The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Michael J Odonnell - One of the best experts on this subject based on the ideXlab platform.
-
a unique Malpighian Tubule architecture in tribolium castaneum informs the evolutionary origins of systemic osmoregulation in beetles
Proceedings of the National Academy of Sciences of the United States of America, 2021Co-Authors: Takashi Koyama, Michael J Odonnell, Muhammad Tayyib Naseem, Dennis Kolosov, Duncan Mahon, Amanda Sofie Seger Jakobsen, Rasmus Lycke Jensen, Barry Denholm, Kenneth Veland HalbergAbstract:Maintaining internal salt and water balance in response to fluctuating external conditions is essential for animal survival. This is particularly true for insects as their high surface-to-volume ratio makes them highly susceptible to osmotic stress. However, the cellular and hormonal mechanisms that mediate the systemic control of osmotic homeostasis in beetles (Coleoptera), the largest group of insects, remain largely unidentified. Here, we demonstrate that eight neurons in the brain of the red flour beetle Tribolium castaneum respond to internal changes in osmolality by releasing diuretic hormone (DH) 37 and DH47-homologs of vertebrate corticotropin-releasing factor (CRF) hormones-to control systemic water balance. Knockdown of the gene encoding the two hormones (Urinate, Urn8) reduces Malpighian Tubule secretion and restricts organismal fluid loss, whereas injection of DH37 or DH47 reverses these phenotypes. We further identify a CRF-like receptor, Urinate receptor (Urn8R), which is exclusively expressed in a functionally unique secondary cell in the beetle Tubules, as underlying this response. Activation of Urn8R increases K+ secretion, creating a lumen-positive transepithelial potential that drives fluid secretion. Together, these data show that beetle Malpighian Tubules operate by a fundamentally different mechanism than those of other insects. Finally, we adopt a fluorescent labeling strategy to identify the evolutionary origin of this unusual Tubule architecture, revealing that it evolved in the last common ancestor of the higher beetle families. Our work thus uncovers an important homeostatic program that is key to maintaining osmotic control in beetles, which evolved parallel to the radiation of the "advanced" beetle lineages.
-
investigations of the signaling cascade involved in diuretic hormone stimulation of Malpighian Tubule fluid secretion in rhodnius prolixus
Journal of Insect Physiology, 2013Co-Authors: Jean-paul Paluzzi, Cynthia Yeung, Michael J OdonnellAbstract:Abstract In insects, the excretory system is comprised of the Malpighian Tubules (MTs) and the hindgut, which collectively function to maintain ionic and osmotic balance of the haemolymph and rid the organism of toxic compounds or elements in excess. Secretion by the Malpighian Tubules of insects is regulated by a variety of hormones including peptidergic factors as well as biogenic amines. In Rhodnius prolixus, two endogenous diuretic hormones have been identified; the biogenic amine serotonin (5-hydroxytryptamine, 5-HT) and the corticotropin releasing factor-related peptide, RhoprCRF. Both factors significantly increase secretion by MTs and are known to elevate intracellular levels of cAMP. Interestingly, applying sub-maximal doses of these two diuretic factors in combination on isolated MTs in vitro reveals synergistic effects as rates of fluid secretion are significantly higher than would be expected if rates of secretion from MTs treated with each factor alone were summed. This observed synergism suggests that different downstream targets may be activated by the two diuretic factors, but that some cellular elicitors may be shared since cAMP is elevated in response to either diuretic hormone. This study investigated the signaling cascade involved in the diuretic hormone regulation of Malpighian Tubule fluid secretion. Bioassays were performed in physiological as well as modified salines (e.g. calcium-free) alone or in the presence of a variety of pharmacological compounds that interfere with prospective intracellular targets, such as the apical cation/H+ exchanger. Intriguingly, only amiloride yielded differential effects on the two diuretics with 5HT-stimulated secretion being blocked, whereas in contrast, RhoprCRF-stimulated secretion was unaffected. In addition, experiments examining the role of extracellular and intracellular calcium on fluid secretion rate showed that both diuretics are dependent on intracellular calcium availability. Finally, fluid secretion stimulated by either diuretic hormone was also sensitive to inhibition of cAMP-dependent protein kinase A. Taken together, these results suggest that each diuretic hormone activates pathways dependent upon intracellular calcium and cAMP.
