TY - JOUR
T1 - Characteristics of channel pores formed by Bacillus thuringiensis mosquito-larvicidal Cry4Aa toxin
AU - Shiraishi, Yuri
AU - Shiozaki, Tomoya
AU - Asakura, Mami
AU - Ide, Toru
AU - Hayakawa, Tohru
N1 - Funding Information:
Culex pipiens eggs were kindly supplied by the Research and Development Laboratory at Dainihon Jochugiku Co., Ltd., Osaka, Japan. This work was supported in part by a research grant for disciplinary science from the Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, and JSPS KAKENHI grant number JP18K05675.
Publisher Copyright:
© 2021, The Japanese Society of Applied Entomology and Zoology.
PY - 2021
Y1 - 2021
N2 - Cry4Aa toxin produced by Bacillus thuringiensis subsp. israelensis exhibits specific toxicity to larvae of medically important mosquito genera. In the present study, we analyzed the characteristics of channel pores formed by recombinant Cry4Aa in a solvent-free planar lipid bilayer. Stable channel currents were observed in electrophysiologic measurements, and the single-channel conductance was 187 ± 10 pS in symmetrical buffer containing 150 mM KCl. The channel pores formed by Cry4Aa were cation-selective, with an estimated PK/PCl permeability ratio of 4.9. In addition, Cry4Aa channel pores exhibited apparent cation preference in the order Na+ > K+, Na+ > Ca2+, and K+ > Ca2+. Although the effect was limited, the cation preference of Cry4Aa channel pores seemed to be correlated with toxicity. Culex pipiens mosquito larvae reared in NaCl solution exhibited greater sensitivity to Cry4Aa, particularly early period after exposure. The presence of cations that preferentially translocate through Cry4Aa channel pores may facilitate excessive influx of water into the midgut cells, leading to colloid-osmotic lysis. Whereas CaCl2 had some effect on the mosquito-larvicidal activity of Cry4Aa, KCl had no effect. The effect of some cations may be mitigated by the variety of ion channels present on the midgut cell membrane.
AB - Cry4Aa toxin produced by Bacillus thuringiensis subsp. israelensis exhibits specific toxicity to larvae of medically important mosquito genera. In the present study, we analyzed the characteristics of channel pores formed by recombinant Cry4Aa in a solvent-free planar lipid bilayer. Stable channel currents were observed in electrophysiologic measurements, and the single-channel conductance was 187 ± 10 pS in symmetrical buffer containing 150 mM KCl. The channel pores formed by Cry4Aa were cation-selective, with an estimated PK/PCl permeability ratio of 4.9. In addition, Cry4Aa channel pores exhibited apparent cation preference in the order Na+ > K+, Na+ > Ca2+, and K+ > Ca2+. Although the effect was limited, the cation preference of Cry4Aa channel pores seemed to be correlated with toxicity. Culex pipiens mosquito larvae reared in NaCl solution exhibited greater sensitivity to Cry4Aa, particularly early period after exposure. The presence of cations that preferentially translocate through Cry4Aa channel pores may facilitate excessive influx of water into the midgut cells, leading to colloid-osmotic lysis. Whereas CaCl2 had some effect on the mosquito-larvicidal activity of Cry4Aa, KCl had no effect. The effect of some cations may be mitigated by the variety of ion channels present on the midgut cell membrane.
KW - Bacillus thuringiensis Cry4Aa toxin
KW - Culex pipiens mosquito larvae
KW - Electrophysiologic analysis of channel pores
UR - http://www.scopus.com/inward/record.url?scp=85117694512&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85117694512&partnerID=8YFLogxK
U2 - 10.1007/s13355-021-00762-6
DO - 10.1007/s13355-021-00762-6
M3 - Article
AN - SCOPUS:85117694512
JO - Applied Entomology and Zoology
JF - Applied Entomology and Zoology
SN - 0003-6862
ER -