Cockroach allergen serine proteinases: Isolation, sequencing and signalling via proteinase-activated receptor-2.

BACKGROUND: Allergy to the German cockroach (Blattella germanica) is a significant asthma risk factor for inner-city communities. Cockroach, like other allergens, contains trypsin-like enzyme activity that contributes to allergenicity and airway inflammation by activating proteinase-activated receptors (PARs). To date, the enzymes responsible for the proteolytic activity of German cockroach allergen have not been characterized. OBJECTIVES: We aimed to identify, isolate and characterize the trypsin-like proteinases in German cockroach allergen extracts used for clinical skin tests. For each enzyme, we sought to determine (1) its substrate and inhibitor enzyme kinetics (Km and IC50), (2) its amino acid sequence and (3) its ability to activate calcium signalling and/or ERK1/2 phosphorylation via PAR2. METHODS: Using a trypsin-specific activity-based probe, we detected three distinct enzymes that were isolated using ion-exchange chromatography. Each enzyme was sequenced by mass spectometery (deconvoluted with an expressed sequence tag library), evaluated kinetically for its substrate/inhibitor profile and assessed for its ability to activate PAR2 signalling. FINDINGS: Each of the three serine proteinase activity-based probe-labelled enzymes isolated was biochemically distinct, with different enzyme kinetic profiles and primary amino acid sequences. The three enzymes showed a 57%-71% sequence identity with a proteinase previously cloned from the American cockroach (Per a 10). Each enzyme was found to activate both Ca++ and MAPK signalling via PAR2. CONCLUSIONS AND RELEVANCE: We have identified three different serine proteinases from the German cockroach that may, via PAR2 activation, play different roles for allergen sensitization in vivo and may represent attractive therapeutic targets for asthma.

Glycosylation and the activation of proteinase-activated receptor 2 (PAR(2)) by human mast cell tryptase.

1. Human mast cell tryptase appears to display considerable variation in activating proteinase-activated receptor 2 (PAR(2)). We found tryptase to be an inefficient activator of wild-type rat-PAR(2) (wt-rPAR(2)) and therefore decided to explore the factors that may influence tryptase activation of PAR(2). 2. Using a 20 mer peptide (P20) corresponding to the cleavage/activation sequence of wt-rPAR(2), tryptase was as efficient as trypsin in releasing the receptor-activating sequence (SLIGRL.). However, in the presence of either human-PAR(2) or wt-r PAR(2) expressing cells, tryptase could only activate PAR(2) by releasing SLIGRL from the P20 peptide, suggesting that PAR(2) expressed on the cells was protected from tryptase activation. 3. Three approaches were employed to test the hypothesis that PAR(2) receptor glycosylation restricts tryptase activation. (a) pretreatment of wt-rPAR(2) expressing cells or human embryonic kidney cells (HEK293) with vibrio cholerae neuraminidase to remove oligosaccharide sialic acid, unmasked tryptase-mediated PAR(2) activation. (b) Inhibiting receptor glycosylation in HEK293 cells with tunicamycin enabled tryptase-mediated PAR(2) activation. (c) Wt-rPAR(2) devoid of the N-terminal glycosylation sequon (PAR(2)T25(-)), but not rPAR(2) devoid of the glycosylation sequon located on extracellular loop-2 (PAR(2)T224A), was selectively and substantially (>30 fold) more sensitive to tryptase compared with the wt-rPAR(2). 4. Immunocytochemistry using antisera that specifically recognized the N-terminal precleavage sequence of PAR(2) demonstrated that tryptase released the precleavage domain from PAR(2)T25(-) but not from wt-rPAR(2). 5. Heparin : tryptase molar ratios of greater than 2 : 1 abrogated tryptase activation of PAR(2)T25(-). 6. Our results indicate that glycosylation of PAR(2) and heparin-inhibition of PAR(2) activation by tryptase could provide novel mechanisms for regulating receptor activation by tryptase and possibly other proteases.

The amino acid sequence of human sperm protamine P1.

Human sperm protamines have been extracted from spermatozoa pooled from several donors, converted to their S-pyridylethylated derivatives and resolved into two major components, P1 and P2, by Bio-Rex 70 chromatography. Protamine P1 was further purified by Bio-Gel P-10 chromatography and sequenced directly on a gas phase protein sequencer for 43 residues. To complete the sequence, P1 was cleaved at methionine 36 and the C-terminal tetradecapeptide was purified by h.p.l.c. and sequenced completely. The 50 residue sequence is: (sequence see text) This sequence has a calculated molecular weight of 6674 and is homologous with four other published mammalian protamine sequences.

Human sperm protamines. Amino-acid sequences of two forms of protamine P2.

