RET Proto-oncogene
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The ''RET'' proto-oncogene encodes a
receptor tyrosine kinase Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase ...
for members of the glial cell line-derived neurotrophic factor (GDNF) family of extracellular signalling molecules. ''RET''
loss of function 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, mitos ...
mutations are associated with the development of
Hirschsprung's disease Hirschsprung's disease (HD or HSCR) is a birth defect in which nerves are missing from parts of the intestine. The most prominent symptom is constipation. Other symptoms may include vomiting, abdominal pain, diarrhea and slow growth. Symptoms us ...
, while
gain of function Gain-of-function research (GoF research or GoFR) is medical research that genetically alters an organism in a way that may enhance the biological functions of gene products. This may include an altered pathogenesis, transmissibility, or host r ...
mutations are associated with the development of various types of human
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
, including
medullary thyroid carcinoma Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin.Hu MI, Vassilopoulou-Sellin R, Lustig R, Lamont JP"Thyroid and Parathyroid Cancers"in Pazdur R, ...
,
multiple endocrine neoplasia Multiple endocrine neoplasia (abbreviated MEN) is a condition which encompasses several distinct syndromes featuring tumors of endocrine glands, each with its own characteristic pattern. In some cases, the tumors are malignant, in others, benig ...
s type 2A and 2B, pheochromocytoma and parathyroid hyperplasia.


Structure

''RET'' is an abbreviation for "rearranged during
transfection Transfection is the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells. It may also refer to other methods and cell types, although other terms are often preferred: "transformation" is typically used to desc ...
", as the
DNA sequence DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...
of this
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
was originally found to be rearranged within a 3T3 fibroblast cell line following its transfection with DNA taken from human
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...
cells. The human
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
''RET'' is localized to
chromosome 10 Chromosome 10 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 10 spans about 133 million base pairs (the building material of DNA) and represents between 4 and 4.5 percent of the tot ...
(10q11.2) and contains 21
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 sequen ...
s. The natural
alternative splicing Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be ...
of the ''RET''
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
results in the production of 3 different
isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...
s of the protein RET. RET51, RET43 and RET9 contain 51, 43 and 9
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
s in their
C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...
tail respectively. The biological roles of
isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...
s RET51 and RET9 are the most well studied ''
in-vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and pl ...
'' as these are the most common isoforms in which RET occurs. Common to each
isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...
is a
domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined **Domain of definition of a partial function **Natural domain of a partial function **Domain of holomorphy of a function * Do ...
structure. Each protein is divided into three domains: an
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 ami ...
extracellular domain with four
cadherin Cadherins (named for "calcium-dependent adhesion") are a type of cell adhesion molecule (CAM) that is important in the formation of adherens junctions to allow cells to adhere to each other . Cadherins are a class of type-1 transmembrane proteins, ...
-like repeats and a
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...
-rich region, a
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...
transmembrane A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequentl ...
domain and a
cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
ic
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
domain, which is split by an insertion of 27
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
s. Within the cytoplasmic
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
domain, there are 16
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...
s (Tyrs) in RET9 and 18 in RET51. Tyr1090 and Tyr1096 are present only in the RET51 isoform. The
extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...
domain of RET contains nine
N-glycosylation ''N''-linked glycosylation, is the attachment of an oligosaccharide, a carbohydrate consisting of several sugar molecules, sometimes also referred to as glycan, to a nitrogen atom (the amide nitrogen of an asparagine (Asn) residue of a protein), ...
sites. The fully glycosylated RET protein is reported to have a
molecular weight A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
of 170
kDa The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...
although it is not clear to which
isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...
this molecular weight relates.


