Isolation and chemical and immunochemical characterization of the peanut-lectin-binding glycoprotein from human milk-fat-globule membranes

Abstract

Membrane glycoprotein with high Mr (HMr-MGP) was purified from neuraminidase-treated Triton X-100-solubilized human milk-fat-globule membranes by peanut-agglutinin (PNA) affinity chromatography. The high carbohydrate content (75%), blood-group-A activity and typical monosaccharide composition (L-fucose, D-galactose, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine in the proportions 0.26:1.00:1.85:1.30) indicate that the isolated HMr-MGP is a mucinous substance. Fractionation of the oligosaccharides from alkaline-borohydride-treated HMr-MGP on Bio-Gel P-2 suggest that the PNA-binding sites are located mainly on longer (tetra- to deca-saccharide) alkali-labile bound oligosaccharide chains. Polyclonal antibodies raised against the HMr-MGP showed an antigenic distribution in histological sections that was comparable with the distribution of peroxidase-labelled-PNA-binding sites in both normal and malignant breast tissues. The positive immunohistological staining of some other tissue components with this antibody indicates that HMr-MGP is not strictly breast-associated. The functional role of HMr-MGP is unknown, but, since its expression is dependent on the differentiation state of secretory epithelial cells, it serves as a differentiation antigen that can be used for better functional characterization of breast cancers.

Inhibition of adhesion of S-fimbriated Escherichia coli to buccal epithelial cells by human milk fat globule membrane components: a novel aspect of the protective function of mucins in the nonimmunoglobulin fraction

“…According to this particular property, mucins which are found in human secretions or in epithelial membranes are suitable candidates for representing organ-characteristic glycosylation and thus express a variety of receptor-analog structures for bacterial adhesins. Mucins are regular constituents of human milk serum (19) and HMFGM (13). The common structural unit of all acidic glycans on secretory milk mucins is the terminal disaccharide unit NeuAcot-(2-3)-GalI, which has been demonstrated to form a receptor analog for S-fimbriated E. coli (22).…”

“…The membrane surrounding the lipid core is derived from the apical plasma membrane of mammary epithelial cells by apocrine secretion (11,12). High-molecular-mass glycoproteins with a high content of 0-glycosidic-linked carbohydrates (termed mucins) are a major constituent of these membranes (7,13,41). As these human milk fat globule membranes (HMFGM) are of epithe-lial origin, we expected them to express carbohydrate structures that might serve as receptor analogs for certain pathogenic bacteria.…”

Development and characterization of a syngeneic monoclonal antibody to a rat mammary tumor metastasis‐associated mucin like cell‐surface antigen (gp580)

“…(1986) have reported a further high-M, component present in HMFG membranes (approx. 550,000) which may be more similar to gp580 than PAS-0, as may the high Mr glycoprotein, also isolated from HMFG (Fischer et al, 1984). Differences in distribution of PAS-0 and gp580 are suggested by the fact that we did not detect significant immunoreactivity of MAb GP2156 with normal rat mammary tissue (data not shown).…”

Differences between individuals in high‐Mr glycoproteins from human mammary epithelia

“…We view evidence of their human diversity in the MFG as a forerunner of what may be revealed in other tissues and cells. Fischer et al [13] have reported that both peanut agglutinin and polyclonal antibodies to the HM, glycoproteins of human MFGs bind to apical membranes of fundic glands in gastric mucosa, distal tubuli of human kidney, cells of histiocytic origin and some mammary carcinomas. A band of glycoprotein comigrating on SDS gels with those in our 4% gel (figs 1 and 2) has been detected in plasma membrane from porcine intestinal mucosal cells (Patton, S. and Patton, J.S., unpublished).…”