Human protamine P2 was purified to homogeneity by solubilizing whole spermatozoa in guanidinium X HCl containing 2-mercaptoethanol, alkylating the resulting protamine thiols with vinylpyridine, removing acid-insoluble material by acid dialysis and using CM-cellulose chromatography to remove non-protamine basic proteins and separate protamines P1 and P2. The P2 preparation contained two components, P2a and P2b, which were sequenced completely without being separated. The peptides obtained from thermolysin and endoproteinase Lys-C digestions were purified by reverse-phase high-pressure liquid chromatography and sequenced using a gas-phase sequencer. P2a contains 57 amino acids and has a relative molecular mass of 7636 while P2b contains 54 amino acids, which are identical to residues 4-57 of P2a, and has a relative molecular mass of 7242. Protamine P2a is approximately 50% homologous with human protamine P1. The amino acid sequence of P2a is: (sequence; see text)

Rainbow trout protamines. Amino acid sequences of six distinct proteins from a single testis.

All the protamines present in detectable amounts in a single mature testis from rainbow trout have been purified to homogeneity using acid extraction, gel filtration chromatography on Bio-Gel P-10, ion-exchange chromatography on carboxymethylcellulose and reverse-phase high-pressure liquid chromatography. Each of the six purified protamines was completely sequenced using automated gas-phase Edman degradation. Each protamine is two-thirds arginine and also contains proline, serine, valine and glycine. Three protamines also contain alanine while two contain isoleucine. Four of the protamines have 32 amino acids while the remaining two have 30. The six protamines have been classified into three families on the basis of their amino acid sequences.

Parallel contractile signal transduction pathways activated by receptors for thrombin and epidermal growth factor-urogastrone in guinea pig gastric smooth muscle: blockade by inhibitors of mitogen-activated protein kinase-kinase and phosphatidyl inositol 3'-kinase.

Using a guinea pig gastric longitudinal smooth muscle preparation, we have compared the contractile signaling pathways triggered by the thrombin receptor-activating peptide, TFLLR-NH2 (TF) and by epidermal growth factor-urogastrone (EGF). In addition to inhibitors of tyrosine kinase [tyrphostin 47/AG213, genistein and the src-selective inhibitor CP118,556/PP1], cyclooxygenase (indomethacin, INDO) and diacylglycerol lipase (U57, 908), we also used the signal pathway probe inhibitors of mitogen-activated protein-kinase-kinase (MEK:PD98059), phosphatidylinositol 3'-kinase [PI3K: Wortmannin (WM) and LY294002], protein kinase C [PKC: GF109203X (GF)], and of the EGF-receptor kinase (PD153035). We found that in addition to the inhibition of both TF and EGF-stimulated contractions by the inhibitors of tyrosine kinase, cyclooxygenase and diacylglycerol lipase, the actions of TF and EGF were also attenuated by PD98059, WM/LY294002 and GF. However, PD153035 blocked only EGF-triggered contractions. The contractile actions of both TF and EGF were dependent on extracellular calcium. In contrast, the contractile action of arachidonic acid, via a presumed cyclooxygenase product that mediated the contractions caused by both TF and EGF, was not blocked by any of the signal pathway probe inhibitors. The contractile actions of both TF and EGF were accompanied by increases in tissue phosphotyrosyl proteins and an increase in tissue c-src kinase activity. We conclude that protease-activated receptor no. 1- (thrombin receptor) mediated contractions in the logitudial muscle, like EGF receptor-activated responses, require the influx of extracellular calcium and use parallel signal pathways upstream of the cyclooxygenase step, involving MEK, PI3K, kinase C and possibly cellular src. The TF-induced response did not involve trans-activation of the EGF receptor kinase; but the converse (i.e., trans-activation of protease-activated receptor no. 1 (thrombin receptor) by the EGF receptor kinase) could not be ruled out.

Phosphorylation of caldesmon by smooth-muscle casein kinase II.

