One of the pathological hallmarks of Alzheimer's disease (AD) is progressive neurodegeneration in cortex and hippocampus of brain that are involved in the learning and memory. The mechanisms underlying the neurodegeneration are not clear. The broad objective of this grant is to investigate the cause for multiple lesions that result in the neurodegeneration. Preliminary data from human AD brain cortical tissue and mouse models for AD suggested that progressive mitochondrial accumulation of Alzheimer's amyloid precursor protein (APP) in a novel transmembrane arrested form may be associated with accumulation of Abeta 42 and apoptosis. A major objective is to study the role of mitochondrial targeting of APP in the pathogenesis of AD using human, animal and neuronal models of Alzheimer's disease. Specifically, we will test whether mitochondrial accumulated APP has a role in the generation and accumulation of Abeta42 a highly amyloidogenic peptide in the secretory pathway and neuronal apoptotic events that are associated with neurodegeneration in Alzheimer's disease.
Specific Aims and the experimental design to accomplish the objectives of the grant are (1) Using human, mouse and aging neuronal models of AD, the effect of PKC mediated phosphorylation on interaction of APP with SRP, Sec 61, Hsp 70 and mitochondrial transport of APP will be studied to understand the mechanism of activation of mitochondrial targeting pathway of APP (2) Characterization of role of APP mediated mitochondrial dysfunction in Abeta 42 generation in the secretory pathway in non familial AD due to the improper interaction of C-terminal 14 amino acids truncated presenilin (PS) with WT/APP will be carried out in AD brains, aging HCN-1A cells and young neuronal cells stably expressing PS and APP mutant constructs. Accumulation of Abeta 42 in the secretory pathway due to Impairment of mitochondrial function will be investigated in mouse and neuronal models of AD by assessing the interaction of vesicular transport proteins with cytosolic proteins responsible for cargo transport.(3) To study the combinatorial role of mitochondrial accumulation of APP and the accumulation of Abeta in the secretory pathway due to mitochondrial dysfunction in accelerating the neuronal degeneration in AD, experiments will be carried out using a combination of cell biological and biochemical approaches to test the modulation of PTP to release of proapoptotic factors and the activation of ER associated caspases.