Kinase activation

RET is the
receptor Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...
for GDNF-family ligands (GFLs). In order to activate RET, GFLs first need to form a
complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...
with a
glycosylphosphatidylinositol Glycosylphosphatidylinositol (), or glycophosphatidylinositol, or GPI in short, is a phosphoglyceride that can be attached to the C-terminus of a protein during posttranslational modification. The resulting GPI-anchored proteins play key roles in ...
(GPI)-anchored
co-receptor A co-receptor is a cell surface receptor that binds a signalling molecule in addition to a primary receptor in order to facilitate ligand recognition and initiate biological processes, such as entry of a pathogen into a host cell. Properties The t ...
. The co-receptors themselves are classified as members of the GDNF receptor-α (GFRα) protein family. Different members of the GFRα family (
GFRα1 GDNF family receptor alpha-1 (GFRα1), also known as the GDNF receptor, is a protein that in humans is encoded by the ''GFRA1'' gene. Function Glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) are two structurally related, ...
, GFRα2, GFRα3, GFRα4) exhibit a specific binding activity for a specific GFLs. Upon GFL-GFRα complex formation, the complex then brings together two molecules of RET, triggering trans-autophosphorylation of specific
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...
residues within the
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
domain of each RET molecule. Tyr900 and Tyr905 within the
activation loop In molecular biology, an intrinsically disordered protein (IDP) is a protein that lacks a fixed or ordered three-dimensional structure, typically in the absence of its macromolecular interaction partners, such as other proteins or RNA. IDPs ran ...
(A-loop) of the kinase domain have been shown to be
autophosphorylation Autophosphorylation is a type of post-translational modification of proteins. It is generally defined as the phosphorylation of the kinase by itself. In eukaryotes, this process occurs by the addition of a phosphate group to serine, threoni ...
sites by
mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...
.
Phosphorylation In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, wh ...
of Tyr905 stabilizes the active conformation of the kinase, which, in turn, results in the
autophosphorylation Autophosphorylation is a type of post-translational modification of proteins. It is generally defined as the phosphorylation of the kinase by itself. In eukaryotes, this process occurs by the addition of a phosphate group to serine, threoni ...
of other tyrosine residues mainly located in the C-terminal tail region of the molecule. The structure shown to the left was taken from the
protein data bank The Protein Data Bank (PDB) is a database for the three-dimensional structural data of large biological molecules, such as proteins and nucleic acids. The data, typically obtained by X-ray crystallography, NMR spectroscopy, or, increasingly, cry ...
cod
2IVT
The structure is that of a
dimer Dimer may refer to: * Dimer (chemistry), a chemical structure formed from two similar sub-units ** Protein dimer, a protein quaternary structure ** d-dimer * Dimer model, an item in statistical mechanics, based on ''domino tiling'' * Julius Dimer ...
formed between two protein molecules each spanning amino acids 703-1012 of the RET molecule, covering RETs intracellular
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
domain. One protein molecule, molecule A is shown in yellow and the other, molecule B in grey. The activation loop is coloured purple and selected tyrosine residues in green. Part of the activation loop from molecule B is absent.
Phosphorylation In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, wh ...
of Tyr981 and the additional tyrosines Tyr1015, Tyr1062 and Tyr1096, not covered by the above structure, have been shown to be important to the initiation of intracellular
signal transduction Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellula ...
processes.


Role of RET signalling during development

Mice deficient in GDNF, GFRα1 or the RET protein itself exhibit severe defects in
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
and
enteric nervous system The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of ...
development. This implicates RET signal transduction as key to the development of normal
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
s and the
enteric nervous system The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of ...
.


Clinical relevance

At least 26 disease-causing mutations in this gene have been discovered. Activating point mutations in RET can give rise to the hereditary cancer syndrome known as
multiple endocrine neoplasia type 2 Multiple endocrine neoplasia type 2 (also known as "Pheochromocytoma and amyloid producing medullary thyroid carcinoma", "PTC syndrome," and "Sipple syndrome") is a group of medical disorders associated with tumors of the endocrine system. The tum ...
(MEN 2). There are three subtypes based on clinical presentation: MEN 2A, MEN 2B, and familial
medullary thyroid carcinoma Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin.Hu MI, Vassilopoulou-Sellin R, Lustig R, Lamont JP"Thyroid and Parathyroid Cancers"in Pazdur R, ...
(FMTC). There is a high degree of correlation between the position of the point mutation and the phenotype of the disease. Chromosomal rearrangements that generate a fusion gene, resulting in the juxtaposition of the C-terminal region of the RET protein with an N-terminal portion of another protein, can also lead to constitutive activation of the RET kinase. These types of rearrangements are primarily associated with
papillary thyroid carcinoma Papillary thyroid cancer or papillary thyroid carcinoma is the most common type of thyroid cancer, representing 75 percent to 85 percent of all thyroid cancer cases.Chapter 20 in: 8th edition. It occurs more frequently in women and presents in th ...
(PTC) where they represent 10-20% of cases, and
non-small cell lung cancer Non-small-cell lung cancer (NSCLC) is any type of epithelial lung cancer other than small-cell lung carcinoma (SCLC). NSCLC accounts for about 85% of all lung cancers. As a class, NSCLCs are relatively insensitive to chemotherapy, compared to sm ...
(NSCLC) where they represent 2% of cases. Several fusion partners have been described in the literature, and the most common ones across both cancer types include
KIF5B Kinesin family member 5B (KIF5B) is a protein that in humans is encoded by the ''KIF5B'' gene. Interactions KIF5B has been shown to interact with: * KLC1, * KLC2, * SNAP-25, * SNAP23, and * YWHAH 14-3-3 protein eta also referred to as 14 ...
,
CCDC6 Coiled-coil domain-containing protein 6 is a protein that in humans is encoded by the ''CCDC6'' gene. Interactions CCDC6 has been shown to interact with PPP4C Serine/threonine-protein phosphatase 4 catalytic subunit is an enzyme that in huma ...
and
NCOA4 Nuclear receptor coactivator 4, also known as Androgen Receptor Activator (ARA70), is a protein that in humans is encoded by the ''NCOA4'' gene. It plays an important role in ferritinophagy, acting as a cargo receptor, binding to the ferritin hea ...
. While older multikinase inhibitors such as
cabozantinib Cabozantinib, sold under the brand names Cometriq and Cabometyx among others, is a medication used to treat medullary thyroid cancer, renal cell carcinoma, and hepatocellular carcinoma. It is a small molecule inhibitor of the tyrosine kinases c ...
or
vandetanib Vandetanib, sold under the brand name Caprelsa, is an anti-cancer medication that is used for the treatment of certain tumours of the thyroid gland. It acts as a kinase inhibitor of a number of cell receptors, mainly the vascular endothelial gr ...
showed modest efficacy in targeting RET-driven malignancies, newer selective inhibitors (such as
selpercatinib Selpercatinib, sold under the brand name Retevmo among others, is a medication for the treatment of cancers in people whose tumors have an alteration (mutation or fusion) in a specific gene ( RET which is short for "rearranged during transfect ...
and pralsetinib) have shown significant activity in both mutations and fusions. The results of the LIBRETTO-001 trial studying selpercatinib showed a progression-free survival of 17.5 months in previously treated RET-positive NSCLC, and 22 months for RET-positive thyroid cancers, which prompted an FDA approval for both these indications in May 2020. Several other selective RET inhibitors are under development, including TPX-0046, a macrocyclic inhibitor of RET and Src intended to inhibit mutations providing resistance to current inhibitors.


Disease database

Th
RET gene variant database
at the
University of Utah The University of Utah (U of U, UofU, or simply The U) is a public research university in Salt Lake City, Utah. It is the flagship institution of the Utah System of Higher Education. The university was established in 1850 as the University of De ...
, identifies (as of November 2014) 166 mutations that are implicated in
MEN2 Multiple endocrine neoplasia type 2 (also known as "Pheochromocytoma and amyloid producing medullary thyroid carcinoma", "PTC syndrome," and "Sipple syndrome") is a group of medical disorders associated with tumors of the endocrine system. The tu ...
.


Interactions

RET proto-oncogene has been shown to
interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...
with: *
DOK1 Docking protein 1 is a protein that in humans is encoded by the ''DOK1'' gene. Function Docking protein 1 is constitutively tyrosine phosphorylated in hematopoietic progenitors isolated from chronic myelogenous leukemia (CML) patients in the c ...
, *
DOK5 Docking protein 5 is a protein that in humans is encoded by the ''DOK5'' gene. Function The protein encoded by this gene is a member of the DOK family of membrane proteins, which are adapter proteins involved in signal transduction. The encode ...
, * GDNF family receptor alpha 1, *
GRB10 Growth factor receptor-bound protein 10 also known as insulin receptor-binding protein Grb-IR is a protein that in humans is encoded by the ''GRB10'' gene. Function The product of this gene belongs to a small family of adaptor proteins that are ...
, *
GRB7 Growth factor receptor-bound protein 7, also known as GRB7, is a protein that in humans is encoded by the ''GRB7'' gene. Function The product of this gene belongs to a small family of adaptor proteins that are known to interact with a number ...
, * Grb2, *
SHC1 SHC-transforming protein 1 is a protein that in humans is encoded by the ''SHC1'' gene. SHC has been found to be important in the regulation of apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of pro ...
, and *
STAT3 Signal transducer and activator of transcription 3 (STAT3) is a transcription factor which in humans is encoded by the ''STAT3'' gene. It is a member of the STAT protein family. Function STAT3 is a member of the STAT protein family. In respons ...
.


References


Further reading

* * * * * * * * *


External links


GeneReviews/NCBI/NIH/UW entry on Multiple Endocrine Neoplasia Type 2
* {{Portal bar, Biology, border=no Tyrosine kinase receptors