Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complement C1s”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1980

Proteolytic cleavage of an activated subcomponent of the first component of rabbit complement, C1s.

When rabbit C1 purified by affinity chromatography on IgG-Sepharose 6B was chromatographed on DEAE-cellulose in the presence of ethylenediaminetetraacetate, C1s was isolated as two forms, C1s(I) and C1s(II), having different molecular weights. On the other hand, incubation of the C1 with soybean trypsin inhibitor before the chromatography resulted in the isolation of C1s(I) alone, indicating that, during the purification, C1s(II) was derived from C1s(I) by proteolytic cleavage of C1s(I) by a contaminating protease, probably plasmin [EC 3.4.21.7]. In fact, C1s(I) was completely converted to C1s(II) or a C1s(II)-like fragment by highly purified plasmin. Analysis of the polypeptide chain structures revealed that C1s(I), which consisted of H and L chains with molecular weights of 70,000 and 36,000, respectively, was converted to C1s(II) by cleavage of the H chain, since C1s(II) consisted of two chains each with a molecular weight of 37,000. This conversion proceeded without any alteration in C1 esterase activity, but was accompanied by loss of the ability to form C1r-C1s complex.

Animals↗
PubMed1991

Identification of the disulfide bonds of human complement C1s.

C1s, one of the three subcomponents of C1, the first component of the complement system, is a complex serine protease. To determine the disulfide-bonding pattern, fragments of C1s were generated by cleavage with pepsin, thermolysin, or subtilisin. Disulfide bonds have been identified by several methods, for example, direct observation of the phenylthiohydantoin derivative of cystine during Edman degradation of isolated peptides and placement in the known cDNA sequence. All of the 26 half-cystines are linked in disulfide bonds occurring at positions 50-68, 120-132, 128-141, 143-156, 160-187, 219-236, 279-326, 306-339, 344-388, 371-406, 410-534, 580-603, and 613-644. All of the disulfide bonds of the earlier described substructures of C1s, the EGF-homologous part, the two SCR units, and the two domains typical for C1s and C1r are localized within these domains.

Amino Acid Sequence↗
PubMed1996

Site-directed mutagenesis of hamster complement C1S: characterization with an active form-specific antibody and possible involvement of C1S in tumorigenicity.

We have previously shown that non-transformed mouse A31 cells became tumorigenic when they were transfected with hamster C1s cDNA expression plasmid BCMGSNeoCS. In the present study, mutations were introduced into the cDNA at the activation cleavage site, Arg423(AGG) and the active center Ser617(AGC). These amino-acids were replaced by His423(CAC) and Thr617(ACC), respectively. The mutated cDNAs were inserted into BCMGSNeo and transfected to A31 and its polyoma-virus-transformed SEA7 cells. C1s produced from these transfectants lost their enzyme activity. Transfectants of these mutated C1s cDNA did not form tumors in nude mice, To distinguish between active and inactive C1s in situ, we have developed novel antibodies, one directed to the NH2-terminal neoepitope of the L chain and the other specific for uncleaved inactive C1s. These antibodies were used to characterize C1s produced by transfectants, so as to determine whether or not it was cleaved at the right position.

Amino Acid Sequence↗
PubMed1988

Domain structure, stability, and interactions of human complement C1s-: characterization of a derivative lacking most of the B chain.

