RESUMEN
Mitochondrial fission occurs in many cellular processes, but the regulation of fission is poorly understood. We show that long-chain acyl-coenzyme A (LCACA) activates two related mitochondrial fission proteins, MiD49 and MiD51, by inducing their oligomerization, which activates their ability to stimulate the DRP1 GTPase. The 1:1 stoichiometry of LCACA:MiD in the oligomer suggests interaction in the previously identified nucleotide-binding pocket, and a point mutation in this pocket reduces LCACA binding and LCACA-induced oligomerization for MiD51. In cells, this LCACA binding mutant does not assemble into puncta on mitochondria or rescue MiD49/51 knockdown effects on mitochondrial length and DRP1 recruitment. Furthermore, cellular treatment with BSA-bound oleic acid, which causes increased LCACA, promotes mitochondrial fission in an MiD49/51-dependent manner. These results suggest that LCACA is an endogenous ligand for MiDs, inducing mitochondrial fission and providing a potential mechanism for fatty-acid-induced mitochondrial division. Finally, MiD49 or MiD51 oligomers synergize with Mff, but not with actin filaments, in DRP1 activation, suggesting distinct pathways for DRP1 activation.
Asunto(s)
Acilcoenzima A , Dinaminas , GTP Fosfohidrolasas , Mitocondrias , Dinámicas Mitocondriales , Proteínas Mitocondriales , Dinámicas Mitocondriales/efectos de los fármacos , Dinaminas/metabolismo , Dinaminas/genética , Humanos , Mitocondrias/metabolismo , Mitocondrias/efectos de los fármacos , Proteínas Mitocondriales/metabolismo , Proteínas Mitocondriales/genética , GTP Fosfohidrolasas/metabolismo , GTP Fosfohidrolasas/genética , Acilcoenzima A/metabolismo , Multimerización de Proteína , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas Asociadas a Microtúbulos/genética , Animales , Unión Proteica , Células HeLa , Células HEK293 , Ácido Oléico/farmacología , Ácido Oléico/metabolismo , Proteínas de la Membrana , Factores de Elongación de PéptidosRESUMEN
Cryptococcus neoformans (Cn) causes meningoencephalitis in immunocompromised individuals. This encapsulated fungus can be found interacting with environmental microbes in soil contaminated with pigeon excrement. Cn survival within polymicrobial and other challenging communities has been shown to affect the evolution of its virulence factors. We compared the survival of 10 serotype A and D strains after interaction with the soil bacterium, Acinetobacter baumannii (Ab). Although co-incubation with Ab stimulated virulence factors production by strains of both cryptococcal serotypes, on average, serotype A strains displayed significantly higher survival rate, number of metabolically active cells within biofilms, and capsular polysaccharide production and release than serotype D strains. Our findings suggest that interactions of Cn with other microorganisms influence the fungus' regulation and production of virulence factors, important elements needed for the successful colonization of the human host.
Asunto(s)
Acinetobacter baumannii/fisiología , Cryptococcus neoformans/fisiología , Interacciones Microbianas , Acinetobacter baumannii/crecimiento & desarrollo , Acinetobacter baumannii/metabolismo , Cryptococcus neoformans/crecimiento & desarrollo , Cryptococcus neoformans/metabolismo , Viabilidad Microbiana , Serogrupo , Factores de Virulencia/metabolismoRESUMEN
Acinetobacter baumannii (Ab) is a common cause of community-acquired pneumonia (CAP) in chronic alcoholics in tropical and sub-tropical climates and associated with a >50% mortality rate. Using a murine model of alcohol (EtOH) administration, we demonstrated that EtOH enhances Ab-mediated pneumonia leading to systemic infection. Although EtOH did not affect neutrophil recruitment to the lungs of treated mice, it decreased phagocytosis and killing of bacteria by these leukocytes leading to increased microbial burden and severity of disease. Moreover, we determined that mice that received EtOH prior to Ab infection were immunologically impaired, which was reflected in increased pulmonary inflammation, sequential dissemination to the liver and kidneys, and decreased survival. Furthermore, immunosuppression by EtOH was associated with deregulation of cytokine production in the organs of infected mice. This study establishes that EtOH impairs immunity in vivo exacerbating Ab infection and disease progression. The ability of Ab to cause disease in alcoholics warrants the study of its virulence mechanisms and host interactions.