A caldesmon kinase activity was partially purified from an extract of chicken gizzard smooth muscle by sequential chromatography on columns of DEAE-Sephacel, MonoQ and Superose 12. This kinase was identified as casein kinase II by Western blotting using peptide-directed antibodies raised against the alpha, alpha' and beta subunits of human casein kinase II; the smooth muscle enzyme consisted of similar subunits of M(r) 43,000 (alpha), 39,000 (alpha'), and 27,000 (beta). Phosphorylation of caldesmon and casein by smooth muscle casein kinase II was optimal at approximately 0.1 M NaCl, did not require second messengers, and was inhibited by heparin. The kinase utilized either GTP or ATP as a substrate. Caldesmon was phosphorylated to approximately 1 mol Pi mol-1 caldesmon by smooth muscle casein kinase II with a Km for caldesmon of 4.9 microM. Two-dimensional thin-layer electrophoresis indicated phosphate incorporation into both serine and threonine. All the incorporated phosphate was recovered in the N-terminal peptide (residues 1-152) generated by cleavage at cysteine 153 with 2-nitro-5-thiocyanobenzoic acid. Purification of tryptic phosphopeptides and N-terminal sequencing revealed two principal sites of phosphorylation: serine 73 and threonine 83. The following four synthetic peptides corresponding to this domain of caldesmon were examined as substrates of casein kinase II: A = RRREVNAQNSVAEEE; B = AQNSVAEEE; C = RSTDDEAA; D = SVAEEETKRSTDDE. Interestingly, only peptides C and D were phosphorylated and both only at threonine. Phosphorylation of intact caldesmon did not affect the pattern of chymotryptic digestion suggesting that it does not induce a significant conformational change in the protein substrate. Phosphorylation also had no effect on the binding of caldesmon to actin or on the caldesmon-mediated inhibition of actomyosin MgATPase activity. However, phosphorylation completely abolished the interaction of caldesmon with immobilized smooth muscle myosin. These results are consistent with the localization of the myosin-binding domain near the N-terminus of caldesmon and of the actin-binding domain near the opposite end of the elongated molecule. Casein kinase II may therefore play a role in regulating caldesmon-myosin interaction and the ability of caldesmon to cross-link actin and myosin filaments in smooth muscle.

Purification and characterization of mouse protamines P1 and P2. Amino acid sequence of P2.

Two mouse protamines, denoted as P1 and P2, have been purified directly from mature sperm nuclei and characterized as distinct polypeptide species. The complete primary structure of P2 was determined by peptide sequencing analyses. P1 and P2 were purified by a sequence of cation-exchange chromatography on Bio-Rex 70 and permeation chromatography on Bio-Gel P10, both in the presence of guanidine hydrochloride. Biochemical analyses demonstrate P1 has a molecular weight of 7400 and is characterized by the presence of arginine, cysteine, lysine, and tyrosine. By contrast, P2 is unusual in containing an abundance of arginine, histidine, lysine, and cysteine, but no tyrosine. The primary structure of P2 was determined from the sequencing of overlapping, high-pressure liquid chromatography purified peptides generated by thermolysin and endoproteinase Lys-C digestions and by chemical cleavage at each of four serine residues. Sequence analyses have demonstrated that P2, with a molecular weight of 8841, contains 62 amino acids, in the sequence NH2-Arg-Gly-His-His-His-His-Arg-His-Arg-Arg-Cys- Ser-Arg-Lys-Arg- Leu-His-Arg-Ile-His-Lys-Arg-Arg-Arg-Ser-Cys-Arg-Arg-Arg-Arg-Arg-His-Ser- Cys-Arg - His-Arg-Arg- Arg-His-Arg-Arg-Gly-Cys-Arg-Arg-Ser-Arg-Arg-Arg-Arg-Arg-Cys-Arg-Cys-Arg- Lys-Cys - Arg-Arg- His-His-COOH. Thus, the primary structure includes six clusters of arginine and histidine, distributed throughout the polypeptide, each ranging from five to eight amino acids in length. Sequence comparisons of mouse and human protamines by the Dayhoff program have revealed greater homology exists between human P2 and mouse P2 than within the P1 family from the two mammalian species.

Increased activity, amount, and altered kinetic properties of IMP dehydrogenase from mycophenolic acid-resistant neuroblastoma cells.

Mouse wild-type neuroblastoma cells (NB cells) were stepwise selected for 10,000-fold increased resistance to mycophenolic acid (NB-Myco cells), an inhibitor of IMP dehydrogenase (IMP:NAD+ oxidoreductase, EC 1.1.1.205). IMP dehydrogenase activity was increased 25-fold, from 3.1 to 75 nmol/min.mg of protein; and a 56.7-kDa peptide was increased in abundance 200-500-fold in NB-Myco as compared to NB cells. Purification and sequence analysis confirmed that the abundant protein was IMP dehydrogenase. The stepwise selection, increased activity and protein abundance, and unstable phenotype are indirect evidence for a process of gene amplification. Kinetic findings consistent with an Ordered Bi Bi mechanism were indicative of IMP dehydrogenase having undergone mutation. The Michaelis constants were unchanged for IMP (14 and 13 microM) and increased 4-fold for NAD from 25 to 94 microM for NB and NB-Myco cells, respectively. The Ki for mycophenolic acid was increased 2400-fold from 1.4 nM to 3.4 microM for the enzyme from NB versus NB-Myco cells, and the Ki for XMP was increased 4-fold from 78 to 336 microM. Mycophenolic acid exhibited uncompetitive inhibition with IMP, consistent with the formation of a dead end E-XMP-inhibitor complex. The cellular GTP concentration was increased 2-fold in resistant cells and, upon removal of mycophenolic acid, further increased to 4.5-fold that of NB cells.

cSrc is a major cytosolic tyrosine kinase in vascular tissue.

