CAPA Neuropeptides Inhibit VA Activity in Malpighian Tubules of the Mosquito, Aedes Aegypti

Abstract Haematophagus insects, such as the female Aedes aegypti mosquito, face the challenge of excess ion and water intake after engorgement on a blood meal. To cope with this, adult female A. aegypti have a specialized excretory system that includes the Malpighian tubules (MTs), which are under rigorous control by several neuroendocrine factors to regulate transepithelial movement of ions/water. Produced in the CNS, the mosquito anti-diuretic hormone is a member of the CAPA peptide family, which share homology to the vertebrate neuromedin U peptide. CAPA peptides inhibit fluid secretion of MTs stimulated by select diuretic factors, 5HT and DH31 through the NOS/cGMP/PKG pathway. However, the anti-diuretic signalling mechanism and downstream cellular targets, such as ion channels and transporters, remain unclear. To study whether the V-type H+-ATPase (VA) plays a role in CAPA inhibition, we performed fluid secretion assays in MTs treated with diuretics and bafilomycin, a known VA inhibitor. Bafilomycin significantly inhibited DH31-stimulated fluid secretion 30 min post treatment compared to diuretic controls (p<0.05, n=22). Similar, however, delayed responses were seen in 5HT-stimulated MTs, while no affect was observed in DH44-stimulated secretion. An indirect way to measure whether CAPA inhibits VA activity was to measure the pH of the secreted fluid from diuretic-stimulated MTs treated with CAPA. In DH31-stimulated MTs supplemented with CAPA, there was an immediate significantly higher pH at 40 min, increasing up to 7.73±0.038 compared to control, 7.56±0.038 (p=0.0007, n=20). The pH of 5HT-stimulated MTs treated with CAPA was seen to significantly increase up to 7.75±0.061 (p=0.03, n=10) at the 60 min mark, in agreement with the delayed response previously seen. Unlike the effects observed with DH31 and 5HT, CAPA did not alter the pH of the secreted fluid in DH44-stimulated MTs. Alkalization of the secreted fluid in response to CAPA suggests inhibition of the proton pump, which may lead to constrained cation entry across the apical membrane of the MTs. To understand Na+/K+-ATPase (NKA) and VA activity in response to CAPA, we performed activity assays in diuretic-stimulated MTs. Adult female MTs treated with DH31 resulted in an increase of both NKA and VA activity compared saline controls. As expected, MTs incubated with both DH31 and AedaeCAPA-1 had a lower NKA and VA activity (p<0.05) resulting in activity levels comparable to saline control levels. The results thus far could suggest a novel mechanism for CAPA inhibition, blocking the VA to hinder fluid secretion. Investigating the pathway of CAPA inhibition and its role in countering diuresis will help provide a deeper understanding of the critical process of diuresis and its signaling mechanism.

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Inhibition of eicosanoid biosynthesis modulates basal fluid secretion in the Malpighian tubules of the yellow fever mosquito (Aedes aegypti)

Journal of Insect Physiology ◽

10.1016/0022-1910(92)90016-7 ◽

1992 ◽

Vol 38 (1) ◽

pp. 1-8 ◽

Cited By ~ 45

Author(s):

David H. Petzel ◽

David W. Stanley-Samuelson

Keyword(s):

Aedes Aegypti ◽

Yellow Fever ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Yellow Fever Mosquito

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A SLC4-like anion exchanger from renal tubules of the mosquito (Aedes aegypti): evidence for a novel role of stellate cells in diuretic fluid secretion

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00729.2009 ◽

2010 ◽

Vol 298 (3) ◽

pp. R642-R660 ◽

Cited By ~ 33

Author(s):

Peter M. Piermarini ◽

Laura F. Grogan ◽

Kenneth Lau ◽

Li Wang ◽

Klaus W. Beyenbach

Keyword(s):

