PgmNr D1378: Uncovering cellular energetics at the neuromuscular junction in a Drosophila model of ALS.

Authors:
E. Manzo 1 ; I. Lorenzini 2 ; A. Joardar 1 ; A. O'Conner 1 ; J. Barrows 1 ; R. Sattler 2 ; D. Zarnescu 1


Institutes
1) University of Arizona, Tucson, AZ; 2) Barrow Neurological Institute, Phoenix, AZ.


Keyword: neural disorder

Abstract:

Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig's Disease, is a fatal neurodegenerative disorder affecting upper and lower motor neurons. TAR DNA-binding protein 43 (TDP-43) is found in cytoplasmic inclusions in almost all non-SOD1 mediated ALS cases and is thought to play a major role in pathogenesis of the disease. Our lab has previously shown that overexpression of either wild type or mutant human TDP-43 in motor neurons of Drosophila melanogaster induces motor deficits and reduces lifespan. Using this model we have performed global metabolomics profiling and identified several significant changes consistent with alterations in glucose and lipid metabolism. Specifically, increased pyruvate in both TDPWT and disease associated TDPG298S models is suggestive of altered glucose metabolism. We also found increased tricarboxylic (TCA) cycle intermediates and pyruvate, which are also upregulated in plasma from ALS patients. Based on these preliminary results we hypothesize that improving glucose and lipid metabolism through genetic and dietary intervention can provide protection against neurodegeneration. We employed molecular and genetic techniques to determine the basis of altered glucose metabolism. Our preliminary data indicate that a high sugar diet, or the genetic expression of either the human glucose transporters 3 or 4 (Glut3 or Glut4) in motor neurons, suppresses toxic effects caused by of TDP-43. Additionally, Glut3 expression is altered in both fly and human iPS motor neurons (MNs) . To further test whether the expression of TDP-43 affects glucose transporter dynamics, we have used total internal reflection fluorescence (TIRF) microscopy, and found that in primary MNs expressing TDPWT, there are comparable levels of Glut4-GFP at the plasma membrane immediately after insulin stimulation. In contrast, 14 min after stimulation, Glut4-GFP persists at the surface in TDP-43 expressing cells but not in controls. These data suggest Glut3/Glut4 alterations in expression and dynamics, in both both fly and iPS MNs, and are consistent with defects in glycolysis identified through metabolomics.  Indeed, pfk mRNA, a key indicator of glycolytic activity is significantly upregulated in TDP-43 expressing flies and iPS MNs with TDP-43 pathology. Taken together, our findings indicate specific metabolic alterations in ALS and highlight the predictive power of Drosophila as a model organism for human disease.