Elastic fiber

Elastic fiber
Subcutaneous tissue from a young rabbit. Highly magnified. (Elastic fibers labeled at right)
Identifiers
FMA63868
Anatomical terminology

Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and airway epithelial cells.[1] These fibers are able to stretch many times their length, and snap back to their original length when relaxed without loss of energy. Elastic fibers include elastin, elaunin and oxytalan.

Elastic fibers are formed via elastogenesis,[2][3] a highly complex process involving several key proteins including fibulin-4, fibulin-5, latent transforming growth factor β binding protein 4, and microfibril associated protein 4.[4][5][6][7] In this process tropoelastin, the soluble monomeric precursor to elastic fibers is produced by elastogenic cells and chaperoned to the cell surface. Following excretion from the cell, tropoelastin self associates into ~200 nm particles by coacervation, an entropically driven process involving interactions between tropoelastin's hydrophobic domains, which is mediated by glycosaminoglycans, heparan, and other molecules.[8][9][10] These particles then fuse to give rise to 1-2 micron spherules which continue to grow as they move down from the cells surface before being deposited onto fibrillin microfibrillar scaffolds.[1]

Following deposition onto microfibrils tropoelastin is insolubilized via extensive crosslinking by members of the lysyl oxidase and lysyl oxidase like family of copper-dependent amine oxidases into amorphous elastin, a highly resilient, insoluble polymer that is metabolically stable over a human lifespan.[1] These two families of enzymes react with the many lysine residues present in tropoelastin to form reactive aldehydes and allysine via oxidative deamination.[11]

These reactive aldehydes and allysines can react with other lysine and allysine residues to form desmosine, isodesmosine, and a number of other polyfunctional crosslinks that join surrounding molecules of tropoelastin into an extensively crosslinked elastin matrix. This process creates a diverse array of intramolecular and intermolecular crosslinks[12] These unique crosslinks are responsible for elastin's durability and persistence. Maintenance of crosslinked elastin is carried out by a number of proteins including lysyl oxidase-like 1 protein.[13]

Mature elastic fibers consist of an amorphous elastin core surrounded by a glycosaminoglycans, heparan sulphate,[14] and number of other proteins such as microfibrillar-associated glycoproteins, fibrillin, fibullin, and the elastin receptor.

  1. ^ a b c Vindin H, Mithieux SM, Weiss AS (November 2019). "Elastin architecture". Matrix Biology. 84: 4–16. doi:10.1016/j.matbio.2019.07.005. PMID 31301399. S2CID 196458819.
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  9. ^ Wu WJ, Vrhovski B, Weiss AS (July 1999). "Glycosaminoglycans mediate the coacervation of human tropoelastin through dominant charge interactions involving lysine side chains". The Journal of Biological Chemistry. 274 (31): 21719–24. doi:10.1074/jbc.274.31.21719. PMID 10419484.
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  13. ^ Liu X, Zhao Y, Gao J, Pawlyk B, Starcher B, Spencer JA, et al. (February 2004). "Elastic fiber homeostasis requires lysyl oxidase-like 1 protein". Nature Genetics. 36 (2): 178–82. doi:10.1038/ng1297. PMID 14745449.
  14. ^ Gheduzzi D, Guerra D, Bochicchio B, Pepe A, Tamburro AM, Quaglino D, et al. (February 2005). "Heparan sulphate interacts with tropoelastin, with some tropoelastin peptides and is present in human dermis elastic fibers". Matrix Biology. 24 (1): 15–25. doi:10.1016/j.matbio.2004.12.001. PMID 15748998.