ABSTRACT
Vesicular transport is essential for delivering cargo to intracellular destinations. Evi5 is a Rab11-GTPase-activating protein involved in endosome recycling. In humans, Evi5 is a high-risk locus for multiple sclerosis, a debilitating disease that also presents with excess iron in the CNS. In insects, the prothoracic gland (PG) requires entry of extracellular iron to synthesize steroidogenic enzyme cofactors. The mechanism of peripheral iron uptake in insect cells remains controversial. We show that Evi5-depletion in the Drosophila PG affected vesicle morphology and density, blocked endosome recycling and impaired trafficking of transferrin-1, thus disrupting heme synthesis due to reduced cellular iron concentrations. We show that ferritin delivers iron to the PG as well, and interacts physically with Evi5. Further, ferritin-injection rescued developmental delays associated with Evi5-depletion. To summarize, our findings show that Evi5 is critical for intracellular iron trafficking via transferrin-1 and ferritin, and implicate altered iron homeostasis in the etiology of multiple sclerosis.
Subject(s)
Drosophila Proteins , Drosophila melanogaster , Ferritins , GTPase-Activating Proteins , Iron , Transferrin , Animals , Drosophila melanogaster/metabolism , Drosophila melanogaster/genetics , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Endosomes/metabolism , Ferritins/metabolism , Ferritins/genetics , Iron/metabolism , Protein Transport , Transferrin/metabolism , GTPase-Activating Proteins/genetics , GTPase-Activating Proteins/metabolismABSTRACT
Regulatory sequences such as promoters not only contain cis-regulatory elements as switches of transcription, but also exhibit particular topological features. In this paper, we introduce a systematic genome scale approach to characterize the roles of structural conformation and stability profile of promoter sequence in gene expression. The average free energy of promoter dinucleotides stacking nearest neighbors are subjected to scrutiny by statistical hidden Markov models to reveal the function of constrains and properties of promoter structure in transcription. When applied for a 1000 bp 5' upstream sequence of genes, the proposed model via assessing free energy profile identified co-expressed genes of Arabidopsis thaliana in response to the auxin hormone. The applied perspective dynamic network which mediates transcription regulation provides a great hindrance to conceive how DNA conformation interacts with cis-regulatory elements, chromatin structure and many other factors. This study indeed drew the complexity of the promoter's regulatory behavior from sequence over the former studies and evokes a new hypothesis to be validated experimentally.