Aedes Aegypti ◽

Anion Exchanger ◽

Xenopus Oocytes ◽

Malpighian Tubule ◽

Stellate Cells ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Renal Tubules ◽

Basal Region ◽

Principal Cells

Transepithelial fluid secretion across the renal (Malpighian) tubule epithelium of the mosquito ( Aedes aegypti ) is energized by the vacuolar-type (V-type) H+-ATPase and not the Na+-K+-ATPase. Located at the apical membrane of principal cells, the V-type H+-ATPase translocates protons from the cytoplasm to the tubule lumen. Secreted protons are likely to derive from metabolic H2CO3, which raises questions about the handling of HCO3−by principal cells. Accordingly, we tested the hypothesis that a Cl/HCO3anion exchanger (AE) related to the solute-linked carrier 4 (SLC4) superfamily mediates the extrusion of HCO3−across the basal membrane of principal cells. We began by cloning from Aedes Malpighian tubules a full-length cDNA encoding an SLC4-like AE, termed AeAE. When expressed heterologously in Xenopus oocytes, AeAE is both N- and O-glycosylated and mediates Na+-independent intracellular pH changes that are sensitive to extracellular Cl−concentration and to DIDS. In Aedes Malpighian tubules, AeAE is expressed as two distinct forms: one is O-glycosylated, and the other is N-glycosylated. Significantly, AeAE immunoreactivity localizes to the basal regions of stellate cells but not principal cells. Concentrations of DIDS that inhibit AeAE activity in Xenopus oocytes have no effects on the unstimulated rates of fluid secretion mediated by Malpighian tubules as measured by the Ramsay assay. However, in Malpighian tubules stimulated with kinin or calcitonin-like diuretic peptides, DIDS reduces the diuretic rates of fluid secretion to basal levels. In conclusion, Aedes Malpighian tubules express AeAE in the basal region of stellate cells, where this transporter may participate in producing diuretic rates of transepithelial fluid secretion.

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Leucokinin mimetic elicits aversive behavior in mosquito Aedes aegypti (L.) and inhibits the sugar taste neuron

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1520404113 ◽

2016 ◽

Vol 113 (25) ◽

pp. 6880-6885 ◽

Cited By ~ 21

Author(s):

Hyeogsun Kwon ◽

Moutaz Ali Agha ◽

Ryan C. Smith ◽

Ronald J. Nachman ◽

Frédéric Marion-Poll ◽

...

Keyword(s):

Aedes Aegypti ◽

Fluid Secretion ◽

Isobutyric Acid ◽

Malpighian Tubules ◽

Mosquito Vector ◽

Electrophysiological Recordings ◽

Accessory Cells ◽

Amino Isobutyric Acid ◽

Aversive Behavior ◽

Multifunctional Peptides

Insect kinins (leucokinins) are multifunctional peptides acting as neurohormones and neurotransmitters. In females of the mosquito vector Aedes aegypti (L.), aedeskinins are known to stimulate fluid secretion from the renal organs (Malpighian tubules) and hindgut contractions by activating a G protein-coupled kinin receptor designated “Aedae-KR.” We used protease-resistant kinin analogs 1728, 1729, and 1460 to evaluate their effects on sucrose perception and feeding behavior. In no-choice feeding bioassays (capillary feeder and plate assays), the analog 1728, which contains α-amino isobutyric acid, inhibited females from feeding on sucrose. It further induced quick fly-away or walk-away behavior following contact with the tarsi and the mouthparts. Electrophysiological recordings from single long labellar sensilla of the proboscis demonstrated that mixing the analog 1728 at 1 mM with sucrose almost completely inhibited the detection of sucrose. Aedae-KR was immunolocalized in contact chemosensory neurons in prothoracic tarsi and in sensory neurons and accessory cells of long labellar sensilla in the distal labellum. Silencing Aedae-KR by RNAi significantly reduced gene expression and eliminated the feeding-aversion behavior resulting from contact with the analog 1728, thus directly implicating the Aedae-KR in the aversion response. To our knowledge, this is the first report that kinin analogs modulate sucrose perception in any insect. The aversion to feeding elicited by analog 1728 suggests that synthetic molecules targeting the mosquito Aedae-KR in the labellum and tarsi should be investigated for the potential to discover novel feeding deterrents of mosquito vectors.

