The angiotensin II receptors, (ATR1) and (ATR2), are a class of
G protein-coupled receptor
G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...
s with
angiotensin II as their
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 elec ...
s.
They are important in the
renin–angiotensin system
The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure, fluid and electrolyte balance, and systemic vascular resistance.
When renal blood flow is reduced, ...
: they are responsible for the
signal transduction of the
vasoconstricting
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
stimulus of the main effector hormone,
angiotensin II.
Structure
The
AT1 and
AT2 receptors share a sequence identity of ~30%, but have a similar affinity for angiotensin II, which is their main ligand.
Members
Overview table
AT1
The AT
1 receptor is the best elucidated angiotensin receptor.
Location within the body
The AT1 subtype is found in the heart, blood vessels, kidney, adrenal cortex, lung and
circumventricular organs
Circumventricular organs (CVOs) ( circum-: around ; ventricular: of ventricle) are structures in the brain characterized by their extensive and highly permeable capillaries, unlike those in the rest of the brain where there exists a bloodâ ...
of brain,
basal ganglia
The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an exter ...
,
brainstem and mediates the vasoconstrictor effects.
Mechanism
The angiotensin receptor is activated by the
vasoconstricting
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
peptide
angiotensin II. The activated receptor in turn couples to
Gq/11 and
Gi/o and thus activates
phospholipase C and increases the cytosolic Ca
2+ concentrations, which in turn triggers cellular responses such as stimulation of
protein kinase C. Activated receptor also inhibits
adenylate cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction:
:A ...
and activates various
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 ...
s.
Effects
Effects mediated by the AT
1 receptor include
vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vess ...
,
aldosterone synthesis and secretion, increased
vasopressin
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then trave ...
secretion,
cardiac
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J. ...
, augmentation of peripheral
noradrenergic activity,
vascular
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
smooth muscle cells proliferation, decreased
renal
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; bloo ...
blood flow, renal
renin
Renin (etymology and pronunciation), also known as an angiotensinogenase, is an aspartic protease protein and enzyme secreted by the kidneys that participates in the body's renin–angiotensin–aldosterone system (RAAS)—also known as the r ...
inhibition, renal tubular
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
reuptake, modulation of central
sympathetic nervous system activity, cardiac contractility, central
osmocontrol and
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
formation.
AT2
AT
2 receptors are more plentiful in the fetus and neonate. The AT
2 receptor remains enigmatic and controversial – is probably involved in vascular growth. Effects mediated by the AT
2 receptor are suggested to include inhibition of
cell growth, fetal tissue development, modulation of extracellular matrix,
neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...
al regeneration,
apoptosis,
cellular differentiation, and maybe
vasodilation
Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstrictio ...
and
left ventricular hypertrophy
Left ventricular hypertrophy (LVH) is thickening of the heart muscle of the left ventricle of the heart, that is, left-sided ventricular hypertrophy and resulting increased left ventricular mass.
Causes
While ventricular hypertrophy occurs ...
.
In humans the AT2 subtype is found in molecular layer of the
cerebellum. In the mouse is found in the adrenal gland, amygdaloid nuclei and, in small numbers, in the paraventricular nucleus of the hypothalamus and the locus coeruleus.
AT3 and AT4
Other poorly characterized subtypes include the AT
3 and AT
4 receptors. The AT
4 receptor is activated by the angiotensin II metabolite
angiotensin IV, and may play a role in regulation of the CNS extracellular matrix, as well as modulation of
oxytocin release.
See also
*
Angiotensin II receptor antagonist
Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT1) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT1 receptor antagonists, are a group of pharmaceuticals tha ...
References
External links
*
{{DEFAULTSORT:Angiotensin receptor
G protein-coupled receptors