Biological activities of a major protein secreted from the rat seminal vesicles after structural modification catalyzed by transglutaminase in vitro

Recombinant human tissue transglutaminase produced into tobacco suspension cell cultures is active and recognizes autoantibodies in the serum of coeliac patients

Human tissue transglutaminase (htTG) is one of the most important member within the transglutaminase family, enzymes that for their capacity of catalyzing post-translational modifications of proteins and peptides, rise an high interest for industrial applications. More recently, for its implication as the major autoantigen in the coeliac disease, availability of human tissue transglutaminase as recombinant form is required for accurate diagnostic tests. The aim of this study was to find an alternative and inexpensive source to produce human tissue transglutaminase. To date, plant systems are proposed as heterologous hosts to produce recombinant proteins for use in disease diagnosis and therapy. Here, we describe the stable expression of human tissue transglutaminase into Nicotiana tabacum cultured cells (cultivar Bright Yellow 2 (BY-2)). The recombinant enzyme was successfully expressed in different plant cell compartments and both apoplast (apo) and chloroplast (chl) purified proteins were shown to be catalytically active and able to bind GTP, a property possessed by the natural counterpart. Importantly, plant produced human tissue transglutaminase recognized autoantibodies in the serum of coeliac patients, suggesting possible applications in the diagnosis of coeliac disease.

The self-association of protein SV-IV and its possible functional implications

The protein SV-IV, a major protein secreted from the rat seminal vesicle epithelium, is a basic protein with immunomodulatory, anti-inflammatory, and procoagulant activity. Predictions suggested that this protein is very flexible, with its three tyrosyl residues presumably located in water-exposed segments of the primary structure. The solution behaviour of the protein was investigated by two types of spectroscopic techniques. Modifications of the spectral characteristics of tyrosyl residues induced by changes of protein concentration were demonstrated by absorption and fluorescence experiments. In addition, secondary structure rearrangements associated with a possible self-association equilibrium were highlighted by far-UV CD spectra. The equilibrium, confirmed by chromatographic techniques, appears to control some biological properties of the protein.

A peptide derivative (1-70 fragment) of protein SV-IV accelerates human blood coagulation in vitro by selective inhibition of the heparin-induced antithrombin III activation process

The effect of two peptide derivatives of the rat SV-IV (SV-IV/A: 1-70 fragment; SV-IV/B: 71-90 fragment) on human blood coagulation was investigated. The SV-IV/A fragment was found to possess the same procoagulant activity of the native protein, whereas SV-IV/B retained only a very small fraction of the activity. The results obtained strongly suggest that the procoagulant activity of SV-IV/A is due, like SV-IV, to a selective inhibition of the antithrombin III (AT III) activation process induced by heparin, an essential cofactor of AT III. The main data supporting this hypothesis are the following: 1) the concentration of active serum AT III decreases when SV-IV/A is present in the clotting system; 2) the plasma treatment with SV-IV/A reduces the concentration of AT III, but not that of other plasma serine protease inhibitors; 3) the recalcification time (RT) of the plasma treated with a rabbit anti-AT III polyclonal antiserum is not modified by SV-IV/A; 4) the presence of SV-IV/A in a reaction mixture containing pure fibrinogen, alpha-thrombin, heparin, and AT III neutralizes the thrombin inhibition induced by AT III; 5) the concentration of the thrombin-AT III complexes, occurring in sera obtained from CaCl2-coagulated plasma, is markedly reduced in the presence of SV-IV/A; 6) appropriate concentrations of heparin neutralize the inhibitory effect of either SV-IV/A or SV-IV on the AT III activity in vitro.

