P3‐001: Expression of Alzheimer‐like pseudophosphorylated tau at Thr212, Thr231 and Ser262 induces a behavioral defect in drosophila melanogaster

Background: The protein tau is one of the major microtubule-binding proteins. It regulates the stability and organization of microtubules, a process controlled by its phosphorylation level. Normal tau contains 2-3 mol of phosphate per mole of protein. Tau is hyperphosphorylated in Alzheimer’s disease and related disorders collectively referred to as tauopathies. This abnormal tau aggregates into neurofibrillary tangles, does not promote microtubule assembly, binds normal tau and inhibits tau-promoted microtubule assembly. It has not been established whether hyperphosphorylation of tau is a cause or consequence of the process of neurodegeneration. In in vitro studies we recently demonstrated that hyperphosphorylated tau promotes neurodegeneration and that the combination of phosphorylation at Thr212, Thr231 and Ser262 produces a toxic effect in the cell (Alonso et al., 2010). Drosophila melanogaster expressing normal or pathogenic human tau develop several pathological features of human disorders, including adult-onset, age-dependent neuronal degeneration and shortened lifespan. We used Drosophila to evaluate the in vivo mechanisms of tau toxicity induced by phosphorylation. Methods: Transgenic flies expressing tau pseudohyperphosphorylated at Thr212, Thr231, and Ser262 (Pstau) mutated in combination by site-directed mutagenesis to Glu were generated. They were under the control of a yeast upstream activating sequence. Ps-tau was expressed in a panneural pattern (elav-GAL4) in the background of wild-type tau (wt-Ps-tau), or FTDP-17 (R406W) mutant tau (R406W-Ps-tau). Results: The lifespan of wt-Ps-tau and R406W-Pstau flies were the same or moderately shortened than flies expressing the wild-type tau, R406W mutant tau and control flies. The expression of Pstau induced locomotors defects (climbing assay) that showed tobe age-dependent. At 20 days old, R406W-Ps-tau flies showed a stronger locomotor dysfunction compare to flies expressing the R406W mutant tau or control flies (60%, 33% and 9% of flies on the bottom respectively). Immunohistological studies on fly brain were carried out to examine neurodegeneration. Our preliminary results showed that brains of flies that expressedPs-tau becamedamaged compared to control fly brain. Conclusions: Our findings show that pseudophosphorylated tau at Thr212, Thr231 and Ser262 induced a toxic effect in Drosophila. The lifespan of the Ps-tau flies was not strongly affected, but most of them survived with a disrupted behavior.