-
inorganic and organic anion transport by insect renal epithelia
Biochimica et Biophysica Acta, 2003Co-Authors: Michael J Odonnell, Juan P Ianowski, Stuart M Linton, Mark R RheaultAbstract:Abstract Insect renal organs typically exhibit high rates of transport of inorganic and organic anions, and therefore provide useful models for the study of epithelial anion transport and its control. Isolated Malpighian Tubules of some species secrete a volume of iso-osmotic fluid equal to their own volume in 10–15 s, which means that cellular Cl− content is exchanged every 3–5 s. Anion transport can also be achieved against extreme thermodynamic gradients. The concentration of K+ and Cl− in the lumen of the Malpighian Tubules of some desert beetles approaches or exceeds saturation. A basolateral Na+:K+:2Cl− cotransporter plays an important role in vectorial ion transport in Malpighian Tubules of many species, but there is also evidence for coupling of Cl− transport to the movement of a single cationic species (Na+ or K+). Although an apical vacuolar H+-ATPase plays a primary role in energizing transepithelial secretion of chloride via channels or cotransporters in the secretory segment of the Malpighian Tubule, several different ATPases have been implicated in reabsorption of Cl− by the lower Malpighian Tubule or hindgut. Chloride transport is known to be controlled by several neuropeptides, amines and intracellular second messengers. Insect renal epithelia are also important in excretion of potentially toxic organic anions, and the transporters involved may play a role in resistance to insecticides of natural or anthropogenic origin.
-
intracellular ion activities in Malpighian Tubule cells of rhodnius prolixus evaluation of na k 2cl cotransport across the basolateral membrane
The Journal of Experimental Biology, 2002Co-Authors: Juan P Ianowski, Robert J Christensen, Michael J OdonnellAbstract:Intracellular ion activities (a(ion)) and basolateral membrane potential (Vbl) were measured in Malpighian Tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103 mmol l(-1) Na+, 6 mmol l(-1) K+ and 93 mmol l(-1) Cl-, intracellular ion activities in unstimulated upper Malpighian Tubules were 21, 86 and 32 mmol l(-1), respectively. In serotonin-stimulated Tubules, aCl was unchanged, whereas aNa increased to 33 mmol l(-1) and aK declined to 71 mmol l(-1). Vbl was -59 mV and -63 mV for unstimulated and stimulated Tubules, respectively. Calculated electrochemical potentials (deltamuF) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated Tubules. Passive movement of K+ out of the cell is favoured in unstimulated Tubules. In stimulated Tubules, deltamuF for K+ is close to 0 mV. The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl- and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (deltamu(net)/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated Tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated Tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian Tubules.
-
anti diuresis in the blood feeding insect rhodnius prolixus stal the peptide cap2b and cyclic gmp inhibit Malpighian Tubule fluid secretion
The Journal of Experimental Biology, 1997Co-Authors: Michael C Quinlan, Nathan J Tublitz, Michael J OdonnellAbstract:Rhodnius prolixus eliminates NaCl-rich urine at high rates following its infrequent but massive blood meals. This diuresis involves stimulation of Malpighian Tubule fluid secretion by diuretic hormones released in response to distention of the abdomen during feeding. The precipitous decline in urine flow that occurs several hours after feeding has been thought until now to result from a decline in diuretic hormone release. We suggest here that insect cardioacceleratory peptide 2b (CAP2b) and cyclic GMP are part of a novel mechanism of anti-diuresis. Secretion rates of 5-hydroxytryptamine-stimulated Malpighian Tubules are reduced by low doses of CAP2b or cyclic GMP. Maximal secretion rates are restored by exposing Tubules to 1 mmol l-1 cyclic AMP. Levels of cyclic GMP in isolated Tubules increase in response to CAP2b, consistent with a role for cyclic GMP as an intracellular second messenger. Levels of cyclic GMP in Tubules also increase as urine output rates decline in vivo, suggesting a physiological role for this nucleotide in the termination of diuresis.
