Insulin-like growth factor-binding protein 3, also known as IGFBP-3, is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
that in humans is encoded by the ''IGFBP3''
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 ...
. IGFBP-3 is one of six
IGF binding proteins
The insulin-like growth factor-binding protein (IGFBP) serves as a transport protein for insulin-like growth factor 1 (IGF-1).
Function
Approximately 98% of IGF-1 is always bound to one of six binding proteins (IGF-BP). IGFBP-3, the most abund ...
(
IGFBP-1 to
IGFBP-6) that have highly conserved structures and bind the insulin-like growth factors
IGF-1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans is ...
and
IGF-2
Insulin-like growth factor 2 (IGF-2) is one of three protein hormones that share structural similarity to insulin. The MeSH definition reads: "A well-characterized neutral peptide believed to be secreted by the liver and to circulate in the blo ...
with high affinity.
IGFBP-7, sometimes included in this family, shares neither the conserved structural features nor the high IGF affinity. Instead,
IGFBP-7 binds
IGF1R
The insulin-like growth factor 1 (IGF-1) receptor is a protein found on the surface of human cells. It is a transmembrane receptor that is activated by a hormone called insulin-like growth factor 1 ( IGF-1) and by a related hormone called IGF-2. ...
, which blocks
IGF-1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans is ...
and
IGF-2
Insulin-like growth factor 2 (IGF-2) is one of three protein hormones that share structural similarity to insulin. The MeSH definition reads: "A well-characterized neutral peptide believed to be secreted by the liver and to circulate in the blo ...
binding, resulting in apoptosis.
Function
IGFBP-3 was first isolated, characterized, and quantitated in human plasma, in 1986.
It has well-documented functions in the circulation, in the extracellular environment, and inside cells. It is the main IGF transport protein in the bloodstream, where it carries the growth factors predominantly in stable complexes that contain the binding protein, either IGF-1 or IGF-2, and a third protein called the
acid-labile subunit or ALS.
For IGFs to reach the tissues from the bloodstream, the circulating complexes are believed to partly dissociate, possibly enhanced by limited proteolysis of IGFBP-3. The IGF-1/IGFBP-3 ratio has sometimes been used as an index of IGF bioavailability in the human circulation, but this ignores IGF-1 binding to other IGFBPs (so the ratio is affected by the concentrations of all six IGFBPs), and the fact that IGF-2, which is three times more abundant than IGF-1 in the bloodstream of adults, occupies the majority of binding sites on circulating IGFBP-3.
Within tissues, IGFBP-3 can bind IGF-1 and IGF-2 released by many cell types, and block their access to the IGF-1 receptor (
IGF1R
The insulin-like growth factor 1 (IGF-1) receptor is a protein found on the surface of human cells. It is a transmembrane receptor that is activated by a hormone called insulin-like growth factor 1 ( IGF-1) and by a related hormone called IGF-2. ...
), which is activated by both IGFs. IGFBP-3 also interacts with cell-surface proteins, affecting cell signaling from outside the cell or after internalization, and also enters the cell nucleus where it binds to nuclear hormone receptors and other ligands. High levels of IGFBP-3 within tumors are associated with increased cancer severity (or worse outcome) for some cancers, but decreased severity or better outcome for others. No cases of IGFBP3 gene deletion in humans have been reported, but mice lacking the gene show near-normal growth.
Gene and protein structure
The IGFBP3 gene (or IBP3), on human chromosome 7, is organized into four protein-coding
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 with a 5th exon in the 3’ untranslated region.
It is located adjacent to the
IGFBP1
Insulin-like growth factor-binding protein 1 (IBP-1) also known as placental protein 12 (PP12) is a protein that in humans is encoded by the ''IGFBP1'' gene.
Function
This gene is a member of the Insulin-like growth factor-binding protein (IGFB ...
gene in tail-to-tail orientation, separated by 20 kb.
