摘要
ω-Conotoxins inhibit N-type voltage-gated calcium(Ca_(v)2.2)channels and exhibit efficacy in attenuating neuropathic pain but have a low therapeutic index.Here,we synthesized and characterized a novelω-conotoxin,Bu8 from Conus bullatus,which consists of 25 amino acid residues and three disulfide bridges.Bu8 selectively and potently inhibits depolarization-activated Ba^(2+ )currents mediated by rat Ca_(v)2.2 expressed in HEK293 T cells(IC_(50)=89 nmol/L).Bu8 is two-fold more potent thanω-conotoxin MVIIA,aω-conotoxin currently used for the treatment of severe chronic pain.It also displays potent analgesic activity in animal pain models of hot plate and acetic acid writhing but has fewer side effects on mouse motor function and lower toxicity in goldfish.Its lower side effects may be attributed to its faster binding rate and higher recovery ratios.The NMR structure demonstrates that Bu8 contains a small irregular tripleβ-strand.The structure-activity relationships of Bu8 Ala mutants and Bu8/MVIIA hybrid mutants demonstrate that the binding mode of Ca_(v)2.2 with the amino acid residues in loop 1 and loop 2 of Bu8 is different from that of MVIIA.This study characterizes a novel,more potentω-conotoxin and provides new insights for designing Ca_(v)2.2 antagonists.
基金
supported by the National Natural Science Foundation of China(grant number 81473192)
the National Basic Research Program of China(grant number 2010CB529802)
