RESUMO
Spinal muscular atrophy (SMA) is a motor neuron disease caused by reduced levels of the survival of motor neuron (SMN) protein. SMN is part of a multiprotein complex that facilitates the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs). SMN has also been found to associate with mRNA-binding proteins, but the nature of this association was unknown. Here, we have employed a combination of biochemical and advanced imaging methods to demonstrate that SMN promotes the molecular interaction between IMP1 protein and the 3' UTR zipcode region of ß-actin mRNA, leading to assembly of messenger ribonucleoprotein (mRNP) complexes that associate with the cytoskeleton to facilitate trafficking. We have identified defects in mRNP assembly in cells and tissues from SMA disease models and patients that depend on the SMN Tudor domain and explain the observed deficiency in mRNA localization and local translation, providing insight into SMA pathogenesis as a ribonucleoprotein (RNP)-assembly disorder.
Assuntos
Chaperonas Moleculares/metabolismo , Neurônios Motores/metabolismo , Ribonucleoproteínas/metabolismo , Regiões 3' não Traduzidas/fisiologia , Actinas/metabolismo , Células Cultivadas , Citoesqueleto/metabolismo , Humanos , Atrofia Muscular Espinal/metabolismo , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Ribonucleoproteínas Nucleares Pequenas/metabolismo , Proteínas do Complexo SMN/metabolismoRESUMO
Dysbindin is a schizophrenia susceptibility factor and subunit of the biogenesis of lysosome-related organelles complex 1 (BLOC-1) required for lysosome-related organelle biogenesis, and in neurons, synaptic vesicle assembly, neurotransmission, and plasticity. Protein networks, or interactomes, downstream of dysbindin/BLOC-1 remain partially explored despite their potential to illuminate neurodevelopmental disorder mechanisms. Here, we conducted a proteome-wide search for polypeptides whose cellular content is sensitive to dysbindin/BLOC-1 loss of function. We identified components of the vesicle fusion machinery as factors downregulated in dysbindin/BLOC-1 deficiency in neuroectodermal cells and iPSC-derived human neurons, among them the N-ethylmaleimide-sensitive factor (NSF). Human dysbindin/BLOC-1 coprecipitates with NSF and vice versa, and both proteins colocalized in a Drosophila model synapse. To test the hypothesis that NSF and dysbindin/BLOC-1 participate in a pathway-regulating synaptic function, we examined the role for NSF in dysbindin/BLOC-1-dependent synaptic homeostatic plasticity in Drosophila. As previously described, we found that mutations in dysbindin precluded homeostatic synaptic plasticity elicited by acute blockage of postsynaptic receptors. This dysbindin mutant phenotype is fully rescued by presynaptic expression of either dysbindin or Drosophila NSF. However, neither reduction of NSF alone or in combination with dysbindin haploinsufficiency impaired homeostatic synaptic plasticity. Our results demonstrate that dysbindin/BLOC-1 expression defects result in altered cellular content of proteins of the vesicle fusion apparatus and therefore influence synaptic plasticity.
Assuntos
Proteínas de Drosophila/metabolismo , Proteínas Associadas à Distrofina/metabolismo , Regulação da Expressão Gênica/fisiologia , Proteínas Sensíveis a N-Etilmaleimida/metabolismo , Plasticidade Neuronal/fisiologia , Sinapses/fisiologia , Animais , Animais Geneticamente Modificados , Linhagem Celular Tumoral , Drosophila , Proteínas de Drosophila/genética , Disbindina , Proteínas Associadas à Distrofina/genética , Regulação da Expressão Gênica/genética , Humanos , Melanoma/patologia , Proteínas Sensíveis a N-Etilmaleimida/genética , Rede Nervosa/fisiologia , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neuroblastoma/patologia , Junção Neuromuscular/genética , Junção Neuromuscular/metabolismo , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/genética , Proteínas SNARE/metabolismo , Sinapses/genética , Vesículas Sinápticas/genética , Vesículas Sinápticas/metabolismoRESUMO
Enteric bacteria are able to resist the high concentrations of bile encountered throughout the gastrointestinal tract. Here we review the current mechanisms identified in the enteric bacteria Salmonella, Escherichia coli, Bacillus cereus and Listeria monocytogenes to resist the dangerous effects of bile. We describe the role of membrane transport systems, and their connection with DNA repair pathways, in conferring bile resistance to these enterics. We discuss the findings from recent investigations that indicate bile tolerance is dependent upon being able to resist the detergent properties of bile at both the membrane and DNA level.
