1
|
Li Z, Soohoo-Hui A, O’Hara FM, Swale DR. ATP-sensitive inward rectifier potassium channels reveal functional linkage between salivary gland function and blood feeding in the mosquito, Aedes aegypti. Commun Biol 2022; 5:278. [PMID: 35347209 PMCID: PMC8960802 DOI: 10.1038/s42003-022-03222-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 03/02/2022] [Indexed: 12/03/2022] Open
Abstract
Reducing saliva secretions into the vertebrate host reduces feeding efficacy by most hematophagous arthropods. However, seminal studies suggested saliva is not a prerequisite for blood feeding in Aedes aegypti. To test this paradigm, we manually transected the salivary duct of female A. aegypti and an inability to salivate was correlated to an inability to imbibe blood. These data justified testing the relevance of inwardly rectifying potassium (Kir) channels in the A. aegypti salivary gland as an antifeedant target site. Pharmacological activation of ATP-gated Kir (KATP) channels reduced the secretory activity of the salivary gland by 15-fold that led to near elimination of blood ingestion during feeding. The reduced salivation and feeding success nearly eliminated horizontal transmission and acquisition of Dengue virus-2 (DENV2). These data suggest mosquito salivation is a prerequisite for blood feeding and provide evidence that KATP channels are critical for salivation, feeding, and vector competency. The salivary gland of Aedes aegypti is needed for efficient blood feeding, and disruption of ATP-gated Kir channels prevents salivation and blood feeding in A. aegypti as well as horizontal transmission and acquisition of Dengue virus2.
Collapse
|
2
|
Piermarini PM, Denton JS, Swale DR. The Molecular Physiology and Toxicology of Inward Rectifier Potassium Channels in Insects. ANNUAL REVIEW OF ENTOMOLOGY 2022; 67:125-142. [PMID: 34606365 DOI: 10.1146/annurev-ento-062121-063338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Inward rectifier K+ (Kir) channels have been studied extensively in mammals, where they play critical roles in health and disease. In insects, Kir channels have recently been found to be key regulators of diverse physiological processes in several tissues. The importance of Kir channels in insects has positioned them to serve as emerging targets for the development of insecticides with novel modes of action. In this article, we provide the first comprehensive review of insect Kir channels, highlighting the rapid progress made in understanding their molecular biology, physiological roles, pharmacology, and toxicology. In addition, we highlight key gaps in our knowledge and suggest directions for future research to advance our understanding of Kir channels and their roles in insect physiology. Further knowledge of their functional roles will also facilitate their exploitation as targets for controlling arthropod pests and vectors of economic, medical, and/or veterinary relevance.
Collapse
Affiliation(s)
- Peter M Piermarini
- Department of Entomology, The Ohio State University, Wooster, Ohio 44691, USA;
| | - Jerod S Denton
- Departments of Anesthesiology & Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37235, USA;
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, Louisiana 70803, USA;
| |
Collapse
|
3
|
Meng X, Wu Z, Yang X, Qian K, Zhang N, Jiang H, Yin X, Guan D, Zheng Y, Wang J. Flonicamid and knockdown of inward rectifier potassium channel gene CsKir2B adversely affect the feeding and development of Chilo suppressalis. PEST MANAGEMENT SCIENCE 2021; 77:2045-2053. [PMID: 33342029 DOI: 10.1002/ps.6232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/17/2020] [Accepted: 12/20/2020] [Indexed: 05/04/2023]
Abstract
BACKGROUND The selective insecticide flonicamid shows highly insecticidal activities against piercing-sucking insects and has been widely used for the control of Hemipteran insect pests, whereas its effects on Lepidopteran insect pests remain largely unknown. Recently, inward rectifier potassium (Kir) channel has been verified to be a target of flonicamid, however, functional characterization of Lepidopteran Kir genes is still lacking. RESULTS Flonicamid shows no insecticidal toxicity against Chilo suppressalis larvae. However, the feeding and growth of larvae were reversibly inhibited by flonicamid (50-1200 mg L-1 ). Flonicamid treatment also remarkably reduced and delayed the pupation and eclosion of Chilo suppressalis. Additionally, five distinct Kir channel genes (CsKir1, CsKir2A, CsKir2B, CsKir3A and CsKir3B) were cloned from Chilo suppressalis. Expression profiles analysis revealed that CsKir2A was predominately expressed in the hindgut of larvae, whereas CsKir2B had high expressions in the Malpighian tubules and hindgut. RNA interference (RNAi)-mediated knockdown of CsKir2B significantly reduced the growth and increased the mortalities of larvae, whereas silencing of CsKir2A had no obvious effects on Chilo suppressalis. CONCLUSION Flonicamid exhibits adverse effects on the growth and development of Chilo suppressalis. CsKir2B might be involved in the feeding behavior of Chilo suppressalis. These results provide valuable information on the effects of flonicamid on non-target insects as well as the function of insect Kir channels, and are helpful in developing new insecticide targeting insect Kir channels. © 2020 Society of Chemical Industry.
