Complementary mass spectrometry based detection of gangliosides and other lipids in the brain

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Rationale: Gangliosides are a major class of glycosphingolipids enriched within the central nervous system (CNS), and like other lipids in the brain play a major role in a wide range of activities including membrane function, axon stability and regeneration, differentiation and neurodegeneration. Using NSERC funding, our lab has developed and used complementary mass spectrometry (MS) approaches including imaging mass spectrometry (IMS) to show that neurons are highly sensitive to changes within the lipid microenvironment. Specifically, we've published that harmful gangliosides GM2 and GM3 are transiently increased following stressful stimuli to neurons in the mouse and rat and brain and that enhancing neuroprotective ganglioside GM1 protects neurons from cell death in vitro and in vivo. Based on these published and preliminary studies we hypothesize that gangliosides GM2 and GM3 are transiently increased following neuronal stress. We further predict that preventing the breakdown of GM1 into GM2 and GM3 can prevent neurodegeneration. Objectives: This proposal builds upon our current NSERC funding with the following objectives: 1) Use siRNA approaches both in vitro and in vivo to target enzymes within the ganglioside degradation pathway to transiently increase GM1 within neurons. This will allow us to test the hypothesis that intrinsically and transiently increasing GM1 can protect neurons against cell death. 2) Build and expand our current lipidomic program by extending imaging mass spectrometry capabilities to detect and image other classes of lipids such as glycerophospholipids and sphingolipids in rodent models of aging and neurodegeneration Approach: Gangliosides, like other lipids, are contained within different cellular compartments of the brain and have the ability to change their structure to meet their external and internal environmental demands. This ability to change structure makes lipids both fascinating and technologically challenging targets to identify and understand. To meet this challenge, we employ complementary mass spectrometry (MS) techniques, including imaging mass spectrometry (IMS) to detect and image gangliosides directly within brain tissue. We will use pharmacological and siRNA mediated intervention to prevent the breakdown of GM1 into GM2 and GM3 to further validate that GM2 and GM3 are fundamental mediators of neurodegeneration. Finally, we will expand our IMS capabilities to image additional lipids within the brain to gain a better understanding on the role for lipids in mediating vulnerability to neurodegeneration. Significance: This proposal will add knowledge on the role of gangliosides and other lipids in mediating neuronal vulnerability and neurodegeneration. This proposal will also push the boundaries of IMS based detection of lipids within intact tissue samples.