Inhibition of neuronal high-voltage activated calcium channels by the omega-phoneutria nigriventer Tx3-3 peptide toxin.
We have investigated the effect of omega-PnTx3-3 (referred to in previous papers simply as Tx3-3), a peptide toxin from the venom of the spider Phoneutria nigriventer, on neuronal high-voltage activated (HVA) Ca(2+) channels, using whole-cell patch-clamp. omega-PnTx3-3 (120 nM) blocked 74+/-8% of the total HVA Ca(2+) currents of cerebellar granule neurones, without affecting the low-voltage activated (LVA) current. P/Q/R-type currents in cerebellar granule neurones, isolated using 4 microM nicardipine and 100 nM omega-conotoxin GVIA, were markedly (79+/-6%) inhibited by 60 nM omega-PnTx3-3. R-type currents, isolated either by additional application of 0.5-1 microM of omega-agatoxin IVA or by pre-incubation with 5 microM omega-conotoxin MVIIC were inhibited almost totally by 120 nM of omega-PnTx3-3. omega-PnTx3-3 reversibly altered the kinetics of the P/Q/R current, increasing the degree of inactivation that occurred during a 50 ms pulse from 20% to 40%. N-type currents, recorded from neuroblastoma N18 cells, were partially (34+/-2%) inhibited by 320 nM omega-PnTx3-3. L-type currents, recorded from GH3 cells, were partially (45+/-12%) inhibited by 80 nM omega-PnTx3-3. We conclude that omega-PnTx3-3 inhibits all known HVA Ca(2+) channels, and most effectively the P/Q- and R-type currents.
Leão
R M
RM
Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais; Caixa Postal 486, 30161-970, Belo Horizonte, MG, Brazil.
Cruz
J S
JS
Diniz
C R
CR
Cordeiro
M N
MN
Beirão
P S
PS
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000494:pharmacology*; D009498:Neurotoxins / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D009479:Neuropeptides; D009498:Neurotoxins; C098736:Tx3 neurotoxin