Some physical properties of the human NN and Me-Vg blood-group antigens

Loss of POMC-mediated antinociception contributes to painful diabetic neuropathy

Painful neuropathy is a frequent complication in diabetes. Proopiomelanocortin (POMC) is an endogenous opioid precursor peptide, which plays a protective role against pain. Here, we report dysfunctional POMC-mediated antinociception in sensory neurons in diabetes. In streptozotocin-induced diabetic mice the Pomc promoter is repressed due to increased binding of NF-kB p50 subunit, leading to a loss in basal POMC level in peripheral nerves. Decreased POMC levels are also observed in peripheral nervous system tissue from diabetic patients. The antinociceptive pathway mediated by POMC is further impaired due to lysosomal degradation of μ-opioid receptor (MOR). Importantly, the neuropathic phenotype of the diabetic mice is rescued upon viral overexpression of POMC and MOR in the sensory ganglia. This study identifies an antinociceptive mechanism in the sensory ganglia that paves a way for a potential therapy for diabetic neuropathic pain.

The macromolecular properties of blood-group substances. Sedimentation-velocity and viscosity measurements

1. Sedimentation-velocity, intrinsic-viscosity and partial-specific-volume measurements on a typical blood-group-specific glycoprotein are reported for a range of environmental conditions. 2. The sedimentation coefficients, S, are strongly concentration-dependent, and follow the reciprocal law; the limiting values at 2 degrees , 25 degrees and 45 degrees , after correction to 25 degrees , show slight dependence on temperature. 3. The intrinsic viscosities, [eta], at 25 degrees and 45 degrees show more marked temperature-dependence, and correspond to a very asymmetric or very expanded molecular conformation. 4. From the value of the ratio K/[eta], where K=S(0).d(1/S)/dc, it is concluded that the molecular conformation is roughly spherical; application of the Einstein viscosity equation then suggests an expansion factor of about 60, compatible with a flexible configuration approaching that of a random coil. 5. The sedimentation coefficient is not affected by variation of ionic strength in the range 0.01-0.50, nor by pH in the range 3-10. 6. Sodium dodecyl sulphate at 1.5% produces a small decrease in S; the effect is greater than would be expected from the observed extent of binding, but is too small to correspond to a significant change in secondary structure; the serological activity is unaffected by sodium dodecyl sulphate. 7. All the properties observed indicate the absence of any secondary structure in blood-group substances.

Thomsen-Friedenreich (T) antigen expression increases sensitivity of natural killer cell lysis of cancer cells

In this study, we demonstrate a correlation between T antigen expression on a panel of human carcinoma cell lines and their sensitivity to porcine NK cell lysis. Specifically, the more T antigen is expressed, the more sensitive the cancer cells are to porcine NK cell lysis. Furthermore, this correlation also exists for these cells and their ability to induce tumors in vivo. In this porcine animal model, the less T antigen is expressed, the more prolific the tumor growth in vivo and vice versa. Using the human colorectal adenocarcinoma cell line SW-48, we used limiting dilution to clone 2 populations of cells, one expressing high and the other low levels of T antigen, clones 143 and 111, respectively. In these cloned cells, the clone that expressed more T antigen was more NK-sensitive in vitro and weakly induced tumor growth in vivo. Inversely, the clone that expressed less T antigen clone was more NK-resistant in vitro and grew more prolific tumors in vivo. Using soluble T antigen in a competitive inhibition assay, there was a decrease in porcine NK cell killing of the T antigen+ human cell line Colo 320HSR. Taken together, these findings suggest a novel role for T antigen in the NK cell recognition of cancer cells, specifically as markers for NK sensitivity in carcinoma cell lines. The significance of T antigens as targets for NK cell-mediated lysis is novel and identifies NK cell-T antigen interactions as potentially significant in the immunotherapy of cancer and its associated metastases.

Carcinoma autoantigens T and Tn and their cleavage products interact with Gal/GalNAc-specific receptors on rat Kupffer cells and hepatocytes

We studied interactions of isolated Thomsen-Friedenreich (T)- and Tn-specific glycoproteins with the Gal/GalNAc-specific receptors on rat Kupffer cells and compared them to those with rat hepatocytes. Immunoreactive T and Tn are specific pancarcinoma epitopes. Electron microscopy of gold-labelled T and Tn antigens revealed their specific binding to Kupffer cells, followed by their uptake via the coated pit/vesicle pathway of receptor-mediated endocytosis. Preincubation of Kupffer cells with GalNAc and GalNAc-BSA, but not GlcNAc or GlcNAc-BSA specifically inhibited binding of the T and Tn glycoproteins. Desialylated, isologous erythrocytes (T RBC) are known to bind to the Gal/GalNAc receptors of rat Kupffer cells and hepatocytes. This attachment was specifically inhibited by T and Tn in a concentration-dependent manner: 50% T RBC-Kupffer cell contacts were inhibited at 8.5.10(-6) mM T and 8.5.10(-5) mM Tn antigen concentrations, respectively. The corresponding figures for hepatocytes were 6.10(-6) mM T and 1.2.10(-6) mM Tn antigen. Amino-terminal cleavage products of the T glycoprotein, possessing clusters terminating in non-reducing Gal/GalNAc, inhibited T RBC binding to Kupffer cells and hepatocytes usually at 10(-2) to 10(-5) mM concentrations, whereas GalNAc, galactose and galactose glycosides inhibited at millimolar concentrations. Galactose-unrelated carbohydrates were inactive at concentrations greater than or equal to 50 mM.

Prelminary examination of rabbit conjunctival mucins

Conjunctival mucins from albino rabbits were fractionated using gel filtration and anion-exchange chromatography. Charge homogeneity of the various conjunctival mucin fractions was confirmed by polyacrylamide gel electrophoresis. The molecular weight characteristics of the isolated fractions varied with the analytical scheme employed. Two schemes yielded mucins with molecular weights of 10(4), 10(5), and 10(6). However, when anion-exchange chromatography was the first step in the fractionation scheme, the dominant mucin had a molecular weight of 1.7 x 10(5). In contrast, when gel filtration chromatography was the first step, the dominant mucin had a molecular weight of 5.7 x 10(4). It was postulated that during migration through the anion-exchange matrix, the low molecular weight conjunctival mucin underwent trimer formation. Comparison with the mucin fractions isolated from tear mucoid threads revealed that the scheme beginning with anion-exchange chromatography preserved the fractionation pattern seen in tear mucoid threads. This result implies that conjunctival mucins undergo an association prior to or after their entry into the tear film. The molecular event of interest in this process is self-association of the species with a molecular weight of 5.7 x 10(4), resulting in a trimer with a molecular weight of 1.7 x 10(5). This trimer appears to resist deaggregation on exposure to a medium of lesser ionic strength. Several explanations are offered for its formation as well as for its stability. The implication of multiple conjunctival (tear) mucins for tear film stability also is discussed.

Conformation of blood-group and virus receptor glycoproteins from red cells and secretions

Optical rotatory dispersion of human blood-group and virus receptor glycoproteins from erythrocytes and secretions was studied in the far-ultraviolet. Erythrocyte membrane blood-group glycoproteins, with potent virus receptor activities, contained significant alpha-helical and extended beta conformations, whereas the glycoproteins of secretions were largely disordered. These conclusions were supported by determination of the Moffitt constants (b(0)) and by measurements of circular dichroism.