Receptors
Three types of atrial natriuretic peptide receptors have been identified on which natriuretic peptides act. They are all cell surface receptors and are designated:
- guanylyl cyclase-A (GC-A) also known as natriuretic peptide receptor-A (NPRA/ANPA) or NPR1
- guanylyl cyclase-B (GC-B) also known as natriuretic peptide receptor-B (NPRB/ANPB) or NPR2
- natriuretic peptide clearance receptor (NPRC/ANPC) or NPR3
NPR-A and NPR-B have a single membrane-spanning segment with an extracellular domain that binds the ligand. The intracellular domain maintains two consensus catalytic domains for guanylyl cyclase activity. Binding of a natriuretic peptide induces a conformational change in the receptor that causes receptor dimerization and activation. Thus, binding of ANP to its receptor causes the conversion of GTP to cGMP and raises intracellular cGMP. As a consequence, cGMP activates a cGMP-dependent kinase (PKG or cGK) that phosphorylates proteins at specific serine and threonine residues. In the medullary collecting duct, the cGMP generated in response to ANP may act not only through PKG but also via direct modulation of ion channels. NPR-C functions mainly as a clearance receptor by binding and sequestering ANP from the circulation. All natriuretic peptides are bound by the NPR-C. Atrial natriuretic peptide and brain natriuretic peptide bind and activate GC-A, whereas CNP binds and activates GC-B.
Read more about this topic: Atrial Natriuretic Peptide
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“Our talk of external things, our very notion of things, is just a conceptual apparatus that helps us to foresee and control the triggerings of our sensory receptors in the light of previous triggering of our sensory receptors.”
—Willard Van Orman Quine (b. 1908)