Collapse
Affiliation(s)
- Xiangkun Meng
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Zhaolu Wu
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Xuemei Yang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Kun Qian
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Nan Zhang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Heng Jiang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Xingcan Yin
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Daojie Guan
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Yang Zheng
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
| | - Jianjun Wang
- College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou, China
| |
Collapse
|
4
|
Lai X, Xu J, Ma H, Liu Z, Zheng W, Liu J, Zhu H, Zhou Y, Zhou X. Identification and Expression of Inward-Rectifying Potassium Channel Subunits in Plutella xylostella. INSECTS 2020; 11:insects11080461. [PMID: 32707967 PMCID: PMC7469208 DOI: 10.3390/insects11080461] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 11/30/2022]
Abstract
In insects, inward-rectifying potassium (Kir) channels regulate vital physiological functions, such as feeding behavior, silk secretion, renal excretion, and immune function. Therefore, they offer promising potential as targets for insecticides. Three types of Kir subunits have been identified in Diptera and Hemiptera, but the Kir subunits of Lepidoptera still remain unclear. This study identified five Kir subunit genes (pxkir1, pxkir2, pxkir3A, pxkir3B, and pxkir4) in the transcriptome of Plutella xylostella. Phylogenetic analysis identified pxkir1, pxkir2, pxkir3A, and pxkir3B as orthologous genes of kir1–3 in other insects. Interestingly, pxkir4 may be encoding a new class of Kir subunit in Lepidoptera that has not been reported to date. To identify further Kir channel subunits of P. xylostella, the gene expression profiles of five pxkir genes were studied by quantitative real-time PCR. These pxkir genes are expressed throughout the development of P. xylostella. pxkir1 and pxkir2 were highly expressed in thoraxes and legs, while pxkir3 (3A and 3B) and pxkir4 had high expression levels in the midgut and Malpighian tubules. This study identified the composition and distribution of Kir subunits in P. xylostella for the first time, and provides useful information for the further study of Kir channel subunits in Lepidoptera.
Collapse
Affiliation(s)
- Xiaoyi Lai
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; (X.L.); (W.Z.)
| | - Jie Xu
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
| | - Haihao Ma
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
- Correspondence: (H.M.); (X.Z.)
| | - Zheming Liu
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
| | - Wei Zheng
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; (X.L.); (W.Z.)
| | - Jia Liu
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
| | - Hang Zhu
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
| | - Yong Zhou
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
| | - Xiaomao Zhou
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; (X.L.); (W.Z.)
- Institute of Agricultural Biotechnology, Hunan Academy of Agricultural Sciences, Changsha 410125, China; (J.X.); (Z.L.); (J.L.); (H.Z.); (Y.Z.)
- Correspondence: (H.M.); (X.Z.)
| |
Collapse
|
5
|
Miller JR, Koren S, Dilley KA, Puri V, Brown DM, Harkins DM, Thibaud-Nissen F, Rosen B, Chen XG, Tu Z, Sharakhov IV, Sharakhova MV, Sebra R, Stockwell TB, Bergman NH, Sutton GG, Phillippy AM, Piermarini PM, Shabman RS. Analysis of the Aedes albopictus C6/36 genome provides insight into cell line utility for viral propagation. Gigascience 2018; 7:1-13. [PMID: 29329394 PMCID: PMC5869287 DOI: 10.1093/gigascience/gix135] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 12/23/2017] [Indexed: 12/25/2022] Open
Abstract
Background The 50-year-old Aedes albopictus C6/36 cell line is a resource for the detection, amplification, and analysis of mosquito-borne viruses including Zika, dengue, and chikungunya. The cell line is derived from an unknown number of larvae from an unspecified strain of Aedes albopictus mosquitoes. Toward improved utility of the cell line for research in virus transmission, we present an annotated assembly of the C6/36 genome. Results The C6/36 genome assembly has the largest contig N50 (3.3 Mbp) of any mosquito assembly, presents the sequences of both haplotypes for most of the diploid genome, reveals independent null mutations in both alleles of the Dicer locus, and indicates a male-specific genome. Gene annotation was computed with publicly available mosquito transcript sequences. Gene expression data from cell line RNA sequence identified enrichment of growth-related pathways and conspicuous deficiency in aquaporins and inward rectifier K+ channels. As a test of utility, RNA sequence data from Zika-infected cells were mapped to the C6/36 genome and transcriptome assemblies. Host subtraction reduced the data set by 89%, enabling faster characterization of nonhost reads. Conclusions The C6/36 genome sequence and annotation should enable additional uses of the cell line to study arbovirus vector interactions and interventions aimed at restricting the spread of human disease.
