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In vivo analysis of lipid phosphate phosphohydrolase function in Drosophila photoreceptors

Reference	BB/C516887/1
Principal Investigator / Supervisor	Professor Raghu Padinjat
Co-Investigators / Co-Supervisors
Institution	Babraham Institute
Department	External Funding Office
Funding type	Research
Value (£)	175,870
Status	Completed
Type	Research Grant
Start date	01/02/2006
End date	31/01/2009
Duration	36 months

Abstract

Bioactive lipid second messengers such as phosphatidic acid (PA) and related lysolipid phosphates (lysophosphatidic acid [LPA], sphingosine-1-phosphate [S1P],ceramide-1-phosphate [C1P] and diacyglycerol pyrophosphate [DGPP]) exert numerous effects on important cellular functions such as proliferation, changes in cell shape, cell migration and programmed cell death. A common structural feature of these lipids is the presence of a terminal phosphomonoester group; removal of this critical group results in functional inactivation of these messengers. Lipid phosphate phosphohydrolases (LPPs) are enzymes that catalyse this reaction. In vitro analysis of LPPs overexpressed in mammalian cell lines has raised two key questions: (1) Are LPPs ectoenzymes that work on extracellular bioactive lipids or can they work on phosphatidic acid generated by intracellular signalling cascades? (2) How do LPPs, enzymes that show considerable substrate promiscuity in vitro, regulate the levels of different lipid messengers with distinct cellular roles in vivo? An important factor limiting the resolution of these two key questions, is that to date there is no identified LPP that functions in the context of a well-defined signalling cascade. We have identified ey-PAP, one of seven LPP genes in the completed Drosophila genome as an eye-enriched gene. Preliminary experiments strongly suggest that ey-PAP functions in Drosophila phototransduction, a well-defined signalling cascade, amenable to genetic analysis in vivo. In this proposal, we intend to analyse the function of ey-PAP during light induced phosphoinositide hydrolysis. Using a combination of molecular genetics, biochemistry and patch-clamp electrophysiology we propose to answer three key questions: (1) Does ey-PAP regulate the levels of PA generated during light induced PIP2 hydrolysis in Drosophila photoreceptors? (2) Does ey-PAP contribute to the amplification of the phototransduction cascade currently thought to depend on the balanceof PA/DAG generated during phosphoinositide hydrolysis? (3) Is ey-PAP the only Drosophila LPP with appropriate substrate specificity to regulate photoreceptor PA levels in in vivo? The results of this study will clarify whether LPPs regulate PA levels during phosphoinositide hydrolysis, a key intracellular cascade that regulates a number of cellular functions. They will also provide the first in vivo analysis of the substrate specificity of a class of enzymes that modulate the levels of a number of key bioactive lipid second messengers in animal cells.

Summary

unavailable

Committee	Closed Committee - Biochemistry & Cell Biology (BCB)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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