1.C.46 The C-type Natriuretic Peptide (CNP) Family

C-type natriuretic peptides (CNPs) are widely distributed in the mammalian central nervous system, the brain, endothelial cells, kidney, and the GI tract. They are also synthesized by many other animals such as fish, frogs, snakes and the platypus. These secreted peptides may play a role in cytokine-associated disorders, septic shock and renal failure in mammals. The CNP from platypus (Ornithorhynchus anatinus) venom yields sustained tonic relaxation of rat uterus. Both human CNP-22 (HsCNP-22) and the highly similar platypus venom CNP-39 (OaCNP-39) form weakly cation-selective, voltage gated, large conductance channels in artificial bilayers. The HsCNP and OaCNP-39 channels exhibit inward rectification, with permeabilities to K⁺> Na⁺> Cs>> choline.

The CNP precursor proteins are large, i.e. >100 residue proteins which can be degraded to small peptides, the active channel-forming constituents being derived from the C-termini. For example, the human CNP (126aas) degrades to three peptides CNP-22, CNP-29 and CNP-53, all derived from the C-terminus of the precursor protein.

The transport reaction catalyzed by the oligomeric channels derived from CNP peptides is:

cations (in) cations (out)