Subversion of innate immune responses by Brucella through the targeted degradation of the TLR signaling adapter, MAL.
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Gram-negative bacteria belonging to the Brucella species cause chronic infections that can result in undulant fever, arthritis, and osteomyelitis in humans. Remarkably, Brucella sp. genomes encode a protein, named TcpB, that bears significant homology with mammalian Toll/IL-1 receptor domains and whose expression causes degradation of the phosphorylated, signal competent form of the adapter MyD88-adapter-like (MAL). This effect of TcpB is mediated through its box 1 region and has no effect on other TLR adapter proteins such as MyD88 or TIR-domain containing adapter protein-inducing IFNbeta. TcpB also does not affect a mutant, signal-incompetent form of MAL that cannot be phosphorylated. Interestingly, the presence of TcpB leads to enhanced polyubiquitination of MAL, which is likely responsible for its accelerated degradation. A Brucella abortus mutant lacking TcpB fails to reduce levels of MAL in infected macrophages. Therefore, TcpB represents a unique pathogen-derived molecule that suppresses host innate-immune responses by specifically targeting an individual adapter molecule in the TLR signaling pathway for degradation.
author list (cited authors)
Sengupta, D., Koblansky, A., Gaines, J., Brown, T., West, A. P., Zhang, D., ... Ghosh, S
complete list of authors
Sengupta, Dola||Koblansky, Alicia||Gaines, Jennifer||Brown, Tim||West, A Phillip||Zhang, Dekai||Nishikawa, Tak||Park, Sung-Gyoo||Roop, R Martin||Ghosh, Sankar