A better understanding of the structure and function of C1 requires knowledge of the regions (domains) of the subcomponents that are responsible for Ca2+-dependent assembly. Toward this end, C1-s was digested with trypsin in the presence of Ca2+, a treatment that rapidly degraded the B chain, leaving a 56-kDa fragment comprised of a complete A chain disulfide linked to a small (less than 4-kDa) residual piece of the B chain. The purified fragment, referred to as C1-s-A, was shown by fast exclusion chromatography to be similar to C1-s in its ability to (1) reversibly dimerize in the presence of Ca2+, (2) substitute for C1-s in the formation of C1-r2-s2 tetramers, and (3) associate with C1-r and C1q to form macromolecular C1. Although C1-s-A was itself catalytically and hemolytically inactive, it competitively inhibited the expression of the hemolytic activity of C1-s in a reconstitution assay. When heated in the absence of Ca2+, C1-s exhibited a low-temperature transition (LTT) near 31 degrees C and a high-temperature transition (HTT) near 51 degrees C, similar to those previously observed in the homologous protein C1-r [Busby, T. F., & Ingham, K. C. (1987) Biochemistry 26, 5564-5571]. The midpoint of the LTT was shifted to 58 degrees C in 5 mM Ca2+ whereas the HTT was unaffected by Ca2+. C1-s-A exhibited only a LTT whose midpoint and Ca2+ dependence were similar to those of the LTT in C1-s. The HTT, which was accompanied by a loss of esterolytic activity, was reproduced in a plasmin-derived fragment representing the catalytic domain. These results provide strong support for the structural and functional independence of the catalytic and interaction domains of C1-s and strengthen current models regarding the role of these domains in various interactions. They also provide direct proof for the occurrence of Ca2+ binding sites on the A chain and demonstrate that all or most of the sites on C1-s that are responsible for its interaction with C1-r and C1q are located on the A chain.

Amino Acid Sequence↗
PubMed1997

Expression and characterization of a 159 amino acid, N-terminal fragment of human complement component C1s.

A 159 residue, N-terminal fragment of the human C1s complement component, C1s alpha(159), was expressed in the baculovirus, insect cell system. The protein was abundantly produced 3 days after infection, reaching levels as high as 40 microg/ml in cell culture media. It had a molecular weight of 18,100 (+/-4.9) Da by laser desorption mass spectrometry, close to the theoretical value of 18,111 Da, confirmed by sequencing. Sedimentation equilibrium and gel filtration column chromatography showed that C1s alpha(159) was a monomer in the presence of EDTA, and a dimer in the presence of Ca2+. The C1s alpha(159)2 dimer had a sedimentation coefficient of 3.1 S. When the C1s alpha(159)2 was mixed with Clq, there was little or no interaction. Likewise, unactivated C1r2 dimer had a sedimentation coefficient of 6.8 S, and when mixed with C1q little or no interaction was observed. When C1s alpha(159)2 was mixed with the 6.8 S C1r2 in Ca2+, a 7.5 S complex was formed, presumably the C1s alpha(159) x C1r x C1r x C1s alpha(159) tetramer. When C1q, which migrated at 10.1 S was mixed with C1s alpha(159)2 and C1r2 in the presence of Ca2+, a C1-like complex, but containing C1s alpha(159) instead of C1s, was formed which migrated at 14.0 S. This C1-like molecule remained unactivated unless challenged with an ovalbumin-antiovalbumin immune complex. In the presence of immune complex, the C1r became activated. This suggested that the presence of the 159 amino acid C1s alpha domain, which held the C1r to the C1q, was sufficient to permit activation by an immune complex, even though the catalytic domains of C1s were not present.

Amino Acid Sequence↗
PubMed1990

Proteolysis of the heavy chain of major histocompatibility complex class I antigens by complement component C1s.

The major histocompatibility complex (MHC) class I antigens contain a light chain, beta 2-microglobulin, non-covalently associated to the transmembrane heavy alpha-chain carrying the allotypic determinants. Since the C1q complement component is known to associate with beta 2-microglobulin, and we recently found that activated C1s complement was capable of cleaving beta 2-microglobulin, we decided to investigate the proteolytic activity of C1 complement towards the heavy chain of class I antigens. Our results demonstrate that human C1s complement cleaves the heavy chain of human class I antigens into at least two fragments, with apparent molecular weights of 22,000 and 24,000 g/mol on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), under both reducing and non-reducing conditions. The cleavage of the heavy chain is inhibited by the presence of C1 esterase inhibitor. The molecular weights of the fragments are in agreement with the cleavage located in the area between the disulphide loops of the alpha 2-and alpha 3-domains of the heavy chain. In addition human C1s complement is able to cleave H-2 antigens from mouse in a similar fashion but not rat MHC class I antigen or mouse MHC class II antigen (I-Ad). Mouse MHC class I antigen-specific determinants could also be detected in supernatant from mouse spleen cells incubated with C1r and C1s. These results indicate the presence in the body fluids of a non-membrane-bound soluble form of the alpha 1-and alpha 2-domains which represent the binding site for antigenic peptides.