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Ade novotranscriptome of the Malpighian tubules in non-blood-fed and blood-fed Asian tiger mosquitoesAedes albopictus: insights into diuresis, detoxification, and blood meal processing

PeerJ ◽

10.7717/peerj.1784 ◽

2016 ◽

Vol 4 ◽

pp. e1784 ◽

Cited By ~ 30

Author(s):

Carlos J. Esquivel ◽

Bryan J. Cassone ◽

Peter M. Piermarini

Keyword(s):

Rna Sequencing ◽

Adult Female ◽

Blood Meal ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Transferase Activity ◽

Purine Catabolism ◽

Xenobiotic Detoxification ◽

Biochemical Assays ◽

Asian Tiger

Background.In adult female mosquitoes, the renal (Malpighian) tubules play an important role in the post-prandial diuresis, which removes excess ions and water from the hemolymph of mosquitoes following a blood meal. After the post-prandial diuresis, the roles that Malpighian tubules play in the processing of blood meals are not well described.Methods.We used a combination of next-generation sequencing (paired-end RNA sequencing) and physiological/biochemical assays in adult female Asian tiger mosquitoes (Aedes albopictus) to generate molecular and functional insights into the Malpighian tubules and how they may contribute to blood meal processing (3–24 h after blood ingestion).Results/Discussion.Using RNA sequencing, we sequenced and assembled the firstde novotranscriptome of Malpighian tubules from non-blood-fed (NBF) and blood-fed (BF) mosquitoes. We identified a total of 8,232 non-redundant transcripts. The Malpighian tubules of NBF mosquitoes were characterized by the expression of transcripts associated with active transepithelial fluid secretion/diuresis (e.g., ion transporters, water channels,V-type H+-ATPase subunits), xenobiotic detoxification (e.g., cytochrome P450 monoxygenases, glutathioneS-transferases, ATP-binding cassette transporters), and purine metabolism (e.g., xanthine dehydrogenase). We also detected the expression of transcripts encoding sodium calcium exchangers, G protein coupled-receptors, and septate junctional proteins not previously described in mosquito Malpighian tubules. Within 24 h after a blood meal, transcripts associated with active transepithelial fluid secretion/diuresis exhibited a general downregulation, whereas those associated with xenobiotic detoxification and purine catabolism exhibited a general upregulation, suggesting a reinvestment of the Malpighian tubules’ molecular resources from diuresis to detoxification. Physiological and biochemical assays were conducted in mosquitoes and isolated Malpighian tubules, respectively, to confirm that the transcriptomic changes were associated with functional consequences. In particular,in vivodiuresis assays demonstrated that adult female mosquitoes have a reduced diuretic capacity within 24 h after a blood meal. Moreover, biochemical assays in isolated Malpighian tubules showed an increase in glutathioneS-transferase activity and the accumulation of uric acid (an end product of purine catabolism) within 24 h after a blood meal. Our data provide new insights into the molecular physiology of Malpighian tubules in culicine mosquitoes and reveal potentially important molecular targets for the development of chemical and/or gene-silencing insecticides that would disrupt renal function in mosquitoes.

