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The basement membrane, also known as base membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tissues including mesothelium and endothelium, and the underlying connective tissue.
L1, also known as L1CAM, is a transmembrane protein member of the L1 protein family, encoded by the L1CAM gene. This protein, of 200-220 kDa, is a neuronal cell adhesion molecule with a strong implication in cell migration, adhesion, neurite outgrowth, myelination and neuronal differentiation. It also plays a key role in treatment-resistant cancers due to its function. It was first identified in 1984 by M. Schachner who found the protein in post-mitotic mice neurons.
Endostatin is a naturally occurring, 20-kDa C-terminal fragment derived from type XVIII collagen. It is reported to serve as an anti-angiogenic agent, similar to angiostatin and thrombospondin.
Perlecan (PLC) also known as basement membrane-specific heparan sulfate proteoglycan core protein (HSPG) or heparan sulfate proteoglycan 2 (HSPG2), is a protein that in humans is encoded by the HSPG2 gene. The HSPG2 gene codes for a 4,391 amino acid protein with a molecular weight of 468,829. It is one of the largest known proteins. The name perlecan comes from its appearance as a "string of pearls" in rotary shadowed images.
neurofibromatosis 1 (NF1) is a gene in humans that is located on chromosome 17. NF1 codes for neurofibromin, a GTPase-activating protein that negatively regulates RAS/MAPK pathway activity by accelerating the hydrolysis of Ras-bound GTP. NF1 has a high mutation rate and mutations in NF1 can alter cellular growth control, and neural development, resulting in neurofibromatosis type 1. Symptoms of NF1 include disfiguring cutaneous neurofibromas (CNF), café au lait pigment spots, plexiform neurofibromas (PN), skeletal defects, optic nerve gliomas, life-threatening malignant peripheral nerve sheath tumors (MPNST), pheochromocytoma, attention deficits, learning deficits and other cognitive disabilities.
Type III Collagen is a homotrimer, or a protein composed of three identical peptide chains (monomers), each called an alpha 1 chain of type III collagen. Formally, the monomers are called collagen type III, alpha-1 chain and in humans are encoded by the COL3A1 gene. Type III collagen is one of the fibrillar collagens whose proteins have a long, inflexible, triple-helical domain.
Collagen IV is a type of collagen found primarily in the basal lamina. The collagen IV C4 domain at the C-terminus is not removed in post-translational processing, and the fibers link head-to-head, rather than in parallel. Also, collagen IV lacks the regular glycine in every third residue necessary for the tight, collagen helix. This makes the overall arrangement more sloppy with kinks. These two features cause the collagen to form in a sheet, the form of the basal lamina. Collagen IV is the more common usage, as opposed to the older terminology of "type-IV collagen". Collagen IV exists in all metazoan phyla, to whom they served as an evolutionary stepping stone to multicellularity.
Type I collagen is the most abundant collagen of the human body, consisting of around 90% of the body's total collagen in vertebrates. Due to this, it is also the most abundant protein type found in all vertebrates. Type I forms large, eosinophilic fibers known as collagen fibers, which make up most of the rope-like dense connective tissue in the body. Collagen I itself is created by the combination of both a proalpha1 and a proalpha2 chain created by the COL1alpha1 and COL1alpha2 genes respectively. The Col I gene itself takes up a triple-helical conformation due to its Glycine-X-Y structure, x and y being any type of amino acid. Collagen can also be found in two different isoforms, either as a homotrimer or a heterotrimer, both of which can be found during different periods of development. Heterotrimers, in particular, play an important role in wound healing, and are the dominant isoform found in the body.
72 kDa type IV collagenase also known as matrix metalloproteinase-2 (MMP-2) and gelatinase A is an enzyme that in humans is encoded by the MMP2 gene. The MMP2 gene is located on chromosome 16 at position 12.2.
Collagen alpha-1(VII) chain is a protein that in humans is encoded by the COL7A1 gene. It is composed of a triple helical, collagenous domain flanked by two non-collagenous domains, and functions as an anchoring fibril between the dermal-epidermal junction in the basement membrane. Mutations in COL7A1 cause all types of dystrophic epidermolysis bullosa, and the exact mutations vary based on the specific type or subtype. It has been shown that interactions between the NC-1 domain of collagen VII and several other proteins, including laminin-5 and collagen IV, contribute greatly to the overall stability of the basement membrane.
Collagen alpha-5(IV) chain is a protein that in humans is encoded by the COL4A5 gene.
Collagen alpha-1(XVIII) chain is a protein that in humans is encoded by the COL18A1 gene.
Collagen alpha-3(IV) chain is a protein that in humans is encoded by the COL4A3 gene.
Collagen alpha-1(IV) chain (COL4A1) is a protein that in humans is encoded by the COL4A1 gene on chromosome 13. It is ubiquitously expressed in many tissues and cell types. COL4A1 is a subunit of the type IV collagen and plays a role in angiogenesis. Mutations in the gene have been linked to diseases of the brain, muscle, kidney, eye, and cardiovascular system. The COL4A1 gene also contains one of 27 SNPs associated with increased risk of coronary artery disease.
Collagen alpha-4(IV) chain is a protein that in humans is encoded by the COL4A4 gene.