Patricia V Pietrantonio - One of the best experts on this subject based on the ideXlab platform.
-
the kinin receptor is expressed in the Malpighian Tubule stellate cells in the mosquito aedes aegypti l a new model needed to explain ion transport
Insect Biochemistry and Molecular Biology, 2011Co-Authors: Cymon N Kersch, Patricia V PietrantonioAbstract:Abstract It is known that insect kinins increase diuresis and fluid secretion in the Aedes aegypti Malpighian Tubule, causing a rapid drop of the transepithelial resistance and increasing chloride conductance from the hemolymph towards the Tubule lumen. The Tubule is composed of both principal and stellate cells. The main route for increased chloride influx upon kinin treatment is proposed to be paracellular, with septate junctions acquiring increased chloride selectivity and conductance. Therefore, kinin treatment renders the Ae. aegypti Tubule a “leaky epithelium”, and under this model the kinin receptor is postulated to be expressed in principal cells. However, in another dipteran, the fruit fly Drosophila melanogaster, the main route for chloride transport is transcellular through stellate cells. In both the fruit fly and the mosquito Anopheles stephensi the kinin receptor has been immunolocalized in stellate cells, where it regulates transepithelial chloride permeability. Here we show that in Ae. aegypti, similarly, the stellate cells express the kinin receptor. This was confirmed through immunohistochemistry with two specific anti-kinin receptor antibodies and confocal analysis. The receptor is detected as a 75 kDa band in western blot. These results indicate that the currently accepted model for chloride transport must be re-evaluated in Ae. aegypti and suggest the kinin regulatory signals controlling intercellular junctions originate in the stellate cells.
-
diuretic hormone 44 receptor in Malpighian Tubules of the mosquito aedes aegypti evidence for transcriptional regulation paralleling urination
Insect Molecular Biology, 2008Co-Authors: Christopher Jagge, Patricia V PietrantonioAbstract:In the mosquito Aedes aegypti (L.), the molecular endocrine mechanisms underlying rapid water elimination upon eclosion and blood feeding are not fully understood. The genome contains a single predicted diuretic hormone 44 (DH44) gene, but two DH44 receptor genes. The identity of the DH44 receptor(s) in the Malpighian Tubule is unknown in any mosquito species. We show that VectorBase gene ID AAEL008292 encodes the DH44 receptor (GPRDIH1) most highly expressed in Malpighian Tubules. Sequence analysis and transcript localization indicate that AaegGPRDIH1 is the co-orthologue of the Drosophila melanogaster DH44 receptor (CG12370-PA). Time-course quantitative PCR analysis of Malpighian Tubule cDNA revealed AaegGPRDIH1 expression changes paralleling periods of excretion. This suggests that target tissue receptor biology is linked to the known periods of release of diuretic hormones from the nervous system pointing to a common up-stream regulatory mechanism.
-
characterization of a leucokinin binding protein in aedes aegypti diptera culicidae Malpighian Tubule
Insect Biochemistry and Molecular Biology, 2000Co-Authors: Patricia V Pietrantonio, Allison Strey, Grant Gibson, David Petzel, Timothy K. HayesAbstract:Abstract The insect myokinin (leucokinin-like) neuropeptide family includes peptides that have different physiological effects such as the induction of hindgut myotropic activity and stimulation of urine production. The C-terminal pentamer of myokinins Phe-X-(Ser/Pro/Ala)-Trp-Gly-amide [X=Phe, His, Asn, Ser or Tyr], had been previously determined as the minimum fragment able to elicit a functional response. The receptor(s) for these insect neuropeptides has not yet been identified. In order to characterize the Malpighian Tubule leucokinin-like peptide receptor(s) from the yellow fever mosquito ( Aedes aegypti) , a leucokinin photoaffinity analogue (LPA) of sequence dAla-dTyr-Bpa-dLys-Phe-Phe-Ser-Trp-Gly-amide was designed based on structure/activity relationships for leucokinins. LPA caused depolarization of the transepithelial voltage (TEV) in female Malpighian Tubule, confirming the activity of the peptide. The effective concentration to give half the maximum depolarization (EC 50 ) was 17 nM. The 125 I-LPA was then used to characterize leucokinin binding proteins in female Malpighian Tubule membranes. It specifically labeled and saturated a protein(s) of about 54 kDa as shown by SDS-PAGE/autoradiography and by competition experiments with excess unlabeled leucokinin analogues. 125 I-LPA bound to the 54 kDa protein(s) with a K d value of 13±3 nM in agreement with the EC 50 for the TEV bioassay. Altogether these data suggest that the 54 kDa protein is an Aedes- leucokinin receptor. This is the first characterization of an insect leucokinin receptor and reveals that LPA is a powerful tool to label insect myokinin receptors.