Animals↗
PubMed1990

Limited proteolysis of beta 2-microglobulin at Lys-58 by complement component C1s.

We have now demonstrated that activated complement component C1s cleaves beta 2-microglobulin at the position identical to that at which beta 2-microglobulin is cleaved in serum of patients suffering from lung cancer. The main cleavage is in the disulphide loop C-terminal to Lys-58, generating a modified form of beta 2-microglobulin with a two-chain structure. The C-terminal Lys-58 in the A chain is highly susceptible to removal by a carboxypeptidase-B-like activity causing the formation of des-Lys58-beta 2-microglobulin. This is the first demonstration of a noncomplement protein substrate for the proteolytic activity of C1s. The C1s-induced cleavage of beta 2-microglobulin can be inhibited in the presence of C1 esterase inhibitor, demonstrating a regulatory function of C1 esterase inhibitor in the C1s-induced cleavage of beta 2-microglobulin.

Amino Acid Sequence↗
PubMed1983

The serine proteinase chain of human complement component C1s. Cyanogen bromide cleavage and N-terminal sequences of the fragments.

Human complement component C1s was purified from fresh blood by conventional methods of precipitation and chromatography. The single-chain zymogen form was activated by treatment with C1r. Reduction and carboxymethylation then allowed the light chain and heavy chain to be separated on DEAE-Sepharose CL-6B in 8 M-urea. Liquid-phase sequencing of the light chain determined 50 residues from the N-terminus. CNBr-cleavage fragments of the light chain were separated by high-pressure liquid chromatography on gel-permeation and reverse-phase columns. N-Terminal sequencing of these fragments determined the order of a further 138 residues, giving a total of 188 residues or about 75% of the light chain. Seven of these eight sequences could be readily aligned with the amino acid sequences of other serine proteinases. The typical serine proteinase active-site residues are clearly conserved in C1s, and the specificity-related side chain of the substrate-binding pocket is aspartic acid, as in trypsin, consistent with the proteolytic action of C1s on C4 at an arginine residue. Somewhat surprisingly, when the C1s sequence is compared with that of complement subcomponent C1r, the percentage difference (59%) is approximately the same as that found between the other mammalian serine proteinases (56-71%).

Amino Acid Sequence↗
PubMed2006

A novel series of arylsulfonylthiophene-2-carboxamidine inhibitors of the complement component C1s.

Inhibiting the classical pathway of complement activation by attenuating the proteolytic activity of the serine protease C1s is a potential strategy for the therapeutic intervention in disease states such as hereditary angioedema, ischemia-reperfusion injury, and acute transplant rejection. A series of arylsulfonylthiophene-2-carboxamidine inhibitors of C1s were synthesized and evaluated for C1s inhibitory activity. The most potent compound had a Ki of 10nM and >1000-fold selectivity over uPA, tPA, FX(a), thrombin, and plasmin.

Amidines↗
PubMed1987

Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence.

