Human C‐reactive protein (CRP) is the major acute phase reactant during acute inflammation. The human CRP promoter is expressed in an inducible and cell‐specific manner when linked to the bacterial CAT gene and transfected into human hepatoma cell cultures. In this paper we analyze the effect of several recombinant cytokines or CRP promoter inducibility in human Hep3B cells. When cytokines are tested singly the major inducer of CRP‐CAT fusions is interleukin‐6 (IL‐6). Maximal CAT gene expression, however, is only achieved when both interleukin‐1 beta (IL‐1 beta) and IL‐6 are present. The response to the two cytokines is cooperative. Cooperativity is maintained when the CRP promoter is linked to a different coding region, that of the bacterial neomycin phosphotransferase II gene. With a series of 5′ and 3′ deletions we show the existence of two distinct and independent regions responsive to IL‐6 and located upstream to the TATA box. The IL‐1 effect is exerted at the level of downstream sequences that are probably important for optimal mRNA translatability or nuclear‐cytoplasmic transport. Inducibility is not influenced by the activation of protein kinases C or A and does not require new protein synthesis.

Transcription of the human C‐reactive protein (CRP) gene is induced by interleukin‐6 (IL‐6) during acute inflammation. Important information for inducible CRP expression is located within the 90 bases preceding the transcriptional start site. We show that the CRP promoter contains two adjacent binding sites (beta and alpha) that interact with at least two hepatocyte‐specific nuclear proteins, H‐APF‐1 and H‐APF‐2. Point mutations that abolish or reduce binding drastically affect the level of CRP gene expression. Binding to beta is identical when extracts from uninduced or IL‐6‐induced Hep3B cells are used. On the contrary, both quantitative and qualitative changes in the alpha binding can be detected with extracts from uninduced cells or from cells treated with IL‐6 or IL‐6 + cycloheximide. A synthetic promoter based on the multimerization of the beta‐binding domain, but not of the alpha‐domain, is highly inducible when transfected in hepatoma cells. These results are discussed in relation to the structure of the promoter region of other acute phase inducible genes.

Protease-activated receptors (PARs) mediate cell activation after proteolytic cleavage of their extracellular amino terminus. Thrombin selectively cleaves PAR1, PAR3, and PAR4 to induce activation of platelets and vascular cells, while PAR2 is preferentially cleaved by trypsin. In pathological situations, other proteolytic enzymes may be generated in the circulation and could modify the responses of PARs by cleaving their extracellular domains. To assess the ability of such proteases to activate or inactivate PARs, we designed a strategy for locating cleavage sites on the exofacial NH(2)-terminal fragments of the receptors. The first extracellular segments of PAR1 (PAR1E) and PAR2 (PAR2E) expressed as recombinant proteins in Escherichia coli were incubated with a series of proteases likely to be encountered in the circulation during thrombosis or inflammation. Kinetic and dose-response studies were performed, and the cleavage products were analyzed by MALDI-TOF mass spectrometry. Thrombin cleaved PAR1E at the Arg41-Ser42 activation site at concentrations known to induce cellular activation, supporting a native conformation of the recombinant polypeptide. Plasmin, calpain and leukocyte elastase, cathepsin G, and proteinase 3 cleaved at multiple sites and would be expected to disable PAR1 by cleaving COOH-terminal to the activation site. Cleavage specificities were further confirmed using activation site defective PAR1E S42P mutant polypeptides. Surface plasmon resonance studies on immobilized PAR1E or PAR1E S42P were consistent with cleavage results obtained in solution and allowed us to determine affinities of PAR1E-thrombin binding. FACS analyses of intact platelets confirmed the cleavage of PAR1 downstream of the Arg41-Ser42 site. Mass spectrometry studies of PAR2E predicted activation of PAR2 by trypsin through cleavage at the Arg36-Ser37 site, no effect of thrombin, and inactivation of the receptor by plasmin, calpain and leukocyte elastase, cathepsin G, and proteinase 3. The inhibitory effect of elastase was confirmed on native PAR1 and PAR2 on the basis of Ca(2+) signaling studies in endothelial cells. It was concluded that none of the main proteases generated during fibrinolysis or inflammation appears to be able to signal through PAR1 or PAR2. This strategy provides results which can be extended to the native receptor to predict its activation or inactivation, and it could likewise be used to study other PARs or protease-dependent processes.

C‐reactive protein (CRP) is a major acute phase reactant in man but not in mouse. It is synthesized in abundant quantities by human hepatocytes during the course of several diseases, mainly acute inflammations. To investigate the regulation of CRP expression, the human CRP gene was introduced into fertilized eggs by microinjection and transgenic mouse lines were derived. The CRP gene is exclusively transcribed in the liver and expression is strictly dependent on experimental inflammation. The kinetics of induction both for RNA and protein synthesis is very fast; RNA is first detectable after 2 h in the liver, the protein after 6 h in the serum. Human CRP levels in the sera of transgenic mice are comparable to those observed in human diseases. Nuclear run‐on experiments indicate that regulation is primarily at the transcriptional level.