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The Journal of Experimental Biology 206, 901-911 (2003)
doi: 10.1242/jeb.00189

norpA and itpr mutants reveal roles for phospholipase C and inositol (1,4,5)- trisphosphate receptor in Drosophila melanogaster renal function

Valerie P. Pollock¹, Jonathan C. Radford¹, Susan Pyne², Gaiti Hasan³, Julian A. T. Dow¹ and Shireen-A. Davies^1,*

¹ Institute of Biomedical and Life Sciences, Division of Molecular Genetics, University of Glasgow, Glasgow G11 6NU, UK
² Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow G4 ONR, UK
³ National Centre for Biological Sciences, UAS-GKVK Campus, Bangalore 560065, India

^* Author for correspondence (e-mail: s.a.davies{at}bio.gla.ac.uk)

Accepted 2 December 2002

Mutants of norpA, encoding phospholipase Cß (PLCß), and itpr, encoding inositol (1,4,5)-trisphosphate receptor (IP₃R), both attenuate response to diuretic peptides of Drosophila melanogaster renal (Malpighian) tubules. Intact tubules from norpA mutants severely reduced diuresis stimulated by the principal cell- and stellate cell-specific neuropeptides, CAP_2b and Drosophila leucokinin (Drosokinin), respectively, suggesting a role for PLCß in both these cell types. Measurement of IP₃ production in wild-type tubules and in Drosokinin-receptor-transfected S2 cells stimulated with CAP_2b and Drosokinin, respectively, confirmed that both neuropeptides elevate IP₃ levels.

In itpr hypomorphs, basal IP₃ levels are lower, although CAP_2b-stimulated IP₃ levels are not significantly reduced compared with wild type. However, CAP_2b-stimulated fluid transport is significantly reduced in itpr alleles. Rescue of the itpr^90B.0 allele with wild-type itpr restores CAP_2b-stimulated fluid transport levels to wild type. Drosokinin-stimulated fluid transport is also reduced in homozygous and heteroallelic itpr mutants.

Measurements of cytosolic calcium levels in intact tubules of wild-type and itpr mutants using targeted expression of the calcium reporter, aequorin, show that mutations in itpr attenuated both CAP_2b- and Drosokinin-stimulated calcium responses. The reductions in calcium signals are associated with corresponding reductions in fluid transport rates.

Thus, we describe a role for norpA and itpr in renal epithelia and show that both CAP_2b and Drosokinin are PLCß-dependent, IP₃-mobilising neuropeptides in Drosophila. IP₃R contributes to the calcium signalling cascades initiated by these peptides in both principal and stellate cells.

Key words: CAP_2b, leucokinin, photoreception, TRP, TRPL, Drosokinin, Drosophila, inositol (1,4,5)-trisphosphate receptor (IP₃R), itpr, norpA

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