Spatiotemporal filtering of mitochondrial calcium and its role in the Drosophila Malpighian tubule

S134

Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S131-S138

via the transcription factor Relish, a NFk-B homologue. Furthermore, we describe novel differential roles for each of the Drosophila cGKs, DG1 and DG2, in Relish activation, AMP production and fly survival. These novel modulatory effects of DG1 and DG2 on the IMD pathway are not associated with the fat body but are effective via the tubules in natural infection assays, and thus constitute an endogenous mechanism of bacterial resistance. doi:10.1016/j.cbpa.2008.04.319

A11.13 Peptidergic regulation of physiology and behavior in insects

we characterize the role of the two sesB isoforms (SesB-1 and SesB-2) in mitochondrial Ca2+ uptake. In parallel using confocal microscopy we assessed changes in mitochondrial biogenesis in sesB mutant flies. doi:10.1016/j.cbpa.2008.04.321

A11.15 Identified Drosophila ion transport peptide splice forms are differentially expressed in central and peripheral neurons throughout postembryogenesis H. Dircksen, L. Kahsai, C. Albus, M. Mandali, D. Nässel (Stockholm University)

N. Tublitz (University of Oregon) This talk discusses several separate mechanisms underlying peptide mediated neuroplasticity in insects. The first is at the cellular level in the moth Manduca sexta. Manduca has a set of larval neurons that express a subset of cardioacceleratory peptides (CAPs). During metamorphosis these neurons undergo a complete transformation, changing their physiological, biochemical and morphological properties. This cellular alteration is hormonally triggered by the insect steroid hormone 20-OH ecdysone. CAP expression in other neurons is also significantly altered during metamorphosis. The second part of the talk will focus on peptide mediated plasticity at the developmental level in the fruit fly Drosophila melanogaster. Two CAPs, CCAP and CAP2b, are expressed in the mesodermally-derived midline mesoderm cells (MMCs) of Drosophila. The MMCs extend a neuronal-like process, express neuronal markers, have voltage-dependent channels, and contain bioactive CAPs. These data suggest that the MMCs act as neurosecretory cells despite their non-neural origins. Other mechanisms will also be presented. doi:10.1016/j.cbpa.2008.04.320

A11.14 Spatiotemporal filtering of mitochondrial calcium and its role in the Drosophila Malpighian tubule

Insect ion transport peptides (ITPs) are members of a large family of arthropod neuropeptides (72–87amino acids (aa) long) originally defined by the homologous crustacean hyperglycemic hormones (CHHs). Insect and crustacean ITP/CHH gene are similar and their products are usually alternatively spliced into one amidated isoform of 72–73aa (ITP/ CHH) which, in locusts, is known to have antidiuretic bioactivity, and into one long isoform (ITPL N 78aa) of unknown function. We have found, in Drosophila melanogaster, that the gene CG13586 gives rise to three identified mRNAs encoding peptide isoforms, one short amidated DrmITP (73aa) and two other longer DrmITPLs (DrmITPL1 and DrmITPL2, both 87aa). The peptides have been identified by biochemical analyses and mass spectrometry. In situ-hybridisation and immunocytochemistry found short DrmITP in several larval neurons most of which even persist into the adult stage: four novel pairs of neurons innervate the corpora cardiaca and allata, and two pairs of hindgut-innervating neurons in the abdominal ganglia. In larvae and pupae, DrmITP-neurons exist as a pair in the SOG, and one pair of peripheral bipolar LBD-neurons in close proximity to the anal organ, a known chloride-transporting organ. Similar bipolar neurons were found on dorsal areas of adult ventral nerve roots. Further LBD and other peripheral neurons are the only site for long isoforms DrmITPL1/L2 of the larva and the adult. Colocalisations of DrmITP with allatostatin-ir are found in hindgut innervating neurons. Partial overlap of branches of DrmITP neurons with those of clock neurons occurs in adult brains. Functional implications are currently investigated.

doi:10.1016/j.cbpa.2008.04.322

S. Terhzaz, P. Cabrero, S. Davies, J. Dow (University of Glasgow)

By generating Drosophila transgenic for both luminescent and fluorescent mitochondrial calcium reporters, we previously showed that in tubule principal cells, mitochondrial calcium tracked changes in cytoplasmic calcium. This resulted in both increased mitochondrial membrane polarisation and elevated cellular ATP levels — the apical plasma membrane V-ATPase is a major consumer of ATP. Using mitochondrial calcium imaging and a potential sensing dye, the apical mitochondria of principal cells were found to be selectively responsive to capa1 neuropeptide signalling. The results highlight the dynamic nature and both spatial and temporal heterogeneity of calcium signalling possible in differentiated, organotypic cells; and also provides a new model for neuroendocrine control of V-ATPase. A great advantage of working with Drosophila is the availability of mutants for pathways of interest. We show here that the mutants of the gene encoding mitochondrial ADP/ATP translocase, sesB, which from our published microarray data is enriched in tubules, impact on mitochondrial function. Based on the interaction between the mitochondrial permeability transition (MPT) pore component sesB and Ca2+ signalling

A11.16 On the breathing patterns of Rhodnius prolixus T. Bradley (University of California, Irvine) The immoderate feeding habits of Rhodnius prolixus have made it a favorite object of study for insect physiologists. The periodic nature of its meals allowed Wigglesworth to gain insights into the release of hormones regulating molting, metamorphosis and growth. The vast size of the meals and their liquid nature provided Maddrell with extraordinary material for examining the processes involved in ion transport in the Malpighian tubules. The size of the meals also dictates substantial increases in the rate of metabolism following feeding as the meal is digested and protein synthesis proceeds prior to the next molt. The metabolic rate increases almost 10-fold over resting, pre-fed rates, although the insect is outwardly quiescent throughout. Rhodnius exhibits a classic pattern of discontinuous respiration in the unfed state. We have taken advantage of the insect's capacity to ramp up