Pyroglutamate-amyloid-β and glutaminyl cyclase are colocalized with amyloid-β in secretory vesicles and undergo activity-dependent, regulated secretion.

BACKGROUND AND AIMS: N-truncated pyroglutamate (pGlu)-amyloid-β [Aβ(3-40/42)] peptides are key components that promote Aβ peptide accumulation, leading to neurodegeneration and memory loss in Alzheimer's disease. Because Aβ deposition in the brain occurs in an activity-dependent manner, it is important to define the subcellular organelle for pGlu-Aβ(3-40/42) production by glutaminyl cyclase (QC) and their colocalization with full-length Aβ(1-40/42) peptides for activity-dependent, regulated secretion. Therefore, the objective of this study was to investigate the hypothesis that pGlu-Aβ and QC are colocalized with Aβ in dense-core secretory vesicles (DCSV) for activity-dependent secretion with neurotransmitters.
METHODS: Purified DCSV were assessed for pGlu-Aβ(3-40/42), Aβ(1-40/42), QC, and neurotransmitter secretion. Neuron-like chromaffin cells were analyzed for cosecretion of pGlu-Aβ, QC, Aβ, and neuropeptides. The cells were treated with a QC inhibitor, and pGlu-Aβ production was measured. Human neuroblastoma cells were also examined for pGlu-Aβ and QC secretion.
RESULTS: Isolated DCSV contain pGlu-Aβ(3-40/42), QC, and Aβ(1-40/42) with neuropeptide and catecholamine neurotransmitters. Cellular pGlu-Aβ and QC undergo activity-dependent cosecretion with Aβ and enkephalin and galanin neurotransmitters. The QC inhibitor decreased the level of secreted pGlu-Aβ. The human neuroblastoma cells displayed regulated secretion of pGlu-Aβ that was colocalized with QC.
CONCLUSIONS: pGlu-Aβ and QC are present with Aβ in DCSV and undergo activity-dependent, regulated cosecretion with neurotransmitters.