Emerging concepts about NAIP/NLIRC4 inflammasomes

Neuronal apoptosis inhibitory protein (NAIP)/NOD-like receptor (NLR) containing a caspase activating and recruitment domain (CARD) 4 (NLRC4) inflammasome complexes are activated in response to proteins from virulent bacteria that reach the cell cytosol. Specific NAIP proteins bind to the agonists and then physically associate with NLRC4 to form an inflammasome complex able to recruit and activate pro-caspase-1. NAIP5 and NAIP6 sense flagellin, component of flagella from motile bacteria, whereas NAIP1 and NAIP2 detect needle and rod components from bacterial type III secretion systems, respectively. Active caspase-1 mediates the maturation and secretion of the pro-inflammatory cytokines, 11,113 and 11,18, and is responsible for the induction of pyroptosis, a pro-inflammatory form of cell death. in addition to these well-known effector mechanisms, novel roles have been described for NAIP/NLRC4 inflammasomes, such as phagosomal maturation, activation of inducible nitric oxide synthase, regulation of autophagy, secretion of inflammatory mediators, antibody production, activation of T cells, among others. These effector mechanisms mediated by NAIP/NLRC4 inflammasomes have been extensively studied in the context of resistance of infections and the potential of their agonists has been exploited in therapeutic strategies to non-infectious pathologies, such as tumor protection. Thus, this review will discuss current knowledge about the activation of NAIP/NLRC4 inflammasomes and their effector mechanisms.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)INCTVUniversidade Federal de São Paulo, Ctr Terapia Celulare & Mol CTC Mol, BR-04044010 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Dept Ciencias Biol, BR-04044010 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Ctr Terapia Celulare & Mol CTC Mol, BR-04044010 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Dept Ciencias Biol, BR-04044010 São Paulo, SP, BrazilFAPESP: 2013/16010-5Web of Scienc

Strategies of aerobic ammonia-oxidizing bacteria for coping with nutrient and oxygen fluctuations

In most natural environments as well as in engineered environments, such as wastewater treatment plants, ammonia-oxidizing bacteria (AOB) experience fluctuating substrate concentrations. Several physiological traits, such as low maintenance energy demand and decay rate, cell-to-cell communication, cell mobility, stable enzymes and RNAs, could allow AOB to maintain themselves under unfavourable circumstances. This review examines whether AOB possess such traits and how these traits might offer advantages over competing organisms such as heterotrophic bacteria during periods of starvation. In addition, within the AOB groups, differences exist in adaptation to and competitiveness under conditions of high or low ammonia or oxygen concentrations. Because these findings are of importance with regard to the ecology and activity of AOB in natural and engineered environments, concluding remarks are directed towards future research objectives that may clarify unanswered questions, thereby contributing to the general knowledge of the ecology and activity of ammonia oxidizer