Monoclonal antibodies to native mouse angiotensin-converting enzyme (CD143): ACE expression quantification, lung endothelial cell targeting and gene delivery

We demonstrated previously that the monoclonal antibody 9B9 to angiotensin-converting enzyme (ACE), which accumulates very selectively into the rat lung after systemic injection, is a powerful tool for immunotargeting of therapeutic agents or genes to the rat lung vascular bed. Bearing in mind a high research and therapeutic potential of lung targeting via ACE, we obtained a new set of rat monoclonal antibodies to different epitopes of mouse ACE in order to expand this approach to mice. Nine new monoclonal antibodies, recognizing epitopes on the N- and C-domains of catalytically active mouse ACE, were obtained and examined for their efficacy to bind ACE both in vitro and in vivo. This set of monoclonal antibodies was proved to be useful for ACE quantification (by flow cytometry and cell enzyme-linked immunosorbent assay) on the surface of different mouse ACE-expressing cells: endothelial cells, monocytes, macrophages, dendritic cells and spermatozoa. Moreover, gene delivery into mouse ACE-expressing cells using adenoviruses increased 40-fold after redirecting of these viruses to ACE (by coating these viruses with anti-ACE monoclonal antibodies). Radiolabelled (I(125)) monoclonal antibodies specifically accumulated in the mouse lung after systemic injection. Monoclonal antibodies 3G8.17, 4B10.5 and 4B10.17 demonstrated the highest level of lung uptake, 40-50% of injected dose, and high selectivity of lung uptake. Influence of monoclonal antibodies on ACE shedding was negligible, except monoclonal antibody 1D10.11. None of the tested monoclonal antibodies inhibited ACE activity in vitro. In conclusion, a new set of rat monoclonal antibodies to mouse ACE was obtained suitable to study ACE biology in mice and for ACE expression quantification on mouse cells in particular. These monoclonal antibodies also demonstrated highly efficient and selective lung accumulation and thus has the potential for targeting drugs/genes to the pulmonary vasculature in different mouse models of human lung diseases, including numerous knockout models.

Development and characterization of rat monoclonal antibodies to denatured mouse angiotensin-converting enzyme

Four new rat monoclonal antibodies, generated to denatured mouse somatic angiotensin-converting enzyme (ACE, CD143), detect mouse ACE with high sensitivity in Western blotting. Epitope mapping for the monoclonal antibodies--B12, 4G6 and 5C4--was also performed. Two monoclonal antibodies--B12 and 5C4--are directed to various epitopes on the N-domain--i.e., they recognized only the somatic isoform of mouse ACE. The monoclonal antibody H7 recognized an epitope on the C-domain of mouse ACE. The monoclonal antibody 4G6 was directed to a sequence on the N-domain of mouse ACE, which is homologous to a region of the C-domain and, as a result, also recognizes mouse testicular ACE (tACE) by means of Western blotting. In paraffin-embedded mouse tissues, all monoclonal antibodies detected all known expression sites of somatic ACE (sACE), e.g., the epithelial cells of the kidney proximal tubules, intestine and epididymis, and heterogeneously in endothelial cells. The monoclonal antibodies 4G6 and H7 additionally stained mouse tACE in spermatozoa and in mature spermatids. The monoclonal antibody 4G6 also demonstrated cross-reactivity with sACE from a broad spectrum of animal species, including human, rat, rabbit and bovine. However, this monoclonal antibody did not recognize the testicular isoform of ACE of these species. This set of monoclonal antibodies is useful for identifying even subtle changes in mouse ACE conformation because of denaturation. These monoclonal antibodies are also sensitive tools for the detection of mouse ACE in biological fluids and tissues by using proteomics approaches. Their high reactivity in paraffin-embedded tissues opens up opportunities to study possible changes in the pattern of ACE expression in knockout mouse models and may prove useful for correlating ACE expression in these models with human diseases.

