The amyloid precursor protein is not enriched in caveolae-like, detergent-insoluble membrane microdomains.
The amyloid precursor protein may be processed by several different pathways, one of which produces the amyloid beta-peptide betaA4 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.
Parkin
E T
ET
Department of Biochemistry and Molecular Biology, University of Leeds, England, U.K.
Hussain
I
I
Turner
A J
AJ
Hooper
N M
NM
D016564:Amyloid beta-Protein Precursor / Q000032:analysis*; D000818:Animals; D015415:Biomarkers; D015220:Calcium Channels / Q000032:analysis; D051242:Caveolin 1; D022461:Caveolins; D002462:Cell Membrane / Q000737:chemistry*; D002531:Cerebellum / Q000737:chemistry*; D003902:Detergents; D017261:Glycosylphosphatidylinositols / Q000032:analysis; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008565:Membrane Proteins / Q000032:analysis*; D051379:Mice; D008809:Mice, Inbred C3H; D009447:Neuroblastoma; D017830:Octoxynol; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D011092:Polyethylene Glycols; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis; D012995:Solubility; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases
D016564:Amyloid beta-Protein Precursor; D015415:Biomarkers; C495540:CAV1 protein, human; D015220:Calcium Channels; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D003902:Detergents; D017261:Glycosylphosphatidylinositols; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008565:Membrane Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase