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Elastic fibers are extracellular components of higher vertebrates and confer elasticity and resilience to numerous tissues and organs such as large blood vessels, lungs, and skin. Their formation and maturation take place in a complex multistage process called elastogenesis. It requires interactions between very different proteins but also other molecules and leads to the deposition and crosslinking of elastin's precursor on a scaffold of fibrillin‐rich microfibrils. Mature fibers are exceptionally resistant to most influences and, under healthy conditions, retain their biomechanical function over the life of the organism. However, due to their longevity, they accumulate damages during aging. These are caused by proteolytic degradation, formation of advanced glycation end products, calcification, oxidative damage, aspartic acid racemization, lipid accumulation, carbamylation, and mechanical fatigue. The resulting changes can lead to diminution or complete loss of elastic fiber function and ultimately affect morbidity and mortality. Particularly, the production of elastokines has been clearly shown to influence several life‐threatening diseases. Moreover, the structure, distribution, and abundance of elastic fibers are directly or indirectly influenced by a variety of inherited pathological conditions, which mainly affect organs and tissues such as skin, lungs, or the cardiovascular system. A distinction can be made between microfibril‐related inherited diseases that are the result of mutations in diverse microfibril genes and indirectly affect elastogenesis, and elastinopathies that are linked to changes in the elastin gene. This review gives an overview on the formation, structure, and function of elastic fibers and their fate over the human lifespan in health and disease. [ABSTRACT FROM AUTHOR]

Elastin is an essential structural protein in the extracellular matrix of vertebrates. It is the core component of elastic fibers, which enable connective tissues such as those of the skin, lungs or blood vessels to stretch and recoil. This function is provided by elastin's exceptional properties, which mainly derive from a unique covalent cross‐linking between hydrophilic lysine‐rich motifs of units of the monomeric precursor tropoelastin. To date, elastin's cross‐linking is poorly investigated. Here, we purified elastin from human tissue and cleaved it into soluble peptides using proteases with different specificities. We then analyzed elastin's molecular structure by identifying unmodified residues, post‐translational modifications and cross‐linked peptides by high‐resolution mass spectrometry and amino acid analysis. The data revealed the presence of multiple isoforms in parallel and a complex and heterogeneous molecular interconnection. We discovered that the same lysine residues in different monomers were simultaneously involved in various cross‐link types or remained unmodified. Furthermore, both types of cross‐linking domains, Lys‐Pro and Lys‐Ala domains, participate not only in bifunctional inter‐ but also in intra‐domain cross‐links. We elucidated the sequences of several desmosine‐containing peptides and the contribution of distinct domains such as 6, 14 and 25. In contrast to earlier assumptions proposing that desmosine cross‐links are formed solely between two domains, we elucidated the structure of a peptide that proves a desmosine formation with participation of three Lys‐Ala domains. In summary, these results provide new and detailed insights into the cross‐linking process, which takes place within and between human tropoelastin units in a stochastic manner. [ABSTRACT FROM AUTHOR]

To provide a basis for the development of approaches to treat elastin-degrading diseases, the aim of this study was to investigate the degradation of the natural substrate tropoelastin by the elastinolytic matrix metalloproteinases MMP-7, MMP-9, and MMP-12 and to compare the cleavage site specificities of the enzymes using complementary MS techniques and molecular modeling. Furthermore, the ability of the three proteases to release bioactive peptides was studied. Tropoelastin was readily degraded by all three MMPs. Eighty-nine cleavage sites in tropoelastin were identified for MMP-12, whereas MMP-7 and MMP-9 were found to cleave at only 58 and 63 sites, respectively. Cleavages occurred predominantly in the N-terminal and C-terminal regions of tropoelastin. With respect to the cleavage site specificities, the study revealed that all three MMPs similarly tolerate hydrophobic and/or aliphatic amino acids, including Pro, Gly, Ile, and Val, at P1′. MMP-7 shows a strong preference for Leu at P1′, which is also well accepted by MMP-9 and MMP-12. Of all three MMPs, MMP-12 best tolerates bulky charged and aromatic amino acids at P1′. All three MMPs showed a clear preference for Pro at P3 that could be structurally explained by molecular modeling. Analysis of the generated peptides revealed that all three MMPs show a similar ability to release bioactive sequences, with MMP-12 producing the highest number of these peptides. Furthermore, the generated peptides YTTGKLPYGYGPGG, YGARPGVGVGGIP, and PGFGAVPGA, containing GxxPG motifs that have not yet been proven to be bioactive, were identified as new matrikines upon biological activity testing. Structured digital abstract • : MMP-7 (uniprotkb: ) cleaves ( ) Tropoelastin (uniprotkb: ) by protease assay ( ) • : MMP-9 (uniprotkb: ) cleaves ( ) Tropoelastin (uniprotkb: ) by protease assay ( ) • : MMP-12 (uniprotkb: ) cleaves ( ) Tropoelastin (uniprotkb: ) by protease assay ( ) [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) is a dynamic 3-dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell-bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well-organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies., (© 2021 Federation of European Biochemical Societies.)