Shireen A Davies - One of the best experts on this subject based on the ideXlab platform.
-
new views on the Malpighian Tubule from post genomic technologies
Current opinion in insect science, 2018Co-Authors: Julian A. T. Dow, Arif Ahmad Pandit, Shireen A DaviesAbstract:Successful insect diversification depends at least in part on the ability to osmoregulate successfully across a broad range of ecological niches. First described in the 17th Century, and Malpighian Tubules have been studied physiologically for 70 years. However, our understanding has been revolutionized by the advent of genomics, transcriptomics, proteomics and metabolomics. Such technologies are natural partners with (though do not obligatorily require) model organisms and transgenic technologies. This review describes the recent impact of multi-omic technologies on our understanding or renal function and control in insects.
-
the corticotropin releasing factor like diuretic hormone 44 dh44 and kinin neuropeptides modulate desiccation and starvation tolerance in drosophila melanogaster
Peptides, 2016Co-Authors: Elizabeth Cannell, Anthony J Dornan, Selim Terhzaz, Kenneth A. Halberg, Shireen A DaviesAbstract:Malpighian Tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance. Gene expression and labelled DH44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH44 in neurons of the pars intercerebralis and DH44 receptor (DH44-R2) in Malpighian Tubule principal cells, indicate that suppression of DH44 signalling improves desiccation tolerance of the intact fly. Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH44 neurons as well as in stellate cells of the Malpighian Tubules. LKR knockdown in DH44-expressing neurons reduces Malpighian Tubule-specific LKR, suggesting interactions between DH44 and LK signalling pathways. Finally, although a role for DK in desiccation tolerance was not defined, we demonstrate a novel role for Malpighian Tubule cell-specific LKR in starvation tolerance. Starvation increases gene expression of epithelial LKR. Also, Malpighian Tubule stellate cell-specific knockdown of LKR significantly reduced starvation tolerance, demonstrating a role for neuropeptide signalling during starvation stress.
-
the Malpighian Tubule rapid insights from post genomic biology
Journal of Insect Physiology, 2006Co-Authors: Julian A. T. Dow, Shireen A DaviesAbstract:Good osmoregulation is critical to the success of insects, and the Malpighian Tubules play a key role in osmoregulation. Recently, the application of genetics and genomics to the Drosophila Tubule has revealed far more extensive roles than ion and water transport. Microarray analysis shows that organic solute transporters dominate the Tubule transcriptome. The Tubule thus has the capability to excrete actively the broadest range of organic solutes and xenobiotics. Such transporters can produce unexpected, emergent roles for the whole tissue; e.g. the Tubule is highly resistant to ouabain not because the Na+, K+ ATPase is unimportant, but because it co-localises with a potent alkaloid excretory mechanism. Reinforcing this role in excretion, the Tubule expresses very high levels of a particular cytochrome P450 s, glutathione-S-transferases and alchohol dehydrogenases which suggest that the Tubule plays a major role in metabolism and detoxification of both endogenous solutes and xenobiotics, such as insecticides. Additionally, the Tubule plays a significant role in immunity; Tubules are capable of sensing bacterial challenge, and mounting an effective killing response by secretion of antimicrobial peptides, entirely independent of the fat body, the canonical immune tissue. The Tubule has also proved to be a good model for some human renal disease, and to act as an organotypic ‘testbed’ for mammalian genes. The Tubule can thus bask in a greatly enhanced reputation as a key tissue for an unexpectedly wide range of functions in the insect.
