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Anna-Pia Papageorgiou, Stephane Heymans, Peroxidasin-like protein: expanding the horizons of matrix biology, Cardiovascular Research, Volume 101, Issue 3, 1 March 2014, Pages 342–343, https://doi.org/10.1093/cvr/cvu017
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This editorial refers to ‘Peroxidasin-like protein: a novel peroxidase homolog in the human heart’ by Z. Péterfi et al., pp. 393–399, this issue.
The extracellular matrix (ECM) is an intertwining network of proteins that provides support to the surrounding cells within a given organ. The ECM consists of collagens, elastins, glycoproteins, proteoglycans, and glycosaminoglycans, and performs a critical function not only during cardiac development and homoeostasis, but also during disease. On the one hand, this function can be structural, allowing for maintained strength and stability. Excessive matrix deposition induces cardiac stiffening, whereas abnormal collagen degradation causes cardiac dilatation.1 On the other hand, this vast entity also acts as a biochemical reservoir for intra- and extracellular communication between the different cardiac cells making the ECM extremely diverse in its function.2
Peterfi et al.3 describe for the first time a novel peroxidase homologue, peroxidasin-like protein (PXDNL), whose expression is exclusive to the heart. This work follows their previous research describing the role of peroxidasin (PXDN) in matrix deposition following a fibrotic stimulus in the kidney.4 Intriguingly, both these proteins are derived from peroxidase-ancestors and have structural domains characteristic of ‘classical’ ECM proteins (Figure 1). They include leucine-rich repeats similar to a subgroup of proteoglycans, such as decorin, mimecan, biglycan, and lumican, and which are important in collagen fibrillogenesis,5 and a Von Willebrand factor domain as found in the ECM protein, von Willebrand A domain-related protein (WARP), which associates with perlecan and collagen type IV in the basement membrane.6,7 PXDNL might also stimulate collagen cross-linking through its typical peroxidase domains, via dityrosine8 or sulfilimine9 bonds, showing the diverse nature of ECM regulators and the various ways in which collagens can be modified. This has led the authors to speculate that PXDNL, as for PXDN, may behave as a typical matrix protein, yet genetic evidence for its biological role modulating collagen cross-linking is lacking and will require additional protein-modifying studies.
