Regulation of chloride permeability by endogenously produced tyramine in the Drosophila Malpighian tubule

Abstract

The Malpighian (renal) tubule of Drosophila melanogaster is a useful model for studying epithelial transport. The purpose of this study was to identify factors responsible for modulating transepithelial chloride conductance in isolated tubules. I have found that tyrosine and several of its metabolites cause an increase in chloride conductance. The most potent of these agonists is tyramine, which is active at low nanomolar concentrations; the pharmacology of this response matches that of the previously published cloned insect tyramine receptor. In addition, the tubule appears capable of synthesizing tyramine from applied tyrosine, as shown by direct measurement of tyrosine decarboxylase activity. Immunohistochemical staining of tubules with an antibody against tyramine indicates that the principal cells are the sites of tyramine production, whereas previous characterization of the regulation of chloride conductance suggests that tyramine acts on the stellate cells. This is the first demonstration of a physiological role for an insect tyramine receptor.

Salt stress alters fluid and ion transport by Malpighian tubules ofDrosophila melanogaster: evidence for phenotypic plasticity

“…Similarly, rearing the larvae on the K-rich diet and bathing them in haemolymph from the same group stimulates fluid and K + secretion, and thapsigargin does not produce further stimulation. Taken together, the results suggest that the diuretic factors responsible for the increase in fluid secretion and K + secretion in tubules isolated from larvae reared on salt-rich diets may act through increases in intracellular Ca (Blumenthal, 2003) are mediated through an increase in intracellular Ca 2+ in the stellate cells. The increase in intracellular Ca 2+ in turn leads to an increase in transepithelial chloride permeability and a consequent collapse of the transepithelial potential.…”

Cell signalling mechanisms for insect stress tolerance

“…cAMP and cGMP have been shown to play a role in stellate cells (Kerr et al, 2004), although the endogenous pathways for cAMP and cGMP are not known for this tubule cell type. Recent research, however, has demonstrated that cGMP acting through DG1 (but not DG2) can inhibit transepithelial responses induced by both tyramine and D. melanogaster leucokinin (Ruka et al, 2013), both of which increase calcium signalling and chloride conductance (Blumenthal, 2003;Cabrero et al, 2013;O'Donnell et al, 1996;Radford et al, 2004;Terhzaz et al, 1999). Thus, a yet-unidentified inhibitory process for tyramine and D. melanogaster leucokinin signalling in stellate cells is cGMP/DG1-mediated.…”

Flight Initiation and Maintenance Deficits in Flies with Genetically Altered Biogenic Amine Levels

“…Furthermore, OA and TA receptor distributions in the insect CNS differ considerably from each other [J. Erber (Technical University Berlin, Berlin, Germany), personal communication]. Functionally, exogenous TA increases chloride conductances in Drosophila malphigian tubules (Blumenthal, 2003), alters body wall muscle excitatory junction potentials (Kutsukake et al, 2000), and can rescue cocaine sensitization in Drosophila (McClung and Hirsh, 1999). In mammals, the physiological roles for trace amines such as TA and OA are mostly unknown, but they have been implicated in a variety of neurological disorders (Branchek and Blackburn, 2003), and receptors specific for TA have been identified (Borowsky et al, 2001).…”