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4-1BB is an inducible costimulatory molecule that can exert regulatory effects on T cells. Polyclonal antibodies against oligopeptides representing an evolutionarily-conserved region of murine 4-1BB, were prepared and used to stain tissues in normal and inflammatory conditions. The 4-1BB mRNA was detected in the PMA-treated spleen and heart, and constitutively in the brain, kidneys and lungs. The 4-1BB-like protein (BBLP) was expressed on mononuclear cells infiltrating islet cells in the pancreata of NOD mice. Expression was prominent in the early phase of insulitis and the level of expression diminished or disappeared in the later phase. BBLP was identified in the gray matter of brain where neuronal cell bodies, dendrites, and fiber terminals reside but was almost entirely absent in the white matter where axonal fibers dwell. A peculiar rosette pattern was observed in a granular layer of cerebellum and scattered in the stria terminalis. The staining pattern strongly resembled the receptor/nerve terminals in the brain and in the peripheral nervous system. Taken together, BBLP may be associated with the early phase of inflammation and with brain function. [Copyright &y& Elsevier]

Pmel 17 cDNA clones, isolated from wild-type and si/si murine melanocytes, were sequenced and compared. A single nucleotide (A) insertion was found in the putative cytoplasmic tail of the si/si Pmel 17 cDNA clone. This insertion is predicted to alter the last 24 amino acids at the C-terminus and to extend the Pmel 17 protein by 12 residues. The mutation was confirmed by the sequence of the PCR-amplified genomic region including the mutation site. Silver Pmel 17 was not recognized by antibodies directed toward the C-terminal amino acids of wild-type Pmel 17, indicating a defect in this region. These results indicate that silver Pmel 17 protein has a major defect at the carboxyl terminus. [ABSTRACT FROM AUTHOR]

Recent advances in melanogenesis have focused on the role of dihydroxyindole-2-carboxylic acid [(HO)2IndCOOH]. For example, it has been shown that formation of (HO)2IndCOOH from depachrome is catalyzed by dopachrome tautomerase, that the melanogenic protein tyrosinase-related protein (TRP)-1 can oxidize (HO)2IndCOOH to its indole quinone, that (HO)2IndCOOH-melanins can be synthesized chemically, that mammalian melanins are naturally rich in (HO)2IndCOOH subunits, and that (HO)2IndCOOH is incorporated into melanins are naturally rich in (HO)2IndCOOH subunits, and that (HO)2IndCOOH is incorporated into melanins of melanomas in mice. The question thus emerges as to the mechanims(s) by which (HO)2IndCOOH and other precursors become incorporated into melanins in vivo. Accordingly, an activity was partially purified that catalyzed melanin formation with (HO)2IndCOOH as a substrate. Analyses of the (HO)2IndCOOH polymerization factor from Cloudman melanoma cells revealed the following: it was proteinaceous in that it was heat labile and destroyed by proteinase K; it was a glycoprotein in that it adhered to wheat germ agglutinin and was eluted with N-acetyl glucosamine; it was located predominantly in the melanosomal fraction of cell homogenates; the activity was reduced by exposure to the metal chelators EDTA and EGTA, but not by phenylthiourea, a tyrosinase inhibitor; activity was found with the mouse pmel 17/silver locus protein immunopurified from human melanoma cells, and was significantly reduced in extracts of mouse melanocytes cultured from silver (si/si) mice compare to extracts from Si/Si melanocytes. In summary, an activity has been identified in human to mouse melanoma cells that catalyzes the superoxide-dependent polymerization of (HO)2IndCOOH to melanin in vitro, and appears to be a function of the pmel 17/silver protein of the human pmel 17 gene and the mouse silver locus. [ABSTRACT FROM AUTHOR]