Glycoproteomics Reveals Decorin Peptides With Anti-Myostatin Activity in Human Atrial Fibrillation

Abstract

Original research article BACKGROUND: Myocardial fibrosis is a feature of many cardiac diseases. We used proteomics to profile glycoproteins in the human cardiac extracellular matrix (ECM). METHODS:Atrial specimens were analyzed by mass spectrometry after extraction of ECM proteins and enrichment for glycoproteins or glycopeptides.RESULTS: ECM-related glycoproteins were identified in left and right atrial appendages from the same patients. Several known glycosylation sites were confirmed. In addition, putative and novel glycosylation sites were detected. On enrichment for glycoproteins, peptides of the small leucine-rich proteoglycan decorin were identified consistently in the flowthrough. Of all ECM proteins identified, decorin was found to be the most fragmented. Within its protein core, 18 different cleavage sites were identified. In contrast, less cleavage was observed for biglycan, the most closely related proteoglycan. Decorin processing differed between human ventricles and atria and was altered in disease. The C-terminus of decorin, important for the interaction with connective tissue growth factor, was detected predominantly in ventricles in comparison with atria. In contrast, atrial appendages from patients in persistent atrial fibrillation had greater levels of full-length decorin but also harbored a cleavage site that was not found in atrial appendages from patients in sinus rhythm. This cleavage site preceded the N-terminal domain of decorin that controls muscle growth by altering the binding capacity for myostatin. Myostatin expression was decreased in atrial appendages of patients with persistent atrial fibrillation and hearts of decorin null mice. A synthetic peptide corresponding to this decorin region dose-dependently inhibited the response to myostatin in cardiomyocytes and in perfused mouse hearts. CONCLUSIONS:This proteomics study is the first to analyze the human cardiac ECM. Novel processed forms of decorin protein core, uncovered in human atrial appendages, can regulate the local bioavailability of antihypertrophic and profibrotic growth factors.glycoproteomics reveals Decorin Peptides With anti-Myostatin activity in human atrial Fibrillation

Systems biology—opportunities and challenges: the application of proteomics to study the cardiovascular extracellular matrix

“…amino acid modifications) ( Figure 1 ). For example, we demonstrated using MS that the C-terminus of decorin, a small leucine-rich proteoglycan, is often cleaved in the left atrium but not in the ventricle 52 . MS data provided an explanation why the use of different antibodies for the same target protein yielded very different results ( Figure 2 ).…”

“…MS data can also be aligned to databases generated using DNA or RNA sequences to infer amino acid sequences. Current MS technologies now allow for the characterization of the ECM composition and turnover in CVD in unprecedented detail that is not possible using other techniques 2–5 , 52 , 57–59 …”

“…Over the past years our group has focused on ECM remodelling in cardiac 2 , 52 , 60 , 61 and vascular tissues 3 , 4 , 57 , 59 using proteomics. In a previous review, we highlighted the potential of proteomics when applied to systems biology 62 .…”

“…Aberrant glycosylation can lead to pathological abnormalities and disease. In the last decade, proteomics has emerged as a powerful platform to characterize glycosylation profiles of ECM proteins, including the cardiovascular field 52 , 58 , 89 . There are two major strategies that can be used to study glycoproteins by MS ( Figure 4 ).…”

“…Specific biological activities have been attributed to certain ECM proteolytic fragments ( Figure 5 ) 5 , 19 , 52 , 104–122 . The term matrikines has been proposed for these fragments.…”