The consolidation of new but not reactivated memory requires hippocampal C/EBPbeta

Long-term memory formation consists of multiple phases. A new memory is initially labile and sensitive to disruption by a variety of interfering events or agents. To become stable, this new memory undergoes a process known as consolidation, which, in the case of declarative memories, occurs within the medial temporal lobes and requires gene expression. When recalled, memories re-enter a new phase of vulnerability and seem to require a reconsolidation process in order to be maintained. Here we show that consolidation but not reconsolidation of inhibitory avoidance memory requires the expression of the transcription factor CCAAT enhancer binding protein beta (C/EBPbeta) in the hippocampus. Furthermore, in the same region, de novo protein synthesis is not essential for memory reconsolidation. C/EBPbeta is an evolutionarily conserved genetic marker that has a selective role in the consolidation of new but not reactivated memories in the hippocampus.

Fornix-dependent induction of hippocampal CCAAT enhancer-binding protein [beta] and [delta] Co-localizes with phosphorylated cAMP response element-binding protein and accompanies long-term memory consolidation

The cAMP response element-binding protein (CREB) is an evolutionarily conserved transcription regulator essential for long-term memory formation. It is not known, however, whether the molecular events downstream of CREB activation are also conserved. An early, cAMP-dependent event necessary for learning-related long-term synaptic plasticity in the invertebrate Aplysia californica is the induction of the transcription factor CCAAT enhancer-binding protein (C/EBP). Here we show that two homologs in the rat, C/EBPbeta and C/EBPdelta, are induced at discrete times after inhibitory avoidance learning and co-localize with phosphorylated CREB in the hippocampus. This induction is blocked by fornix lesions, which are known to disrupt activation of CREB in the hippocampus and to impair memory consolidation. These results indicate that C/EBPs are evolutionarily conserved components of the CREB-dependent gene cascade activated in long-term memory.

A monoclonal antibody against a peptide sequence of fibrinogen gamma chain acts as an inhibitor of factor XIII-mediated crosslinking of human fibrin

Recurrent hemorrhage has been reported in humans as a result of acquired antibody inhibitors which interfere with the crosslinking of fibrin by factor XIII. One type of these inhibitors (Type III) prevents activated factor XIII from acting on fibrin. We have generated an antifibrin monoclonal antibody, called mAb 4A5, which binds to a peptide sequence at the carboxyl-terminus of human fibrinogen gamma-chains. MAb 4A5 acts like a Type III inhibitor and prevents proper factor XIII-mediated crosslinking. Pre-incubation of fibrinogen or pooled human plasma with mAb 4A5, but not mAb D2 (specific for the carboxyl terminus of fibrin alpha-chains), resulted in clots which are soluble in either 5 M urea or 1% monochloroacetic acid. SDS-PAGE and immunoblotting analysis of these clots confirmed that mAb 4A5 inhibited gamma-chain crosslinking in plasma clots and fibrin clots. Results from a factor XIII activity assay demonstrated that biotinylcadaverine crosslinking into fibrin by factor XIII could be inhibited by mAb 4A5 but not mAb D2, arguing that mAb 4A5 acted by binding the crosslinking site of factor XIII. Studies of the immunoreactivity of these mAbs with 12 different animal species showed that the gamma-chain epitope recognized by mAb 4A5 was more conserved than the alpha-chain epitope recognized by mAb D2. The species fibrinogens, recognized by mAb 4A5 in binding assays, also showed impaired crosslinking when mAb 4A5 was present during the clotting reaction

A microtiter assay for factor XIII using fibrinogen and biotinylcadaverine as substrates

Efforts to develop an improved assay for plasma and tissue transglutaminase have led us to a convenient, sensitive microtiter plate assay for coagulation factor XIII using human fibrinogen as an immobilized substrate. Factor XIII was activated in the presence of calcium, thrombin, and immobilized fibrinogen and then assayed by adding biotinylcadaverine. The reaction was terminated by adding EDTA and the level of incorporated biotin was measured with streptavidin-beta-galactosidase. In this assay, the analytical range for human platelet factor XIII was 0.01-100 ng and 1-100 ng for guinea pig liver transglutaminase. Fibrinogen-coated plates gave more than 100-fold increase in sensitivity compared with N,N-dimethylcasein-coated microtiter plates. The intraassay coefficient of variation was less than 5% (n = 12) and interassay less than 6% (n = 4). The sensitivity of this assay reduced the volumes of plasma samples required and consequently eliminated the need to remove fibrinogen from such test samples. As expected, factor XIII activity could be inhibited by putrescine and antibodies against factor XIII as well as by a monoclonal antibody that bound to the carboxyl terminus of human fibrin gamma-chains. The assay provided a sensitive, simple, and rapid method for measuring factor XIII.

Characterization of a monoclonal antibody directed against the carboxyl-terminus of human factor XIII. An epitope exposed upon denaturation and conserved across species lines

By deriving an anti-peptide monoclonal antibody, mAb 7A4, we characterized the relatively unstudied carboxyl-terminal end of the a-chain of human factor XIII, the plasma transglutaminase. MAb 7A4 was directed against the last eight amino acids (Gln-Ile-Gln-Arg-Arg-Pro-Ser-Met) and bound with a dissociation constant of 3.4 x 10(-8)M. In a solid assay format, mAb 7A4 bound equally well to factor XIII obtained from human plasma, platelets or placenta. However, in a solution-phase assay format, the epitope was largely unavailable but could be readily exposed by heat denaturation. Immunoblotting showed that this epitope is conserved among all species of plasma factor XIII tested except rabbit suggesting that the carboxyl-terminus might be an important structural element. Other competitive binding experiments with synthetic peptides as inhibitors pointed toward the final carboxyl-terminal amino acid, Met-731, as an immunochemically important determinant. This was used advantageously to confirm the finding that the carboxyl-terminal Met-731 is largely absent from placental factor XIII (1) as compared to platelet or plasma factor XIII.