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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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Amino acid plots of AgAmt (A) and AgRh50 (B) depicting the 11 transmembrane domains.AgRh50a and AgRh50b differ only in their C-terminal regions.
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pone-0111858-g002: Amino acid plots of AgAmt (A) and AgRh50 (B) depicting the 11 transmembrane domains.AgRh50a and AgRh50b differ only in their C-terminal regions.

Mentions: The An. gambiae genome encodes two candidate ammonium transporter genes, AGAP003989 and AGAP002011, one representative from each of the Amt and Rhesus subfamilies, which we have named AgAmt and AgRh50, respectively (Figure 1). AgAmt appears to encode a single transcript (Figure 1) and a conceptual peptide of 591 amino acids (Figure 2A). AgRh50 appears to encode 2 alternatively spliced transcripts, AgRh50a and AgRh50b (Figure 1), the latter containing a novel 175 bp exon near the 3′ end of the transcript that was not predicted in the An. gambiae genome annotation (Figure 1). The transcripts for AgRh50a and AgRh50b encode conceptual peptides of 470 and 497 amino acids, respectively (Figure 2B). In addition, both peptides are predicted to form 11 transmembrane helices with an extracellular N-terminus and intracellular C-terminus (Figure 2), similar to other known ammonium transporters [47]. AgAmt and AgRh50 are clearly distinguishable as members of the two major ammonium transporter subfamilies (Figure 3) and share significant homologies with proteins encoded in several other insect genomes that are also putative ammonium transporters (Figure 3, Table S1).


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

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

Amino acid plots of AgAmt (A) and AgRh50 (B) depicting the 11 transmembrane domains.AgRh50a and AgRh50b differ only in their C-terminal regions.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0111858-g002: Amino acid plots of AgAmt (A) and AgRh50 (B) depicting the 11 transmembrane domains.AgRh50a and AgRh50b differ only in their C-terminal regions.
Mentions: The An. gambiae genome encodes two candidate ammonium transporter genes, AGAP003989 and AGAP002011, one representative from each of the Amt and Rhesus subfamilies, which we have named AgAmt and AgRh50, respectively (Figure 1). AgAmt appears to encode a single transcript (Figure 1) and a conceptual peptide of 591 amino acids (Figure 2A). AgRh50 appears to encode 2 alternatively spliced transcripts, AgRh50a and AgRh50b (Figure 1), the latter containing a novel 175 bp exon near the 3′ end of the transcript that was not predicted in the An. gambiae genome annotation (Figure 1). The transcripts for AgRh50a and AgRh50b encode conceptual peptides of 470 and 497 amino acids, respectively (Figure 2B). In addition, both peptides are predicted to form 11 transmembrane helices with an extracellular N-terminus and intracellular C-terminus (Figure 2), similar to other known ammonium transporters [47]. AgAmt and AgRh50 are clearly distinguishable as members of the two major ammonium transporter subfamilies (Figure 3) and share significant homologies with proteins encoded in several other insect genomes that are also putative ammonium transporters (Figure 3, Table S1).

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