Tubby Protein | |||||||||||
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Identifiers | |||||||||||
Symbol | Tub | ||||||||||
Pfam | PF01167 | ||||||||||
InterPro | IPR000007 | ||||||||||
PROSITE | PDOC00923 | ||||||||||
SCOP2 | 1c8z / SCOPe / SUPFAM | ||||||||||
OPM superfamily | 104 | ||||||||||
OPM protein | 1i7e | ||||||||||
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The tubby protein is encoded by the TUB gene. It is an upstream cell signaling protein common to multicellular eukaryotes. The first tubby gene was identified in mice, and proteins that are homologous to tubby are known as "tubby-like proteins" (TULPs). They share a common and characteristic tertiary structure that consists of a beta barrel packed around an alpha helix in the central pore. The gene derives its name from its role in metabolism; mice with a mutated tubby gene develop delayed-onset obesity, sensorineural hearing loss, and retinal degeneration. [1] [2] [3]
Tubby proteins are classified as α+β proteins and have a 12-beta stranded barrel surrounding a central alpha helix. Tubby proteins can bind the small cell signaling molecule phosphatidylinositol, which is typically localized to the cell membrane. A similar structural fold to the Tubby like proteins has been identified in the Scramblase family of proteins. [4]
Tubby proteins have been implicated as transcription factors [5] and as potential signaling factors coupled to G-protein activity. [6] They are associated with neuronal differentiation and development, and in mammals are implicated in three disease processes when mutated: obesity, retinal degeneration, and hearing loss. [5] In mice, mutations in tubby proteins are known to affect life span and fat storage [7] as well as carbohydrate metabolism. [8] Tubby domains associate with cytoplasmic side of cell membranes through binding of different phosphoinositides [9]
CD36, also known as platelet glycoprotein 4, fatty acid translocase (FAT), scavenger receptor class B member 3 (SCARB3), and glycoproteins 88 (GP88), IIIb (GPIIIB), or IV (GPIV) is a protein that in humans is encoded by the CD36 gene. The CD36 antigen is an integral membrane protein found on the surface of many cell types in vertebrate animals. It imports fatty acids inside cells and is a member of the class B scavenger receptor family of cell surface proteins. CD36 binds many ligands including collagen, thrombospondin, erythrocytes parasitized with Plasmodium falciparum, oxidized low density lipoprotein, native lipoproteins, oxidized phospholipids, and long-chain fatty acids.
Peripherin is a type III intermediate filament protein expressed mainly in neurons of the peripheral nervous system. It is also found in neurons of the central nervous system that have projections toward peripheral structures, such as spinal motor neurons. Its size, structure, and sequence/location of protein motifs is similar to other type III intermediate filament proteins such as desmin, vimentin and glial fibrillary acidic protein. Like these proteins, peripherin can self-assemble to form homopolymeric filamentous networks, but it can also heteropolymerize with neurofilaments in several neuronal types. This protein in humans is encoded by the PRPH gene. Peripherin is thought to play a role in neurite elongation during development and axonal regeneration after injury, but its exact function is unknown. It is also associated with some of the major neuropathologies that characterize amyotropic lateral sclerosis (ALS), but despite extensive research into how neurofilaments and peripherin contribute to ALS, their role in this disease is still unidentified.
Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors, which are members of the nuclear receptor family of intracellular receptors, and membrane estrogen receptors (mERs), which are mostly G protein-coupled receptors. This article refers to the former (ER).
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.
Sterol regulatory element-binding proteins (SREBPs) are transcription factors that bind to the sterol regulatory element DNA sequence TCACNCCAC. Mammalian SREBPs are encoded by the genes SREBF1 and SREBF2. SREBPs belong to the basic-helix-loop-helix leucine zipper class of transcription factors. Unactivated SREBPs are attached to the nuclear envelope and endoplasmic reticulum membranes. In cells with low levels of sterols, SREBPs are cleaved to a water-soluble N-terminal domain that is translocated to the nucleus. These activated SREBPs then bind to specific sterol regulatory element DNA sequences, thus upregulating the synthesis of enzymes involved in sterol biosynthesis. Sterols in turn inhibit the cleavage of SREBPs and therefore synthesis of additional sterols is reduced through a negative feed back loop.