The encoded protein includes a 27-residue
signal peptide
A signal peptide (sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequence or leader peptide) is a short peptide (usually 16-30 amino acids long) present at the N-ter ...
followed by the 264-residue mature protein. IGFBP-3 shares with the other five high-affinity IGFBPs and a 3-domain structure:
# A conserved
N-terminal domain
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 ...
containing a cysteine rich region (12 cysteine residues) with multiple intra-domain
disulfide bond
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
s, an IGFBP motif (GCGCCXXC), the primary site of IGF binding.
# A highly variable central or linker domain (only 15% conservation between IGFBPs).
# A conserved
C-terminal domain
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 ...
containing secondary IGF binding residues, a cysteine rich region (6 cysteine residues), an 18 residue basic motif that binds
heparin
Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...
, the acid labile subunit (ALS), and a
nuclear localization sequence A nuclear localization signal ''or'' sequence (NLS) is an amino acid sequence that 'tags' a protein for import into the cell nucleus by nuclear transport. Typically, this signal consists of one or more short sequences of positively charged lysines o ...
.
The linker domain is the site of most
post-translational modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosome ...
, which include
glycosylation
Glycosylation is the reaction in which a carbohydrate (or ' glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not al ...
,
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 ...
, and limited
proteolysis
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called protease ...
. By electrophoretic analysis IGFBP-3 appears as a doublet, owing to the occupancy of either two or three of its
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 by carbohydrate. Hypoglycosylated IGFBP-3 may be seen after extended glucose starvation.
Many
protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s are known to cleave IGFBP-3 at single linker-domain sites, and in the circulation of pregnant women, IGFBP-3 is entirely proteolyzed, yet still capable of carrying normal amounts of IGF-1 and IGF-2. Binding capacity appears to be retained after proteolysis because of a cooperative interaction between the two proteolyzed fragments, that together maintain an active IGF-binding site.
Sites and regulation of production
IGFBP-3 mRNA is expressed in all tissue examined, with kidney, stomach, placenta, uterus and liver showing highest expression in rat tissues.
Rat liver IGFBP-3 mRNA is found in nonparenchymal cells including sinusoidal endothelium, but not in
hepatocyte
A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass.
These cells are involved in:
* Protein synthesis
* Protein storage
* Transformation of carbohydrates
* Synthesis of cholesterol, ...
s.
In contrast, human hepatocytes do express IGFBP-3.
IGFBP-3 levels in human serum are, like IGF-1, dependent on
growth hormone
Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in h ...
(GH); for example, serum IGFBP-3 is increased in acromegaly and low in GH-deficient children. However, IGFBP-3 gene expression in human liver is GH-independent.
Because it is stabilized in human serum by forming complexes with IGF-1 and ALS, which are both GH-dependent, serum IGFBP-3 also appears regulated by GH. Its production by some non-hepatic tissues may also be directly GH-regulated.
Immunoassay
An immunoassay (IA) is a biochemical test that measures the presence or concentration of a macromolecule or a small molecule in a solution through the use of an antibody (usually) or an antigen (sometimes). The molecule detected by the immunoass ...
s for serum IGFBP-3 are often used as part of the diagnosis of childhood GH-deficiency.
The most widely studied IGFBP3
polymorphism, at nucleotide-202 in the promoter region, is significantly associated with circulating IGFBP-3 levels, although the mechanism is unclear.
In some studies circulating IGFBP-3 also appears to be nutritionally regulated, although this may not be seen at the mRNA level. IGFBP-3 has been identified in human lymph, nipple aspirate, milk, amniotic fluid, follicular fluid, seminal plasma, urine, peritoneal dialysate, synovial fluid, tear fluid, and cerebrospinal fluid, in addition to serum.
Many factors increase IGFBP-3 production by cells, including
transforming growth factor-β
Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other sign ...
(TGFβ), tumor necrosis factor-α, vitamin D, retinoic acid, IGF-1, and stimuli such as chemotherapy that activate the tumor suppressor p53.
Estrogen inhibits IGFBP-3 production, and its tissue levels are lower in estrogen receptor (ER)-positive breast cancers than in ER-negative cancers.
Interactions
The main IGFBP-3 ligands in the circulation are IGF-1 and IGF-2, and the acid-labile subunit (ALS).
The serum proteins
transferrin
Transferrins are glycoproteins found in vertebrates which bind to and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Fe3+ ions. Human transferrin is encode ...