Collapse
Affiliation(s)
- Jason R Miller
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA.,College of Natural Sciences and Mathematics, Shepherd University, Shepherdstown, WV 25443, USA
| | - Sergey Koren
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Kari A Dilley
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA
| | - Vinita Puri
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA
| | - David M Brown
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA
| | - Derek M Harkins
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA
| | | | - Benjamin Rosen
- USDA 10300 Baltimore Ave., Bldg 306 Barc-East, Beltsville, MD 20705-2350, USA
| | - Xiao-Guang Chen
- Department of Pathogen Biology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou 510515, China
| | - Zhijian Tu
- Department of Biochemistry and the Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA
| | - Igor V Sharakhov
- Department of Entomology and the Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA.,Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, Tomsk, Russia
| | - Maria V Sharakhova
- Department of Entomology and the Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, USA.,Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, Tomsk, Russia
| | - Robert Sebra
- Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | | | - Granger G Sutton
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA
| | - Adam M Phillippy
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Peter M Piermarini
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA.,Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691, USA
| | - Reed S Shabman
- J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA.,ATCC, 217 Perry Parkway, Gaithersburg, MD 20877, USA
| |
Collapse
|
6
|
Piermarini PM, Inocente EA, Acosta N, Hopkins CR, Denton JS, Michel AP. Inward rectifier potassium (Kir) channels in the soybean aphid Aphis glycines: Functional characterization, pharmacology, and toxicology. JOURNAL OF INSECT PHYSIOLOGY 2018; 110:57-65. [PMID: 30196125 PMCID: PMC6173977 DOI: 10.1016/j.jinsphys.2018.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/05/2018] [Accepted: 09/05/2018] [Indexed: 05/21/2023]
Abstract
Inward rectifier K+ (Kir) channels contribute to a variety of physiological processes in insects and are emerging targets for insecticide development. Previous studies on insect Kir channels have primarily focused on dipteran species (e.g., mosquitoes, fruit flies). Here we identify and functionally characterize Kir channel subunits in a hemipteran insect, the soybean aphid Aphis glycines, which is an economically important insect pest and vector of soybeans. From the transcriptome and genome of Ap. glycines we identified two cDNAs, ApKir1 and ApKir2, encoding Kir subunits that were orthologs of insect Kir1 and Kir2, respectively. Notably, a gene encoding a Kir3 subunit was absent from the transcriptome and genome of Ap. glycines, similar to the pea aphid Acyrthosiphon pisum. Heterologous expression of ApKir1 and ApKir2 in Xenopus laevis oocytes enhanced K+-currents in the plasma membrane; these currents were inhibited by barium and the small molecule VU041. Compared to ApKir2, ApKir1 mediated currents that were larger in magnitude, more sensitive to barium, and less inhibited by small molecule VU041. Moreover, ApKir1 exhibited stronger inward rectification compared to ApKir2. Topical application of VU041 in adult aphids resulted in dose-dependent mortality within 24 h that was more efficacious than flonicamid, an established insecticide also known to inhibit Kir channels. We conclude that despite the apparent loss of Kir3 genes in aphid evolution, Kir channels are important to aphid survival and represent a promising target for the development of new insecticides.
Collapse
Affiliation(s)
- Peter M Piermarini
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA.
