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Antennal-expressed ammonium transporters in the malaria vector mosquito Anopheles gambiae.

Pitts RJ, Derryberry SL, Pulous FE, Zwiebel LJ - PLoS ONE (2014)

Bottom Line: While the molecular underpinnings of mosquito olfaction and host seeking are becoming better understood, many questions remain unanswered.Functional expression of AgAmt in Xenopus laevis oocytes facilitates inward currents in response to both ammonium and methylammonium, while AgRh50 is able to partially complement a yeast ammonium transporter mutant strain, validating their conserved roles as ammonium transporters.Accordingly, AgAmt and AgRh50 represent new and potentially important targets for the development of novel vector control strategies.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America; Vanderbilt Institute for Global Health, Nashville, Tennessee, United States of America.

ABSTRACT
The principal Afrotropical malaria vector mosquito, Anopheles gambiae remains a significant threat to human health. In this anthropophagic species, females detect and respond to a range of human-derived volatile kairomones such as ammonia, lactic acid, and other carboxylic acids in their quest for blood meals. While the molecular underpinnings of mosquito olfaction and host seeking are becoming better understood, many questions remain unanswered. In this study, we have identified and characterized two candidate ammonium transporter genes, AgAmt and AgRh50 that are expressed in the mosquito antenna and may contribute to physiological and behavioral responses to ammonia, which is an important host kairomone for vector mosquitoes. AgAmt transcripts are highly enhanced in female antennae while a splice variant of AgRh50 appears to be antennal-specific. Functional expression of AgAmt in Xenopus laevis oocytes facilitates inward currents in response to both ammonium and methylammonium, while AgRh50 is able to partially complement a yeast ammonium transporter mutant strain, validating their conserved roles as ammonium transporters. We present evidence to suggest that both AgAmt and AgRh50 are in vivo ammonium transporters that are important for ammonia sensitivity in An. gambiae antennae, either by clearing ammonia from the sensillar lymph or by facilitating sensory neuron responses to environmental exposure. Accordingly, AgAmt and AgRh50 represent new and potentially important targets for the development of novel vector control strategies.

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I–V Plot of whole cell conductances in oocytes expressing AgAmt.Current-voltage relationship for AgAmt cRNA injected oocytes to ammonium chloride (orange) and methylammonium chloride (purple). The x-axis shows voltage measured in millivolts and the y-axis shows current measured in microamps.
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pone-0111858-g006: I–V Plot of whole cell conductances in oocytes expressing AgAmt.Current-voltage relationship for AgAmt cRNA injected oocytes to ammonium chloride (orange) and methylammonium chloride (purple). The x-axis shows voltage measured in millivolts and the y-axis shows current measured in microamps.

Mentions: A current-voltage plot was generated by measuring ion-induced currents at several different membrane holding potentials in order to further examine the relationship between AgAmt-dependent ammonium and methylammonium conductances (Figure 6). The slope of current/voltage (I/V = conductance) in response to 200 µM ammonium chloride was much greater than the corresponding slope in response to 200 µM methylammonium chloride (Figure 6). This result clearly shows that ammonium elicits a larger whole-cell conductance than methylammonium at the same concentrations. In addition, the reversal potential of each ion, defined as the voltage at which the recorded current is zero, was approximately 20 mV for ammonium and >40 mV for methylammonium under these conditions.


Antennal-expressed ammonium transporters in the malaria vector mosquito Anopheles gambiae.

Pitts RJ, Derryberry SL, Pulous FE, Zwiebel LJ - PLoS ONE (2014)

I–V Plot of whole cell conductances in oocytes expressing AgAmt.Current-voltage relationship for AgAmt cRNA injected oocytes to ammonium chloride (orange) and methylammonium chloride (purple). The x-axis shows voltage measured in millivolts and the y-axis shows current measured in microamps.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216128&req=5

pone-0111858-g006: I–V Plot of whole cell conductances in oocytes expressing AgAmt.Current-voltage relationship for AgAmt cRNA injected oocytes to ammonium chloride (orange) and methylammonium chloride (purple). The x-axis shows voltage measured in millivolts and the y-axis shows current measured in microamps.
Mentions: A current-voltage plot was generated by measuring ion-induced currents at several different membrane holding potentials in order to further examine the relationship between AgAmt-dependent ammonium and methylammonium conductances (Figure 6). The slope of current/voltage (I/V = conductance) in response to 200 µM ammonium chloride was much greater than the corresponding slope in response to 200 µM methylammonium chloride (Figure 6). This result clearly shows that ammonium elicits a larger whole-cell conductance than methylammonium at the same concentrations. In addition, the reversal potential of each ion, defined as the voltage at which the recorded current is zero, was approximately 20 mV for ammonium and >40 mV for methylammonium under these conditions.

Bottom Line: While the molecular underpinnings of mosquito olfaction and host seeking are becoming better understood, many questions remain unanswered.Functional expression of AgAmt in Xenopus laevis oocytes facilitates inward currents in response to both ammonium and methylammonium, while AgRh50 is able to partially complement a yeast ammonium transporter mutant strain, validating their conserved roles as ammonium transporters.Accordingly, AgAmt and AgRh50 represent new and potentially important targets for the development of novel vector control strategies.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America; Vanderbilt Institute for Global Health, Nashville, Tennessee, United States of America.

ABSTRACT
The principal Afrotropical malaria vector mosquito, Anopheles gambiae remains a significant threat to human health. In this anthropophagic species, females detect and respond to a range of human-derived volatile kairomones such as ammonia, lactic acid, and other carboxylic acids in their quest for blood meals. While the molecular underpinnings of mosquito olfaction and host seeking are becoming better understood, many questions remain unanswered. In this study, we have identified and characterized two candidate ammonium transporter genes, AgAmt and AgRh50 that are expressed in the mosquito antenna and may contribute to physiological and behavioral responses to ammonia, which is an important host kairomone for vector mosquitoes. AgAmt transcripts are highly enhanced in female antennae while a splice variant of AgRh50 appears to be antennal-specific. Functional expression of AgAmt in Xenopus laevis oocytes facilitates inward currents in response to both ammonium and methylammonium, while AgRh50 is able to partially complement a yeast ammonium transporter mutant strain, validating their conserved roles as ammonium transporters. We present evidence to suggest that both AgAmt and AgRh50 are in vivo ammonium transporters that are important for ammonia sensitivity in An. gambiae antennae, either by clearing ammonia from the sensillar lymph or by facilitating sensory neuron responses to environmental exposure. Accordingly, AgAmt and AgRh50 represent new and potentially important targets for the development of novel vector control strategies.

Show MeSH
Related in: MedlinePlus