,
fibronectin
Fibronectin is a high- molecular weight (~500-~600 kDa) glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin also binds to other extracellular matrix proteins such as collage ...
,
and
plasminogen
Plasmin is an important enzyme () present in blood that degrades many blood plasma proteins, including fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein (in the zymogen form of plasminogen) is encode ...
are also known to bind IGFBP-3. In the cell and tissue environment many other interactions have been described (see Table). Two unrelated cell-surface proteins have been designated as IGFBP-3 receptors: low density lipoprotein receptor-related protein 1 (
LRP1
Low density lipoprotein receptor-related protein 1 (LRP1), also known as alpha-2-macroglobulin receptor (A2MR), apolipoprotein E receptor (APOER) or cluster of differentiation 91 (CD91), is a protein forming a receptor found in the plasma membra ...
), also known as alpha-2-macroglobulin receptor or type V TGFβ receptor
and the transmembrane protein
TMEM219
Transmembrane protein 219 also known as insulin-like growth factor-binding protein 3 receptor or IGFBP-3R is a protein that in humans is encoded by the TMEM219 gene. IGFBP-3R acts as a cell death receptor for IGFBP3
Insulin-like growth factor-bi ...
.
Both are believed to mediate antiproliferative effects. Functional interactions with the
EGF receptor EGF may refer to:
* E.G.F., a Gabonese company
* East Grand Forks, Minnesota, a city
* East Garforth railway station in England
* Epidermal growth factor
* Equity Group Foundation, a Kenyan charity
* European Gendarmerie Force, a military unit of ...
and the type I/type II
TGFβ receptor system have also been reported, and other cell-surface proteins such as proteoglycans also bind IGFBP-3. IGFBP-3 can enter cells by both clathrin-mediated and caveolin-mediated endocytosis.
possibly involving the transferrin receptor.
IGFBP-3 enters the cell nucleus by a mechanism that is incompletely understood, but involves its binding to
importin-β.
Within the nucleus, it can modulate
nuclear hormone receptor
In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These receptors work with other proteins to regulate the expression of specif ...
activity by direct binding to
retinoid X receptor
The retinoid X receptor (RXR) is a type of nuclear receptor that is activated by 9-cis retinoic acid, which is discussed controversially to be of endogenous relevance, and 9-''cis''-13,14-dihydroretinoic acid, which is likely to be the major e ...
,
retinoic acid receptor
The retinoic acid receptor (RAR) is a type of nuclear receptor which can also act as a ligand-activated transcription factor that is activated by both all-trans retinoic acid and 9-cis retinoic acid the retinoid active derivatives of Vitamin A ...
,
vitamin D receptor
The vitamin D receptor (VDR also known as the calcitriol receptor) is a member of the nuclear receptor family of transcription factors. Calcitriol (the active form of vitamin D, 1,25-(OH)2vitamin D3) binds to VDR, which then forms a heterodimer ...
,
PPARγ
Peroxisome proliferator- activated receptor gamma (PPAR-γ or PPARG), also known as the glitazone reverse insulin resistance
receptor, or NR1C3 (nuclear receptor subfamily 1, group C, member 3) is a type II nuclear receptor functioning as a tran ...
,
and
nur77
The nuclear receptor 4A1 (NR4A1 for "nuclear receptor subfamily 4 group A member 1") also known as Nur77, TR3, and NGFI-B is a protein that in humans is encoded by the ''NR4A1'' gene.
Nuclear receptor 4A1 (NR4A1) is a member of the '' NR4A'' nucl ...
,
IGFBP-3 also interacts with DNA-dependent protein kinase within the nucleus to promote the repair of DNA damage.
Cellular actions
IGFBP-3 exerts
antiproliferative
Cytostasis (cyto – cell; stasis – stoppage) is the inhibition of cell growth and multiplication. Cytostatic refers to a cellular component or medicine that inhibits cell division.