Inhibition of zymosan-induced air-pouch inflammation by rat seminal vesicle protein and by its spermidine derivative

The anti-inflammatory effect of one of the major proteins secreted by rat seminal vesicles (SVIV) and of its spermidine derivative (Spd2-SVIV) was evaluated by measuring polymorphonuclear leukocyte migration, protein release, platelet-activating factor (PAF) and prostaglandin E2 levels in the mouse air-pouch exudate following zymesan treatment. Both proteins were found to markedly reduce dose dependently PAF and prostaglandin E2 levels in the exudate as well as the other parameters. Concurrent injection of either arachidonic acid or PAF, directly into the pouch, significantly counteracted the anti-inflammatory effect of SVIV and of its polyaminated derivative. These results support the notion that the molecular mechanism of the anti-inflammatory activity of SVIV and Spd2-SVIV is linked to the inhibition of both phospholipase A2 and acetyl:lyso-PAF acetyltransferase.

The pharmacology of immunosuppressant drugs in skin transplant rejection in mice and other rodents

1. Skin transplantation in rodents is a convenient, widely used method, particularly in mice. It is used as much as an indicator of immune responsiveness as for pharmacological studies. 2. Many differences exist in experimental protocols, both for transplantation and drug administration and in this review, the increase in graft survival time with respect to control times is used to indicate drug effects, in an attempt to account for these differences. 3. The mechanisms underlying skin graft rejection in rodents are described, emphasising the crucial role of both helper and effector T cells. 4. The pharmacology of clinically-used immunosuppressants, including CsA, FK506, rapamycin and purine or pyrimidine synthesis inhibitors, in rodent models of skin transplantation is reviewed. 5. The effects of other potential immunosuppressants and compounds modulating immune responses are described, including the effects of UV light and involvement of platelet-derived factors, prostaglandins and thromboxanes.

Dynamics of the seminal vesicle epithelium

In newborn rodents, seminal vesicle epithelium (SVEP) cells display a poorly developed rough endoplasmic reticulum (RER) and Golgi complex, and they show no signs of secretion. From puberty onward, secretory material starts to appear, and the RER and Golgi complex progressively develop and reorganize until the adult ultrastructure is established around 40-60 days of age. Multivesicular bodies and lysosomes follow in this development but lysosomes evolve to lipofucsin granules with aging. The duration of the secretory cycle in SVEP cells is shorter than in other exocrine cells and the secretory protein pattern depends on the animal species, androgen status, and sexual activity. SVEP cells are also involved in endocytosis, which is coupled to exocytosis, and their endocytic pathway intersects the exocytic pathway in Golgi cisterns. The structure and function of SVEP cells depends mainly on testosterone, but other hormones and factors, such as the neuropeptide VIP, also influence their activity. Castration leads to programmed death and regression of SVEP cells to an extent that depends on the animal species. In addition, castration induces changes in the secretory protein pattern and delays its intracellular transport. Endocytic kinetics is also delayed following castration. Primary cultures of SVEP cells in a bicameral system are proposed as a model to investigate the activities of SVEP cells further.

Biological activities of CNBr fragments of a major protein secreted from the rat seminal vesicle epithelium

Two fragments of SV-IV, one of the major proteins secreted from the rat seminal vesicle epithelium, were produced in vitro by protein cleavage with CNBr at level of the single methionine residue (Met-70) occurring in its polypeptide chain. After their purification by reversed-phase chromatography, SV-IV/A (1-70 fragment) and SV-IV/B (71-90 fragment) were assayed as transglutaminase substrates, and their anti-inflammatory, anti-thrombotic and immunosuppressive properties were evaluated in comparison with native SV-IV. Both fragments retained the SV-IV ability to act as transglutaminase substrates in vitro; fast atom bombardment mass spectrometry analyses of the reaction products pointed to Gln-9 and Gln-86 as acyl donor sites, and to Lys-59, -79 and -80 as acyl acceptor sites. In contrast, only SV-IV/A was shown to possess, like SV-IV, the property of inhibiting both the intensity of the carrageenin-induced rat foot edema and the platelet aggregation induced in vivo by different agents. Finally, the two protein fragments were found to be completely unable to inhibit both the mitogen-induced proliferation of human T cells and the mixed lymphocyte reaction.