| | - Edna Alfaro Inocente
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
| | - Nuris Acosta
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
| | - Corey R Hopkins
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Jerod S Denton
- Departments of Anesthesiology and Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andrew P Michel
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
| |
Collapse
|
7
|
Piermarini PM, Akuma DC, Crow JC, Jamil TL, Kerkhoff WG, Viel KCMF, Gillen CM. Differential expression of putative sodium-dependent cation-chloride cotransporters in Aedes aegypti. Comp Biochem Physiol A Mol Integr Physiol 2017; 214:40-49. [PMID: 28923771 DOI: 10.1016/j.cbpa.2017.09.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/08/2017] [Accepted: 09/08/2017] [Indexed: 11/18/2022]
Abstract
The yellow fever mosquito, Aedes aegypti, has three genes that code for proteins with sequence similarity to vertebrate Na+-K+-Cl- cotransporters (NKCCs) of the solute-linked carrier 12 superfamily of cation-chloride cotransporters (CCCs). We hypothesized that these mosquito NKCC orthologues have diverged to perform distinct roles in salt secretion and absorption. In phylogenetic analyses, one protein (aeNKCC1) groups with a Drosophila melanogaster NKCC that mediates salt secretion whereas two others (aeCCC2 and aeCCC3) group with a Drosophila transporter that is not functionally characterized. The aeCCC2 and aeCCC3 genes probably result from a tandem gene duplication in the mosquito lineage; they have similar exon structures and are consecutive in genomic DNA. Predicted aeCCC2 and aeCCC3 proteins differ from aeNKCC1 and vertebrate NKCCs in residues from the third transmembrane domain known to influence ion and inhibitor binding. Quantitative PCR revealed that aeNKCC1 and aeCCC2 were approximately equally expressed in larvae and adults, whereas aeCCC3 was approximately 100-fold more abundant in larvae than in adults. In larval tissues, aeCCC2 was approximately 2-fold more abundant in Malpighian tubules compared to anal papillae. In contrast, aeCCC3 was nearly 100-fold more abundant in larval anal papillae compared to Malpighian tubules, suggesting a role in absorption. Western blots with polyclonal antibodies against isoform-specific peptides revealed stronger aeCCC2 immunoreactivity in adults versus larvae, whereas aeCCC3 immunoreactivity was stronger in larvae versus adults. The differential expression pattern of aeCCC2 and aeCCC3, and their sequence divergence in transmembrane domains, suggests that they may have different roles in transepithelial salt transport.
Collapse
Affiliation(s)
- Peter M Piermarini
- Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, United States
| | - Daniel C Akuma
- Department of Biology, Kenyon College, Gambier, OH, United States
| | - John C Crow
- Department of Biology, Kenyon College, Gambier, OH, United States
| | - Taylor L Jamil
- Department of Biology, Kenyon College, Gambier, OH, United States
| | - Willa G Kerkhoff
- Department of Biology, Kenyon College, Gambier, OH, United States
| | | | | |
Collapse
|
8
|
Swale DR, Li Z, Guerrero F, Pérez De León AA, Foil LD. Role of inward rectifier potassium channels in salivary gland function and sugar feeding of the fruit fly, Drosophila melanogaster. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2017; 141:41-49. [PMID: 28911739 DOI: 10.1016/j.pestbp.2016.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/11/2016] [Accepted: 11/14/2016] [Indexed: 06/07/2023]
Abstract
The arthropod salivary gland is of critical importance for horizontal transmission of pathogens, yet a detailed understanding of the ion conductance pathways responsible for saliva production and excretion is lacking. A superfamily of potassium ion channels, known as inward rectifying potassium (Kir) channels, is overexpressed in the Drosophila salivary gland by 32-fold when compared to the whole body mRNA transcripts. Therefore, we aimed to test the hypothesis that pharmacological and genetic depletion of salivary gland specific Kir channels alters the efficiency of the gland and reduced feeding capabilities using the fruit fly Drosophila melanogaster as a model organism that could predict similar effects in arthropod disease vectors. Exposure to VU041, a selective Kir channel blocker, reduced the volume of sucrose consumption by up to 3.2-fold and was found to be concentration-dependent with an EC50 of 68μM. Importantly, the inactive analog, VU937, was shown to not influence feeding, suggesting the reduction in feeding observed with VU041 is due to Kir channel inhibition. Next, we performed a salivary gland specific knockdown of Kir1 to assess the role of these channels specifically in the salivary gland. The genetically depleted fruit flies had a reduction in total volume ingested and an increase in the time spent feeding, both suggestive of a reduction in salivary gland function. Furthermore, a compensatory mechanism appears to be present at day 1 of RNAi-treated fruit flies, and is likely to be the Na+-K+-2Cl- cotransporter and/or Na+-K+-ATPase pumps that serve to supplement the inward flow of K+ ions, which highlights the functional redundancy in control of ion flux in the salivary glands. These findings suggest that Kir channels likely provide, at least in part, a principal potassium conductance pathway in the Drosophila salivary gland that is required for sucrose feeding.
