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BMC Cell Biol. 2005 Aug 11;6:30.

Inhibition of dynamin-dependent endocytosis increases shedding of the amyloid precursor protein ectodomain and reduces generation of amyloid beta protein.

Author information

1
Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA 02118, USA. rmcarey@bu.edu

Abstract

BACKGROUND:

The amyloid precursor protein (APP) is transported via the secretory pathway to the cell surface, where it may be cleaved within its ectodomain by alpha-secretase, or internalized within clathrin-coated vesicles. An alternative proteolytic pathway occurs within the endocytic compartment, where the sequential action of beta- and gamma-secretases generates the amyloid beta protein (Abeta). In this study, we investigated the effects of modulators of endocytosis on APP processing.

RESULTS:

Human embryonic kidney cells were transfected with a dominant negative mutant of dynamin I, an important mediator of clathrin-dependent endocytosis, and APP proteolysis was analyzed. Overexpression of the mutant dynamin (dyn I K44A) resulted in increased shedding of the APP ectodomain (sAPPalpha), accumulation of the C-terminal alpha-secretase product C83, and a reduction in the release of Abeta. Levels of mature APP on the cell surface were increased in cells expressing dyn I K44A, and internalization of surface-immunolabeled APP, assessed by fluorescence microscopy, was inhibited. Dynamin is a substrate for protein kinase C (PKC), and it was hypothesized that activators of PKC, which are known to stimulate alpha-secretase-mediated cleavage of APP, might exert their effects by inhibiting dynamin-dependent endocytosis. However, the internalization of surface-biotinylated APP was unaffected by treatment of cells with phorbol 12-myristate 13-acetate in the presence of the alpha-secretase inhibitor TAPI-1.

CONCLUSION:

The results indicate that APP is internalized by a dynamin-dependent process, and suggest that alterations in the activity of proteins that mediate endocytosis might lead to significant changes in Abeta production.

PMID:
16095541
PMCID:
PMC1208872
DOI:
10.1186/1471-2121-6-30
[Indexed for MEDLINE]
Free PMC Article

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