Regina-Celeste Ahmad

Publications (2)47.64 Total impact

• Source

  Available from: Rita M Tavares

  Article: The ubiquitin-editing enzyme A20 restricts nucleotide-binding oligomerization domain containing 2-triggered signals.

  Osamu Hitotsumatsu, Regina-Celeste Ahmad, Rita Tavares, Min Wang, Dana Philpott, Emre E Turer, Bettina L Lee, Nataliya Shiffin, Rommel Advincula, Barbara A Malynn, Catherine Werts, Averil Ma
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  ABSTRACT: Muramyl dipeptide (MDP), a product of bacterial cell-wall peptidoglycan, activates innate immune cells by stimulating nucleotide-binding oligomerization domain containing 2 (NOD2) -dependent activation of the transcription factor NFkappaB and transcription of proinflammatory genes. A20 is a ubiquitin-modifying enzyme that restricts tumor necrosis factor (TNF) receptor and Toll-like receptor (TLR) -induced signals. We now show that MDP induces ubiquitylation of receptor- interacting protein 2 (RIP2) in primary macrophages. A20-deficient cells exhibit dramatically amplified responses to MDP, including increased RIP2 ubiquitylation, prolonged NFkappaB signaling, and increased production of proinflammatory cytokines. In addition, in vivo responses to MDP are exaggerated in A20-deficient mice and in chimeric mice bearing A20-deficient hematopoietic cells. These exaggerated responses occur independently of the TLR adaptors MyD88 and TRIF as well as TNF signals. These findings indicate that A20 directly restricts NOD2 induced signals in vitro and in vivo, and provide new insights into how these signals are physiologically restricted.
  Immunity 04/2008; 28(3):381-90. · 21.64 Impact Factor
• Source

  Available from: migindia.biz

  Article: The ubiquitin-modifying enzyme A20 is required for termination of Toll-like receptor responses.

  David L Boone, Emre E Turer, Eric G Lee, Regina-Celeste Ahmad, Matthew T Wheeler, Colleen Tsui, Paula Hurley, Marcia Chien, Sophia Chai, Osamu Hitotsumatsu, Elizabeth McNally, Cecile Pickart, Averil Ma
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  ABSTRACT: A20 is a cytoplasmic protein required for the termination of tumor necrosis factor (TNF)-induced signals. We show here that mice doubly deficient in either A20 and TNF or A20 and TNF receptor 1 developed spontaneous inflammation, indicating that A20 is also critical for the regulation of TNF-independent signals in vivo. A20 was required for the termination of Toll-like receptor-induced activity of the transcription factor NF-kappaB and proinflammatory gene expression in macrophages, and this function protected mice from endotoxic shock. A20 accomplished this biochemically by directly removing ubiquitin moieties from the signaling molecule TRAF6. The critical function of this deubiquitinating enzyme in the restriction of TLR signals emphasizes the importance of the regulation of ubiquitin conjugation in innate immune cells.
  Nature Immunology 11/2004; 5(10):1052-60. · 26.01 Impact Factor