Research About The Roles Of Decorin Related To Duck Skeletal Muscle Protein Metabolism

Decorin is a small leucine-richproteoglycans/glycoproteins, plays an important role in myogenesis and skeletal muscle development. It has been reported that a spatiotemporal relation between the onset of myogenesis and the research indicates thatdecorin also promotes FSTexpression and represses MSTN expression in C2C12, and then to promote the synthesis of protein. Endoplasmic reticulum (ER) plays a crucial role in synthesis and folding of proteins, TGF-β cells signal pathway is a more important protein metabolism mutes, is also a research hotspot. Decorin is TGF-βantagonists and natural regulator, have an obvious effect on muscle mass.Thus, decorin and endoplasmic reticulumplay an extremely important role in muscle protein metabolism, however, whether or not duck decorin can stimulate muscle development through an ER stress-dependent in duck muscle cells was not determined and needs further elucidation. In this study, we first treated duck myoblasts with tunicamycin to trigger ER stress, and then determined whether ER stress can stimulates myoblasts protein synthesis, which is mediated by decorin-related pathway. In the second study, we transfected the decorin gene into muscle myoblast in vitro to establish that whether over-expression decorin promotes myotube hypertrophy by an ER stress-related pathway. In addition, to better understand the mechanism of endoplasmic reticulum and decorin in duck muscle growth and development,4-PBA, which is a chemical chaperone that inhibits palmitate-induced ER stress, was added in cultured duck myoblast The main results are as follows:1. Tunicamycin was added in cultured duck myoblast, and the qRT-PCR assay was performed to analysis the expression of ER stress marker genes and found that tunicamycin increased the expression of BIP、XBP-1、ATF6and EIF2a mRNA than that in control group and then induced ER stress. Meanwhile, the expression levels of MyoD and MyoG were both up-regulated, suggesting that ER stress could regulate the proliferation and differentiation of myoblasts in duck.2. The expression levels of genes related to muscle protein metabolism were analyzed by qRT-PCR. Our result suggests that ER stress increases the expression of decorin, FST mRNA than that in control groups, decreased the expression of MSTN, and then promotes myotube hypertrophy, which suggest that tunicamycin-induced ER stress stimulates muscle cells protein synthesis and may mediated by decor in-related pathway.3. The transfection assay showed that, MyoD、MyoG、FST were up-regulated by over-expressiondecorin and MSTN were down-regulated by over-expression decorin, showing that decorin probably have major roles in myoblast proliferation and differentiation, and then promotes myotube hypertrophy.4. The qRT-PCR assay was performed to analysis the expression of ER stress marker genes after transfected by pEGFP-N1-decorin in duck myoblasts cell culture in vitro. decorin gene-transfer led to higher expression of the BIP、XBP1、ATF6expression than did non-transfected myoblasts (control), while EIF2a is expressed at a low level in control groups, suggesting that over-expression of decorin did not induce ER stress to a sufficiently high level to activate the whole UPR system, and decorin gene transfer strongly activates the IRE-1pathway thereby stimulates skeletal muscle cell growth, indicating decorin stimulating myotube hypertrophy in duck myoblasts may mediated by an ER stress-related pathway.5.4-PBA, another ER stress inhibitor, was added in cultured duck myoblast in decorin gene transfection group and tunicamycin-treated group, respectively.4-PBA alleviates tunicamycin-induced ER stress and reverses decorin-induced ER stress in duck myoblast, showing that over-expression decorin can stimulate duck muscle hypertrophy mainly dependent on the involvement of ER stress.