Collagen alpha-1(XV) chain is a protein that in humans is encoded by the COL15A1 gene.
Tumstatin is a protein fragment cleaved from collagen that serves as both an antiangiogenic and proapoptotic agent. It has similar function to canstatin, endostatin, restin, and arresten, which also affect angiogenesis. Angiogenesis is the growth of new blood vessels from pre-existing blood vessels, and is important in tumor growth and metastasis. Angiogenesis is stimulated by many growth factors, the most prevalent of which is vascular endothelial growth factor (VEGF).
Megf8 also known as Multiple Epidermal Growth Factor-like Domains 8, is a protein coding gene that encodes a single pass membrane protein, known to participate in developmental regulation and cellular communication. It is located on chromosome 19 at the 49th open reading frame in humans (19q13.2). There are two isoform constructs known for MEGF8, which differ by a 67 amino acid indel. The isoform 2 splice version is 2785 amino acids long, and predicted to be 296.6 kdal in mass. Isoform 1 is composed of 2845 amino acids and predicted to weigh 303.1 kdal. Using BLAST searches, orthologs were found primarily in mammals, but MEGF8 is also conserved in invertebrates and fishes, and rarely in birds, reptiles, and amphibians. A notably important paralog to multiple epidermal growth factor-like domains 8 is ATRNL1, which is also a single pass transmembrane protein, with several of the same key features and motifs as MEGF8, as indicated by Simple Modular Architecture Research Tool (SMART) which is hosted by the European Molecular Biology Laboratory located in Heidelberg, Germany. MEGF8 has been predicted to be a key player in several developmental processes, such as left-right patterning and limb formation. Currently, researchers have found MEGF8 SNP mutations to be the cause of Carpenter syndrome subtype 2.
Knobloch syndrome is a rare genetic disorder presenting severe eyesight problems and often a defect in the skull. It was named after the ophthalmologist William Hunter Knobloch (1926–2005), who first described the syndrome in 1971. A usual occurrence is a degeneration of the vitreous humour and the retina, two components of the eye. This breakdown often results in the separation of the retina from the eye, called retinal detachment, which can be recurrent. Extreme myopia (near-sightedness) is a common feature. The limited evidence available from electroretinography suggests that a cone-rod pattern of dysfunction is also a feature.
Seipin is a homo-oligomeric integral membrane protein in the endoplasmic reticulum (ER) that concentrates at junctions with cytoplasmic lipid droplets (LDs). Alternatively, seipin can be referred to as Berardinelli–Seip congenital lipodystrophy type 2 protein (BSCL2), and it is encoded by the corresponding gene of the same name, i.e. BSCL2. At protein level, seipin is expressed in cortical neurons in the frontal lobes, as well as motor neurons in the spinal cord. It is highly expressed in areas like the brain, testis and adipose tissue. Seipin's function is still unclear but it has been localized close to lipid droplets, and cells knocked out in seipin which have anomalous droplets. Hence, recent evidence suggests that seipin plays a crucial role in lipid droplet biogenesis.
References
- ↑ Heljasvaara R, Aikio M, Ruotsalainen H, Pihlajaniemi T (January 2017). "Collagen XVIII in tissue homeostasis and dysregulation - Lessons learned from model organisms and human patients". Matrix Biology. 57–58: 55–75. doi:10.1016/j.matbio.2016.10.002. PMID 27746220.
- ↑ Rygh CB, Løkka G, Heljasvaara R, Taxt T, Pavlin T, Sormunen R, et al. (January 2014). "Image-based assessment of microvascular function and structure in collagen XV- and XVIII-deficient mice". The Journal of Physiology. 592 (2): 325–36. doi:10.1113/jphysiol.2013.263574. PMC 3922497 . PMID 24218547.
- ↑ Kinnunen AI, Sormunen R, Elamaa H, Seppinen L, Miller RT, Ninomiya Y, et al. (March 2011). "Lack of collagen XVIII long isoforms affects kidney podocytes, whereas the short form is needed in the proximal tubular basement membrane". The Journal of Biological Chemistry. 286 (10): 7755–64. doi: 10.1074/jbc.m110.166132 . PMC 3048663 . PMID 21193414.
- 1 2 Manon-Jensen T, Kjeld NG, Karsdal MA (2016). "Collagen-mediated hemostasis". Journal of Thrombosis and Haemostasis. 14 (3): 438–448. doi:10.1111/jth.13249. ISSN 1538-7836. PMID 26749406. S2CID 11216275.
- 1 2 3 Alexander G Marneros BR. "Physiological role of collagen XVIII and endostatin". The FASEB Journal – via Research Gate.
- ↑ Menzel O, Bekkeheien RC, Reymond A, Fukai N, Boye E, Kosztolanyi G, Aftimos S, Deutsch S, Scott HS, Olsen BR, Antonarakis SE (2004). "Knobloch syndrome: Novel mutations in COL18A1, evidence for genetic heterogeneity, and a functionally impaired polymorphism in endostatin". Human Mutation. 23 (1): 77–84. doi: 10.1002/humu.10284 . ISSN 1098-1004. PMID 14695535. S2CID 6550422.