Structure and Function of FS50, a salivary protein from the flea Xenopsylla cheopis that blocks the sodium channel NaV1.5.
Naturally occurring toxins have been invaluable tools for the study of structural and functional relationships of voltage-gated sodium channels (VGSC). Few studies have been made of potential channel-modulating substances from blood-feeding arthropods. He we describe the characterization FS50, a salivary protein from the flea, Xenopsylla cheopis, that exhibits an inhibitory activity against the NaV1.5 channel with an IC50of 1.58 μM. The pore-blocking mechanism of this toxin is evident from the kinetics of activation and inactivation suggesting that FS50 does not interfere with the voltage sensor of NaV1.5. FS50 exhibits high specificity for NaV1.5, since 10 μM FS50 had no discernable effect on voltage-gated Na+, K+and Ca2+channels in rat dorsal root ganglia or VGSC forms individually expressed in HEK 293T cells. Furthermore, intravenous injection of FS50 into rats and monkeys elicited recovery from arrhythmia induced by BaCl2, as would be expected from a blockade of NaV1.5. The crystal structure of FS50 revealed a βαββ domain similar to that of scorpion β toxin and a small N-terminal βαβ domain. Site-directed mutagenesis experiments have implicated a basic surface including the side chains of Arg 6, His 11 and Lys 32 as potentially important in the FS50 NaV1.5 interaction.
Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, Guangdong, China.|The Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Rockville, Maryland 20852 USA.
Xueqing
X
Xu
Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, Guangdong, China.
Bei
B
Zhang
The Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China.
Shilong
S
Yang
The Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China.
Su
S
An
The Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Rockville, Maryland 20852 USA.
José M C
JM
Ribeiro
The Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Rockville, Maryland 20852 USA.
John F
JF
Andersen
D000818:Animals; D002460:Cell Line; D005727:Ganglia, Spinal / Q000187:drug effects; D057809:HEK293 Cells; D000882:Haplorhini; D006801:Humans; D016297:Mutagenesis, Site-Directed / Q000379:methods; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000378:metabolism*; D000072417:Protein Domains / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012471:Salivary Proteins and Peptides / Q000494:pharmacology*; D012604:Scorpion Venoms / Q000494:pharmacology; D005423:Siphonaptera / Q000378:metabolism*; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology*; D058260:Xenopsylla / Q000378:metabolism*
D062554:NAV1.5 Voltage-Gated Sodium Channel; D012471:Salivary Proteins and Peptides; D012604:Scorpion Venoms; D061567:Voltage-Gated Sodium Channel Blockers