title: FK506-binding proteins regulate smooth muscle contractility by altering neurotransmitter release.
abstract: To determine the roles of FK506-binding proteins, receptors for the immunosuppressant FK506, in tachykinin release, we examined the effects of the FK506 derivative ascomycin, [3S-[3R[E(1S,3S,4S)],4S,5R,8S,9E,12R,14R,15S,16R,18S,1 9S,26aR]]-8-ethyl- 5,6,8,11,12,13,14,15,16,17,18,19,24,25,26,26a-hexadecahydro- 5,19-dihydroxy- 3-[2-(4-hydroxy-3-methoxycyclohexyl)-1-methylethenyl]-14,16- dimethoxy- 4,10,12,18-tetramethyl-15,19-epoxy-3H-pyrido[2,1-c][1,4]oxaazacyclotr icosine -1,7,20,21(4H,23H)-tetrone, on the contractility of the rabbit iris sphincter muscle. Ascomycin (10(-7) to 10(-5) M) caused concentration-dependent contractions, which were greatly attenuated by preexposure to rapamycin (10(-5) M), a FK506 receptor antagonist. Similarly, this contractile effect was abolished by preexposure to FK888 (10(-6) M), a tachykinin receptor antagonist, and to capsaicin (10(-5) M), a tachykinin-depleting agent. L-type voltage-dependent Ca2+ channel blockers, nicardipine (10(-5) M) and verapamil (5 x 10(-5) M), inhibited the ascomycin-induced contraction, but the N-type channel blocker omega-conotoxin (10(-6) M) did not. These results suggest that ascomycin stimulates tachykinin release by its binding to FK506-binding proteins and the subsequent activation of L-type Ca2+ channels. Thus, FK506-binding proteins may regulate muscle contractility by altering transmitter release from peripheral tachykininergic nerves.
authors.affiliation: Ophthalmic Research Division, Santen Pharmaceutical Co. Ltd., Nara, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kageyama
authors.forename: H
authors.initials: H
authors.lastname: Fujita
authors.forename: W
authors.initials: W
authors.lastname: Goto
authors.forename: K
authors.initials: K
authors.lastname: Nakata
authors.forename: E
authors.initials: E
authors.lastname: Shirasawa
authors.forename: A
authors.initials: A
authors.lastname: Kanai
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D007498:Iris / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011090:Polyenes / Q000494:pharmacology; D011817:Rabbits; D018039:Receptors, Tachykinin / Q000037:antagonists & inhibitors; D020123:Sirolimus; D009435:Synaptic Transmission / Q000187:drug effects*; D015320:Tachykinins / Q000378:metabolism*; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D004151:Dipeptides; D007166:Immunosuppressive Agents; D007211:Indoles; D011090:Polyenes; D018039:Receptors, Tachykinin; D015320:Tachykinins; C078949:FK 888; C058028:immunomycin; D002211:Capsaicin; D020123:Sirolimus; D016559:Tacrolimus