Collapse
Affiliation(s)
- Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States.
| | - Zhilin Li
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
| | - Felix Guerrero
- United States Department of Agriculture-Agricultural Research Service, Knipling-Bushland United States Livestock Insects Research Laboratory, Veterinary Pest Genomics Center, 2700 Fredericksburg Rd., Kerrville, TX 78028, United States
| | - Adalberto A Pérez De León
- United States Department of Agriculture-Agricultural Research Service, Knipling-Bushland United States Livestock Insects Research Laboratory, Veterinary Pest Genomics Center, 2700 Fredericksburg Rd., Kerrville, TX 78028, United States
| | - Lane D Foil
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States
| |
Collapse
|
9
|
Swale DR, Engers DW, Bollinger SR, Gross A, Inocente EA, Days E, Kanga F, Johnson RM, Yang L, Bloomquist JR, Hopkins CR, Piermarini PM, Denton JS. An insecticide resistance-breaking mosquitocide targeting inward rectifier potassium channels in vectors of Zika virus and malaria. Sci Rep 2016; 6:36954. [PMID: 27849039 PMCID: PMC5111108 DOI: 10.1038/srep36954] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/19/2016] [Indexed: 01/01/2023] Open
Abstract
Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae.) aegypti Kir1 channels that incapacitates adult female mosquitoes from representative insecticide-susceptible and -resistant strains of An. gambiae (G3 and Akron, respectively) and Ae. aegypti (Liverpool and Puerto Rico, respectively) following topical application. VU041 is selective for mosquito Kir channels over several mammalian orthologs, with the exception of Kir2.1, and is not lethal to honey bees. Medicinal chemistry was used to develop an analog, termed VU730, which retains activity toward mosquito Kir1 but is not active against Kir2.1 or other mammalian Kir channels. Thus, VU041 and VU730 are promising chemical scaffolds for developing new classes of insecticides to combat insecticide-resistant mosquitoes and the transmission of mosquito-borne diseases, such as Zika virus, without harmful effects on humans and beneficial insects.
Collapse
Affiliation(s)
- Daniel R Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Darren W Engers
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Sean R Bollinger
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Aaron Gross
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Edna Alfaro Inocente
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Emily Days
- Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Fariba Kanga
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Reed M Johnson
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Liu Yang
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Jeffrey R Bloomquist
- Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA
| | - Corey R Hopkins
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Jerod S Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Institute for Global Health, Vanderbilt University, Nashville, TN 37203, USA
| |
Collapse
|
10
|
Dynamic expression of genes encoding subunits of inward rectifier potassium (Kir) channels in the yellow fever mosquito Aedes aegypti. Comp Biochem Physiol B Biochem Mol Biol 2016; 204:35-44. [PMID: 27836744 DOI: 10.1016/j.cbpb.2016.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 10/13/2016] [Accepted: 11/03/2016] [Indexed: 01/06/2023]
Abstract
Inward rectifier potassium (Kir) channels play fundamental roles in neuromuscular, epithelial, and endocrine function in mammals. Recent research in insects suggests that Kir channels play critical roles in the development, immune function, and excretory physiology of fruit flies and/or mosquitoes. Moreover, our group has demonstrated that mosquito Kir channels may serve as valuable targets for the development of novel insecticides. Here we characterize the molecular expression of 5 mRNAs encoding Kir channel subunits in the yellow fever mosquito, Aedes aegypti: Kir1, Kir2A-c, Kir2B, Kir2B', and Kir3. We demonstrate that 1) Kir mRNA expression is dynamic in whole mosquitoes, Malpighian tubules, and the midgut during development from 4th instar larvae to adult females, 2) Kir2B and Kir3 mRNA levels are reduced in 4th instar larvae when reared in water containing an elevated concentration (50mM) of KCl, but not NaCl, and 3) Kir mRNAs are differentially expressed in the Malpighian tubules, midgut, and ovaries within 24h after blood feeding. Furthermore, we provide the first characterization of Kir mRNA expression in the anal papillae of 4th instar larval mosquitoes, which indicates that Kir2A-c is the most abundant. Altogether, the data provide the first comprehensive characterization of Kir mRNA expression in Ae. aegypti and offer insights into the putative physiological roles of Kir subunits in this important disease vector.
