FNDC5 is a membrane protein comprised by a short cytoplasmic domain, a transmembrane segment, and an ectodomain consisting of a fibronectin type III (FNIII) domain. The ectodomain has been proposed to be cleaved to a soluble peptide hormone named “irisin”. Irisin is secreted from muscle in response to exercise, and may regulate energy metabolism, stem cell differentiation, and neuronal development. The circulating irisin converts white fat into the more thermogenic beige fat, and may mediate some beneficial effects of exercise in humans and the potential for generating weight loss. In mice, expression of Irisin has been shown to regulate obesity and diabetes. A similar function is suggested in human.
Lyophilized protein should be stored at -20˚C, though stable at room temperature for 3 weeks. Reconstituted protein solution can be stored at 4-7˚C for 2-7 days. Aliquots of reconstituted samples are stable at -20˚C for 3 months.