Proteomic Analysis Reveals PGAM1 Altering cis‐9, trans‐11 Conjugated Linoleic Acid Synthesis in Bovine Mammary Gland

Abstract

cis‐9, trans‐11 Conjugated linoleic acid (CLA) is one of the most extensively studied CLA isomers due to its multiple isomer‐specific effects. However, the molecular mechanisms of cis‐9,trans‐11 CLA synthesis in ruminant mammary gland are still not clearly understood. This process may be mediated, to a certain extent, by trans‐11 C18:1 regulated by stearoyl‐CoA desaturase‐1 (SCD1) and/or its syntrophic proteins. This study aimed to investigate the effects of TVA on SCD1‐mediated cis‐9,trans‐11 CLA synthesis in MAC‐T cells and its potential molecular mechanism. Results showed that trans‐11 C18:1 was continually taken up and converted into cis‐9,trans‐11 CLA in MAC‐T cells during the 4‐h incubation of 50 μM trans‐11 C18:1. SCD1 protein expression increased more than twofold at 2 h (P < 0.01) and 2.5 h (P < 0.05) before decreasing to less than half of the normal level at 4 h (P < 0.05). One up‐regulated (RAS guanyl releasing protein 4 isoform 1 [RASGRP4]) and six down‐regulated proteins (glucosamine‐6‐phosphate deaminase 1 [GNPDA1], triosephosphate isomerase [TPI1], phosphoglycerate mutase 1 [PGAM1], heat shock protein beta‐1 [HSPB1], annexin A3 [ANXA3], thiopurine S‐methyltransferase [TPMT]) were found in MAC‐T cells treated with trans‐11 C18:1. Of these seven identified proteins, the presence of GNPDA1 and PGAM1 was verified in several models. More trans‐11 C18:1 was taken up after PGAM1 knockdown by small interfering RNA (siRNA). In conclusion, our data suggested that PGAM1 may have a negative relationship with SCD1 and seemed to be involved in cis‐9, trans‐11 CLA synthesis by facilitating the absorption of trans‐11 C18:1 in the bovine mammary gland.