Theangiotensin II receptors,(ATR1) and(ATR2), are a class ofG protein-coupled receptors withangiotensin II as theirligands.^[1] They are important in therenin–angiotensin system: they are responsible for thesignal transduction of thevasoconstricting stimulus of the main effector hormone,angiotensin II.^[2]

TheAT₁ andAT₂ receptors share a sequence identity of ~30%, but have a similar affinity for angiotensin II, which is their main ligand.

The AT₁ receptor is the best elucidated angiotensin receptor.

The AT1 subtype is found in the heart, blood vessels, kidney, adrenal cortex, lung andcircumventricular organs of brain,basal ganglia,brainstem^[4] and mediates the vasoconstrictor effects.

The angiotensin receptor is activated by thevasoconstricting peptideangiotensin II. The activated receptor in turn couples toG_q/11 andG_i/o and thus activatesphospholipase C and increases the cytosolic Ca²⁺ concentrations, which in turn triggers cellular responses such as stimulation ofprotein kinase C. Activated receptor also inhibitsadenylate cyclase and activates varioustyrosine kinases.^[2]

Effects mediated by the AT₁ receptor includevasoconstriction,aldosterone synthesis and secretion, increasedvasopressin secretion,cardiachypertrophy, augmentation of peripheralnoradrenergic activity,vascularsmooth muscle cells proliferation, decreasedrenal blood flow, renalrenin inhibition, renal tubularsodium reuptake, modulation of centralsympathetic nervous system activity, cardiac contractility, centralosmocontrol andextracellular matrix formation.^[5]

AT₂ receptors are more plentiful in the fetus and neonate. The AT₂ receptor remains enigmatic and controversial – is probably involved in vascular growth. Effects mediated by the AT₂ receptor are suggested to include inhibition ofcell growth, fetal tissue development, modulation of extracellular matrix,neuronal regeneration,apoptosis,cellular differentiation, and maybevasodilation andleft ventricular hypertrophy.^[6] In humans the AT2 subtype is found in molecular layer of thecerebellum. 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.^[7]

Other poorly characterized subtypes include the AT₃ and AT₄ receptors. The AT₄ receptor is activated by the angiotensin II metaboliteangiotensin IV, and may play a role in regulation of the CNS extracellular matrix, as well as modulation ofoxytocin release.^[8][9][10]

• Angiotensin II receptor antagonist

• Receptors,+Angiotensin at the U.S. National Library of MedicineMedical Subject Headings (MeSH)

• Genes on human chromosome 3
• Genes on human chromosome X
• G protein-coupled receptors

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