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Proteolytic Activation (proteolytic + activation)

Distribution by Scientific Domains

Chemistry	62%
Medical Sciences	25%

Selected Abstracts

Proteolytic activation and function of the cytokine Spätzle in the innate immune response of a lepidopteran insect, Manduca sexta

FEBS JOURNAL, Issue 1 2010
Chunju An
The innate immune response of insects includes induced expression of genes encoding a variety of antimicrobial peptides. The signaling pathways that stimulate this gene expression have been well characterized by genetic analysis in Drosophila melanogaster, but are not well understood in most other insect species. One such pathway involves proteolytic activation of a cytokine called Spätzle, which functions in dorsal,ventral patterning in early embryonic development and in the antimicrobial immune response in larvae and adults. We have investigated the function of Spätzle in a lepidopteran insect, Manduca sexta, in which hemolymph proteinases activated during immune responses have been characterized biochemically. Two cDNA isoforms for M. sexta Spätzle-1 differ because of alternative splicing, resulting in a 10 amino acid residue insertion in the pro-region of proSpätzle-1B that is not present in proSpätzle-1A. The proSpätzle-1A cDNA encodes a 32.7 kDa polypeptide that is 23% and 44% identical to D. melanogaster and Bombyx mori Spätzle-1, respectively. Recombinant proSpätzle-1A was a disulfide-linked homodimer. M. sexta hemolymph proteinase 8 cleaved proSpätzle-1A to release Spätzle-C108, a dimer of the C-terminal 108 residue cystine-knot domain. Injection of Spätzle-C108, but not proSpätzle-1A, into larvae stimulated expression of several antimicrobial peptides and proteins, including attacin-1, cecropin-6, moricin, lysozyme, and the immunoglobulin domain protein hemolin, but did not significantly affect the expression of two bacteria-inducible pattern recognition proteins, immulectin-2 and ,-1,3-glucan recognition protein-2. The results of this and other recent studies support a model for a pathway in which the clip-domain proteinase pro-hemolymph proteinase 6 becomes activated in plasma upon exposure to Gram-negative or Gram-positive bacteria or to ,-1,3-glucan. Hemolymph proteinase 6 then activates pro-hemolymph proteinase 8, which in turn activates Spätzle-1. The resulting Spätzle-C108 dimer is likely to function as a ligand to activate a Toll pathway in M. sexta as a response to a wide variety of microbial challenges, stimulating a broad response to infection. Structured digital abstract ,,MINT-7295125: Spätzle 1A (uniprotkb:C8BMD1) and Spätzle 1A (uniprotkb:C8BMD1) bind (MI:0407) by comigration in gel electrophoresis (MI:0807) [source]

Proteolytic activation of internalized cholera toxin within hepatic endosomes by cathepsin D

FEBS JOURNAL, Issue 17 2005
Clémence Merlen
We have defined the in vivo and in vitro metabolic fate of internalized cholera toxin (CT) in the endosomal apparatus of rat liver. In vivo, CT was internalized and accumulated in endosomes where it underwent degradation in a pH-dependent manner. In vitro proteolysis of CT using an endosomal lysate required an acidic pH and was sensitive to pepstatin A, an inhibitor of aspartic acid proteases. By nondenaturating immunoprecipitation, the acidic CT-degrading activity was attributed to the luminal form of endosomal cathepsin D. The rate of toxin hydrolysis using an endosomal lysate or pure cathepsin D was found to be high for native CT and free CT-B subunit, and low for free CT-A subunit. On the basis of IC50 values, competition studies revealed that CT-A and CT-B subunits share a common binding site on the cathepsin D enzyme, with native CT and free CT-B subunit displaying the highest affinity for the protease. By immunofluorescence, partial colocalization of internalized CT with cathepsin D was confirmed at early times of endocytosis in both hepatoma HepG2 and intestinal Caco-2 cells. Hydrolysates of CT generated at low pH by bovine cathepsin D displayed ADP-ribosyltransferase activity towards exogenous Gs, protein suggesting that CT cytotoxicity, at least in part, may be related to proteolytic events within endocytic vesicles. Together, these data identify the endocytic apparatus as a critical subcellular site for the accumulation and proteolytic degradation of endocytosed CT, and define endosomal cathepsin D an enzyme potentially responsible for CT cytotoxic activation. [source]