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Role of an apical K,Cl cotransporter in urine formation by renal tubules of the yellow fever mosquito (Aedes aegypti)

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00223.2011 ◽

2011 ◽

Vol 301 (5) ◽

pp. R1318-R1337 ◽

Cited By ~ 26

Author(s):

Peter M. Piermarini ◽

Rebecca M. Hine ◽

Matthew Schepel ◽

Jeremy Miyauchi ◽

Klaus W. Beyenbach

Keyword(s):

Aedes Aegypti ◽

Epithelial Transport ◽

Input Resistance ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Cell Swelling ◽

Renal Tubules ◽

Transport Pathway ◽

Principal Cells

The K,Cl cotransporters (KCCs) of the SLC12 superfamily play critical roles in the regulation of cell volume, concentrations of intracellular Cl−, and epithelial transport in vertebrate tissues. To date, the role(s) of KCCs in the renal functions of mosquitoes and other insects is less clear. In the present study, we sought molecular and functional evidence for the presence of a KCC in renal (Malpighian) tubules of the mosquito Aedes aegypti . Using RT-PCR on Aedes Malpighian tubules, we identified five alternatively spliced partial cDNAs that encode putative SLC12-like KCCs. The majority transcript is AeKCC1-A1; its full-length cDNA was cloned. After expression of the AeKCC1-A protein in Xenopus oocytes, the Cl−-dependent uptake of 86Rb+ is 1) activated by 1 mM N-ethylmaleimide and cell swelling, 2) blocked by 100 μM dihydroindenyloxyalkanoic acid (DIOA), and 3) dependent upon N-glycosylation of AeKCC1-A. In Aedes Malpighian tubules, AeKCC1 immunoreactivity localizes to the apical brush border of principal cells, which are the predominant cell type in the epithelium. In vitro physiological assays of Malpighian tubules show that peritubular DIOA (10 μM): 1) significantly reduces both the control and diuretic rates of transepithelial fluid secretion and 2) has negligible effects on the membrane voltage and input resistance of principal cells. Taken together, the above observations indicate the presence of a KCC in the apical membrane of principal cells where it participates in a major electroneutral transport pathway for the transepithelial secretion of fluid in this highly electrogenic epithelium.

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Dibutyryl cAMP activates bumetanide-sensitive electrolyte transport in Malpighian tubules

AJP Cell Physiology ◽

10.1152/ajpcell.1991.261.3.c521 ◽

1991 ◽

Vol 261 (3) ◽

pp. C521-C529 ◽

Cited By ~ 66

Author(s):

J. L. Hegarty ◽

B. Zhang ◽

T. L. Pannabecker ◽

D. H. Petzel ◽

M. D. Baustian ◽

...

Keyword(s):

Yellow Fever ◽

Apical Membrane ◽

Basolateral Membrane ◽

Fluid Secretion ◽

Ringer Solution ◽

Malpighian Tubules ◽

Membrane Voltage ◽

Dibutyryl Camp ◽

K Secretion ◽

Transepithelial Voltage

The effects of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) and bumetanide (both 10(-4) M) on transepithelial Na+, K+, Cl-, and fluid secretion and on tubule electrophysiology were studied in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. Peritubular DBcAMP significantly increased Na+, Cl-, and fluid secretion but decreased K+ secretion. In DBcAMP-stimulated tubules, bumetanide caused Na+, Cl-, and fluid secretion to return to pre-cAMP control rates and K+ secretion to decrease further. Peritubular bumetanide significantly increased Na+ secretion and decreased K+ secretion so that Cl- and fluid secretion did not change. In bumetanide-treated tubules, the secretagogue effects of DBcAMP are blocked. In isolated Malpighian tubules perfused with symmetrical Ringer solution, DBcAMP significantly hyperpolarized the transepithelial voltage (VT) and depolarized the basolateral membrane voltage (Vbl) with no effect on apical membrane voltage (Va). Total transepithelial resistance (RT) and the fractional resistance of the basolateral membrane (fRbl) significantly decreased. Bumetanide also hyperpolarized VT and depolarized Vbl, however without significantly affecting RT and fRbl. Together these results suggest that, in addition to stimulating electroconductive transport, DBcAMP also activates a nonconductive bumetanide-sensitive transport system in Aedes Malpighian tubules.

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