The role of PP2a in regulating postembryonic neurogenesis in the fly, Drosophila melanogaster
CALS Impact Statement
Using a series of molecular markers and genetic tools, we established that PP2A activity is required for a number of key steps in the morphogenesis of Drosophila`s eye and wing discs. Interestingly, PP2A acts as a positive regulator of EGFR and wingless signaling pathways in the eye and wing discs respectively. Our results also suggest that in the developing eye and wing discs that tws is primarily a regulatory subunit involved in regulating PP2A activity. Our data reveals a role for PP2A/tws activity in regulating postembryonic neurogenesis in the larval central nervous system. Our data suggests that PP2A/tws interacts with the Ras/Mapk signaling pathway. However we have yet to identify receptor(s) involved in regulating neurogenesis within the larval central nervous system.
In the average eukaryotic cell, one out of three proteins undergo reversible phosphorylation. While there has been a major focus on the role of kinases in the regulation of signaling pathways, it is now apparent that protein phosphatases are highly regulated enzymes that play a key role in the control of protein phosphorylation and of signaling activity. Based on in vitro biochemical studies, Protein Phosphatase 2A (PP2A) is predicted to play a key role in almost all cellular processes. However, it is puzzling to reconcile the broad range of possible PP2A substrates in vitro with the exquisite temporal and spatial specificity required of PP2A-dependent dephosphorylation events in vivo. One solution to this puzzle is offered by variation in the availability of the regulatory subunits that associate with the PP2A catalytic subunit. It is thought that variation in associated regulatory subunits is responsible for targeting PP2A-mediated dephosphorylation. One prediction of this model is that the lack of a specific regulatory subunit in vivo will result in a defect in a specific range of dephosphorylation reactions, while retaining the ability to perform another set of reactions. However, in most instances it is difficult to test this prediction. We will exploit the genetic and molecular tools available for Drosophila to test the function role of PP2A and its regulator subunits of PP2A in regulating the development of Drosophila's nervous system
Our preliminary data suggests that PP2A activity plays a key role in regulating a number of key signaling pathways during eye development. Early in eye development PP2A activity plays a role in the specification of the eye. Later PP2A activity is required for the specification of a subset of the photoreceptors and supporting cells in the developing retina. Our results also reveal that the role of PP2A in regulating these events is dependent upon the B regulatory subunit associated with the holoenzyme. At each of these steps the heterotrimeric Protein Phosphatase 2A (PP2A) plays a key role in regulating neurogenesis by targeting the Ras/Erk signaling pathway. Based on these data we hypothesize that altering the B regulatory subunits will allow the PP2A holoenzyme to target different components of the Ras/Erk pathway. In an effort to address this hypothesis on the role of PP2A in regulating neurogenesis, the following specific aims are proposed:
This project is designed to have an impact beyond advancing the discovery and understanding of the regulation of protein phosphatases. Included in the proposal is a request for funds to support the training of both graduate and undergraduate research assistants. A special effort will be made to use this project as a vehicle to recruit and underrepresented minorities for these positions. Our laboratory has a long and strong track record on involving minority students in our research activities. Currently, two of the four of undergraduate research assistants working in the laboratory are under members of represented minorities and we regularly host minority undergraduates from other campuses participating in Cornell's Leadership Alliance Summer Research Program.