Cytostasis is an important prerequisite for structured multic ...
effects in many cell types by blocking the ability of
IGF-1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans is ...
and
IGF-2
Insulin-like growth factor 2 (IGF-2) is one of three protein hormones that share structural similarity to insulin. The MeSH definition reads: "A well-characterized neutral peptide believed to be secreted by the liver and to circulate in the blo ...
to activate the
IGF1R
The insulin-like growth factor 1 (IGF-1) receptor is a protein found on the surface of human cells. It is a transmembrane receptor that is activated by a hormone called insulin-like growth factor 1 ( IGF-1) and by a related hormone called IGF-2. ...
(which stimulates cell proliferation). For example, in
esophageal epithelial
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
cells, responsiveness to IGF-1 stimulation is suppressed by secreted IGFBP-3 and restored when IGFBP-3 is downregulated by
epidermal growth factor
Epidermal growth factor (EGF) is a protein that stimulates cell growth and differentiation by binding to its receptor, EGFR. Human EGF is 6-k Da and has 53 amino acid residues and three intramolecular disulfide bonds.
EGF was originally descr ...
.
IGFBP-3 can also inhibit cell function by mechanisms that are independent of effects on IGF1R signaling, even in cells that entirely lack IGF1R.
IGF (or IGF1R) independent effects are commonly studied using mutant forms of IGFBP-3 with decreased IGF binding affinity. Thus, IGFBP-3-induced apoptosis in differentiating
chondrocyte
Chondrocytes (, from Greek χόνδρος, ''chondros'' = cartilage + κύτος, ''kytos'' = cell) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteog ...
precursor cells is seen equally with a non-IGF binding IGFBP-3 mutant, demonstrating that the mechanism does not involve IGF binding.
IGF1R-independent growth inhibition by IGFBP-3 may involve the induction of pro-apoptotic proteins such as
Bax and
Bad
Bad or BAD may refer to:
Common meanings
*Evil, the opposite of moral good
* Erroneous, inaccurate or incorrect
* Unhealthy, or counter to well-being
* Antagonist, the threat or obstacle of moral good
Acronyms
* BAD-2, a Soviet armored troll ...
and may be mediated by ceramides (pro-
apoptotic
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes includ ...
lipids),
or potentiate
ceramide
Ceramides are a family of waxy lipid molecules. A ceramide is composed of N-acetylsphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make up ...
action
IGFBP-3 interaction with nuclear hormone receptors may also lead to inhibition of cell proliferation.
Contrasting with the typical growth-inhibitory effects of IGFBP-3, stimulation of cell proliferation by IGFBP-3 has also been observed. This can occur either by enhancing IGF-stimulated proliferation
or in the absence of IGF-1. In endothelial cells and mammary epithelial cells, the stimulatory effect of IGFBP-3 has been shown to involve activation of the enzyme
sphingosine kinase
Sphingosine kinase (SphK) is a conserved lipid kinase that catalyzes formation sphingosine-1-phosphate (S1P) from the precursor sphingolipid sphingosine. Sphingolipid metabolites, such as ceramide, sphingosine and sphingosine-1-phosphate, are ...
, and generation of the bioactive lipid,
sphingosine-1-phosphate
Sphingosine-1-phosphate (S1P) is a signaling sphingolipid, also known as lysosphingolipid. It is also referred to as a bioactive lipid mediator. Sphingolipids at large form a class of lipids characterized by a particular aliphatic aminoalcohol, ...
, which promotes growth by transactivating the EGFR receptor.
Role in cancer
Based on cell growth experiments, animal cancer models, and
epidemiological studies
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evidenc ...
, it appears that IGFBP-3 functions as a low-
penetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
tumor suppressor
A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a 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 in a loss or red ...
gene.
Dysregulation of IGFBP-3 has been implicated in many cancers.
Downregulation of its tissue expression by promoter
hypermethylation
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...
in some cancers, such as
hepatoma
Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide.
It occurs in t ...
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 ...
may be associated with poor patient outcome. However, consistent with the dual inhibitory and stimulatory roles of IGFBP-3 seen in cell culture, there are other cancer types, such as breast cancer,
pancreatic cancer,
and clear cell
renal cell cancer
Renal cell carcinoma (RCC) is a kidney cancer that originates in the lining of the proximal convoluted tubule, a part of the very small tubes in the kidney that transport primary urine. RCC is the most common type of kidney cancer in adults, resp ...
in which high tissue IGFBP-3 expression has been linked to poor prognostic features or patient outcome. The mechanisms regulating these contrasting effects of IGFBP-3 in vivo are not well understood.
