Specific antibodies to PAS IV, a glycoprotein of bovine milk-fat-globule membrane, bind to a similar protein in cardiac endothelial cells and epithelial cells of lung bronchioles

A review and proposed nomenclature for major proteins of the milk-fat globule membrane

The characteristics and possible functions of the most abundant proteins associated with the bovine milk-fat globule membrane are reviewed. Under the auspices of the Milk Protein Nomenclature Committee of the ADSA, a revised nomenclature for the major membrane proteins is proposed and discussed in relation to earlier schemes. We recommend that proteins be assigned specific names as they are identified by molecular cloning and sequencing techniques. The practice of identifying proteins according to their Mr, electrophoretic mobility, or staining characteristics should be discontinued, except for uncharacterized proteins. The properties and amino acid sequences of the following proteins are discussed in detail: MUC1, xanthine dehydrogenase/oxidase, CD36, butyrophilin, adipophilin, periodic acid Schiff 6/7 (PAS 6/7), and fatty acid binding protein. In addition, a compilation of less abundant proteins associated with the bovine milk-fat globule membrane is presented.

Identification of CD36 as the first gene dependent on the B-cell differentiation factor Oct-2

The Oct-2 transcription factor is expressed predominantly in B lymphocytes and has been shown previously to be important for the terminal phase of B-cell differentiation in mice. A number of genes specifically expressed in B cells contain Oct-2-binding sites in their regulatory regions. However, the analysis of expression levels of these genes in Oct-2-deficient B cells revealed that they were unaffected. Hence, there were no genes known that critically depend on Oct-2 for their expression. To understand the molecular basis for the Oct-2 effect on B-cell development, we searched for Oct-2 target genes by subtractive cDNA cloning. We show here that expression of the murine CD36 gene in B cells and macrophages requires a functional Oct-2 protein. Nuclear run-on experiments demonstrate that this gene is regulated transcriptionally by Oct-2. Moreover, CD36 levels correlated with the levels of Oct-2 expression in several mouse B-cell and macrophage cell lines. Finally, compared to wild-type and heterozygous mice, CD36 mRNA levels were markedly reduced in spleens and B-cell-enriched splenocyte fractions from oct-2-/- mice. The data identify CD36 as the first target gene critically dependent on Oct-2 for its expression. Because CD36 expression is also dependent on Oct-2 in vivo, it is a candidate gene through which Oct-2 could affect B-cell differentiation.

Antigenic and functional differences in adhesion of Plasmodium falciparum-infected erythrocytes to human and bovine CD36

Cytoadherence by Plasmodium falciparum-infected erythrocytes (PRBC) to microvascular endothelium is, in part, mediated by the specific interaction between a parasite-derived erythrocyte surface ligand and a specific binding site on human CD36. We describe the selection for increased adhesion of PRBC to bovine CD36 and demonstrate that the molecular interaction between PRBC and bovine CD36 is independent of and distinct from the OKM5/8 monoclonal antibody epitopes which block PRBC-human CD36 binding.

Binding of sulfosuccinimidyl fatty acids to adipocyte membrane proteins: isolation and amino-terminal sequence of an 88-kD protein implicated in transport of long-chain fatty acids

We recently reported (Harmon et al., J. Membrane Biol. 124:261-268, 1991) that sulfo-N-succinimidyl derivatives of long-chain fatty acids (SS-FA) specifically inhibited transport of oleate by rat adipocytes. These compounds bound to an 85-90 kD membrane protein which was also labeled by another inhibitor of FA transport [3H]DIDS (4,4'-diisothiocyanostilbene-2-2'-sulfonate). These results indicated that the protein was a strong candidate as the transporter for long-chain fatty acids. In this report we determined that the apparent size of the protein is 88 kD and its isoelectric point is 6.9. We used [3H]SS-oleate (SSO), which specifically labels the 88-kD protein, to isolate it from rat adipocyte plasma membranes. Identification of 15 amino acids at the N-terminus region revealed strong sequence homology with two previously described membrane glycoproteins: CD36, a ubiquitous protein originally identified in platelets and PAS IV, a protein that is enriched in the apical membranes of lipid-secreting mammary cells during lactation. Antibody against PAS IV cross-reacted with the adipocyte protein. This, together with the N-terminal sequence homology, suggested that the adipocyte protein belongs to a family of related intrinsic membrane proteins which include CD36 and PAS IV.