The complete amino acid sequence (673 residues plus 15 residues of leader sequence) of human complement component C1s has been determined by nucleotide sequencing of cDNA clones from a human liver library probed with synthetic oligonucleotides. Much of the sequence is supported by independent amino acid sequence information. The cDNA sequence contains an anomalous "intron-like" sequence, including a stop codon, that can be discounted because of the amino acid sequence evidence. The N-terminal chain (422 residues) of C1s, like that of C1r with which it is broadly homologous, contains five domains: domains I and III are homologous to one another and to similar regions in C1r, domain II is homologous to the epidermal growth factor sequence found in C1r and several other proteins, and domains IV and V are homologous to one another and to the 60-residue repeating sequence found in C1r, C2, factor B, C4-binding protein and some apparently unrelated proteins. The sequence of the C-terminal chain (251 residues) agrees with that already established to be the "serine protease" domain of C1s.

Amino Acid Sequence↗
PubMed2002

Plasma protein adsorption pattern on characterized ceramic biomaterials.

The protein/biomaterial interactions of three biomaterials used in hard tissue surgery were studied in vitro. A dynamic flow system and two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) were used to investigate the adsorption of proteins from diluted human plasma on hydroxyapatite, alumina and zirconia, with regard to total protein binding capacity, relative binding capacity for specific proteins and flow-through and desorption patterns. The ceramics were characterized regarding physicochemical properties; namely, chemical composition by elementary analyses and specific surface, pore volume and pore size distribution using the BET-method and Hg-porosimetry. The materials were found to adsorb a surprisingly low amount of plasma proteins, leaving more than 70% of the surface free. The cellular response will therefore be highly affected by the physico-chemical properties of the material, in contrast to a surface fully covered with proteins. Regarding the adsorption of proteins, most proteins exhibited similar flow-through patterns on the three adsorbents. The exceptions with different flow-through patterns were apolipoprotein D (Apo D), apolipoprotein J (Apo J), complement factor C1s (C1s), complement factor C3 (C3), ceruloplasmin, fibrinogen, alpha1 B glycoprotein and alpha2 HS glycoprotein and serum retinal-binding protein (SRBP). The role of these proteins on acceptance or rejection of implants has to be investigated.

Adsorption↗
PubMed2026

Proteomic profiling of cephalic vein reveals potential biomarkers for arteriovenous fistula neointimal hyperplasia in ESRD patients.

Arteriovenous fistula (AVF) is the preferred vascular access for patients with end-stage renal disease; however, its failure is primarily due to neointimal hyperplasia. Five patients who underwent initial AVF surgery served as the control group, and another five patients with failed AVF surgery served as the experimental group. Herein, we employed mass spectrometry (MS)-based quantitative proteomics coupled with tandem mass tag labeling to screen differentially expressed proteins (DEPs) in the anastomotic cephalic vein, followed by bioinformatics analyses and verification experiments. A total of 121 DEPs were identified in the failed AVF group. GO analysis was primarily enriched in protein binding, nucleic acid binding, enzyme binding, mRNA binding, cadherin binding, catalytic activity, and cell adhesion molecule binding. KEGG pathways were mainly enriched in cell aggregation and adhesion, actin cytoskeleton, extracellular matrix-receptor interaction, PI3K-Akt signaling pathway, complement and coagulation cascades, and cholesterol metabolism. Protein-protein interaction network consisted of 86 (71.07%) DEPs, including complement VII (C7), factor IX (F9), SERPINC1, microfibril-associated glycoprotein 4 (MFAP4), complement C1s subcomponent, complement C1q subcomponent subunit A, complement C1q subcomponent subunit B, tissue factor, and von Willebrand factor, which interacting with numerous other proteins. In the expanded validation for different patients, C7, F9, SERPINC1, and MFAP4, were verified by immunohistochemical staining and Western blotting, which were consistent with the proteomics results. Collectively, this study identifies a series of potential diagnostic biomarkers, and explores the underlying mechanisms associated with AVF dysfunction.

Humans↗
PubMed1998

C1-esterase inhibitor blocks T lymphocyte proliferation and cytotoxic T lymphocyte generation in vitro.

