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. 2021 Nov 11;9:777026. doi: 10.3389/fcell.2021.777026

FIGURE 3.

FIGURE 3

A secreted isoform of FNDC5 (sFNDC5) mediates GLP-1 induced lipolysis and autophagy of β cells. (A) INS-1 cells expressed a long (mFNDC5) and a short FNDC5 (sFNDC5) transcript in agarose analysis. (B) Sequencing chromatograph of the novel secreted FNDC5 isoform. (C,D) Schematic representation of the gene and protein structure of sFNDC5 and mFNDC5. SP, signal peptide; H, hydrophobic transmembrane domain; C, C-terminal domain. (E,F) r-sFNDC5 (50 nM) induced the expression of lipolysis genes but not autophagy-related genes in FNDC5 KO βLox5 cells. Wild-type cells were used as the control. Cells were treated with r-sFNDC5 (50 nM) for 16 h (n = 3). (G) r-sFNDC5 (50 nM) induced the expression of LC3 I/II in wild type but not FNDC5 KO βLox5 cells. Cells were treated with r-sFNDC5 (50 nM) for 24 h (n = 3). β-Actin expression was used as a control in western blotting analysis. Each experiment was repeated three times. Values are mean ± SEM. *p < 0.05 and **p < 0.01.