We are interested in identifying, in vascular tissue, nonreceptor tyrosine kinases that may be responsible for the contractile actions of G-protein-coupled agonists such as angiotensin II. By using a series of chromatographic steps, including ion exchange, hydrophobic, and affinity chromatography, we have isolated a major fraction of tyrosine kinase activity from the cytosolic fraction of porcine aorta tissue. According to (i) its immunologic cross-reactivity with the monoclonal anti-cSrc antibody, m327, and with the N-terminally directed monoclonal cSrc2-17 antibody, (ii) its inhibition by the C-terminal cSrc kinase, CSK, and (iii) its specificity for phosphorylating tyrosine 15 in the cdc2(6-20) peptide kinase substrate, we conclude that the kinase we have isolated represents porcine cSrc. A substantial proportion of the enzyme (>70%) was recovered in the cytoplasmic fraction from aorta tissue. The profile of inhibition of the human and porcine cSrc enzymes by a spectrum of tyrosine kinase inhibitors (PP1 >> AG82 > AG490 approximately/= genistein > AG10) was compared with the profile of inhibition of angiotensin II mediated contraction in a porcine coronary vascular preparation (AG10 >> genistein > or = AG82 > or = AG490; PP1 inactive). The different inhibitory profiles indicated that cSrc does not represent the vascular tyrosine kinase responsible for the contractile actions of angiotensin II. We suggest, nonetheless, that cSrc plays a key role for other actions of angiotensin II in intact vascular tissue, such as the regulation of mitogen-activated protein kinase activity and gene transcription.

Proteinase-activated receptor 2 (PAR(2)): development of a ligand-binding assay correlating with activation of PAR(2) by PAR(1)- and PAR(2)-derived peptide ligands.

A cloned rat proteinase-activated receptor (PAR)(2)-expressing cell line (KNRK-rPAR(2)) was used to study the structure-activity relationships (elevated intracellular Ca(2+)) for a series of: 1) PAR(1)-derived receptor-activating ligands (PAR(1)-APs) [SFLLR (P5), SFLLR-NH(2) (P5-NH(2)), SFLLRNP (P7), SFLLRNP-NH(2) (P7-NH(2)), and TFLLR-NH(2) (TF-NH(2))] and 2) PAR(2)-derived-activating-peptides (PAR(2)-APs) [SLIGRL-NH(2) (SL-NH(2)), SLIGR-NH(2) (GR-NH(2)), and SLIGKV-NH(2) (KV-NH(2))]. The activities of the PAR-APs were compared with the PAR(2)-AP analog trans-cinnamoyl-Leu-Ile-Gly-Arg-Leu-Orn-NH(2) tc-NH(2)), which as a [(3)H]propionyl derivative ([(3)H]propionyl-tc-NH(2)) was used to develop a radioligand-binding assay for PAR(2). The relative potencies of the PAR-APs in the Ca(2+)-signaling assay were tc-NH(2) = SL-NH(2) > KV-NH(2) congruent with P5-NH(2) > GR-NH(2) > P7-NH(2) > P7 > P5 > TF-NH(2). The reverse sequence PAR-APs, LSIGRL-NH(2) (LS-NH(2)), LRGILS-NH(2) (LR-NH(2)), FSLLRY-NH(2) (FSY-NH(2)), and FSLLR-NH(2) (FS-NH(2)), as well as the Xenopus PAR(1)-AP TFRIFD-NH(2), were inactive. The relative biological potencies of the peptides were in accord with their ability to compete for the binding of [(3)H]propionyl-tc-NH(2) (tc-NH(2) = SL-NH(2) > GR-NH(2) congruent with P5-NH(2) > P5) to KNRK-rPAR(2) cells, whereas inactive peptides (FS-NH(2); LR-NH(2)) showed no appreciable binding competition. Our data therefore validate a ligand-binding assay for the use in studies of PAR(2) and indicate that the relative biological potencies of the PAR(1)-APs for activating rat PAR(2) parallel their ability to activate human PAR(1). The relative receptor-binding activities of the PAR-APs, although in general agreement with their relative biological activities, point to differences in the intrinsic receptor-activating activities between the several PAR-APs. The binding assay we have developed should prove of use for the further study of PAR(2)-ligand interactions.