Collapse
|
11
|
Wu Y, Baum M, Huang CL, Rodan AR. Two inwardly rectifying potassium channels, Irk1 and Irk2, play redundant roles in Drosophila renal tubule function. Am J Physiol Regul Integr Comp Physiol 2015. [PMID: 26224687 DOI: 10.1152/ajpregu.00148.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inwardly rectifying potassium channels play essential roles in renal physiology across phyla. Barium-sensitive K(+) conductances are found on the basolateral membrane of a variety of insect Malpighian (renal) tubules, including Drosophila melanogaster. We found that barium decreases the lumen-positive transepithelial potential difference in isolated perfused Drosophila tubules and decreases fluid secretion and transepithelial K(+) flux. In those insect species in which it has been studied, transcripts from multiple genes encoding inwardly rectifying K(+) channels are expressed in the renal (Malpighian) tubule. In Drosophila melanogaster, this includes transcripts of the Irk1, Irk2, and Irk3 genes. The role of each of these gene products in renal tubule function is unknown. We found that simultaneous knockdown of Irk1 and Irk2 in the principal cell of the fly tubule decreases transepithelial K(+) flux, with no additive effect of Irk3 knockdown, and decreases barium sensitivity of transepithelial K(+) flux by ∼50%. Knockdown of any of the three inwardly rectifying K(+) channels individually has no effect, nor does knocking down Irk3 simultaneously with Irk1 or Irk2. Irk1/Irk2 principal cell double-knockdown tubules remain sensitive to the kaliuretic effect of cAMP. Inhibition of the Na(+)/K(+)-ATPase with ouabain and Irk1/Irk2 double knockdown have additive effects on K(+) flux, and 75% of transepithelial K(+) transport is due to Irk1/Irk2 or ouabain-sensitive pathways. In conclusion, Irk1 and Irk2 play redundant roles in transepithelial ion transport in the Drosophila melanogaster renal tubule and are additive to Na(+)/K(+)-ATPase-dependent pathways.
Collapse
Affiliation(s)
- Yipin Wu
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Michel Baum
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, Texas; and Department of Pediatrics, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Chou-Long Huang
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Aylin R Rodan
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| |
Collapse
|
12
|
Calkins TL, Woods-Acevedo MA, Hildebrandt O, Piermarini PM. The molecular and immunochemical expression of innexins in the yellow fever mosquito, Aedes aegypti: insights into putative life stage- and tissue-specific functions of gap junctions. Comp Biochem Physiol B Biochem Mol Biol 2015; 183:11-21. [PMID: 25585357 DOI: 10.1016/j.cbpb.2014.11.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 11/17/2014] [Accepted: 11/21/2014] [Indexed: 11/28/2022]
Abstract
Gap junctions (GJ) mediate direct intercellular communication by forming channels through which certain small molecules and/or ions can pass. Connexins, the proteins that form vertebrate GJ, are well studied and known to contribute to neuronal, muscular and epithelial physiology. Innexins, the GJ proteins of insects, have only recently received much investigative attention and many of their physiological roles remain to be determined. Here we characterize the molecular expression of six innexin (Inx) genes in the yellow fever mosquito Aedes aegypti (AeInx1, AeInx2, AeInx3, AeInx4, AeInx7, and AeInx8) and the immunochemical expression of one innexin protein, AeInx3, in the alimentary canal. We detected the expression of no less than four innexin genes in each mosquito life stage (larva, pupa, adult) and tissue/body region from adult males and females (midgut, Malpighian tubules, hindgut, head, carcass, gonads), suggesting a remarkable potential molecular diversity of GJ in mosquitoes. Moreover, the expression patterns of some innexins were life stage and/or tissue specific, suggestive of potential functional specializations. Cloning of the four full-length cDNAs expressed in the Malpighian tubules of adult females (AeInx1, AeInx2, AeInx3, and AeInx7) revealed evidence for 1) alternative splicing of AeInx1 and AeInx3 transcripts, and 2) putative N-glycosylation of AeInx3 and AeInx7. Finally, immunohistochemistry of AeInx3 in the alimentary canal of larval and adult female mosquitoes confirmed localization of this innexin to the intercellular regions of Malpighian tubule and hindgut epithelial cells, suggesting that it is an important component of GJ in these tissues.
Collapse
Affiliation(s)
- Travis L Calkins
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, United States
| | - Mikal A Woods-Acevedo
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, United States
| | - Oliver Hildebrandt
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, United States
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, United States.
