title: Cobinamides are novel coactivators of nitric oxide receptor that target soluble guanylyl cyclase catalytic domain.
abstract: Soluble guanylyl cyclase (sGC), a ubiquitously expressed heme-containing receptor for nitric oxide (NO), is a key mediator of NO-dependent processes. In addition to NO, a number of synthetic compounds that target the heme-binding region of sGC and activate it in a NO-independent fashion have been described. We report here that dicyanocobinamide (CN2-Cbi), a naturally occurring intermediate of vitamin B(12) synthesis, acts as a sGC coactivator both in vitro and in intact cells. Heme depletion or heme oxidation does not affect CN2-Cbi-dependent activation. Deletion mutagenesis demonstrates that CN2-Cbi targets a new regulatory site and functions though a novel mechanism of sGC activation. Unlike all known sGC regulators that target the N-terminal regulatory regions, CN2-Cbi directly targets the catalytic domain of sGC, resembling the effect of forskolin on adenylyl cyclases. CN2-Cbi synergistically enhances sGC activation by NO-independent regulators 3-(4-amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine (BAY41-2272), 4-[((4-carboxybutyl){2-[(4-phenethylbenzyl)oxy]phenethyl}amino) methyl [benzoic]-acid (cinaciguat or BAY58-2667), and 5-chloro-2-(5-chloro-thiophene-2-sulfonylamino-N-(4-(morpholine-4-sulfonyl)-phenyl)-benzamide sodium salt (ataciguat or HMR-1766). BAY41-2272 and CN2-Cbi act reciprocally by decreasing the EC(50) values. CN2-Cbi increases intracellular cGMP levels and displays vasorelaxing activity in phenylephrine-constricted rat aortic rings in an endothelium-independent manner. Both effects are synergistically potentiated by BAY41-2272. These studies uncover a new mode of sGC regulation and provide a new tool for understanding the mechanism of sGC activation and function. CN2-Cbi also offers new possibilities for its therapeutic applications in augmenting the effect of other sGC-targeting drugs.
authors.affiliation: Department of Internal Medicine, Division of Cardiology, UT Health Science Center in Houston, Medical School, 1941 East Rd., Houston, TX 77054, USA.
authors.forename: Iraida
authors.initials: I
authors.lastname: Sharina
authors.forename: Michael
authors.initials: M
authors.lastname: Sobolevsky
authors.forename: Marie-Francoise
authors.initials: MF
authors.lastname: Doursout
authors.forename: Dorota
authors.initials: D
authors.lastname: Gryko
authors.forename: Emil
authors.initials: E
authors.lastname: Martin
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D003038:Cobamides / Q000494:pharmacology*; D006162:Guanylate Cyclase / Q000187:drug effects*; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects*; D000071756:Soluble Guanylyl Cyclase; D013329:Structure-Activity Relationship; D014805:Vitamin B 12 / Q000494:pharmacology
chemical_list: C423582:3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine; D003038:Cobamides; D011720:Pyrazoles; D011725:Pyridines; D018160:Receptors, Cytoplasmic and Nuclear; C017142:cobinamide; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D014805:Vitamin B 12