Alzheimer beta/A4-amyloid precursor protein: evidence for putative amyloidogenic fragment

J Neurochem. 1992 Jan;58(1):383-6. doi: 10.1111/j.1471-4159.1992.tb09322.x.


Recombinant baculovirus was used to overexpress human Alzheimer beta/A4-amyloid precursor protein (APP) in Spodoptera frugiperda (Sf9) cells. Lysates of these cells were then analyzed for the presence of carboxyl-terminal fragments of APP by an immunoblotting assay using either an antibody against the APP cytoplasmic domain (rabbit anti-human 695APP645-694) or an antibody against the amino terminus of beta/A4-amyloid (rabbit anti-human 695APP586-606). Anti-human 695APP645-694 identified APP holoprotein, a 25-kDa species, and a prominent group of carboxyl-terminal fragments of 17, 16, and 14 kDa, whereas anti-human 695APP586-606 identified APP holoprotein and a single prominent low-molecular-mass protein species comigrating with the 17-kDa carboxyl-terminal fragment identified by anti-human 695APP645-694. No immunoreactive species was detected at these molecular mass positions when either antibody was used for analysis of lysates of either uninfected Sf9 cells or Sf9 cells infected with wild-type Autographa californica baculovirus. For each antibody, specific immunoreactivity was abolished by preabsorption with the corresponding peptide immunogen. The incorporation of a beta/A4-amyloid amino-terminal epitope into a 17-kDa fragment of APP suggests that, in the baculoviral overexpression system, the electrophoretic microheterogeneity of APP carboxyl-terminal fragments is due, at least in part, to alternative proteolysis of APP. If such carboxyl-terminal fragments of APP containing an intact beta/A4-amyloid domain are produced in human brain, then they may represent intermediates in the conversion of APP to deposited beta/A4-amyloid.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alzheimer Disease / metabolism*
  • Amyloid / biosynthesis*
  • Amyloid beta-Peptides / metabolism*
  • Amyloid beta-Protein Precursor
  • Baculoviridae / genetics
  • Baculoviridae / metabolism
  • Cell Line
  • Humans
  • Peptide Fragments / metabolism*
  • Protein Precursors / metabolism*
  • Recombination, Genetic
  • Virus Diseases / metabolism


  • Amyloid
  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Peptide Fragments
  • Protein Precursors