Intracellular localization of amyloid beta peptide in SH-SY5Y neuroblastoma cells

• Amyloid-beta peptide (A beta), the main component of Alzheimer's disease (AD) senile plaques, has been found to accumulate within the lysosomal compartment of AD neurons. We have previously shown that in differentiated SH-SY5Y neuroblastoma cells cultured under normal conditions, the majority of A beta is localized extralysosomally, while oxidative stress significantly increases intralysosomal A beta content through activation of macroautophagy. It is, however, not clear which cellular compartments contain extralysosomal A beta in intact SH-SY5Y cells, and how oxidative stress influences the distribution of extralysosomal A beta. Using confocal laser scanning microscopy and immunoelectron microscopy, we showed that in differentiated neuroblastoma cells cultured under normal conditions A beta (A beta(40), A beta(42), and A beta oligomers) is colocalized with both membrane-bound organelles (endoplasmic reticulum, Golgi complexes, multivesicular bodies/late endosomes, lysosomes, exocytotic vesicles and mitochondria) and non-membrane-bound cytosolic structures. Neuroblastoma cells stably transfected with A beta PP Swedish KM670/671NL double mutation showed enlarged amount of A beta colocalized with membrane compartments. Suppression of exocytosis by 5 nM tetanus toxin resulted in a significant increase of the amount of cytosolic A beta as well as A beta colocalized with exocytotic vesicles, endoplasmic reticulum, Golgi complexes, and lysosomes. Hyperoxia increased A beta localization in the endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes, but not in the secretory vesicles. These results indicate that in SH-SY5Y neuroblastoma cells intracellular A beta is not preferentially localized to any particular organelle and, to a large extent, is secreted from the cells. Challenging cells to hyperoxia, exocytosis inhibition, or A beta overproduction increased intracellular A beta levels but did not dramatically changed its localization pattern.

Nyckelord

Alzheimer’s disease

Amyloid β-protein

Endosomes

Exocytosis

Lysosomes

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