-
The Drosophila melanogaster Malpighian Tubule
Advances in Insect Physiology, 2001Co-Authors: Julian A. T. Dow, Shireen A DaviesAbstract:Publisher Summary This chapter reviews the morphology, function, and development of Malpighian Tubule of Drosophila melanogaster . Recent results have provided a reference point for Tubule studies for insect physiologists and a unique resource for developmental and genetic analysis of fundamental questions of differentiated cell function. It is noted that the formation of the Drosophila melanogaster Malpighian Tubule is better understood than that of any other insect and it provides a model for epithelial development in general. In addition to the standard Drosophila techniques of close microscopic examination, genetic screens, enhancer trapping, and reporter gene expression, there are some specific tools that have made progress much easier.
-
fluid secretion by the drosophila Malpighian Tubule
Integrative and Comparative Biology, 1998Co-Authors: Julian A. T. Dow, Shireen A Davies, Ali M SoozenAbstract:SYNOPSIS. Drosophila melanogaster is a good model for studies in molecular physiology. The Malpighian (renal) Tubule can be studied with classical transport physiological and electrophysiological techniques, and displays those transport specialisations that are conserved among Tubules of those insects studied to date. In addition, the endocrinology of fluid secretion and the pharmacology of the second messenger control systems are both closely similar to those of other insects. At a more general level, the use of an electrogenic, proton-motive plasma membrane VATPase to energise secondary active transport is now know to be general to most insect, and several vertebrate, epithelia. In addition to its similarity to epithelia in a number of economically and biomedically significant organisms, D. melanogaster possesses unique advantages as an experimental model, by virtue of the sophisticated genetic tools that are available. This article summarises recent progress in two areas in which D. melanogaster has provided new insights into epithelial function: the control of epithelial fluid secretion by the nitric oxide synthase/nitric oxide/cyclic GMP signalling pathways; and the genetic analysis of the structural organisation of this tiny model, and its reconciliation with physiological properties.
Julian A. T. Dow - One of the best experts on this subject based on the ideXlab platform.
-
new views on the Malpighian Tubule from post genomic technologies
Current opinion in insect science, 2018Co-Authors: Julian A. T. Dow, Arif Ahmad Pandit, Shireen A DaviesAbstract:Successful insect diversification depends at least in part on the ability to osmoregulate successfully across a broad range of ecological niches. First described in the 17th Century, and Malpighian Tubules have been studied physiologically for 70 years. However, our understanding has been revolutionized by the advent of genomics, transcriptomics, proteomics and metabolomics. Such technologies are natural partners with (though do not obligatorily require) model organisms and transgenic technologies. This review describes the recent impact of multi-omic technologies on our understanding or renal function and control in insects.
-
immune and stress response cross talk in the drosophila Malpighian Tubule
Journal of Insect Physiology, 2012Co-Authors: Shireenanne Davies, Julian A. T. Dow, Gayle Overend, Sujith Sebastian, Maria Cundall, Pablo Cabrero, Selim TerhzazAbstract:The success of insects is in large part due to their ability to survive environmental stress, including heat, cold, and dehydration. Insects are also exposed to infection, osmotic or oxidative stress, and to xenobiotics or toxins. The molecular mechanisms of stress sensing and response have been widely investigated in mammalian cell lines, and the area of stress research is now so vast to be beyond the scope of a single review article. However, the mechanisms by which stress inputs to the organism are sensed and integrated at the tissue and cellular level are less well understood. Increasingly, common molecular events between immune and other stress responses are observed in vivo; and much of this work stems of efforts in insect molecular science and physiology. We describe here the current knowledge in the area of immune and stress signalling and response at the level of the organism, tissue and cell, focussing on a key epithelial tissue in insects, the Malpighian Tubule, and drawing together the known pathways that modulate responses to different stress insults. The Tubules are critical for insect survival and are increasingly implicated in responses to multiple and distinct stress inputs. Importantly, as Tubule function is central to survival, they are potentially key targets for insect control, which will be facilitated by increased understanding of the complexities of stress signalling in the organism.