| |
Collapse
|
13
|
Raphemot R, Rouhier MF, Swale DR, Days E, Weaver CD, Lovell KM, Konkel LC, Engers DW, Bollinger SF, Hopkins C, Piermarini PM, Denton JS. Discovery and characterization of a potent and selective inhibitor of Aedes aegypti inward rectifier potassium channels. PLoS One 2014; 9:e110772. [PMID: 25375326 PMCID: PMC4222822 DOI: 10.1371/journal.pone.0110772] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/16/2014] [Indexed: 12/12/2022] Open
Abstract
Vector-borne diseases such as dengue fever and malaria, which are transmitted by infected female mosquitoes, affect nearly half of the world's population. The emergence of insecticide-resistant mosquito populations is reducing the effectiveness of conventional insecticides and threatening current vector control strategies, which has created an urgent need to identify new molecular targets against which novel classes of insecticides can be developed. We previously demonstrated that small molecule inhibitors of mammalian Kir channels represent promising chemicals for new mosquitocide development. In this study, high-throughput screening of approximately 30,000 chemically diverse small-molecules was employed to discover potent and selective inhibitors of Aedes aegypti Kir1 (AeKir1) channels heterologously expressed in HEK293 cells. Of 283 confirmed screening ‘hits’, the small-molecule inhibitor VU625 was selected for lead optimization and in vivo studies based on its potency and selectivity toward AeKir1, and tractability for medicinal chemistry. In patch clamp electrophysiology experiments of HEK293 cells, VU625 inhibits AeKir1 with an IC50 value of 96.8 nM, making VU625 the most potent inhibitor of AeKir1 described to date. Furthermore, electrophysiology experiments in Xenopus oocytes revealed that VU625 is a weak inhibitor of AeKir2B. Surprisingly, injection of VU625 failed to elicit significant effects on mosquito behavior, urine excretion, or survival. However, when co-injected with probenecid, VU625 inhibited the excretory capacity of mosquitoes and was toxic, suggesting that the compound is a substrate of organic anion and/or ATP-binding cassette (ABC) transporters. The dose-toxicity relationship of VU625 (when co-injected with probenecid) is biphasic, which is consistent with the molecule inhibiting both AeKir1 and AeKir2B with different potencies. This study demonstrates proof-of-concept that potent and highly selective inhibitors of mosquito Kir channels can be developed using conventional drug discovery approaches. Furthermore, it reinforces the notion that the physical and chemical properties that determine a compound's bioavailability in vivo will be critical in determining the efficacy of Kir channel inhibitors as insecticides.
Collapse
Affiliation(s)
- Rene Raphemot
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - Matthew F. Rouhier
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, United States of America
| | - Daniel R. Swale
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Emily Days
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - C. David Weaver
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - Kimberly M. Lovell
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Leah C. Konkel
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Darren W. Engers
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Sean F. Bollinger
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Corey Hopkins
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute for Global Health, Vanderbilt University, Nashville, TN, United States of America
- Department of Chemistry, Vanderbilt University School of Medicine, Nashville TN, United States of America
| | - Peter M. Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, United States of America
- * E-mail: (PMP); (JSD)
| | - Jerod S. Denton
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States of America
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, United States of America
- Institute for Global Health, Vanderbilt University, Nashville, TN, United States of America
- * E-mail: (PMP); (JSD)
| |
Collapse
|
14
|
Raphemot R, Estévez-Lao TY, Rouhier MF, Piermarini PM, Denton JS, Hillyer JF. Molecular and functional characterization of Anopheles gambiae inward rectifier potassium (Kir1) channels: a novel role in egg production. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2014; 51:10-9. [PMID: 24855023 PMCID: PMC4121989 DOI: 10.1016/j.ibmb.2014.05.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 05/03/2014] [Accepted: 05/10/2014] [Indexed: 05/21/2023]
Abstract
Inward rectifier potassium (Kir) channels play essential roles in regulating diverse physiological processes. Although Kir channels are encoded in mosquito genomes, their functions remain largely unknown. In this study, we identified the members of the Anopheles gambiae Kir gene family and began to investigate their function. Notably, we sequenced the A. gambiae Kir1 (AgKir1) gene and showed that it encodes all the canonical features of a Kir channel: an ion pore that is composed of a pore helix and a selectivity filter, two transmembrane domains that flank the ion pore, and the so-called G-loop. Heterologous expression of AgKir1 in Xenopus oocytes revealed that this gene encodes a functional, barium-sensitive Kir channel. Quantitative RT-PCR experiments then showed that relative AgKir1 mRNA levels are highest in the pupal stage, and that AgKir1 mRNA is enriched in the adult ovaries. Gene silencing of AgKir1 by RNA interference did not affect the survival of female mosquitoes following a blood meal, but decreased their egg output. These data provide evidence for a new role of Kir channels in mosquito fecundity, and further validates them as promising molecular targets for the development of a new class of mosquitocides to be used in vector control.
