The apoptotic initiator Caspase-8: its functional ubiquity and genetic diversity during animal evolution

The caspases, a family of cysteine proteases, play multiple roles in apoptosis, inflammation, and cellular differentiation. Caspase-8 (Casp8), which was first identified in humans, functions as an initiator caspase in the apoptotic signaling mediated by cell-surface death receptors. To understand the evolution of function in the Casp8 protein family, casp8 orthologs were identified from a comprehensive range of vertebrates and invertebrates, including sponges and cnidarians, and characterized at both the gene and protein levels. Some introns have been conserved from cnidarians to mammals, but both losses and gains have also occurred; a new intron arose during teleost evolution, whereas in the ascidian Ciona intestinalis, the casp8 gene is intronless and is organized in an operon with a neighboring gene. Casp8 activities are near ubiquitous throughout the animal kingdom. Exogenous expression of a representative range of nonmammalian Casp8 proteins in cultured mammalian cells induced cell death, implying that these proteins possess proapoptotic activity. The cnidarian Casp8 proteins differ considerably from their bilaterian counterparts in terms of amino acid residues in the catalytic pocket, but display the same substrate specificity as human CASP8, highlighting the complexity of spatial structural interactions involved in enzymatic activity. Finally, it was confirmed that the interaction with an adaptor molecule, Fas-associated death domain protein, is also evolutionarily ancient. Thus, despite structural diversity and cooption to a variety of new functions, the ancient origins and near ubiquitous distribution of this activity across the animal kingdom emphasize the importance and utility of Casp8 as a central component of the metazoan molecular toolkit

Eosinophilic Cholangitis Without Biliary Stricture After the Treatment of Eosinophilic Esophagitis

Eosinophilic cholangitis (EC) is an uncommon, benign, self-limiting disease, which typically causes bile duct stricture with eosinophil infiltration. We report the case of a 70-year-old woman who presented with abdominal pain diagnosed with EC after treatment for eosinophilic esophagitis. All previous reported cases of EC had bile duct stricture seen on magnetic resonance cholangiopancreatography or cholangiogram during endoscopic retrograde cholangiopancreatography, but only wall thickness of the common bile duct was noted in our case. Although rare, EC should be considered when wall thickening of the bile duct is observed, even without stricture