Lecticans, also known as hyalectans, are a family of proteoglycans (a type protein that is attached to chains of negatively charged polysaccharides) that are components of the extracellular matrix. There are four members of the lectican family: aggrecan, brevican, neurocan, and versican. Lecticans interact with hyaluronic acid and tenascin-R to form a ternary complex. [1]
Aggrecan is a major component of extracellular matrix in cartilage whereas versican is widely expressed in a number of connective tissues including those in vascular smooth muscle, skin epithelial cells, and the cells of central and peripheral nervous system. The expression of neurocan and brevican is largely restricted to neural tissues. [1]
All four lecticans contain an N-terminal globular domain (G1 domain) that in turn contains an immunoglobulin V-set domain and a Link domain that binds hyaluronic acid; a long extended central domain (CS) that is modified with covalently attached sulfated glycosaminoglycan chains, and a C-terminal globular domain (G3 domain) containing of one or more EGF repeats, a C-type lectin domain and a CRP-like domain. Aggrecan has in addition a globular domain (G2 domain) that is situated between the G1 and CS domains. [1]
Collagen is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content. Collagen consists of amino acids bound together to form a triple helix of elongated fibril known as a collagen helix. It is mostly found in connective tissue such as cartilage, bones, tendons, ligaments, and skin.
Integrins are transmembrane receptors that facilitate cell-extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, organization of the intracellular cytoskeleton, and movement of new receptors to the cell membrane. The presence of integrins allows rapid and flexible responses to events at the cell surface.
In biology, the extracellular matrix (ECM) is a three-dimensional network of extracellular macromolecules, such as collagen, enzymes, and glycoproteins, that provide structural and biochemical support to surrounding cells. Because multicellularity evolved independently in different multicellular lineages, the composition of ECM varies between multicellular structures; however, cell adhesion, cell-to-cell communication and differentiation are common functions of the ECM.
Hyaluronic acid, also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans as it is non-sulfated, forms in the plasma membrane instead of the Golgi apparatus, and can be very large: human synovial HA averages about 7 million Da per molecule, or about 20,000 disaccharide monomers, while other sources mention 3–4 million Da.
Laminins are high-molecular weight proteins of the extracellular matrix. They are a major component of the basal lamina, a protein network foundation for most cells and organs. The laminins are an important and biologically active part of the basal lamina, influencing cell differentiation, migration, and adhesion.
Chondroblasts, or perichondrial cells, is the name given to mesenchymal progenitor cells in situ which, from endochondral ossification, will form chondrocytes in the growing cartilage matrix. Another name for them is subchondral cortico-spongious progenitors. They have euchromatic nuclei and stain by basic dyes.
Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin. Ground substance is active in the development, movement, and proliferation of tissues, as well as their metabolism. Additionally, cells use it for support, water storage, binding, and a medium for intercellular exchange. Ground substance provides lubrication for collagen fibers.
Versican is a large extracellular matrix proteoglycan that is present in a variety of human tissues. It is encoded by the VCAN gene.
CTGF, also known as CCN2 or connective tissue growth factor, is a matricellular protein of the CCN family of extracellular matrix-associated heparin-binding proteins. CTGF has important roles in many biological processes, including cell adhesion, migration, proliferation, angiogenesis, skeletal development, and tissue wound repair, and is critically involved in fibrotic disease and several forms of cancers.
Aggrecan (ACAN), also known as cartilage-specific proteoglycan core protein (CSPCP) or chondroitin sulfate proteoglycan 1, is a protein that in humans is encoded by the ACAN gene. This gene is a member of the lectican family. The encoded protein is an integral part of the extracellular matrix in cartilagenous tissue and it withstands compression in cartilage.
Matrilysin also known as matrix metalloproteinase-7 (MMP-7), pump-1 protease (PUMP-1), or uterine metalloproteinase is an enzyme in humans that is encoded by the MMP7 gene. The enzyme has also been known as matrin, putative metalloproteinase-1, matrix metalloproteinase pump 1, PUMP-1 proteinase, PUMP, metalloproteinase pump-1, putative metalloproteinase, MMP).
A disintegrin and metalloproteinase with thrombospondin motifs 4 is an enzyme that in humans is encoded by the ADAMTS4 gene.
Perineuronal nets (PNNs) are specialized extracellular matrix structures responsible for synaptic stabilization in the adult brain. PNNs are found around certain neuron cell bodies and proximal neurites in the central nervous system. PNNs play a critical role in the closure of the childhood critical period, and their digestion can cause restored critical period-like synaptic plasticity in the adult brain. They are largely negatively charged and composed of chondroitin sulfate proteoglycans, molecules that play a key role in development and plasticity during postnatal development and in the adult.
Laminin subunit alpha-1 is a protein that in humans is encoded by the LAMA1 gene.
A disintegrin and metalloproteinase with thrombospondin motifs 1 is an enzyme that in humans is encoded by the ADAMTS1 gene.
Collagen alpha-3(VI) chain is a protein that in humans is encoded by the COL6A3 gene. This protein is an alpha chain of type VI collagen that aids in microfibril formation. As part of type VI collagen, this protein has been implicated in Bethlem myopathy, Ullrich congenital muscular dystrophy (UCMD), and other diseases related to muscle and connective tissue.
Tenascin-R is a protein that in humans is encoded by the TNR gene.
Chondroitin sulfate proteoglycans (CSPGs) are proteoglycans consisting of a protein core and a chondroitin sulfate side chain. They are known to be structural components of a variety of human tissues, including cartilage, and also play key roles in neural development and glial scar formation. They are known to be involved in certain cell processes, such as cell adhesion, cell growth, receptor binding, cell migration, and interaction with other extracellular matrix constituents. They are also known to interact with laminin, fibronectin, tenascin, and collagen. CSPGs are generally secreted from cells.
In molecular biology, the protein domain SdrG C terminal refers to the C terminus domain of an adhesin found only on the cell walls of bacteria. More specifically, SdrG is only found in gram-positive bacteria. This particular domain binds to a glycoprotein named fibrinogen. SdrG stands for serine-aspartate dipeptide repeats, which as its name suggests, contains repeats of two amino acids, serine and aspartate.
A Link domain or Link module, also known as Xlink domain, is a protein domain that binds to hyaluronic acid. It is important in blood cell migration and apoptosis. The link domain is found in some extracellular proteins in vertebrates such as the hyalectans. It appears to be involved in extracellular matrix assembly and stability, cell adhesion, and migration.
This transmembrane receptor-related article is a stub. You can help Wikipedia by expanding it. |