The Amyloid Precursor Protein Is Not Enriched in Caveolae-Like, Detergent-Insoluble Membrane Microdomains |
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Authors: | Edward T Parkin Ishrut Hussain Anthony J Turner Nigel M Hooper |
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Institution: | Department of Biochemistry and Molecular Biology, University of Leeds, Leeds, England |
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Abstract: | Abstract: The amyloid precursor protein may be processed by several different pathways, one of which produces the amyloid β-peptide βA4 present in the amyloid plaques characteristic of Alzheimer's disease. A recent report suggested that axonal-amyloid precursor protein is present in a membrane fraction "with caveolae-like properties." In the present study we have isolated detergent-insoluble, caveolae-like membranes from both mouse cerebellum and the human neuroblastoma cell line SH-SY5Y. Detergent-insoluble membranes from mouse cerebellum retained nearly all of the glycosylphosphatidylinositol-anchored proteins—alkaline phosphatase, 5'-nucleotidase, and the F3 protein—while excluding the majority of the plasmalemmal marker protein alkaline phosphodiesterase I. Although the inositol trisphosphate receptor was highly enriched in this detergent-insoluble fraction, neither amyloid precursor protein nor clathrin immunoreactivity could be detected. Similar results were obtained with SH-SY5Y cells, where 5'-nucleotidase activity was enriched at least 30-fold in the detergent-insoluble membranes, but no amyloid precursor protein or clathrin immunoreactivity could be detected. Caveolin could not be detected in microsomal membranes from either mouse cerebellum or SH-SY5Y cells. These observations suggest that amyloid precursor protein is not normally present in detergent-insoluble, caveolae-like membrane microdomains. |
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Keywords: | Amyloid precursor protein Caveolae Clathrin-coated vesicles Detergent-insoluble membranes Glycosylphosphatidylinositol anchor |
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