Regulation of apoptosis by alpha-subunits of G12 and G13 proteins via apoptosis signal-regulating kinase-1

Many growth factors and G protein-coupled receptors activate mitogen-activated protein (MAP) kinase pathways. The MAP kinase pathways are involved in the regulation of the ubiquitous process of apoptosis or programmed cell death. Two related MAP kinase kinase kinases, apoptosis-signal regulating kinase 1 (ASK1) and MAP kinase kinase kinase 1 (MEKK1), stimulate c-Jun kinase (JNK) activity and induce apoptosis. Transient transfection of dominant negative and constitutively active components of the JNK pathway in COS-7 cells showed that two G protein subunits, Galpha12 and Galpha13, stimulated the JNK pathway in a ASK1- and MEKK1-dependent manner. Moreover, the mutationally activated Galpha12 and Galpha13 stimulated the kinase activity of ASK1. Both Galpha12 and Galpha13 employ small GTPases, Cdc42 and Rac1, to transduce signal to MEKK1 and, subsequently, to JNK. However, activation of JNK by Cdc42 and Rac1 did not require ASK1. Additionally, ASK1 and MEKK1 are involved in the apoptosis induced by Galpha12 and Galpha13. We conclude that Galpha12 and Galpha13 can induce apoptosis using two separate MAP kinase pathways; one is initiated by ASK1, and the other is initiated by MEKK1. Furthermore, Bcl-2 can block apoptosis induced by Galpha12 and Galpha13. This death-sparing function was associated with increased Bcl-2 phosphorylation, suggesting that phosphorylation of Bcl-2 may be a critical mechanism protecting cells from Galpha12- and Galpha13-induced apoptosis.

7-ketocholesterol inhibits VLDL secretion by cultured human and rabbit hepatocytes

7-ketocholesterol, one of the major product of autoxidation of dietary cholesterol, was found to inhibit secretion of very low density lipoprotein [14C]cholesterol, [14C]triacylglycerol and [35S]apoprotein B,E,C by cultured human and rabbit hepatocytes. A parallel inhibition (about 35%) of cholesterol synthesis but not of triacylglycerol formation was observed. Incubation with 10 micrograms/ml of oxysterol also reduced the total apo-B secretion measured by ELISA and increased intracellular apo-B mRNA level. These results seem to indicate that 7-ketocholesterol decreases secretion of very low density lipoprotein (VLDL) particles and exerts inhibitory effects on apo-B production at the co-translational or posttranslational level.

Recessive nonsense-suppression in yeast Saccharomyces cerevisiae: the study of 80 S ribosomes accumulated in suppressor strain under non-permissive conditions

The shift of recessive suppressor mutant of yeast Saccharomyces cerevisiae from permissive to restrictive conditions is accompanied by polysome decay and accumulation of 80 S ribosomes (Smirnov et al., 1976). In this paper some properties of 80 S ribosomes are studied. It is demonstrated that polysome decay under non-permissive conditions is not the consequence of the impairment of RNA synthesis. More than 70% of 80 S ribosomes accumulated under non-permissive conditions contain bound peptidyl-tRNAs localized in P-ribosomal site. tRNA moiety of bound peptidyl-tRNA is able to accept all 20 natural amino acids after chemical deacylation. Therefore it is not a specific isoacceptor species but rather total tRNA that is bound to ribosomes. The polypeptide residues of these peptidyl-tRNAs are heterogeneous in size. Their molecular weights are comparable with the molecular weights of the completed polypeptides. Some of the 80 S ribosomes accumulated under non-permissive conditions contain poly-A+ RNA. In conclusion, possible mechanism of the impairment of translation under non-permissive conditions in recessive suppressor strain is discussed.

Recessive nonsense-suppression in yeast: involvement of 60S ribosomal subunit

The ribosomal protein patterns of recessive suppressor strain and parent strain of Saccharomyces cerevisiae were analyzed by two-dimensional polyacrylamide gel electrophoresis. About 30 proteinspots were found for ribosomal proteins of small subunit for both mutant and parent strain. These patterns do not differ from each other neither in intensity of staining, nor in mobility of spots. 41 protein spots were found in electrophoregrams of 60S ribosomal proteins both from parent strain and recessive suppressor strain. The electrophoretic picture of the 60S proteins from the parent and mutant strains is similar except the intensity of staining of the L30 spot. This protein is present in 60S subunit of suppressor strain and completely absent or only weakly stained on electrophoregrams of ribosomal proteins of parent strain. The possible relationships between the content of L30 protein and the mechanism of recessive suppression in yeast are discussed.