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Background The CD38 transmembrane glycoprotein is an ADP-ribosyl cyclase that moonlights as a receptor in cells of the immune system. Both functions are independently implicated in numerous areas related to human health. This study originated from an inherent interest in studying CD38 in the cynomolgus monkey (Macaca fascicularis), a species closely related to humans that also represents a cogent animal model for the biomedical analysis of CD38. Results A cDNA was isolated from cynomolgus macaque peripheral blood leukocytes and is predicted to encode a type II membrane protein of 301 amino acids with 92% identity to human CD38. Both RT-PCR-mediated cDNA cloning and genomic DNA PCR surveying were possible with heterologous human CD38 primers, demonstrating the striking conservation of CD38 in these primates. Transfection of the cDNA coincided with: (i) surface expression of cynomolgus macaque CD38 by immunofluorescence; (ii) detection of ~42 and 84 kDa proteins by Western blot and (iii) the appearance of ecto-enzymatic activity. Monoclonal antibodies were raised against the cynomolgus CD38 ectodomain and were either species-specific or cross-reactive with human CD38, in which case they were directed against a common disulfide-requiring conformational epitope that was mapped to the C-terminal disulfide loop. Conclusion This multi-faceted characterization of CD38 from cynomolgus macaque demonstrates its high genetic and biochemical similarities with human CD38 while the immunological comparison adds new insights into the dominant epitopes of the primate CD38 ectodomain. These results open new prospects for the biomedical and pharmacological investigations of this receptor-enzyme.

A peculiar characteristic of highly concentrated cytosolic recombinant human glyoxalase II (GII) solutions is to undergo partial precipitation. Previous work indicated that anionic phospholipids (PLs) exert a noncompetitive inhibition on the enzymatic activity of the soluble enzyme. In this study, FTIR spectroscopy was used to analyze the structural properties and the thermal stability of the soluble protein in the absence and in the presence of liposomes made of different phospholipids (PLs). The structural analysis was performed on the precipitate as well. The interaction of acidic PLs with GII lowered the thermal stability of the enzyme and inhibited protein intermolecular interactions (aggregation) brought about by thermal denaturation. Infrared data indicated that ionic and hydrophobic interactions occur between GII and acidic PLs causing small changes in the secondary structure of the enzyme. No interactions of the protein with egg phosphatidylcholine liposomes were detected. The results are consistent with the destabilization of the protein tertiary structure, and indicate that GII possesses hydrophobic part(s) that interact with the acyl chains of PLs. Data on precipitated GII did not show remarkable modification of secondary structure, suggesting that hydrophobic stretches of the enzyme may also be involved in the protein-protein association (precipitation) at high GII concentration. The alterations in the GII structure and the noncompetitive inhibition exerted by acidic PLs are strictly related.

Insulin secretion is one of the functions mediated by CD38, a nonlineage pleiotropic cell surface receptor. The molecule is the target of an autoimmune response, because serum autoantibodies (aAbs) to CD38 have been detected in diabetic patients. In the healthy Caucasian population, the CD38 gene is bi-allelic (86% CD38*B and 14% CD38*A), whereas an Arg140Trp mutation has been identified in Japanese diabetic patients. We investigated the relationship between CD38 and diabetes in Caucasian patients by characterizing anti-CD38 aAbs in terms of prevalence and function (agonistic/nonagonistic activity) and by exploring the potential influence of the CD38 genetic background. A novel enzymatic immunoassay, using recombinant soluble CD38 as the target antigen, was developed for the analysis of anti-CD38 aAb titers. Sera from 19.15% of type 1 and 16.67% of type 2 diabetic patients were positive. The majority of anti-CD38 aAbs (57.14%) displayed agonistic properties, i.e., they demonstrated the capability to trigger Ca2+ release in lymphocytic cell lines. In agreement with these functional features, the presence of anti-CD38 aAbs in type 2 diabetic patients was associated with significantly higher levels of fasting plasma C-peptide and insulin, as compared with anti-CD38-counterparts. No diabetic subject carrying the Arg140Trp mutation and no preferential association between diabetes or aAb status and the CD38*A allele was found in the study population. These results show the significance of anti-CD38 aAbs as a new diagnostic marker of beta-cell autoimmunity in diabetes. Moreover, the prevalent agonistic activity of these aAbs suggests that they could mediate relevant effects on target cells by means of Ca2+ mobilization.

The malignant mesothelioma (MM) is often complicated by thromboembolic episodes, with thrombomodulin (TM) playing a role in the anti-coagulant process. We analyzed TM expression in biopsies of MM patients and in normal mesothelial tissue. The role of DNA methylation-associated gene silencing in TM expression was investigated. A correlation between low TM expression and high level of TM promoter methylation was found in MM biopsies. Low expression of TM was restored in MM cells by their treatment with 5-aza-2'-deoxycytidine while the epigenetic agent did not affect TM expression in Met-5A cells. Methylation of the TM promoter is responsible for silencing of TM expression in MM tissue.