Összes szerző

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Umair Naseem Muhammad

az alábbi absztraktok szerzői között szerepel:

Kashmala Shakeel
Isolation of novel peptide toxins from the venom of the scorpion Centruroides bonito which block Kv1.2 ion channel with picomolar affinity

Aug 30 - szerda

15:30 – 17:00

II. Poszterszekció

P44

Isolation of novel peptide toxins from the venom of the scorpion Centruroides bonito which blocks Kv1.2 ion channel with picomolar affinity 

Kashmala Shakeel¹, Muhammad Umair Naseem¹, Lourival D Possani², Gyorgy Panyi¹

¹ Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Hungary

² Departamento de Medicina Molecular y Bioprocesos, Universidad Nacional Autónoma de México, Mexico

Seven new peptide toxins named as CboK1 to CboK7 were isolated from the venom of the Mexican scorpion Centruroides bonito by liquid chromatography. The primary structure of these peptides were determined by Edman degradation. Mass spectrometry analysis was used to determine the molecular weights which range between 3760.4 Da to 4357.9 Da, comprising 32 to 39 amino acid residues cross-linked with three tightly folded disulfide-bridges. The amino acid sequence alignment with known potassium scorpion toxins (KTx) and phylogenetic tree analysis unveiled that CboK1 (α-KTx 10.5) and CboK2 (α-KTx 10.6) belong to α-KTx 10 subfamily, whereas CboK3 (α-KTx 2.22), CboK4 (α-KTx 2.23), CboK6 (α-KTx 2.21), CboK7 (α-KTx 2.24) bears more than 95% amino acid similarity with the members of α-KTx 2 subfamily, and CboK5 is 100% identical with previously described Ce3 toxin (α-KTx 2.10). The electrophysiological assays (whole-cell patch clamp) revealed that except CboK1, all other six peptide toxins blocked the voltage-gated potassium channel Kv1.2 with high affinity, having Kd values in the picomolar range (24-763 pM) and inhibited the Kv1.3 ion channel with comparatively less potency (Kd values between 20-171 nM). Moreover, CboK2 and CboK3 inhibited ~10% and CboK7 inhibited ~50% of Kv1.1 currents at 100 nM concentration. Among all CboK7 (α-KTx 2.24) has the highest affinity for Kv1.2 ion channel with Kd value of 24 pM, and reasonable selectivity over Kv1.3 (~1000-fold) and Kv1.1 (~6000-fold) ion channels. These distinguishable characteristics of the CboK7 toxin may provide a framework for developing tools to treat Kv1.2-related gain of function channelopathies.

Muhammad Umair Naseem
Cm39 (α-KTx 4.8): A novel scorpion toxin that inhibits voltage-gated K+ channel Kv1.2 and small- and intermediate-conductance Ca2+-activated K+ channels KCa2.2 and KCa3.1

Aug 30 - szerda

15:30 – 17:00

II. Poszterszekció

P48

Cm39 (α-KTx 4.8): A novel scorpion toxin that inhibits voltage-gated K⁺ channel Kv1.2 and small- and intermediate-conductance Ca²⁺-activated K⁺ channels KCa2.2 and KCa3.1

Muhammad Umair Naseem¹, Georgina Gurrola-Briones², Margarita R. Romero-Imbachi³, Jesus Borrego¹, Edson Carcamo-Noriega², José Beltrán-Vidal³, Fernando Z. Zamudio², Kashmala Shakeel¹, Lourival D. Possani², Gyorgy Panyi¹

¹ University of Debrecen, Faculty of Medicine, Department of Biophysics and Cell Biology, Hungary

² Departamento de Medicina Molecular y Bioprocesos, Universidad Nacional Autónoma de México, Mexico

³ Departamento de Biología, Facultad de Ciencias Naturales, Universidad del Cauca, Colombia

A novel peptide toxin, Cm39, was identified in the venom of the Colombian scorpion Centruroides margaritatus. It is composed of 37 amino acid residues with a MW of 3980.2 Da and folded by three disulfide bonds. The Cm39 sequence also contains the Lys-Tyr (KY) functional dyad required to block voltage-gated K⁺ (Kv) channel. Amino acid sequence comparison with previously known K⁺ channel inhibitor scorpion toxins (KTx) and phylogenetic analysis revealed that Cm39 is a new member of α-KTx 4 family and registered with systematic number of α-KTx4.8. The full chemical synthesis and proper folding of Cm39 was obtained. The pharmacological properties of the synthetic peptide were determined using patch-clamp electrophysiology. Cm39 inhibits the voltage-gated K⁺ channel hKv1.2 with high affinity (K_d = 65 nM). The conductance-voltage relationship of Kv1.2 was not altered in the presence of Cm39, the analysis of the toxin binding kinetics was consistent with a bimolecular interaction between the peptide and the channel, and therefore the pore blocking mechanism is proposed for the toxin-channel interaction. Cm39 also inhibits the Ca²⁺-activated KCa2.2 and KCa3.1 channels, with K_d = 575 nM, and K_d = 59 nM, respectively, however, the peptide does not inhibit hKv1.1, hKv1.3, hKv1.4, hKv1.5, hKv1.6, hKv11.1, mKCa1.1 potassium channels or the hNav1.5 and hNav1.4 sodium channels at 1 µM concentration. Understanding the unusual selectivity profile of Cm39 motivates further experiments to reveal novel interactions with the vestibule of toxin-sensitive channels [1].

References

[1] Naseem MU, Gurrola-Briones G, Romero-Imbachi MR, Borrego J, Carcamo-Noriega E, Beltrán-Vidal J, Zamudio FZ, Shakeel K, Possani LD and Panyi G, (2023) Toxins 15(1), p.41.