Type II keratin
Type II keratins (or Type II cytokeratins) constitutes the Type II intermediate filaments (IFs) of the intracytoplasmatic cytoskeleton, which is present in all mammalian epithelial cells. The type 2 cytokeratins consist of basic or neutral, high molecular weight proteins which in vivo are arranged in pairs of heterotypic Type I and Type II keratin chains, coexpressed during differentiation of simple and stratified epithelial tissues.[1] It has been seen that Type II Keratins are developed before Type 1 keratins during human embryonic development.[2]
Type II cytokeratins are encoded on chromosome 12q and encompasses: CK1, CK2, CK3, CK4, CK5, CK6, CK7 and CK8. Their molecular weight ranges from 52 kDa (CK8) to 67 kDa (CK18).
Overall, keratin type 2 plays a crucial role in maintaining the strength and integrity of the skin, hair, and nails. Mutations in keratin genes can lead to various genetic disorders that affect these tissues, such as epidermolysis bullosa simplex, a rare condition characterized by blistering and erosion of the skin and mucous membranes.[3]
Keratin 2 Types: 2A and 2B
Type II Keratins are divided into 2 subtypes: Type IIA Keratins and Type IIB Keratins. Type 2A keratins are expressed in tissues that require high levels of mechanical stress, such as the soles of the feet, while type 2B keratins are expressed in tissues that are subject to less stress, such as the palms of the hands.[1]
Type IIA Keratins
Type IIA Keratins are characterized by their expression in tissues that undergo high stress, like soles of the feet or palms of the hand. There are several different type 2A keratins that have been identified in humans, including K1, K2, K9, K10, K77, and K78. These keratins are expressed in a tissue-specific manner, with K1, K2, and K10 being predominantly expressed in the epidermis, while K9, K77, and K78 are expressed in the nail bed and hair follicles.[3]
Type IIA keratins have a unique structural feature that allows them to form coiled-coil dimers, which then assemble into tetramers and eventually into intermediate filaments. This structural organization provides the mechanical strength and resilience necessary to withstand the stresses experienced by the tissues in which they are expressed.[6] Mutations in type 2A keratin genes can lead to various genetic disorders, such as epidermolytic hyperkeratosis (EHK) and palmoplantar keratoderma (PPK), which are characterized by hyperkeratosis and blistering of the skin on the palms and soles.[7]
Type IIB Keratins
Type IIB keratins are a group of intermediate filament proteins that are primarily expressed in epithelial tissues, such as the skin, nails, and hair follicles. They belong to the keratin family of proteins, which are characterized by their highly conserved alpha-helical coiled-coil domains.[8] Keratin type IIB is encoded by the KRT6B gene and is often co-expressed with the equivalent keratin type IIA (KRT6A) in a variety of epithelial tissues.[9] Together, these two proteins form heterodimers that assemble into intermediate filaments, which provide mechanical stability and resistance to mechanical stress.[8] In addition to their structural role, type IIB keratins have been shown to play important roles in wound healing, inflammation, and cell migration. Dysregulation of type IIB keratin expression or mutations in the KRT6B gene have been associated with a variety of skin disorders, including psoriasis, epidermolysis bullosa, and pachyonychia congenita.[8]
See also
References
- ^ a b Schweizer, Jürgen; Bowden, Paul E.; Coulombe, Pierre A.; Langbein, Lutz; Lane, E. Birgitte; Magin, Thomas M.; Maltais, Lois; Omary, M. Bishr; Parry, David A.D.; Rogers, Michael A.; Wright, Mathew W. (17 July 2006). "New consensus nomenclature for mammalian keratins". Journal of Cell Biology. 174 (2): 169–174. doi:10.1083/jcb.200603161. PMC 2064177. PMID 16831889. Archived from the original on 2020-02-11. Retrieved 1 June 2023.
- ^ Lu, Hong; Hesse, Michael; Peters, Bettina; Magin, Thomas M. (August 2005). "Type II keratins precede type I keratins during early embryonic development". European Journal of Cell Biology. 84 (8): 709–718. doi:10.1016/j.ejcb.2005.04.001. ISSN 0171-9335. PMID 16180309.
- ^ a b Moll, Roland; Divo, Markus; Langbein, Lutz (2008-06-01). "The human keratins: biology and pathology". Histochemistry and Cell Biology. 129 (6): 705–733. doi:10.1007/s00418-008-0435-6. ISSN 1432-119X. PMC 2386534. PMID 18461349.
- ^ "KRT1 expression in human". www.bgee.org. Retrieved 1 June 2023.
- ^ "UniProt". www.uniprot.org. Retrieved 2023-05-03.
- ^ Irvine, A. D.; McLean, W. H. (May 1999). "Human keratin diseases: the increasing spectrum of disease and subtlety of the phenotype-genotype correlation". The British Journal of Dermatology. 140 (5): 815–828. doi:10.1046/j.1365-2133.1999.02810.x. ISSN 0007-0963. PMID 10354017. S2CID 21429676.
- ^ Chamcheu, Jean Christopher; Siddiqui, Imtiaz A.; Syed, Deeba N.; Adhami, Vaqar M.; Liovic, Mirjana; Mukhtar, Hasan (2011-04-15). "Keratin Gene Mutations in Disorders of Human Skin and its Appendages". Archives of Biochemistry and Biophysics. 508 (2): 123–137. doi:10.1016/j.abb.2010.12.019. ISSN 0003-9861. PMC 3142884. PMID 21176769.
- ^ a b c Justin T. Jacob, Pierre A. Coulombe, Raymond Kwan, and M. Bishr Omary (2018). "Types I and II Keratin Intermediate Filaments". Cold Spring Harbor Perspectives in Biology. 10 (4): a018275. doi:10.1101/cshperspect.a018275. PMC 5880164. PMID 29610398.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Hatzfeld, M.; Burba, M. (1 July 1994). "Function of type I and type II keratin head domains: their role in dimer, tetramer and filament formation". Journal of Cell Science. 107 (7): 1959–1972. doi:10.1242/jcs.107.7.1959. Archived from the original on 2022-08-04. Retrieved 1 June 2023.
External links
- Type+II+Keratin at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- Proteopedia page on keratins