mTORC2 ‐AKT‐LAT1 Signalling Participates in Methionine‐induced β‐CASEIN Expression in Mammary Epithelial Cells of Dairy Cows

This study investigated the role of the mammalian target of rapamycin complex 2 (mTORC2)-protein kinase B (AKT) signalling in methionine (Met)-induced L-type amino acid transporter 1 (LAT1) expression and milk protein production. Primary mammary epithelial cells (MECs) from mammary parenchymal tissues of 3 lactating cows and MAC-T bovine MECs were cultured with or without 0.6 mM Met. Rapamycin-insensitive companion of mTOR (RICTOR) siRNA, the mTORC1 inhibitor rapamycin and the AKT activator SC79 were used to evaluate the effects of mTORC2-AKT signalling on Met-induced LAT1 expression and function. Each experiment was performed three times. Data were analysed with a two-sided unpairedt test or ANOVA with the Bonferroni multiple-comparison test. Western blotting showed that Met stimulation increased RICTOR expression (~244.67%;p< 0.05; control, 0.15 ±0.026; Met, 0.517±0.109) and AKT-S473 levels (~281.42%;p< 0.01; control, 0.253 ±0.067; Met, 0.965±0.019) in both primary MECs and MAC-T cells. Rapamycin-induced mTORC1 signalling inhibition decreased only Met-induced β-CASEIN expression by ~21.24% (p< 0.01; Met, 0.777 ±0.01; Met and rapamycin, 0.612±0.04) and did not affect Met-stimulated AKT-S473 levels, suggesting that mTORC2-AKT activation upon Met stimulation also contributes to milk protein synthesis. LAT1 participates in Met-induced β-CASEIN expression. In dairy cow MECs, mTORC2 inhibition byRICTOR siRNA decreased LAT1 levels on the plasma membrane by ~45.13%...

Source: Journal of Animal Physiology and Animal Nutrition - March 25, 2023 Category: Zoology Authors: Xiaoyu Duan, Chuanping Liu, Xiaoqing Gong, Yang Yang, Hongtao Jiao, Ye Lin, Xiaoming Hou Tags: ORIGINAL ARTICLE Source Type: research