We have previously shown that activated C1s complement and activated T cells cleave beta2-microglobulin (beta2m) in vitro leading to the formation of desLys58 beta2m. This process can specifically be inhibited by C1-esterase inhibitor (C1-inh). Furthermore we showed that exogenously added desLys58 beta2m in nanomolar amounts to a one-way allogenic mixed lymphocyte culture (MLC) increased the endogenous production of IL-2 and the generation of allo-specific cytotoxic T lymphocytes. C1-inh was purified from fresh human plasma and added to human or murine MLC and mitogen-stimulated lymphocyte cultures grown in the presence of complement-inactivated serum. Read-outs were cell proliferation, lymphokine production and development of T cell-mediated cytotoxicity. We found that addition of C1-inh to MLC and mitogen-exposed murine and human lymphocyte cultures inhibited proliferation, the development of allospecific cytotoxic activity, and changed the endogenous production of IL-2, IL-4, IL-10, IL-12 and IFN-gamma. These data clearly demonstrate a regulatory function of C1-inh on T cell-mediated immune functions.

Animals↗
PubMed1987

The complement component C1s catalysed hydrolysis of peptide 4-nitroanilide substrates.

The kinetic parameter kcat/Km has been determined for the hydrolysis of peptide 4-nitroanilides, catalysed by complement component C1s. Substrates based on the C-terminal sequence of human C4a (Leu-Gln-Arg) were synthesised. Replacement of the glutamine residue by glycine or serine increased kcat/Km. Substitution of valine for the leucine residue increased kcat/Km, while substitution of glycine or lysine for the leucine residue decreased kcat/Km slightly. D-Val-Ser-Arg 4-nitroanilide is the most reactive 4-nitroanilide substrate towards C1s, so far. These results are discussed in relation to the amino acid sequences near the bonds cleaved by C1s in C4, C2 and C1 inhibitor.

Amino Acid Sequence↗
PubMed2004

A novel series of potent and selective small molecule inhibitors of the complement component C1s.

Activation of the classical pathway of complement has been implicated in disease states such as hereditary angioedema, ischemia-reperfusion injury and acute transplant rejection. The trypsin-like serine protease C1s represents a pivotal upstream point of control in the classical pathway of complement activation and is therefore likely to be a useful target in the therapeutic intervention of these disease states. A series of thiopheneamidine-based inhibitors of C1s has been optimized to give a 70 nM inhibitor that inhibits the classical pathway of complement activation in vitro.

Binding Sites↗
PubMed2005

Functional role of the linker between the complement control protein modules of complement protease C1s.

C1s is the modular serine protease responsible for cleavage of C4 and C2, the protein substrates of the first component of C (C1). Its catalytic domain comprises two complement control protein (CCP) modules connected by a four-residue linker Gln340-Pro-Val-Asp343 and a serine protease domain. To assess the functional role of the linker, a series of mutations were performed at positions 340-343 of human C1s, and the resulting mutants were produced using a baculovirus-mediated expression system and characterized functionally. All mutants were secreted in a proenzyme form and had a mass of 77,203-77,716 Da comparable to that of wild-type C1s, except Q340E, which had a mass of 82,008 Da, due to overglycosylation at Asn391. None of the mutations significantly altered C1s ability to assemble with C1r and C1q within C1. Whereas the other mutations had no effect on C1s activation, the Q340E mutant was totally resistant to C1r-mediated activation, both in the fluid phase and within the C1 complex. Once activated, all mutants cleaved C2 with an efficiency comparable to that of wild-type C1s. In contrast, most of the mutations resulted in a decreased C4-cleaving activity, with particularly pronounced inhibitory effects for point mutants Q340K, P341I, V342K, and D343N. Comparable effects were observed when the C4-cleaving activity of the mutants was measured inside C1. Thus, flexibility of the C1s CCP1-CCP2 linker plays no significant role in C1 assembly or C1s activation by C1r inside C1 but plays a critical role in C4 cleavage by adjusting positioning of this substrate for optimal cleavage by the C1s active site.

Amino Acid Motifs↗