Anti-obesity and anti-tumor pro-apoptotic peptides are sufficient to cause release of cytochrome c from vesicles.

Peptides that target tissue for an apoptotic death have potential as therapeutics in a variety of disease conditions. The class of peptides described herein enters the cell through a specific receptor-mediated interaction. Once inside the cell, the peptide migrates toward the mitochondria, where the membrane barrier is disrupted. These experiments demonstrate that upon treatment with these short peptides large unilamellar vesicles are not lysed, a graded mode of leakage is observed and the transient pores formed by these peptides are large enough to release entrapped cytochrome c from the vesicles.

T cells and the thymus in developing zebrafish.

The expression of genes encoding T cell receptor (TCR) alpha was used to follow the development of the thymus and to analyze the distribution of T cells in zebrafish. In the thymus, expression was first detected, by in situ hybridization, at four days post fertilization. In RNA extracted from whole fish, TCRalpha transcripts were also detected at four days and reached adult levels at three weeks. At six weeks, TCRalpha was expressed throughout the thymus, whereas rag1 expression was localized to the peripheral regions. Expression of TCRalpha outside the thymus was detected at nine days. In adult peripheral organs, the greatest expression was in the pronephros, mesonephros and intestine; expression in the spleen became greater as fish age. Three new, relatively highly expressed, TCR Valpha families were identified.

Secretory antibody formation: conserved binding interactions between J chain and polymeric Ig receptor from humans and amphibians.

Abs of the secretory Ig (SIg) system reinforce numerous innate defense mechanisms to protect the mucosal surfaces against microbial penetration. SIgs are generated by a unique cooperation between two distinct cell types: plasma cells that produce polymers of IgA or IgM (collectively called pIgs) and polymeric Ig receptor (pIgR)-expressing secretory epithelial cells that mediate export of the pIgs to the lumen. Apical delivery of SIgs occurs by cleavage of the pIgR to release its extracellular part as a pIg-bound secretory component, whereas free secretory components are derived from an unoccupied receptor. The joining chain (J chain) is crucial in pIg/SIg formation because it serves to polymerize Igs and endows them with a binding site for the pIgR. In this study, we show that the J chain from divergent tetrapods including mammals, birds, and amphibians efficiently induced polymerization of human IgA, whereas the J chain from nurse shark (a lower vertebrate) did not. Correctly assembled polymers showed high affinity to human pIgR. Sequence analysis of the J chain identified two regions, conserved only in tetrapods, which by mutational analysis were found essential for pIgA-pIgR complexing. Furthermore, we isolated and characterized pIgR from the amphibian Xenopus laevis and demonstrated that its pIg binding domain showed high affinity to human pIgA. These results showed that the functional site of interaction between pIgR, J chain and Ig H chains is conserved in these species and suggests that SIgs originated in an ancestor common to tetrapods.

J chain in the nurse shark: implications for function in a lower vertebrate.

J chain is a small polypeptide covalently attached to polymeric IgA and IgM. In humans and mice, it plays a role in binding Ig to the polymeric Ig receptor for transport into secretions. The putative orthologue of mammalian J chain has been identified in the nurse shark by sequence analysis of cDNA and the polypeptide isolated from IgM. Conservation with J chains from other species is relatively poor, especially in the carboxyl-terminal portion, and, unlike other J chains, the shark protein is not acidic. The only highly conserved segment in all known J chains is a block of residues surrounding an N-linked glycosylation site. Of the eight half-cystine residues that are conserved in mammalian J chains, three are lacking in the nurse shark, including two in the carboxyl-terminal segment that have been reported to be required for binding of human J chain-containing IgA to secretory component. Taken together with these data, the relative abundance of J chain transcripts in the spleen and their absence in the spiral valve (intestine) suggest that J chain in nurse sharks may not have a role in Ig secretion. Analysis of J chain sequences in diverse species is in agreement with accepted phylogenetic relationships, with the exception of the earthworm, suggesting that the reported presence of J chain in invertebrates should be reassessed.