Expression of the amyloid precursor protein of Alzheimer's disease on the surface of transfected HeLa cells.
The principal component of the amyloid which accumulates in Alzheimer's Disease brain is a 4-kDa beta A4 fragment of the amyloid precursor protein (APP). Although APP has the structural features of an integral transmembrane receptor, there has been limited evidence for expression of APP at the plasma membrane. The function of APP and related molecules is unknown. Using rabbit antisera to purified human brain APP, surface labeling of APP is demonstrable in HeLa cells transfected with the APP695 isoform. Indirect immunofluorescence indicates the presence of APP at the surface of unfixed or aldehyde-fixed cells; preembedding immunoelectron microscopy using 5- or 1-nm gold particles and silver enhancement confirms plasma membrane labeling as well as labeling within intracellular membrane vesicles. Immunolabeling of unfixed cells at 4 degrees C followed by incubation at 37 degrees C shows APP within endocytic vesicles. Transfected HeLa cells with prominent surface APP were larger with more extensive microvilli than nonimmunoreactive HeLa cells. This is consistent with the postulated role of APP as a mediator of cell surface adhesion and membrane-matrix stabilization.
Culvenor
J G
JG
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
Friedhuber
A
A
Fuller
S J
SJ
Beyreuther
K
K
Masters
C L
CL
D000544:Alzheimer Disease / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000032:analysis / Q000096:biosynthesis*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D007106:Immune Sera; D016253:Microscopy, Immunoelectron; D011817:Rabbits / Q000276:immunology; D011994:Recombinant Proteins / Q000032:analysis / Q000096:biosynthesis; D014162:Transfection
D016564:Amyloid beta-Protein Precursor; D007106:Immune Sera; D011994:Recombinant Proteins