Expression of mutant amyloid precursor proteins decreases adhesion and delays differentiation of Hep-1 cells
1Molecular Neurobiology Unit, Laboratory of Cellular and Molecular Biology, Intramural Research Program, Gerontology Research Center, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA. kusiak@vax.grc.nia.hin.gov
Abstract:
The amyloid precursor protein (APP) is a type I integral membrane protein and is processed to generate several intra-cellular and secreted fragments. The physiological role of APP and its processed fragments is unclear. Several mutations have been discovered in APP, which are causative of early-onset, familial, neurological disease, including Alzheimer's disease (FAD). These mutations alter the processing of APP and lead to excess production and extra-cellular deposition of A-beta peptide (Abeta). We have examined the role of APP in a cell culture model of endothelial cell function. The endothelial cell line, Hep-1, was stably transfected with wild-type (wt) and FAD mutant forms of APP (mAPP). Secretion of sAPPalpha was reduced in cell lines over-expressing mAPP when these cells were grown on several different substrates. Levels of secreted Abeta were increased as measured by ELISA in the mutant cell lines. Cell adhesion to laminin-, fibronectin-, collagen I-, and collagen IV-coated culture flasks was reduced in all mAPP-expressing cell lines, while in lines over-expressing wt-APP, adhesiveness was slightly increased. Cell lines over-expressing mAPP differentiated more slowly into capillary network-like structures on Matrigel than those expressing wt-APP. No differences were detected among all cell lines in a migration/invasion assay. The results suggest that APP may have a role in cell adhesiveness and maturation of endothelial cells into capillary-like networks. The reduction in adhesion and differentiation in mutant cell lines may be due to reduced amounts of sAPPalpha released into the culture media or toxic effects of increased extracellular Abeta.
Insights
Amyloid precursor protein (APP) mutations impact endothelial cell function, reducing cell adhesion and capillary network formation. These changes may stem from altered APP processing, affecting sAPPalpha secretion and A-beta peptide levels.
Area of Science:
- Cell Biology
- Neuroscience
- Biochemistry
Background:
- The amyloid precursor protein (APP) is integral to cell membranes and processed into various fragments.
- The precise physiological functions of APP and its fragments remain largely unknown.
- Mutations in APP are linked to early-onset familial Alzheimer's disease (FAD), altering APP processing and increasing A-beta peptide deposition.
Purpose of the Study:
- To investigate the role of wild-type (wt) and FAD mutant APP (mAPP) in endothelial cell function using a cell culture model.
- To determine how APP mutations affect endothelial cell adhesion, differentiation, and A-beta peptide secretion.
Main Methods:
- Stable transfection of the Hep-1 endothelial cell line with wt-APP and mAPP.
- Measurement of secreted sAPPalpha and extracellular A-beta peptide levels using ELISA.
- Assessment of cell adhesion to various extracellular matrix proteins (laminin, fibronectin, collagen I, collagen IV).
- Evaluation of endothelial cell differentiation into capillary-like structures on Matrigel and migration/invasion assays.
Main Results:
- Over-expression of mAPP led to reduced sAPPalpha secretion and increased extracellular A-beta peptide levels.
- mAPP-expressing cells exhibited decreased adhesion to multiple substrates compared to wt-APP cells.
- Endothelial cells expressing mAPP showed slower differentiation into capillary-like networks on Matrigel.
- No significant differences in migration or invasion capabilities were observed between cell lines.
Conclusions:
- APP plays a role in endothelial cell adhesion and the maturation into capillary-like networks.
- FAD-associated APP mutations impair endothelial cell adhesion and differentiation.
- These impairments may result from reduced sAPPalpha secretion or toxic effects of elevated extracellular A-beta peptide.
Related Concept Videos
01:22Lysosomal Hydrolases
02:18Alternative RNA Splicing
There are five types of alternative RNA splicing that vary in the ways the pre-mRNA segments are removed or retained in the mature mRNA. The first...