Role in diuresis of a calcitonin receptor (GPRCAL1) expressed in a distal-proximal gradient in renal organs of the mosquito Aedes aegypti (L.).

Hyeogsun Kwon,Hsiao-Ling Lu,Michael T Longnecker,Patricia V Pietrantonio,Immo A Hansen

doi:10.1371/journal.pone.0050374

Hyeogsun Kwon, Hsiao-Ling Lu + Show 3 more

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https://doi.org/10.1371/journal.pone.0050374

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Journal: PloS one	Publication Date: Nov 29, 2012
Citations: 80	License type: CC BY 4.0

Affiliation: Texas A&M University

Abstract

Evolution of anthropophilic hematophagy in insects resulted in the coordination of various physiological processes for survival. In female mosquitoes, a large blood meal provides proteins for egg production and as a trade-off, rapid elimination of the excess water and solutes (Na+, Cl−) is critical for maintaining homeostasis and removing excess weight to resume flight and avoid predation. This post-prandial excretion is achieved by the concerted action of multiple hormones. Diuresis and natriuresis elicited by the calcitonin-like diuretic hormone 31 (DH31) are believed to be mediated by a yet uncharacterized calcitonin receptor (GPRCAL) in the mosquito Malpighian tubules (MTs), the renal organs. To contribute knowledge on endocrinology of mosquito diuresis we cloned GPRCAL1 from MT cDNA. This receptor is the ortholog of the DH31 receptor from Drosophila melanogaster that is expressed in principal cells of the fruit fly MT. Immunofluorescence similarly showed AaegGPRCAL1 is present in MT principal cells in A. aegypti, however, exhibiting an overall gradient-like pattern along the tubule novel for a GPCR in insects. Variegated, cell-specific receptor expression revealed a subpopulation of otherwise phenotypically similar principal cells. To investigate the receptor contribution to fluid elimination, RNAi was followed by urine measurement assays. In vitro, MTs from females that underwent AaegGPRcal1 knock-down exhibited up to 57% decrease in the rate of fluid secretion in response to DH31. Live females treated with AaegGPRcal1 dsRNA exhibited 30% reduction in fluid excreted after a blood meal. The RNAi-induced phenotype demonstrates the critical contribution of this single secretin-like family B GPCR to fluid excretion in invertebrates and highlights its relevance for the blood feeding adaptation. Our results with the mosquito AaegGPRCAL1 imply that the regulatory function of calcitonin-like receptors for ion and fluid transport in renal organs arose early in evolution.

Highlights

Insect diuresis is regulated by the concerted action of different hormones, among them, peptide hormones such as calcitoninlike diuretic hormone 31 (DH31), corticotropin-releasing factor (CRF)-like diuretic hormone 44 (DH44), insect kinins, CAPAperiviscerokinins, arginine vasopressin-like insect diuretic hormones and serotonin [1,2,3,4]
AaegGPRcal1 is the ortholog of the D. melanogaster calcitonin receptor-like receptor 1 (DmelGPRcal1) (64% amino acid sequence identity) that is activated by Dmel-DH31 (76% amino acid sequence identity to Aaeg-DH31) [21]
Phylogenetic analyses based on sequence alignments (Fig. S2) showed that in the secretin GPCR group, corticotropin releasing hormone 1 (CRHR1) receptors and the calcitonin receptor-like receptor (CALCRL)/calcitonin receptor (CALCR) group belong to two independent clusters, each including receptors from protostomes anddeuterostomes (Fig. S3)

Summary

Introduction

Insect diuresis is regulated by the concerted action of different hormones, among them, peptide hormones such as calcitoninlike diuretic hormone 31 (DH31), corticotropin-releasing factor (CRF)-like diuretic hormone 44 (DH44), insect kinins, CAPAperiviscerokinins, arginine vasopressin-like insect diuretic hormones and serotonin [1,2,3,4] These act on cognate receptors in the renal organs, the Malpighian tubules (MTs), to stimulate ion transport for primary urine production and subsequent fluid excretion. Transport is achieved by channels and co-transporters in the MT principal and stellate cells and through septate junctions between principal cells and is energized by an apical vacuolar H+-ATPase (V-ATPase) in the principal cells The latter have the fastest ion transporting capacity of any cell so far studied, resulting in high rates of fluid secretion [7,8,9,10]. The immediate fluid excretion from females that eliminates excess weight is believed to have contributed to the successful adaptation to blood feeding in mosquitoes, at minimum by avoiding predation [11]

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