The combination of SAXS with computational biology techniques can provide insight to understand the neuroprotective effect of GAPDH protofibrils

AVILA CL; BARBOSA LR,; ITRI R,; CHEHÍN RN

Mar del Plata

Congreso; X Reunion Anual de la Asociación Argentina de Cristalografia; 2014

Asociación Argentina de Cristalografia

Parkinson disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra of the midbrain. Although the precise causes of cell death are unknown, the misfolding and aggregation of alfa-synuclein (AS) is almost certainly involved in PD pathogenesis. Neurotoxicity is currently attributed to certain oligomeric intermediates formed during the aggregation pathway of AS, which can alter membrane permeability and promote mitochondrial, proteasomal and membrane trafficking dysfunction [1]. We have conducted in vitro experiments on SH-SY5Y cells showing that the toxicity exerted by AS could be abolished by protofibrilar species of Glyceraldehide-3-phosphate dehydrogenase (GAPDH) that are formed in the presence of glycosamineglycanes [2]. Indeed, GAPDH and glycosamineglycanes were found associated to AS fibrillar deposits in Parkinson disease [3]. Using SAXS and computational modelling we characterized the structure of GAPDH protofibrils at the atomic level and proposed that the toxic oligomers of AS might be sequestered by interaction with an hydrophobic patch present at the protofibril´s end (Figure 1) [2]. The described mechanism for the mitigation of AS toxicity might be relevant at the extracellular space, where both GAPDH and glycosamineglycanes are present [4], inhibiting the spreading of the disease. We conducted molecular dynamic studies in order to understand how glycosamineglycanes interact with GAPDH, driving the conformational changes that result in dissociation of the protein from the native tetrameric state into dimers which constitute the building block for the formation of the protofibrils. This information constitutes the first step to design small organic molecules that could be administered to reinforce the protective mechanism of formation of GAPDH protofibrils at the extracellular level, without interfering with the cytosolic GAPDH. [1] R. Kodali and R. Wetzel, Curr Opin Struct Biol. 17(2007): p. 48-57. [2] A.J. Rzepiela, et al., J Comput Chem. 31(2010): p. 1333-43. [3] J. Olah, et al., FEBS Lett. 580(2006): p. 5807-14. [4] R. Yamaji, et al., Biochim Biophys Acta. 1726(2005): p. 261-71.