Dynamics of the Skeletal Muscle Secretome during Myoblast Differentiation

Abstract

During recent years, increased efforts have focused on elucidating the secretory function of skeletal muscle. Through secreted molecules, skeletal muscle affects local muscle biology in an auto/paracrine manner as well as having systemic effects on other tissues. Here we used a quantitative proteomics platform to investigate the factors secreted during the differentiation of murine C2C12 skeletal muscle cells. Using triple encoding stable isotope labeling by amino acids in cell culture, we compared the secretomes at three different time points of muscle differentiation and followed the dynamics of protein secretion. We identified and quantitatively analyzed 635 secreted proteins, including 35 growth factors, 40 cytokines, and 36 metallopeptidases. The extensive presence of these proteins that can act as potent signaling mediators to other cells and tissues strongly highlights the important role of the skeletal muscle as a prominent secretory organ. In addition to previously reported molecules, we identified many secreted proteins that have not previously been shown to be released from skeletal muscle cells nor shown to be differentially released during the process of myogenesis. We found 188 of these secreted proteins to be significantly regulated during the process of myogenesis. Comparative analyses of selected secreted proteins revealed little correlation between their mRNA and protein levels, indicating pronounced regulation by posttranscriptional mechanisms. Furthermore, analyses of the intracellular levels of members of the semaphorin family and their corresponding secretion dynamics demonstrated that the release of secreted proteins is tightly regulated by the secretory pathway, the stability of the protein, and/or the processing of secreted proteins. Finally, we provide 299 unique hydroxyproline sites mapping to 48 distinct secreted proteins and have discovered a novel hydroxyproline motif. Molecular & Cellular Proteomics 9:2482-2496, 2010.

Comprehensive proteome analysis of human skeletal muscle in cachexia and sarcopenia: a pilot study

“…Other notable differences were the detection and quantification of matrix metalloprotease‐14 (MMP‐14) exclusively at the early time points of unperturbed myoblasts but not in TNFα‐treated cultures. Matrix metalloprotease‐14 is vital for the migration of myoblasts into collagen I matrix33 and was also detected in the secretome of myoblasts during differentiation 34. Hence, our data suggest that TNFα interferes at a very early stage of myogenesis with expression of proteins involved in muscle regeneration.…”

Conditioned media from human palatine tonsil mesenchymal stem cells regulates the interaction between myotubes and fibroblasts by IL‐1Ra activity

“…TGF‐β is one of the secretory proteins from myotubes 16, we compared the extent of secreted TGF‐β in the same cell supernatant. In contrast with IL‐1β, we confirmed TGF‐β was released from all experimental cell supernatant with tendency of slight increase in the presence of T‐CM.…”

Hematopoietic Microenvironment in the Fetal Liver: Roles of Different Cell Populations

“…These cells may enter the liver and other organs of the embryo when they migrate from the dermomyotome to populate areas where skeletal muscles are to be formed. However, in view of the data that skeletal myoblasts secrete a wide range of regulatory molecules, including stromal cell-derived factor-1 and hematopoietic cytokines such as macrophage colonystimulating factor [47], their specific role in the maintenance of liver hematopoiesis cannot be excluded.…”