Irisin and FNDC5 in retrospect: An exercise hormone or a transmembrane receptor?
Abstract
FNDC5 (fibronectin domain-containing [protein] 5) was initially discovered and characterized
by two groups in 2002. In 2011 FNDC5 burst into prominence as the parent of irisin,
a small protein containing the fibronectin type III domain. Irisin was proposed to
be secreted by skeletal muscle cells in response to exercise, and to circulate to
fat tissue where it induced a transition to brown fat. Since brown fat results in
dissipation of energy, this pathway is of considerable interest for metabolism and
obesity. Here I review the original discoveries of FNDC5 and the more recent discovery
of irisin. I note in particular three problems in the characterization of irisin:
the antibodies used to detect irisin in plasma lack validity; the recombinant protein
used to demonstrate activity in cell culture was severely truncated; and the degree
of shedding of soluble irisin from the cell surface has not been quantitated. The
original discovery proposing that FNDC5 may be a transmembrane receptor may deserve
a new look.
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https://hdl.handle.net/10161/9280Published Version (Please cite this version)
10.4161/adip.26082Publication Info
Erickson, Harold P (2013). Irisin and FNDC5 in retrospect: An exercise hormone or a transmembrane receptor?.
Adipocyte, 2(4). pp. 289-293. 10.4161/adip.26082. Retrieved from https://hdl.handle.net/10161/9280.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Harold Paul Erickson
James B. Duke Distinguished Professor Emeritus
Recent research has been on cytoskeleton (eukaryotes and bacteria); a skirmish to
debunk the irisin story; a reinterpretation of proposed multivalent binders of the
coronavirus spike protein. I have also published an ebook on "Principles of Protein-Protein
Association" suitable for a course module or individual learning.

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