (dyspnea, cyanosis and sudden cardiovascular collapse). Strategies against the embolism will be basically symptomatic therapy. The physiological change with pregnancy results in the need of careful pre-anesthetic airway evaluation for parturients. A difficult or failed intubation drill is also extremely important. Recently, laryngeal mask airway has been successfully used in these parturients. During resuscitation of a pregnant woman, left uterine displacement is essential. For a patient who has not responded after 4 to 5 minutes of ACLS, immediate cesarean delivery should be considered.
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PMID:[Crisis management during obstetric surgery]. 1946 96

Bleeding head injury is associated with gastric stasis, a symptom of collapse of autonomic control of the gut described by Cushing around 1932. Recent work suggests that the proteinase thrombin, produced secondary to bleeding, may be the root cause. Results from our in vivo physiological studies show that fourth ventricular injection of PAR1 agonists, as well as thrombin itself, produced significant reductions in gastric transit in the awake rat. We expected that the PAR1 effect to inhibit gastric transit was the result of direct action on vagovagal reflex circuitry in the dorsal medulla. Surprisingly, our immunohistochemical studies demonstrated that PAR1 receptors are localized exclusively to the astrocytes and not the neurons in the nucleus of the solitary tract (NST; principal locus integrating visceral afferent input and part of the gastric vagovagal reflex control circuitry). Our in vitro calcium imaging studies of hindbrain slices revealed that PAR1 activation initially causes a dramatic increase in astrocytic calcium, followed seconds later by an increase in calcium signal in NST neurons. The neuronal effect, but not the astrocytic effect, of PAR1 activation was eliminated by glutamate receptor antagonism. TTX did not eliminate the effects of PAR1 activation on either glia or neurons. Thus, we propose that glia are the primary CNS sensors for PAR agonists and that the response of these glial cells drives the activity of adjacent (e.g., NST) neurons. These results show, for the first time, that changes in autonomic control can be directly signaled by glial detection of local chemical stimuli.
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PMID:Proteinase-activated receptors in the nucleus of the solitary tract: evidence for glial-neural interactions in autonomic control of the stomach. 1962 19

Oncolytic viruses (OVs) have been engineered or selected for cancer cell-specific infection however, we have found that following intravenous administration of vesicular stomatitis virus (VSV), tumor cell killing rapidly extends far beyond the initial sites of infection. We show here for the first time that VSV directly infects and destroys tumor vasculature in vivo but leaves normal vasculature intact. Three-dimensional (3D) reconstruction of infected tumors revealed that the majority of the tumor mass lacks significant blood flow in contrast to uninfected tumors, which exhibit relatively uniform perfusion. VSV replication in tumor neovasculature and spread within the tumor mass, initiates an inflammatory reaction including a neutrophil-dependent initiation of microclots within tumor blood vessels. Within 6 hours of intravenous administration of VSV and continuing for at least 24 hours, we observed the initiation of blood clots within the tumor vasculature whereas normal vasculature remained clot free. Blocking blood clot formation with thrombin inhibitors prevented tumor vascular collapse. Our results demonstrate that the therapeutic activity of an OV can go far beyond simple infection and lysis of malignant cells.
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PMID:Targeting tumor vasculature with an oncolytic virus. 2136 41

Trypsin-like proteases (TLPs) are a large family of enzymes responsible for digestion, blood coagulation, fibrinolysis, development, fertilization, apoptosis and immunity. A current paradigm posits that the irreversible transition from an inactive zymogen to the active protease form enables productive interaction with substrate and catalysis. Analysis of the entire structural database reveals two distinct conformations of the active site: one fully accessible to substrate (E) and the other occluded by the collapse of a specific segment (E*). The allosteric E*-E equilibrium provides a reversible mechanism for activity and regulation in addition to the irreversible zymogen to protease conversion and points to new therapeutic strategies aimed at inhibiting or activating the enzyme. In this review, we discuss relevant examples, with emphasis on the rational engineering of anticoagulant thrombin mutants.
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PMID:Allostery in trypsin-like proteases suggests new therapeutic strategies. 2172 12


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