-
Insights into the Malpighian Tubule from functional genomics
Journal of Experimental Biology, 2009Co-Authors: Julian A. T. DowAbstract:Classical physiological study of the Malpighian Tubule has led to a detailed understanding of fluid transport and its control across several species. With the sequencing of the Drosophila genome, and the concurrent development of post-genomic technologies such as microarrays, proteomics, metabolomics and systems biology, completely unexpected roles for the insect Malpighian Tubule have emerged. As the insect body plan is simpler than that of mammals, tasks analogous to those performed by multiple mammalian organ systems must be shared out among insect tissues. As well as the classical roles in osmoregulation, the Malpighian Tubule is highly specialized for organic solute transport, and for metabolism and detoxification. In Drosophila , the adult Malpighian Tubule is the key tissue for defence against insecticides such as DDT; and it can also detect and mount an autonomous defence against bacterial invasion. While it is vital to continue to set insights obtained in Drosophila into the context of work in other species, the combination of post-genomic technologies and physiological validation can provide insights that might not otherwise have been apparent for many years.
-
the Malpighian Tubule rapid insights from post genomic biology
Journal of Insect Physiology, 2006Co-Authors: Julian A. T. Dow, Shireen A DaviesAbstract:Good osmoregulation is critical to the success of insects, and the Malpighian Tubules play a key role in osmoregulation. Recently, the application of genetics and genomics to the Drosophila Tubule has revealed far more extensive roles than ion and water transport. Microarray analysis shows that organic solute transporters dominate the Tubule transcriptome. The Tubule thus has the capability to excrete actively the broadest range of organic solutes and xenobiotics. Such transporters can produce unexpected, emergent roles for the whole tissue; e.g. the Tubule is highly resistant to ouabain not because the Na+, K+ ATPase is unimportant, but because it co-localises with a potent alkaloid excretory mechanism. Reinforcing this role in excretion, the Tubule expresses very high levels of a particular cytochrome P450 s, glutathione-S-transferases and alchohol dehydrogenases which suggest that the Tubule plays a major role in metabolism and detoxification of both endogenous solutes and xenobiotics, such as insecticides. Additionally, the Tubule plays a significant role in immunity; Tubules are capable of sensing bacterial challenge, and mounting an effective killing response by secretion of antimicrobial peptides, entirely independent of the fat body, the canonical immune tissue. The Tubule has also proved to be a good model for some human renal disease, and to act as an organotypic ‘testbed’ for mammalian genes. The Tubule can thus bask in a greatly enhanced reputation as a key tissue for an unexpectedly wide range of functions in the insect.
-
The Drosophila melanogaster Malpighian Tubule
Advances in Insect Physiology, 2001Co-Authors: Julian A. T. Dow, Shireen A DaviesAbstract:Publisher Summary This chapter reviews the morphology, function, and development of Malpighian Tubule of Drosophila melanogaster . Recent results have provided a reference point for Tubule studies for insect physiologists and a unique resource for developmental and genetic analysis of fundamental questions of differentiated cell function. It is noted that the formation of the Drosophila melanogaster Malpighian Tubule is better understood than that of any other insect and it provides a model for epithelial development in general. In addition to the standard Drosophila techniques of close microscopic examination, genetic screens, enhancer trapping, and reporter gene expression, there are some specific tools that have made progress much easier.
Andrew Donini - One of the best experts on this subject based on the ideXlab platform.
-
active transport of brilliant blue fcf across the drosophila midgut and Malpighian Tubule epithelia
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2020Co-Authors: Dawson B H Livingston, Hirva Patel, Andrew Donini, Heath A. MacmillanAbstract:Under conditions of stress, many animals suffer from epithelial barrier disruption that can cause molecules to leak down their concentration gradients, potentially causing a loss of organismal homeostasis, further injury or death. Drosophila is a common insect model, used to study barrier disruption related to aging, traumatic injury, or environmental stress. Net leak of a non-toxic dye (Brilliant blue FCF) from the gut lumen to the hemolymph is often used to identify barrier failure under these conditions, but Drosophila are capable of actively transporting structurally-similar compounds. Here, we examined whether cold stress (like other stresses) causes Brilliant blue FCF (BB-FCF) to appear in the hemolymph of flies fed the dye, and if so whether Drosophila are capable of clearing this dye from their body following chilling. Using in situ midgut leak and transport assays as well as Ramsay assays of Malpighian Tubule transport, we tested whether these ionoregulatory epithelia can actively transport BB-FCF. In doing so, we found that the Drosophila midgut and Malpighian Tubules can mobilize BB-FCF via an active transcellular pathway, suggesting that elevated concentrations of the dye in the hemolymph may occur from increased paracellular permeability, reduced transcellular clearance, or both. Summary statement: Drosophila are able to actively secrete Brilliant blue FCF, a commonly used marker of barrier dysfunction.
