Tityustoxin‐K(alpha) blockade of the voltage‐gated potassium channel Kv1.3

Abstract

1 We investigated the action of TsTX-Ka on cloned Kv1.3 channels of the Shaker subfamily of voltage-gated potassium channels, using the voltage -clamp technique. Highly purified TsTX-Ka was obtained from the venom of the Brazilian scorpion Tityus serrulatus using a new purification protocol. Our results show that TsTX-Ka blocks Kv1.3 with high affinity in two expression systems. 2 TsTX-Ka blockade of Kv1.3 channels expressed in Xenopus oocytes was found to be completely reversible and to exhibit a pH dependence. The K D was 3.9 nm at pH 7.5, 9.5 nm at pH 7.0 and 94.5 nm at pH 6.5. 3 The blocking properties of TsTX-Ka in a mammalian cell line (L929), stably transfected to express Kv1.3, were studied using the patch -clamp technique. In this preparation, the toxin had a K D of 19.8 nm at pH 7.4. 4 TsTX-Ka was found to affect neither the voltage-dependence of activation, nor the activation and deactivation time constants. The block appeared to be independent of the transmembrane voltage and the toxin did not interfere with the C-type inactivation process. 5 Taken as a whole, our findings indicate that TsTX-Ka acts as a simple blocker of Kv1.3 channels. It is concluded that this toxin is a useful tool for probing not only the physiological roles of Kv1.2, but also those mediated by Kv1.3 channels.

Cellular Mechanisms and Behavioral Consequences of Kv1.2 Regulation in the Rat Cerebellum

“…Since endogenous secretin regulates Kv1.2, and since secretin acts through AC, we investigated whether AC regulates surface Kv1.2 in Purkinje cell dendrites, pinceaus of BC axon terminals, or both. To accomplish this, we developed a fluorescent dye-conjugated derivative of the relatively specific Kv1.2 specific toxin tityustoxin-Kα (TsTx) (Werkman et al, 1993; Rodrigues et al, 2003). We used a strategy similar to that developed to generate fluorescent conjugates of a less specific potassium channel inhibitory peptide, Hongotoxin (Pragl et al, 2002).…”

Potassium channel blockers from the venom of the Brazilian scorpion Tityus serrulatus ( )

“…The channel's blockage appeared independent of the trans-membrane voltage and the toxin did not interfere with the C-type inactivation process. In conclusion, TsTX-K alpha is a useful tool to study the physiological roles not only of the K v 1.2, but also of the K v 1.3 channels (Rodrigues et al, 2003). K v 1.3 channel constitutes a therapeutic target because its blockage in effector-memory T cells suppresses calcium-signalling, production of cytokine and cell-proliferation.…”

Preferential Expression and Function of Voltage-Gated, O 2 -Sensitive K + Channels in Resistance Pulmonary Arteries Explains Regional Heterogeneity in Hypoxic Pulmonary Vasoconstriction

“…Correolide's specificity for Kv1.5 channels (at least in PAs) is supported by the finding that its ability to depolarize PASMCs is blocked by pretreatment with anti-Kv1.5, but not anti-Kv2.1, antibodies ( Figure 7E). Theoretically, correolide can inhibit Kv1.2; however, tityustoxin, an inhibitor of Kv1.2/Kv1.3, 44 inhibits only a small portion of the hypoxiasensitive I K ( Figure 4C). Moreover, after exposure to antiKv1.5 plus anti-Kv2.1, little responsiveness to hypoxia remains ( Figure 8A).…”