Agouti-signaling protein is a protein that in humans is encoded by the ASIP gene. It is responsible for the distribution of melanin pigment in mammals. Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte produces phaeomelanin, or eumelanin. This interaction is responsible for making distinct light and dark bands in the hairs of animals such as the agouti, which the gene is named after. In other species such as horses, agouti signalling is responsible for determining which parts of the body will be red or black. Mice with wildtype agouti will be grey, with each hair being partly yellow and partly black. Loss of function mutations in mice and other species cause black fur coloration, while mutations causing expression throughout the whole body in mice cause yellow fur and obesity.
Hephaestin, also known as HEPH, is a protein which in humans is encoded by the HEPH gene.
Niemann-Pick disease, type C1 (NPC1) is a disease of a membrane protein that mediates intracellular cholesterol trafficking in mammals. In humans the protein is encoded by the NPC1 gene.
The photoreceptor cell-specific nuclear receptor (PNR), also known as NR2E3, is a protein that in humans is encoded by the NR2E3 gene. PNR is a member of the nuclear receptor super family of intracellular transcription factors.
Retinal guanylyl cyclase 1 also known as guanylate cyclase 2D, retinal is an enzyme that in humans is encoded by the GUCY2D gene.
X-linked retinitis pigmentosa GTPase regulator is a GTPase-binding protein that in humans is encoded by the RPGR gene. The gene is located on the X-chromosome and is commonly associated with X-linked retinitis pigmentosa (XLRP). In photoreceptor cells, RPGR is localized in the connecting cilium which connects the protein-synthesizing inner segment to the photosensitive outer segment and is involved in the modulation of cargo trafficked between the two segments.
Peripherin-2 is a protein, that in humans is encoded by the PRPH2 gene. Peripherin-2 is found in the rod and cone cells of the retina of the eye. Defects in this protein result in one form of retinitis pigmentosa, an incurable blindness.
Rod cGMP-specific 3',5'-cyclic phosphodiesterase subunit beta is the beta subunit of the protein complex PDE6 that is encoded by the PDE6B gene. PDE6 is crucial in transmission and amplification of visual signal. The existence of this beta subunit is essential for normal PDE6 functioning. Mutations in this subunit are responsible for retinal degeneration such as retinitis pigmentosa or congenital stationary night blindness.
Homeobox protein OTX2 is a protein that in humans is encoded by the OTX2 gene.
Tubby-related protein 1 is a protein that in humans is encoded by the TULP1 gene.
Tubby protein homolog is a protein that in humans is encoded by the TUB gene.
Dentatorubral–pallidoluysian atrophy (DRPLA) is an autosomal dominant spinocerebellar degeneration caused by an expansion of a CAG repeat encoding a polyglutamine tract in the atrophin-1 protein. It is also known as Haw River Syndrome and Naito–Oyanagi disease. Although this condition was perhaps first described by Smith et al. in 1958, and several sporadic cases have been reported from Western countries, this disorder seems to be very rare except in Japan.
Tenomodulin, also referred to as tendin, myodulin, Tnmd, or TeM, is a protein encoded by the TNMD (Tnmd) gene and was discovered independently by Brandau and Shukunami in 2001 as a gene sharing high similarity with the already known chondromodulin-1 (Chm1). It is a tendon-specific gene marker known to be important for tendon maturation with key implications for the residing tendon stem/progenitor cells (TSPCs) as well as for the regulation of endothelial cell migration in chordae tendineae cordis in the heart and in experimental tumour models. It is highly expressed in tendons, explaining the rationale behind its name and the establishment as being marker gene for tendinous and ligamentous lineages.
Retinal degeneration is a retinopathy which consists in the deterioration of the retina caused by the progressive death of its cells. There are several reasons for retinal degeneration, including artery or vein occlusion, diabetic retinopathy, R.L.F./R.O.P., or disease. These may present in many different ways such as impaired vision, night blindness, retinal detachment, light sensitivity, tunnel vision, and loss of peripheral vision to total loss of vision. Of the retinal degenerative diseases retinitis pigmentosa (RP) is a very important example.
Retinal gene therapy holds a promise in treating different forms of non-inherited and inherited blindness.