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Sci Rep. 2018 Feb 2;8(1):2207. doi: 10.1038/s41598-018-20684-8.

Demonstration of ion channel synthesis by isolated squid giant axon provides functional evidence for localized axonal membrane protein translation.

Author information

1
National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA.
2
Bioinformatics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA.
3
Facultad de Ciencias, Universidad de Chile, Santiago, 7750000, Chile.
4
Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, 2366103, Chile. ramon.latorre@uv.cl.
5
Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois, 60637, USA. fbezanilla@peds.bsd.uchicago.edu.
6
National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA. holmgren@ninds.nih.gov.

Abstract

Local translation of membrane proteins in neuronal subcellular domains like soma, dendrites and axon termini is well-documented. In this study, we isolated the electrical signaling unit of an axon by dissecting giant axons from mature squids (Dosidicus gigas). Axoplasm extracted from these axons was found to contain ribosomal RNAs, ~8000 messenger RNA species, many encoding the translation machinery, membrane proteins, translocon and signal recognition particle (SRP) subunits, endomembrane-associated proteins, and unprecedented proportions of SRP RNA (~68% identical to human homolog). While these components support endoplasmic reticulum-dependent protein synthesis, functional assessment of a newly synthesized membrane protein in axolemma of an isolated axon is technically challenging. Ion channels are ideal proteins for this purpose because their functional dynamics can be directly evaluated by applying voltage clamp across the axon membrane. We delivered in vitro transcribed RNA encoding native or Drosophila voltage-activated Shaker KV channel into excised squid giant axons. We found that total K+ currents increased in both cases; with added inactivation kinetics on those axons injected with RNA encoding the Shaker channel. These results provide unambiguous evidence that isolated axons can exhibit de novo synthesis, assembly and membrane incorporation of fully functional oligomeric membrane proteins.

PMID:
29396520
PMCID:
PMC5797086
DOI:
10.1038/s41598-018-20684-8
[Indexed for MEDLINE]
Free PMC Article

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