P1.19. LOST ENZYME, LOST INTEGRITY: ARGINASE 2 DELETION DISRUPTS MITOCHONDRIA IN STRIATAL NEURONS
Martyna Nalepa1, Jakub Szymanowski2, Aleksandra Skweres1, Katarzyna Czarnecka1, Aleksandra Owczarek1, Magdalena Gewartowska3, Karolina Szczepanowska4, Michał Węgrzynowicz1
1 Mossakowski Medical Research Institute, Polish Academy of Sciences, Laboratory of Molecular Basis of Neurodegeneration, 5 Pawinskiego St.,Warsaw, Poland
2 Mossakowski Medical Research Institute, Polish Academy of Sciences, Laboratory of Advanced Microscopy Techniques, 5 Pawinskiego St., Warsaw, Poland
3 Mossakowski Medical Research Institute, Polish Academy of Sciences, Electron Microscopy Research Unit, 5 Pawinskiego St., Warsaw, Poland
4 International Institute of Molecular Mechanisms and Machines, Polish Academy of Sciences, Laboratory of Metabolic Quality Control, 6 Flisa St., Warsaw, Poland
INTRODUCTION: Arginase 2 (Arg2) is the major cerebral arginase isoenzyme highly enriched in the striatum, a brain region critical for motor control and selectively affected in Huntingtons’ disease (HD). Although Arg2 loss precedes symptom onset in HD mouse models, its role in striatal pathology remains unclear.
AIM(S): This study aimed to determine cellular localization of striatal Arg2 and assess the consequences of its loss to define its potential involvement in HD pathogenesis.
METHOD(S): Immunohistochemistry was used to identify Arg2-expressing cells. A deep learning-based segmentation and quantification tool (Cellpose), enabled precise unbiased image analysis. The effects of Arg2 loss on the striatum were investigated using Arg2 knockout (Arg2 / ) mice. High-resolution NMR spectroscopy was used to compare striatal metabolite profiles in control and Arg2 / mice. Proteomic differences were assessed with LC-MS, and the integrity of electron transport chain (ETC) complexes was analyzed using blue native (BN) gel electrophoresis. Neuronal mitochondria ultrastructure was examined by electron microscopy (EM).
RESULTS: Arg2 was found to be selectively localized in medium spiny neurons (MSNs), the major projecting neurons of the striatum and primary target in HD. NMR revealed distinct metabolic profiles between control and Arg2-/- mice. Proteomic profiling revealed reduced levels of mitochondrial ETC subunits and BN gels showed decreased assembly of complexes I, III and IV. EM showed mitochondria swelling, cristae disruption, and increased fragmentation Arg2-/- neurons.
CONCLUSIONS: These findings emphasize a crucial role for Arg2 in maintaining striatal metabolism and mitochondrial integrity in MSNs. Given the selective expression of Arg2 in this neuronal population and its early loss in HD models, Arg2 may contribute to the selective vulnerability of MSNs in HD.
FINANCIAL SUPPORT: National Science Centre, Poland (2018/30/E/NZ1/00144) and MMRI PAS (Internal Fund 040)