RESUMO
Recently, mutations in the gene of Janus kinase 2 (Jak2) were discovered in patients suffering from chronic myeloproliferative disorders (MPD) and leukemia. As suppressors of cytokine signaling (SOCS) proteins are potent feedback inhibitors of Jak-mediated signaling, we investigated their role in signal transduction through constitutively active Jak2 mutants. We selected two mutants, Jak2-V617F and Jak2-K539L, found in patients with MPDs and Jak2-T875N identified in acute megakaryoblastic leukemia. We found SOCS family members to be induced through Jak2-V617F in human leukemia cell lines expressing the mutant allele and in stable HEK transfectants inducibly expressing constitutively active Jak2 mutants. SOCS proteins were recruited to the membrane and bound to the constitutively active Jaks. In contrast to wild-type Jak2, the mutant proteins were constitutively ubiquitinated and degraded through the proteasome. Taken together, we show a SOCS-mediated downregulation of the constitutively active, disease-associated mutant Jak2 proteins. Furthermore, a threshold level of mutant Jak expression has to be overcome to allow full cytokine-independent constitutive activation of signaling proteins, which may explain progression to homozygocity in MPDs as well as gene amplification in severe phenotypes and leukemia.
Assuntos
Citocinas/fisiologia , Janus Quinase 2/fisiologia , Transdução de Sinais/fisiologia , Proteínas Supressoras da Sinalização de Citocina/fisiologia , Linhagem Celular Tumoral , Regulação para Baixo , Humanos , Mutação , Complexo de Endopeptidases do Proteassoma/fisiologia , Transporte Proteico , RNA Mensageiro/análise , Fator de Transcrição STAT5/metabolismo , Proteína 1 Supressora da Sinalização de Citocina , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de Citocina/genéticaRESUMO
The aerobic degradation of phenanthrene by a Pseudomonas migulae strain under classical mechanical aeration and under photosynthetic oxygenation (using a Chlorella sorokiniana strain) in a two-phase partitioning bioreactor (TPPB) constructed with silicone oil as organic phase was investigated. When traditional mechanical aeration was used, an increase in the aeration and/or in the agitation rate enhanced phenanthrene biodegradation. Thus, phenanthrene removal rates (based on the total liquid volume of cultivation) ranged from 22 +/- 1 to 36 +/- 2 mg/l h at 100 rpm and 1 vvm and 400 rpm and 3 vvm, respectively. On the other hand, during phenanthrene biodegradation using the algal-bacterial microcosm a maximum rate of 8.1 +/- 1.2 mg/l h at 200 rpm and 8000 lux of illuminance was achieved.
Assuntos
Reatores Biológicos , Fenantrenos/metabolismo , Pseudomonas/metabolismo , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Análise de Variância , Biodegradação Ambiental , Chlorella/metabolismo , Cromatografia Líquida de Alta Pressão , Oxigênio/metabolismo , Espectrofotometria UltravioletaRESUMO
A 43-L column photobioreactor was tested for the treatment of acetonitrile using a symbiotic consortium consisting of a Chlorella sorokiniana strain and a Comamonas strain. Complete biodegradation of 1 g acetonitrile/l was achieved in 79 hours under continuous illumination at 500 microE/m(2)s and 26 degrees C. When the photobioreactor was operated at 26 degrees C under a 14/10 hours light/dark illumination regime at 500 microE/m(2)s, complete mineralization of 1 g acetonitrile/l was achieved in 111 hours. However, when acetonitrile was supplied at 2 g/l, the biodegradation process was severely inhibited by the increase of pH and NH4+ concentration during cultivation. In addition to saving energy for aeration, the microalgae assimilated 33% of the NH4+ released during acetonitrile biodegradation, which significantly reduces the need for subsequent nitrogen removal.
