Merlin (also called neurofibromin 2 or schwannomin) is a

cytoskeletal protein The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all Cell (biology), cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane ...

. In humans, it is a tumor suppressor protein involved in

neurofibromatosis type II Neurofibromatosis type II (also known as MISME syndrome – multiple inherited schwannomas, meningiomas, and ependymomas) is a genetic condition that may be inherited or may arise spontaneously, and causes benign tumors of the brain, spinal cord, ...

. Sequence data reveal its similarity to the ERM protein family. ''Merlin'' is an

acronym An acronym is a type of abbreviation consisting of a phrase whose only pronounced elements are the initial letters or initial sounds of words inside that phrase. Acronyms are often spelled with the initial Letter (alphabet), letter of each wor ...

for "

Moesin Moesin is a protein that in humans is encoded by the ''MSN'' gene. Moesin (for membrane-organizing extension spike protein) is a member of the ERM protein family which includes ezrin and radixin. ERM proteins appear to function as cross-linkers ...

Ezrin Ezrin also known as cytovillin or villin-2 is a protein that in humans is encoded by the ''EZR'' gene. Structure The N-terminus of ezrin contains a FERM domain which is further subdivided into three subdomains. The C-terminus contains an ...

Radixin Radixin is a protein that in humans is encoded by the ''RDX'' gene. Radixin is a cytoskeletal protein that may be important in linking actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoske ...

-like protein".

Gene

Human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

merlin is coded by the gene ''NF2'' in

chromosome 22 Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 51 million DNA base pairs and representing b ...

Mouse A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus'' ...

merlin gene is located on chromosome 11 and

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...

merlin gene on chromosome 17. Fruit fly merlin gene (symbol ''Mer'') is located on chromosome 1 and shares 58% similarity to its human homologue. Other merlin-like genes are known from a wide range of animals, and the derivation of merlin is thought to be in early

metazoa Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hol ...

. Merlin is a member of the ERM family of proteins including ezrin, moesin, and radixin, which are in the protein 4.1 superfamily of proteins. Merlin is also known as ''schwannomin'', a name derived from the most common type of tumor in the NF2 patient phenotype, the schwannoma.

Structure

Vertebrate merlin is a 70 kDa protein. There are 10 known

isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene and are the result of genetic differences. While many perform the same or similar biological roles, some isoforms have uniqu ...

s of human merlin molecule (the full molecule being 595

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s in length). The two most common of these are also found in the mouse and are called ''type 1'' and ''type 2'', differing by the absence or presence of

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...

16 or 17, respectively). All the known varieties have a conserved

N-terminal The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amin ...

part, which contains a FERM domain (a domain found in most cytoskeletal-membrane organizing proteins). The FERM domain is followed by an alpha-helical domain and a

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...

tail. Merlin can dimerize with itself and heterodimerize with other ERM family proteins.

Function

Merlin is a

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

-cytoskeleton scaffolding protein, i.e. linking

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ...

filaments to cell membrane or membrane

glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

s. Human merlin is predominantly found in

nervous tissue Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain ...

, but also in several other

fetal A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic stage, the fetal stage of development takes place. Prenatal development is a ...

tissues, and is mainly located in

adherens junction In cell biology, adherens junctions (or zonula adherens, intermediate junction, or "belt desmosome") are protein complexes that occur at cell–cell junctions and cell–matrix junctions in epithelial and endothelial tissues, usually more basa ...

s. Its tumor suppressor properties are probably associated with contact-mediated growth inhibition. ''Drosophila'' merlin is expressed in embryonic

hindgut The hindgut (or epigaster) is the posterior ( caudal) part of the alimentary canal. In mammals, it includes the distal one third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and up to the ano-rectal junct ...

salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...

s, and imaginal discs, and has apparently a slightly different role than in vertebrates. The

phosphorylation In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writ ...

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

518 is known to alter the functional state of merlin. The signaling pathway of merlin is proposed to include several salient cell growth controlling molecules, including eIF3c,

CD44 The CD44 antigen is a cell-surface glycoprotein involved in cell–cell interactions, cell adhesion and migration. In humans, the CD44 antigen is encoded by the ''CD44'' gene on chromosome 11. CD44 has been referred to as HCAM (homing cell adhes ...

protein kinase A In cell biology, protein kinase A (PKA) is a family of serine-threonine kinases whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, in ...

, and

p21 activated kinase p21 activated kinases (PAKs) are members of a family of enzymes. They serve as targets for the small GTP binding proteins CDC42 Cell division control protein 42 homolog (Cdc42 or CDC42) is a protein that in humans is encoded by the ''CDC42'' ge ...

s. Work in ''Drosophila'' identified Merlin as an upstream regulator of the Hippo tumor suppressor pathway, a function that is conserved in mammals. The Hippo pathway is a well conserved signalling pathway that coordinately regulates cell proliferation and apoptosis.

Mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

s of the NF2 gene cause a human autosomal dominant disease called neurofibromatosis type 2. It is characterized by the development of tumors of the nervous system, most commonly of bilateral

vestibular schwannoma A vestibular schwannoma (VS), also called acoustic neuroma, is a benign tumor that develops on the vestibulocochlear nerve that passes from the inner ear to the brain. The tumor originates when Schwann cells that form the insulating myelin sheath ...

s (also called acoustic neuromas). NF2 belongs to the

tumor suppressor A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a cell (biology), cell during cell division and replication. If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated, it results ...

group of genes.

Interactions

Merlin (protein) has been shown to interact with: *

CUL4A Cullin-4A is a protein that in humans is encoded by the ''CUL4A'' gene. CUL4A belongs to the cullin family of ubiquitin ligase proteins and is highly homologous to the CUL4B protein. CUL4A regulates numerous key processes such as DNA repair, chrom ...

, *

DDB1 DNA damage-binding protein 1 is a protein that in humans is encoded by the ''DDB1'' gene. Gene The gene's position is on chromosome 11q12-q13. Protein The DDB1 gene encodes the large subunit of DNA damage-binding protein, a heterodimer compos ...

, * EZR, * HGS, * MED28, * RIT1, * SDCBP, * SPTBN1, and * VPRBP.

References

External links

GeneReviews/NCBI/NIH/UW entry on Neurofibromatosis 2

{{PDB_Gallery, geneid=4771 Cytoskeleton Peripheral membrane proteins Human proteins Tumor suppressor genes