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XB-ART-48138
Proc Natl Acad Sci U S A 2013 May 28;11022:8906-11. doi: 10.1073/pnas.1214062110.
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Multiple actions of phi-LITX-Lw1a on ryanodine receptors reveal a functional link between scorpion DDH and ICK toxins.

Smith JJ , Vetter I , Lewis RJ , Peigneur S , Tytgat J , Lam A , Gallant EM , Beard NA , Alewood PF , Dulhunty AF .


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We recently reported the isolation of a scorpion toxin named U1-liotoxin-Lw1a (U1-LITX-Lw1a) that adopts an unusual 3D fold termed the disulfide-directed hairpin (DDH) motif, which is the proposed evolutionary structural precursor of the three-disulfide-containing inhibitor cystine knot (ICK) motif found widely in animals and plants. Here we reveal that U1-LITX-Lw1a targets and activates the mammalian ryanodine receptor intracellular calcium release channel (RyR) with high (fM) potency and provides a functional link between DDH and ICK scorpion toxins. Moreover, U1-LITX-Lw1a, now described as ϕ-liotoxin-Lw1a (ϕ-LITX-Lw1a), has a similar mode of action on RyRs as scorpion calcines, although with significantly greater potency, inducing full channel openings at lower (fM) toxin concentrations whereas at higher pM concentrations increasing the frequency and duration of channel openings to a submaximal state. In addition, we show that the C-terminal residue of ϕ-LITX-Lw1a is crucial for the increase in full receptor openings but not for the increase in receptor subconductance opening, thereby supporting the two-binding-site hypothesis of scorpion toxins on RyRs. ϕ-LITX-Lw1a has potential both as a pharmacological tool and as a lead molecule for the treatment of human diseases that involve RyRs, such as malignant hyperthermia and polymorphic ventricular tachycardia.

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Species referenced: Xenopus laevis
Genes referenced: akr1c1 cilk1

References [+] :
Ahern, Single channel activity of the ryanodine receptor calcium release channel is modulated by FK-506. 1994, Pubmed