Collapse
Affiliation(s)
- Rene Raphemot
- Department of Anesthesiology, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Tania Y Estévez-Lao
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew F Rouhier
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA
| | - Jerod S Denton
- Department of Anesthesiology, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA; Institute for Global Health, Vanderbilt University, Nashville, TN 37232, USA.
| | - Julián F Hillyer
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Institute for Global Health, Vanderbilt University, Nashville, TN 37232, USA.
| |
Collapse
|
15
|
Rouhier MF, Hine RM, Park ST, Raphemot R, Denton J, Piermarini PM, Beyenbach KW. Excretion of NaCl and KCl loads in mosquitoes. 2. Effects of the small molecule Kir channel modulator VU573 and its inactive analog VU342. Am J Physiol Regul Integr Comp Physiol 2014; 307:R850-61. [PMID: 25056106 DOI: 10.1152/ajpregu.00106.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of two small molecules VU342 and VU573 on renal functions in the yellow fever mosquito Aedes aegypti was investigated in vitro and in vivo. In isolated Malpighian tubules, VU342 (10 μM) had no effect on the transepithelial secretion of Na(+), K(+), Cl(-), and water. In contrast, 10 μM VU573 first stimulated and then inhibited the transepithelial secretion of fluid when the tubules were bathed in Na(+)-rich or K(+)-rich Ringer solution. The early stimulation was blocked by bumetanide, suggesting the transient stimulation of Na-K-2Cl cotransport, and the late inhibition of fluid secretion was consistent with the known block of AeKir1, an Aedes inward rectifier K(+) channel, by VU573. VU342 and VU573 at a hemolymph concentration of about 11 μM had no effect on the diuresis triggered by hemolymph Na(+) or K(+) loads. VU342 at a hemolymph concentration of 420 μM had no effect on the diuresis elicited by hemolymph Na(+) or K(+) loads. In contrast, the same concentration of VU573 significantly diminished the Na(+) diuresis by inhibiting the urinary excretion of Na(+), Cl(-), and water. In K(+)-loaded mosquitoes, 420 μM VU573 significantly diminished the K(+) diuresis by inhibiting the urinary excretion of K(+), Na(+), Cl(-), and water. We conclude that 1) the effects of VU573 observed in isolated Malpighian tubules are overwhelmed in vivo by the diuresis triggered with the coinjection of Na(+) and K(+) loads, and 2) at a hemolymph concentration of 420 μM VU573 affects Kir channels systemically, including those that might be involved in the release of diuretic hormones.
Collapse
Affiliation(s)
- Matthew F Rouhier
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio
| | - Rebecca M Hine
- Department of Biomedical Sciences, Cornell University, Ithaca, New York; and
| | - Seokhwan Terry Park
- Department of Biomedical Sciences, Cornell University, Ithaca, New York; and
| | - Rene Raphemot
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jerod Denton
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio
| | - Klaus W Beyenbach
- Department of Biomedical Sciences, Cornell University, Ithaca, New York; and
| |
Collapse
|
16
|
Pharmacological validation of an inward-rectifier potassium (Kir) channel as an insecticide target in the yellow fever mosquito Aedes aegypti. PLoS One 2014; 9:e100700. [PMID: 24959745 PMCID: PMC4069099 DOI: 10.1371/journal.pone.0100700] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 05/27/2014] [Indexed: 12/13/2022] Open
Abstract
Mosquitoes are important disease vectors that transmit a wide variety of pathogens to humans, including those that cause malaria and dengue fever. Insecticides have traditionally been deployed to control populations of disease-causing mosquitoes, but the emergence of insecticide resistance has severely limited the number of active compounds that are used against mosquitoes. Thus, to improve the control of resistant mosquitoes there is a need to identify new insecticide targets and active compounds for insecticide development. Recently we demonstrated that inward rectifier potassium (Kir) channels and small molecule inhibitors of Kir channels offer promising new molecular targets and active compounds, respectively, for insecticide development. Here we provide pharmacological validation of a specific mosquito Kir channel (AeKir1) in the yellow fever mosquito Aedes aegypti. We show that VU590, a small-molecule inhibitor of mammalian Kir1.1 and Kir7.1 channels, potently inhibits AeKir1 but not another mosquito Kir channel (AeKir2B) in vitro. Moreover, we show that a previously identified inhibitor of AeKir1 (VU573) elicits an unexpected agonistic effect on AeKir2B in vitro. Injection of VU590 into the hemolymph of adult female mosquitoes significantly inhibits their capacity to excrete urine and kills them within 24 h, suggesting a mechanism of action on the excretory system. Importantly, a structurally-related VU590 analog (VU608), which weakly blocks AeKir1 in vitro, has no significant effects on their excretory capacity and does not kill mosquitoes. These observations suggest that the toxic effects of VU590 are associated with its inhibition of AeKir1.
Collapse
|