Fig. 3: FARS phenylalanylates IR Lys1057/1079.
From: Phenylalanine impairs insulin signaling and inhibits glucose uptake through modification of IRβ
a Me-Phe has negligible effects on insulin signaling in IR-KO HepG2 cells. Phosphorylation of the components of the insulin signaling pathway was detected in HepG2 and IR-KO HepG2 cells in the absence and presence of Me-Phe. b FARSA/B overexpression has no effect on 2-DG uptake in IR-silenced 3T3-L1 adipocytes. 2-DG uptake was detected in 3T3-L1 adipocytes and IR-silenced 3T3-L1 adipocytes (n = 5). c Me-Phe fails to inhibit 2-DG uptake in IR-silenced 3T3-L1 adipocytes. 2-DG uptake was detected in WT and IR-silenced 3T3-L1 adipocytes in the absence and presence of Me-Phe (n = 5). d Me-Phe increases F-K1057/1079 levels. The levels of F-K1057/1079 were detected in 3T3-L1 adipocytes at the indicated time points after the cells were treated with Me-Phe. e FARSA/B overexpression increases F-K1057/1079 levels. F-K1057/1079 levels were detected in 3T3-L1 adipocytes and in 3T3-L1 adipocytes overexpressing FARSA/B. f FARSA/B phenylalanylates IR K1057 and K1079 peptides. The ability of recombinant FARSA/B and FARSAY412R/F438R/B to phenylalanylate K1057-and K1079-containing IR peptides in vitro was tested. The formation of phenylalanylated products (red arrows) was assayed by mass spectrometry. g FARSA/B phenylalanylates IRβ. The abilities of recombinant FARSA/B and FARSAY412R/F438R/B to phenylalanylate recombinant IR were tested. The formation of F-K1057/1079 was detected using western blotting. h FARSA knockdown reduces F-K1057/1079 levels. F-K1057/1079 levels were detected in 3T3-L1 adipocytes and FARSA-knockdown 3T3-L1 adipocytes. i hFARSA overexpression increases F-K1057/1079 levels. The levels of F-K1057/1079 were detected in the liver and muscle tissues of C57 and hFARSA-transgenic C57 mice. j Phenylalanine treatment increases F-K1057/1079 levels. The levels of F-K1057/1079 were quantified in 3T3-L1 adipocytes that were untreated or treated with phenylalanine. k Aspartame increases F-K1057/1079 levels. The levels of F-K1057/1079 were detected in 3T3-L1 adipocytes at the indicated doses after the cells were treated with aspartame (APM). Significance was indicated as two-tailed, unpaired, t test for (k), one-way ANOVA test for (b, c). Values are expressed as the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001.
