Psalmotoxin
Psalmotoxin | |||||||
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UniProt P60514 | | ||||||
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See TCDB 8.B.10 |
Unknown parameter name
Psalmotoxin (PcTx1) is a spider toxin from the venom of the Trinidad tarantula Psalmopoeus cambridgei.[1][2] It selectively blocks Acid Sensing Ion Channel 1-a (ASIC1a), which is a proton-gated sodium channel.
Sources
Psalmotoxin is a toxin produced in the venom glands of the South American tarantula Psalmopoeus cambridgei.[2]
Chemistry
The psalmotoxin structure can be classified as an inhibitor cystine knot (ICK) protein. Many ion channel effectors from snail, spider, and scorpion venoms share a similar ICK structure, although they possess very different pharmalogical profiles. Among ICK toxins, psalmotoxin is the only peptide known to act on homomeric ASIC1 channels.[3]
Psalmotoxin is a 40-
Target
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Psalmopoeus_cambridgei_1.jpg/220px-Psalmopoeus_cambridgei_1.jpg)
Psalmotoxin can bind to a particular
ASICs are
The expression of ASIC1a is high in both the
Mode of action
Binding of psalmotoxin to ASIC1a is reported to increase the affinity of ASIC1a for H+. This increase in affinity for H+ results in the shift of ASIC1a into the desensitized state at resting H+-concentrations (pH = 7.4). The channel being desensitized means that the ion channel is bound to its ligand, H+, but is not able to let ions pass through the ion channel. The underlying mechanism of how this increase in affinity for H+ accounts for a shift of the ASIC1a channels into the desensitized state is not yet specified.[6]
Psalmotoxin also interacts with ASIC1b. In contrast to psalmotoxin binding to ASIC1a, binding of psalmotoxin to ASIC1b results in promoting the opening of the channel. This agonistic effect of psalmotoxin on ASIC1b only occurs in slightly acidic conditions (pH = 7.1).[14]
Toxicity
The role of psalmotoxin in prey capture and the importance of ASIC1a channels as targets of venom components remains unclear.[1]
Therapeutic uses
Psalmotoxin is currently not used for therapeutic purposes, but understanding the psalmotoxin/ASIC1a interaction may be of therapeutic value. Recently, it has been shown that activation of ASIC1a during the acidosis accompanying brain ischemia leads to significant Ca2+ influx, which contributes to neuronal cell death. Inhibition of ASIC1a by psalmotoxin significantly decreased ischemic neuronal cell death. Therefore, it is suggested that desensitized ASIC1's by pharmacological intervention could be beneficial for patients at risk of having a stroke.[15] For the same reasons, psalmotoxin could contribute in the search for a cure for gliomas.[16] Inhibition of ASIC1a in the amygdala by psalmotoxin could have an anxiolytic effect.[17] As ASIC's play a role in nociception, psalmotoxin could be helpful in designing new analgesic drugs acting directly against pain at the nociceptor level.[2]