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EXTRA VIEW

Exosome-dependent and independent mechanisms are involved in prion-like transmission of propagated Cu/Zn superoxide dismutase misfolding

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Pages 331-335 | Received 07 Jul 2014, Accepted 19 Sep 2014, Published online: 31 Dec 2014
 

Abstract

Amyotrophic lateral sclerosis (ALS), a fatal adult-onset degenerative neuromuscular disorder with a poorly defined etiology, progresses in an orderly spatiotemporal manner from one or more foci within the nervous system, reminiscent of prion disease pathology. We have previously shown that misfolded mutant Cu/Zn superoxide dismutase (SOD1), mutation of which is associated with a subset of ALS cases, can induce endogenous wild-type SOD1 misfolding in the intracellular environment in a templating fashion similar to that of misfolded prion protein. Our recent observations further extend the prion paradigm of pathological SOD1 to help explain the intercellular transmission of disease along the neuroaxis. It has been shown that both mutant and misfolded wild-type SOD1 can traverse cell-to-cell either as protein aggregates that are released from dying cells and taken up by neighboring cells via macropinocytosis, or released to the extracellular environment on the surface of exosomes secreted from living cells. Furthermore, once propagation of misfolded wild-type SOD1 has been initiated in human cell culture, it continues over multiple passages of transfer and cell growth. Propagation and transmission of misfolded wild-type SOD1 is therefore a potential mechanism in the systematic progression of ALS pathology.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Funding

NRC is the Canada Research Chair in Neurodegeneration and Protein Misfolding Diseases at the University of British Columbia, and is supported by donations from the Webster Foundation, the Allen T. Lambert Neural Research Fund and the Temerty Family Foundation, and also by grants from PrioNet Canada, the Canadian Institutes of Health Research (CIHR), and Biogen-Idec Corp.