The amino acid sensor MetRS is required for methionine-induced milk protein synthesis in a domestic pigeon model.

This study was conducted to investigate whether methionyl-tRNA synthetase (MetRS) is a mediator of Met-induced crop milk protein synthesis via the janus kinase 2 (JAK2)/signal transducer and activator of transcription 5 (STAT5) signalling pathway in breeding pigeons. In Experiment 1, a total of 216 pairs of breeding pigeons were divided into 3 groups (control, Met-deficient, and Met-rescue groups). In Experiments 2 and 3, forty pairs of breeding pigeons from each experiment were allocated into 4 groups. The 2 nd experiment included a control group and 3 MetRS inhibitor (REP8839) groups. The 3 rd experiment included a Met-deficient group, Met-sufficient group, REP8839 + Met-deficient group, and REP8839 + Met-sufficient group. Experiment 1 showed that Met supplementation increased crop development, crop milk protein synthesis, the protein expression of MetRS and JAK2/STAT5 signalling pathway, and improved squab growth. Experiment 2 showed that crop development, crop milk protein synthesis, and the protein expression of MetRS and the JAK2/STAT5 signalling pathway were decreased, and squab growth was inhibited by the injection of 1.0 mg/kg BW REP8839, which was the selected dose for the 3 rd experiment. These results showed that Met supplementation increased crop development, crop milk protein synthesis, and the expression of MetRS and JAK2/STAT5 signalling pathway and rescued squab growth after the injection of REP8839. Moreover, the Co-IP results showed that there was an interaction between MetRS and JAK2. Taken together, these findings indicate that MetRS mediates Met-induced crop milk protein synthesis via the JAK2/STAT5 signalling pathway, resulting in improved squab growth in breeding pigeons.