Introduction
Alexander Nyström and Leena Bruckner-Tuderman Biology of the Extracellular Matrix 95
Key features
Extracellular matrices (ECMs) represent specifically organized networks of collagens, elastin, glycoproteins, and proteoglycans that have distinct structural roles and specific functional properties
ECMs are biologically active, interact with cells, and regulate their functions during development, regeneration, and normal tissue turnover
Mutations in ECM genes cause a broad spectrum of human diseases, from Ehlers–Danlos syndrome to epidermolysis bullosa. ECM components are also targeted in autoimmune diseases, e.g., bullous pemphigoid, bullous systemic lupus erythematosus, lichen sclerosus
The collagen family contains 28 different subtypes. All collagens consist of three polypeptide α-chains folded into a triple helix. In each chain, every third amino acid is glycine (Gly), and thus the sequence can be expressed as (Gly-X-Y)n. A hallmark of collagens is the presence of hydroxyproline (Hyp) in the Y position of this repeat sequence. Collagens are expressed in all tissues of the human body, and distinct sets of collagens co-polymerize into highly organized suprastructures, e.g., fibrils and filaments, in a tissue-specific manner
Elastin provides tissues with elasticity. Elastin monomers contain repetitive hydrophobic sequences and are highly cross-linked. The cross-links between several individual molecules provide both elasticity and insolubility to elastic fibers, which can be stretched by 100% or more and still return to their original form. The elastic fibers in the dermis contain a microfibrillar component that connects the fibers to surrounding structures