| Autor: |
Herzig V; Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.; Centre for Bioinnovation, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia.; School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia., Chen YC; Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan., Chin YK; Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.; Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia., Dekan Z; Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia., Chang YW; Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan., Yu HM; Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan., Alewood PF; Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia., Chen CC; Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan., King GF; Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.; Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, St. Lucia, QLD 4072, Australia. |
| Abstrakt: |
Inhibition of T-type calcium channels (Ca V 3) prevents development of diseases related to cardiovascular and nerve systems. Further, knockout animal studies have revealed that some diseases are mediated by specific subtypes of Ca V 3. However, subtype-specific Ca V 3 inhibitors for therapeutic purposes or for studying the physiological roles of Ca V 3 subtypes are missing. To bridge this gap, we employed our spider venom library and uncovered that Avicularia spec. ("Amazonas Purple", Peru) tarantula venom inhibited specific T-type Ca V channel subtypes. By using chromatographic and mass-spectrometric techniques, we isolated and sequenced the active toxin ω-Avsp1a, a C-terminally amidated 36 residue peptide with a molecular weight of 4224.91 Da, which comprised the major peak in the venom. Both native (4.1 μM) and synthetic ω-Avsp1a (10 μM) inhibited 90% of Ca V 3.1 and Ca V 3.3, but only 25% of Ca V 3.2 currents. In order to investigate the toxin binding site, we generated a range of chimeric channels from the less sensitive Ca V 3.2 and more sensitive Ca V 3.3. Our results suggest that domain-1 of Ca V 3.3 is important for the inhibitory effect of ω-Avsp1a on T-type calcium channels. Further studies revealed that a leucine of T-type calcium channels is crucial for the inhibitory effect of ω-Avsp1a. |