Neuroprotective signal transduction in model motor neurons exposed to thrombin: G-protein modulation effects on neurite outgrowth, Ca2+ mobilization, and apoptosis ,

DEVELOPMENTAL NEUROBIOLOGY, Issue 2 2001
Irina V. Smirnova
Abstract Thrombin, the ultimate protease in the blood coagulation cascade, mediates its known cellular effects by unique proteolytic activation of G-protein-coupled protease-activated receptors (PARs), such as PAR1, PAR3, and PAR4, and a "tethered ligand" mechanism. PAR1 is variably expressed in subpopulations of neurons and largely determines thrombin's effects on morphology, calcium mobilization, and caspase-mediated apoptosis. In spinal cord motoneurons, PAR1 expression correlates with transient thrombin-mediated [Ca2+]i flux, receptor cleavage, and elevation of rest [Ca2+]i activating intracellular proteases. At nanomolar concentrations, thrombin retracts neurites via PAR1 activation of the monomeric, 21 kDa Ras G-protein RhoA, which is also involved in neuroprotection at lower thrombin concentrations. Such results suggest potential downstream targets for thrombin's injurious effects. Consequently, we employed several G-protein-specific modulators prior to thrombin exposure in an attempt to uncouple both heterotrimeric and monomeric G-proteins from motoneuronal PAR1. Cholera toxin, stimulating Gs, and lovastatin, which blocks isoprenylation of Rho, reduced thrombin-induced calcium mobilization. In contrast, pertussis toxin and mastoparan, inhibiting or stimulating Go/Gi, were found to exacerbate thrombin action. Effects on neuronal rounding and apoptosis were also detected, suggesting therapeutic utility may result from interference with downstream components of thrombin signaling pathways in human motor neuron disorders, and possibly other neurodegenerative diseases. Published 2001 John Wiley & Sons, Inc. J Neurobiol 48: 87,100, 2001 [source]

Proteolytic activation and function of the cytokine Spätzle in the innate immune response of a lepidopteran insect, Manduca sexta

A type-II , -turn, proline-containing, cyclic pentapeptide as a building block for the construction of models of the cleavage site of pro-oxytocin

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2001
Monica Dettin
Abstract Previous studies have indicated that proteolytic activation of pro-hormones and pro-proteins occurs most frequently at the level of basic amino acids arranged in doublets and that the dibasic sites are situated in or next to , -turns. Investigations utilizing synthetic peptides reproducing the N -terminal processing domain of pro-oxytocin-neurophysin have suggested a close relationship between the secondary structure of the cleavage locus and enzyme recognition, the minimal recognized sequence being the -Pro-Leu-Gly-Gly-Lys-Arg-Ala-Val-Leu- segment of the native precursor. NMR investigations and energy minimization studies have demonstrated that this sequence is organized in two type-II , -turns involving the -Pro-Leu-Gly-Gly- and -Lys-Arg-Ala-Val- sequences. To further strengthen the above reported hypothesis and to study the role of turn subtypes, a new proline containing cyclic substrate of the processing enzyme, in which the N -terminal side that comes before the Lys-Arg pair is constrained to adopt a type-II , -turn, has been synthesized. The presence of a type-II , -turn structure in this cyclic peptide model has been demonstrated by a combined NMR, CD and FT-IR absorption investigation. A preliminary study shows that PC1 is able to recognize and process our constrained substrate. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source]

Review article: Coagulation cascade and therapeutics update: Relevance to nephrology.

