Chloroquine inhibits intracellular degradation but not secretion of Alzheimer β/A4 amyloid precursor protein

Gregg L. Caporaso, Samuel E. Gandy, Joseph D. Buxbaum, Paul Greengard

Research output: Contribution to journalArticlepeer-review

196 Scopus citations

Abstract

The metabolic fate of the Alzheimer β/A4 amyloid precursor protein (APP) includes intraamyloid proteolysis that leads to the production of secreted N-terminal and cell-associated C-terminal fragments. The cellular sites at which this processing occurs are not known. We have examined the route of APP processing in metabolically labeled PC12 cells. The lysosomotropic drug chloroquine exerted inhibitory effects on the degradation of mature APP holoprotein. In addition, recovery of a C-terminal fragment resulting from normal intraamyloid cleavage was significantly increased in the presence of chloroquine, suggesting that further degradation of the C-terminal fragment was inhibited. Chloroquine had virtually no effect on APP maturation (N- and O-glycosylation and tyrosine sulfation) or secretion. Treatment with either monensin (which inhibits distal Golgi function) or brefeldin A (which causes resorption of the Golgi into the endoplasmic reticulum and fusion of the trans-Golgi network with the endosomal system) prevented normal APP maturation and abolished APP secretion and recovery of C-terminal fragments, indicating that intact Golgi function is necessary for APP maturation and processing. Our results suggest that a substantial proportion of APP is degraded in an intracellular acidic compartment but that the coupled APP cleavage/secretion event occurs in a chloroquine-insensitive compartment. The observations are consistent with the existence of multiple cellular routes for the trafficking and proteolysis of APP. (.

Original languageEnglish
Pages (from-to)2252-2256
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume89
Issue number6
DOIs
StatePublished - 1992
Externally publishedYes

Keywords

  • Brefeldin A
  • Dementia
  • Monensin
  • Proteolysis

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