Since IGFBP-3 is abundant in the bloodstream of healthy adults (typically 2–4 mg/L), and is largely stabilized by its complex formation with IGFs and ALS, it is unlikely that tumor-derived IGFBP-3 has a large influence on circulating levels. There have been many studies linking circulating IGFBP-3 levels to the presence, or risk, of various cancers, or to patient outcomes.
but unequivocal conclusions have often been lacking. For example, high plasma IGFBP-3 levels were associated with a reduced prospective risk of colorectal cancer in women.
but in a study including men and women, colon cancer risk was positively associated with plasma IGFBP-3, while there was no significant association for rectal cancer.
A large systematic review concluded that circulating IGFBP-3 levels showed a modest association with increased risk for a number of cancers, but the results vary among sites.
IGFBP-3 protein levels decrease during the progression of
prostate cancer
Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that sur ...
from benign to metastatic disease
[ For IGFBP-3 it refers to ] although production of the protein does not cease completely. IGFBP-3 is still made (at a lower level) by prostate cancer cells and secreted into the surrounding environment. However, instead of the full length, functional protein, IGFBP-3 is found to be cleaved.
This decreases the affinity of IGF binding to IGFBP-3, making the growth factors more likely to bind the IGF1R and promote cell survival.
Table: IGFBP-3 binding partners
IGFBP3 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:
*
ADAM12
Disintegrin and metalloproteinase domain-containing protein 12 (previously Meltrin) is an enzyme that in humans is encoded by the ''ADAM12'' gene. ADAM12 has two splice variants: ADAM12-L, the long form, has a transmembrane region and ADAM12-S, a ...
*
ADAM28
*
COL1A1
Collagen, type I, alpha 1, also known as alpha-1 type I collagen, is a protein that in humans is encoded by the gene. ''COL1A1'' encodes the major component of type I collagen, the fibrillar collagen found in most connective tissues, including c ...
*
FN1
*
IGFALS
Insulin-like growth factor binding protein, acid labile subunit, also known as IGFALS, is a protein which in humans is encoded by the ''IGFALS'' gene.
Function
The protein encoded by this gene is a serum protein that binds insulin-like growt ...
*
IGF1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans is ...
,
*
IGF2
Insulin-like growth factor 2 (IGF-2) is one of three protein hormones that share structural similarity to insulin. The MeSH definition reads: "A well-characterized neutral peptide believed to be secreted by the liver and to circulate in the bloo ...
[
* HSPA5]
*Humanin
Humanin is a micropeptide encoded in the mitochondrial genome by the 16S ribosomal RNA gene, MT-RNR2. Its structure contains a three-turn α-helix, and no symmetry.
In ''in vitro'' and animal models, it appears to have cytoprotective effects. ...
* PLG
* RXRA
Retinoid X receptor alpha (RXR-alpha), also known as NR2B1 (nuclear receptor subfamily 2, group B, member 1) is a nuclear receptor that in humans is encoded by the ''RXRA'' gene.
Function
Retinoid X receptors (RXRs) and retinoic acid receptor ...
* TF
* KPNB1
Importin subunit beta-1 is a protein that in humans is encoded by the ''KPNB1'' gene.
Function
Nucleocytoplasmic transport, a signal- and energy-dependent process, takes place through nuclear pore complexes embedded in the nuclear envelope. T ...
* PRKDC
* EGFR
* LTBP1
See also
* Mecasermin rinfabate
Mecasermin rinfabate (INN, USAN) (brand name Iplex), also known as /, is a drug consisting of recombinant human insulin-like growth factor 1 (IGF-1) and recombinant human insulin-like growth factor binding protein-3 (IGFBP-3) which is used for ...
, Recombinant IGF-1 with IGFBP-3 used for a variety of indications.
Notes
References
Further reading
*
*
*
{{Growth factor receptor modulators