科研之友
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摘要
Spider venoms are rich sources of peptidic ion channel modulators with important therapeutical potential. We screened a panel of 60 spider venoms to find modulators of ion channels involved in pain transmission. We isolated, synthesized and pharmacologically characterized Cd1a, a novel peptide from the venom of the spider Ceratogyrus darlingi. Cd1a reversibly paralysed sheep blowflies (PD50 of 1318 pmol/g) and inhibited human Ca(v)2.2 (IC50 2.6 mu M) but not Ca(v)1.3 or Ca(v)3.1 (IC50 > 30 mu M) in fluorimetric assays. In patch-clamp electrophysiological assays Cd1a inhibited rat Ca(v)2.2 with similar potency (IC50 3 mu M) without influencing the voltage dependence of Ca(v)2.2 activation gating, suggesting that Cd1a doesn't act on Ca(v)2.2 as a classical gating modifier toxin. The Cd1a binding site on Ca(v)2.2 did not overlap with that of the pore blocker omega-conotoxin GVIA, but its activity at Ca(v)2.2-mutant indicated that Cd1a shares some molecular determinants with GVIA and MVIIA, localized near the pore region. Cd1a also inhibited human Na(v)1.1-1.2 and Na(v)1.7-1.8 (IC50 0.1-6.9 mu M) but not Na(v)1.3-1.6 (IC50 > 30 mu M) in fluorimetric assays. In patch-clamp assays, Cd1a strongly inhibited human Na(v)1.7 (IC50 16 nM) and produced a 29 mV depolarising shift in Na(v)1.7 voltage dependence of activation. Cd1a (400 pmol) fully reversed Na(v)1.7-evoked pain behaviours in mice without producing side effects. In conclusion, Cd1a inhibited two anti-nociceptive targets, appearing to interfere with Ca(v)2.2 inactivation gating, associated with the Ca(v)2.2 alpha-subunit pore, while altering the activation gating of Na(v)1.7. Cd1a was inactive at some of the Na-v and Ca-v channels expressed in skeletal and cardiac muscles and nodes of Ranvier, apparently contributing to the lack of side effects at efficacious doses, and suggesting potential as a lead for development of peripheral pain treatments.
- 出版日期2017-9-7
