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The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation.

Publication ,  Journal Article
Schumacher, MA; Chinnam, N; Ohashi, T; Shah, RS; Erickson, HP
Published in: J Biol Chem
November 22, 2013

Irisin was recently identified as a putative myokine that is induced by exercise. Studies suggest that it is produced by cleavage of the FNDC5 (fibronectin domain-containing protein 5) receptor; irisin corresponds to the extracellular receptor ectodomain. Data suggesting that irisin stimulates white-to-brown fat conversion have led to the hypothesis that it does so by binding an unknown receptor, thus functioning as a myokine. As brown fat promotes energy dissipation, myokines that elicit the transformation of white to brown fat have potentially profound benefits in the treatment of obesity and metabolic disorders. Understanding the molecular basis for such exercise-induced phenomena is thus of considerable interest. Moreover, FNDC5-like receptors are highly conserved and have been shown to be critical for neuronal development. However, the structural and molecular mechanisms utilized by these proteins are currently unknown. Here, we describe the crystal structure and biochemical characterization of the FNDC5 ectodomain, corresponding to the irisin myokine. The 2.28 Å structure shows that irisin consists of an N-terminal fibronectin III (FNIII)-like domain attached to a flexible C-terminal tail. Strikingly, the FNIII-like domain forms a continuous intersubunit β-sheet dimer, previously unobserved for any FNIII protein. Biochemical data confirm that irisin is a dimer and that dimerization is unaffected by glycosylation. This finding suggests a possible mechanism for receptor activation by the irisin domain as a preformed myokine dimer ligand or as a paracrine or autocrine dimerization module on FNDC5-like receptors.

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Published In

J Biol Chem

DOI

EISSN

1083-351X

Publication Date

November 22, 2013

Volume

288

Issue

47

Start / End Page

33738 / 33744

Location

United States

Related Subject Headings

  • Structure-Activity Relationship
  • Recombinant Proteins
  • Protein Structure, Tertiary
  • Protein Structure, Secondary
  • Protein Structure, Quaternary
  • Protein Multimerization
  • Humans
  • Glycosylation
  • Fibronectins
  • Crystallography, X-Ray
 

Citation

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Schumacher, M. A., Chinnam, N., Ohashi, T., Shah, R. S., & Erickson, H. P. (2013). The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation. J Biol Chem, 288(47), 33738–33744. https://doi.org/10.1074/jbc.M113.516641
Schumacher, Maria A., Nagababu Chinnam, Tomoo Ohashi, Riddhi Sanjay Shah, and Harold P. Erickson. “The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation.J Biol Chem 288, no. 47 (November 22, 2013): 33738–44. https://doi.org/10.1074/jbc.M113.516641.
Schumacher MA, Chinnam N, Ohashi T, Shah RS, Erickson HP. The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation. J Biol Chem. 2013 Nov 22;288(47):33738–44.
Schumacher, Maria A., et al. “The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation.J Biol Chem, vol. 288, no. 47, Nov. 2013, pp. 33738–44. Pubmed, doi:10.1074/jbc.M113.516641.
Schumacher MA, Chinnam N, Ohashi T, Shah RS, Erickson HP. The structure of irisin reveals a novel intersubunit β-sheet fibronectin type III (FNIII) dimer: implications for receptor activation. J Biol Chem. 2013 Nov 22;288(47):33738–33744.

Published In

J Biol Chem

DOI

EISSN

1083-351X

Publication Date

November 22, 2013

Volume

288

Issue

47

Start / End Page

33738 / 33744

Location

United States

Related Subject Headings

  • Structure-Activity Relationship
  • Recombinant Proteins
  • Protein Structure, Tertiary
  • Protein Structure, Secondary
  • Protein Structure, Quaternary
  • Protein Multimerization
  • Humans
  • Glycosylation
  • Fibronectins
  • Crystallography, X-Ray