Self-association regions in the CARD of Bcl-10

摘要

Many apoptotic signals are mediated by the association of proteins containing homologous domains, such as death domains (DD), death effector domains (DED), and caspase recruitment domains (CARD). Several CARD-containing proteins appear now to be directly involved in modulation of nuclear factor-kB (NF-kB) [1] and in the regulation of inflammatory responses and apoptosis. Among these, Bcl-10 (apoptosis regulator B-cell lymphoma 10) is one of the best studied for its correlation with MALT lymphomas [2, 3] and more recently as a downstream effector of lymphocyte antigen receptors to promote the activation of the IkappaB kinase complex leading to the phosphorylation and degradation of IkappaB [2], Bcl-10 has a bipartite structure consisting of an N-terminal CARD domain and a C-terminal serine-threonine rich domain acting as a regulatory unit that undergoes multiple phosphorylation by several kinases. Most activities of Bcl-10 are accomplished by a dimeric form of the protein; in lymphomas it has been found that a gene translocation event causes over-expression and oligomerization and that the CARD domain mediates the protein self-association [3]. In order to investigate the Bcl-10 CARD regions responsible of protein-protein interactions, here we followed an approach whereby, after protein proteolysis and peptide fractionation, fragments of the CARD domain are utilized as competitors in a self-association ELISA-like assay. The fragments identified have a nM activity and have been characterized by NMR to determine their structural properties in solution.