Abstract Body

It is largely unknown when and what kind of molecular events initiate Alzheimer’s disease pathology. We asked this question by comprehensive mass analysis detecting 70,000-100,000 phosphopeptides (confidence>95%) from cerebral cortex tissues of four AD mouse models at multiple time points together with human AD brains, and discovered several proteins whose phosphorylation states were changed before appearance of extracellular Abeta aggregates.

The first one was pSer46-MARCKS, which was mainly localized in degenerative neurites. Antibody against pSer46-MARCKS was very sensitive and detected a single necrotic neuron with intracellular Abeta accumulation surrounded by degenerative neurites. Chronological changes of morphology suggested that residual Abeta after primary necrosis became the seed for extracellular Abeta aggregates and induced secondary necrosis of surrounding neurons.

Intracellular Abeta interacted with YAP, an essential molecule for cell survival, deprived it from nucleus, suppressed TEAD-YAP-dependent transcription, and finally induced necrosis. Gene therapy with AAV expressing YAPdeltaC, a neuron-specific isoform lacking the binding domain for p73 but able to interact with TEAD, suppressed necrosis and decreased extracellular Abeta aggregates in mouse models at later time points.

Secondary necrosis was mediated by Abeta and HMGB1 both released from necrotic neurons as DAMPs, while the ability of HMGB1 to induce neurite degeneration was higher than Abeta. HMGB1 is also well known as a ligand of TLR2/4, and triggers brain inflammation. In this regard, we have developed anti-HMGB1 antibody that effectively inhibits secondary necrosis and neurite degeneration in mouse models.

We revealed the ultra-early phase pathology and molecular targets for tacking the initial molecular branches.