BMPR2
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Bone morphogenetic protein receptor type II or BMPR2 is a
serine/threonine receptor kinase A serine/threonine protein kinase () is a kinase enzyme, in particular a protein kinase, that phosphorylates the OH group of the amino-acid residues serine or threonine, which have similar side chains. At least 350 of the 500+ human pr ...
. It binds
Bone morphogenetic proteins Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of piv ...
, members of the TGF beta superfamily of ligands, which are involved in
paracrine signalling Paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over ...
. BMPs are involved in a host of cellular functions including
osteogenesis Osteoblasts (from the Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts function ...
,
cell growth Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than ...
and
cell differentiation Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellula ...
. Signaling in the BMP pathway begins with the binding of a BMP to the type II receptor. This causes the recruitment of a BMP type I receptor, which it phosphorylates. The Type I receptor phosphorylates an R-SMAD a transcriptional regulator.


Function

Unlike the TGFβ type II receptor, which has a high affinity for TGF-β1, BMPR2 does not have a high affinity for BMP-2, BMP-7 and BMP-4, unless it is co-expressed with a type I BMP receptor. On ligand binding, forms a receptor complex consisting of two type II and two type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate, then bind and activate SMAD transcriptional regulators. Binds to BMP-7, BMP-2 and, less efficiently, BMP-4. Binding is weak but enhanced by the presence of type I receptors for BMPs. In TGF beta signaling all of the receptors exist in homodimers before ligand binding. In the case of BMP receptors only a small fraction of the receptors exist in homomeric forms before
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
binding. Once a ligand has bound to a receptor, the amount of homomeric receptor oligomers increase, suggesting that the equilibrium shifts towards the homodimeric form. The low affinity for ligands suggests that BMPR2 may differ from other type II TGF beta receptors in that the ligand may bind the type I receptor first.


Oocyte Development

BMPR2 is expressed on both human and animal granulosa cells, and is a crucial receptor for bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF 9). These two protein signaling molecules and their BMPR2 mediated effects play an important role in follicle development in preparation for ovulation. However, BMPR2 can't bind BMP15 and GDF9 without the assistance of bone morphogenetic protein receptor 1B (BMPR1B) and transforming growth factor β receptor 1 (TGFβR1) respectively. There is evidence that the BMPR2 signaling pathway is disrupted in the case of polycystic ovary syndrome, possibly by hyperaldosterism. It appears that the hormones estrogen and follicle stimulating hormone (FSH) have roles in regulating expression of BMPR2 in granulosa cells. Experimental treatment in animal models with estradiol with or without FSH increased BMPR2 mRNA expression while treatment with FSH alone decreased BMPR2 expression. However, in human granulosa-like tumor cell line (KGN), treatment with FSH increased BMPR2 expression.


Clinical significance

At least 70 disease-causing mutations in this gene have been discovered. An inactivating mutation in the ''BMPR2'' gene has been linked to pulmonary arterial hypertension. BMPR2 functions to inhibit the proliferation of vascular smooth muscle tissue. It functions by promoting the survival of pulmonary arterial endothelial cells, therefore preventing arterial damage and adverse inflammatory responses. It also inhibits pulmonary arterial proliferation in response to growth factors, which prevents the closing of arteries by proliferating endothelial cells. When this gene is inhibited, vascular smooth muscle proliferates and can cause pulmonary hypertension, which, among other things, can lead to cor pulmonale, a condition that causes the right side of the heart to fail. The dysfunction of BMPR2 can also lead to an elevation in pulmonary arterial pressure due to an adverse response of the pulmonary circuit to injury. It is especially important to screen for BMPR2 mutations in relatives of patients with idiopathic pulmonary hypertension, for these mutations are present in >70% of familial cases. There have been studies which has correlated BMPR2 with exercise induced elevation of PA pressure by measuring tricuspid regurgitation velocity by echocardiography.


References


External links


BMPR2 gene variant database

GeneReviews/NCBI/NIH/UW entry on Heritable Pulmonary Arterial Hypertension

OMIM entries on Heritable Pulmonary Arterial Hypertension
* {{DEFAULTSORT:Bmpr2 Bone morphogenetic protein Developmental genes and proteins TS domain S/T kinase Receptors EC 2.7.11