Inhibition of cathepsin B reduces beta-amyloid production in regulated secretory vesicles of neuronal chromaffin cells: evidence for cathepsin B as a candidate beta-secretase of Alzheimer's disease

Biol Chem. 2005 Sep;386(9):931-40. doi: 10.1515/BC.2005.108.


The regulated secretory pathway of neurons is the major source of extracellular A beta that accumulates in Alzheimer's disease (AD). Extracellular A beta secreted from that pathway is generated by beta-secretase processing of amyloid precursor protein (APP). Previously, cysteine protease activity was demonstrated as the major beta-secretase activity in regulated secretory vesicles of neuronal chromaffin cells. In this study, the representative cysteine protease activity in these secretory vesicles was purified and identified as cathepsin B by peptide sequencing. Immunoelectron microscopy demonstrated colocalization of cathepsin B with A beta in these vesicles. The selective cathepsin B inhibitor, CA074, blocked the conversion of endogenous APP to A beta in isolated regulated secretory vesicles. In chromaffin cells, CA074Me (a cell permeable form of CA074) reduced by about 50% the extracellular A beta released by the regulated secretory pathway, but CA074Me had no effect on A beta released by the constitutive pathway. Furthermore, CA074Me inhibited processing of APP into the COOH-terminal beta-secretase-like cleavage product. These results provide evidence for cathepsin B as a candidate beta-secretase in regulated secretory vesicles of neuronal chromaffin cells. These findings implicate cathepsin B as beta-secretase in the regulated secretory pathway of brain neurons, suggesting that inhibitors of cathepsin B may be considered as therapeutic agents to reduce A beta in AD.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alzheimer Disease / enzymology
  • Alzheimer Disease / metabolism*
  • Amino Acid Sequence
  • Amyloid Precursor Protein Secretases
  • Amyloid beta-Peptides / antagonists & inhibitors
  • Amyloid beta-Peptides / biosynthesis*
  • Amyloid beta-Peptides / metabolism
  • Animals
  • Cathepsin B / antagonists & inhibitors*
  • Cathepsin B / isolation & purification
  • Cathepsin B / metabolism
  • Cattle
  • Chromaffin Cells / drug effects
  • Chromaffin Cells / enzymology
  • Chromaffin Cells / metabolism*
  • Cysteine Endopeptidases / metabolism
  • Cysteine Proteinase Inhibitors / pharmacology
  • Endopeptidases / metabolism*
  • Molecular Sequence Data
  • Neurons / drug effects
  • Neurons / enzymology
  • Neurons / metabolism*
  • Secretory Vesicles / enzymology
  • Secretory Vesicles / metabolism*


  • Amyloid beta-Peptides
  • Cysteine Proteinase Inhibitors
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Cysteine Endopeptidases
  • Cathepsin B