NEPHROLOGY, Issue 5 2009
Part 1: Overview of coagulation, history of anticoagulants, thrombophilias
SUMMARY Coagulation involves the regulated sequence of proteolytic activation of a series of zymogens to achieve appropriate and timely haemostasis in an injured vessel, in an environment that overwhelmingly favours an anticoagulant state. In the non-pathological state, the inciting event involves exposure of circulating factor VII/VIIa to extravascularly expressed tissue factor, which brings into motion the series of steps which results in amplification of the initial stimulus, culminating in the conversion of fibrinogen to fibrin and clot formation. The precisely synchronized cascade of events is counter-balanced by a system of anticoagulant mechanisms, which serve to ensure that the haemostatic effect is regulated and does not extend inappropriately. Conversely, in pathological states, these events can escape normal control mechanisms, due to either inherited or acquired defects, which lead to thrombosis. Current anticoagulant therapy, although based on medications that have been in existence for upwards of 80 years, is moving towards targeted therapy for specific coagulation factors and events in the coagulation cascade, based on the current knowledge of the main triggers and key events within the series of reactions that culminates in haemostasis. It remains to be seen whether these newer medications will become first-line therapies for thrombosis in the coming decade. This review aims to elucidate the main events within the coagulation cascade as it is currently understood to operate in vivo, with a brief discussion focusing on hypercoagulable states, and also a short review of the history of anticoagulants as they relate to this model. [source]

Vibrio cholerae cytolysin is composed of an ,-hemolysin-like core

PROTEIN SCIENCE, Issue 2 2003
Rich Olson
VCC, Vibrio cholerae cytolysin; ,HL, ,-hemolysin; LukF, leukocidin F component Abstract The enteric pathogen Vibrio cholerae secretes a water-soluble 80-kD cytolysin, Vibrio cholerae cytolysin (VCC) that assembles into pentameric channels following proteolytic activation by exogenous proteases. Until now, VCC has been placed in a unique class of pore-forming toxins, distinct from paradigms such as Staphyloccal ,-hemolysin. However, as reported here, amino acid sequence analysis and three-dimensional structure modeling indicate that the core component of the VCC toxin is related in sequence and structure to a family of hemolysins from Staphylococcus aureus that include leukocidin F and ,-hemolysin. Furthermore, our analysis has identified the channel-forming region of VCC and a potential lipid head-group binding site, and suggests a conserved mechanism of assembly and lysis. An additional domain in the VCC toxin is related to plant lectins, conferring additional target cell specificity to the toxin. [source]

Vascular and Biology 03

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue S1 2002
C. Parr
Background: Hepatocyte growth factor (HGF) elicits a number of functions that are tumourigenic and known to enhance the metastatic potential of tumour cells. HGF is produced as pro-HGF and requires proteolytic activation, by HGF activator, to evoke a biological response. The HGF inhibitors, HAI-1 and HAI-2, suppress the conversion of pro-HGF, through their interaction with HGF activator. This study quantitated the expression of HGF, its receptor and its inhibitors in breast cancer. Methods: Breast cancer tissues from patients (n = 97) were obtained with background normal tissues. RNA was extracted from these tissues, and HGF, c-Met, HAI-1 and HAI-2 expression was quantified using a real-time quantitative PCR (RTQ-PCR) techniques. Results: Levels of HGF and its receptor were found to be significantly higher in breast cancer than normal background tissues. The level of HAI-1 and 2 was also seen to be higher in tumour tissues. The mean results (copy number mL,1) are given in the Table below: In addition, patients with progressive diseases had a higher level of HGF (62.7 copies mL,1), than those with stable disease (43.8 copies mL,1), over a 5-year follow-up period. Furthermore, tumour tissues from node-positive patients expressed lower HAI-2 levels (341.3 copies mL,1), than the node-negative breast cancer tissues (1021.5 copies mL,1). Conclusions: This study has shown that the quantity of HGF, c-Met, HAI-1 and HAI-2 expressed in breast cancer tissues was significantly higher than that of background breast samples, and that the level of HGF is associated with progressive disease. [source]