Proteomic analysis reveals similarity of expression profile in aggregated lymphoid nodules in the abomasum with Peyer’s patches of Bactrian camel

Abstract

Background Aggregated lymphoid nodules area (ALNA) is a distinctive anatomical feature of the abomasum in Bactrian camels, consisting of the reticular mucosal folds region (RMFR) and the longitudinal mucosal folds region (LMFR). ALNA exhibits many of the same characteristics histologically as Peyer's patches (PPs) in the intestinal tract. We analyzed the functional characteristics of ALNA in gastrointestinal mucosal immunity. Results We quantified the expressed proteins in ALNA using iTRAQ-based proteomic analysis in six Bactrian camels. In the experiment, we sampled the RMFR and LMFR separately from the ALNA and compared their proteomic quantification results with samples from the PPs. A total of 1790 proteins were identified, among which only 22 differentially expressed proteins (DEPs) were found between RMFR and PPs, 35 DEPs were found between LMFR and PPs, and 19 DEPs were found between LMFR and RMFR. There was no direct correlation between DEPs and immune-related functions. Subsequently, the abundance changes of 10 DEPs were verified at the transcriptional level by qPCR. Such as TPM1, MYH11 and HSPB1 were significantly up-regulated in LMFR vs PPs, but down-regulated in RMFR vs PPs. The expression levels of CR2 and GALS2 were found to be significantly increased in RMFR vs PPs, respectively, while decreased in LMFR. The expression of 10 genes was largely consistent with the corresponding protein expression. Besides, InnateDB was used to identify information on immune-associated proteins in ALNA, over 87.7% of proteins have been recognized in the same orthogroups of a human immune-related gene. Those proteins are recognized as involving a variety of functions, including the treatment and presentation of antigens, the intracellular activation of T-cells, the T-cell and B-cell receptor pathways, and the regulation of actin polycondensation. Conclusions The experimental findings indicate that the immune-related proteins present in ALNA and PPs exhibit similarities. Despite differences in structural phenotypes between LMFR and RMFR, proteins expressed in the two structures are highly similar and play similar roles in mucosal immune responses.