Atali_2020_FEBS.Open.Bio_10_2805

Humanin (HN) is known to bind amyloid beta (Abeta)-inducing cytoprotective effects, while binding of acetylcholinesterase (AChE) to Abeta increases its aggregation and cytotoxicity. Previously, we showed that binding of HN to Abeta blocks aggregation induced by AChE and that HN decreases but does not abolish Abeta-AChE interactions in A549 cell media. Here, we set out to shed light on factors that modulate the interactions of Abeta with HN and AChE. We found that binding of either HN or AChE to Abeta is not affected by heparan sulfate, while ATP, thought to reduce misfolding of Abeta, weakened interactions between AChE and Abeta but strengthened those between Abeta and HN. Using media from either A549 or H1299 lung cancer cells, we observed that more HN was bound to Abeta upon addition of ATP, while levels of AChE in a complex with Abeta were decreased by ATP addition to A549 cell media. Exogenous addition of ATP to either A549 or H1299 cell media increased interactions of endogenous HN with Abeta to a comparable extent despite differences in AChE expression in the two cell lines, and this was correlated with decreased binding of exogenously added HN to Abeta. Treatment with exogenous ATP had no effect on cell viability under all conditions examined. Exogenously added ATP did not affect viability of cells treated with AChE-immunodepleted media, and there was no apparent protection against the cytotoxicity resulting from immunodepletion of HN. Moreover, exogenously added ATP had no effect on the relative abundance of oligomer versus total Abeta in either cell line.