-
functional plasticity of the gut and the Malpighian Tubules underlies cold acclimation and mitigates cold induced hyperkalemia in drosophila melanogaster
The Journal of Experimental Biology, 2018Co-Authors: Gil Y. Yerushalmi, Heath A. Macmillan, Lidiya Misyura, Andrew DoniniAbstract:At low temperatures, Drosophila , like most insects, lose the ability to regulate ion and water balance across the gut epithelia, which can lead to a lethal increase of [K + ] in the hemolymph (hyperkalemia). Cold-acclimation, the physiological response to a prior low temperature exposure, can mitigate or entirely prevent these ion imbalances, but the physiological mechanisms that facilitate this process are not well understood. Here, we test whether plasticity in the ionoregulatory physiology of the gut and Malpighian Tubules of Drosophila may aid in preserving ion homeostasis in the cold. Upon adult emergence, D. melanogaster females were subjected to seven days at warm (25°C) or cold (10°C) acclimation conditions. The cold acclimated flies had a lower critical thermal minimum (CT min ), recovered from chill coma more quickly, and better maintained hemolymph K + balance in the cold. The improvements in chill tolerance coincided with increased Malpighian Tubule fluid secretion and better maintenance of K + secretion rates in the cold, as well as reduced rectal K + reabsorption in cold-acclimated flies. To test whether modulation of ion-motive ATPases, the main drivers of epithelial transport in the alimentary canal, mediate these changes, we measured the activities of Na + -K + -ATPase and V-type H + -ATPase at the Malpighian Tubules, midgut, and hindgut. Na + /K + -ATPase and V-type H + -ATPase activities were lower in the midgut and the Malpighian Tubules of cold-acclimated flies, but unchanged in the hindgut of cold acclimated flies, and were not predictive of the observed alterations in K + transport. Our results suggest that modification of Malpighian Tubule and gut ion and water transport likely prevents cold-induced hyperkalemia in cold-acclimated flies and that this process is not directly related to the activities of the main drivers of ion transport in these organs, Na + /K + - and V-type H + -ATPases.
-
A mosquito entomoglyceroporin, Aedes aegypti AQP5, participates in water transport across the Malpighian Tubules of larvae.
The Journal of Experimental Biology, 2017Co-Authors: Lidiya Misyura, Gil Y. Yerushalmi, Andrew DoniniAbstract:ABSTRACT The mosquito Aedes aegypti is the primary vector for arboviral diseases such as Zika fever, dengue fever, chikungunya and yellow fever. The larvae reside in hypo-osmotic freshwater habitats, where they face dilution of their body fluids from osmotic influx of water. The Malpighian Tubules help maintain ionic and osmotic homeostasis by removing excess water from the hemolymph; however, the transcellular pathway for this movement remains unresolved. Aquaporins are transmembrane channels thought to permit transcellular transport of water from the hemolymph into the Malpighian Tubule lumen. Immunolocalization of A . aegypti aquaporin 5 (AaAQP5) revealed expression by Malpighian Tubule principal cells of the larvae, with localization to both the apical and basolateral membranes. Knockdown of AaAQP5 with double-stranded RNA decreased larval survival, reduced rates of fluid, K + and Na + secretion by the Malpighian Tubules, and reduced Cl − concentrations in the hemolymph. These findings indicate that AaAQP5 participates in transcellular water transport across the Malpighian Tubules of larval A . aegypti where global AaAQP5 expression is important for larval survival.