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Related Concept Videos

Amyloid Fibrils03:03

Amyloid Fibrils

Amyloid fibrils are aggregates of misfolded proteins.  Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils. 
Amyloid deposits were observed as early as 1639 in the liver and the spleen.   In 1854, Rudolph Virchow performed iodine staining, normally used to...
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Lysosomal Hydrolases01:22

Lysosomal Hydrolases

Lysosomes are the site for the degradation of macromolecules and biological polymers released during membrane trafficking events such as secretory, endocytic, autophagic, and phagocytic pathways. The membrane-enclosed area of the lysosome, called the lumen, contains hydrolytic enzymes active in an acidic environment. These acid hydrolases are functional at a pH between 4.5 and 5 and are involved in cellular processes such as cell signaling, energy metabolism, restoration of the plasma membrane,...
Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
Amyloid Fibrils03:03

Amyloid Fibrils

Amyloid fibrils are aggregates of misfolded proteins.  Under most circumstances, misfolded proteins are either refolded by chaperone proteins or degraded by the proteasome. However, in the case of a mutation or a disease, these proteins can accumulate to form large clusters and often further assemble to form elongated fibers, called fibrils. 
Amyloid deposits were observed as early as 1639 in the liver and the spleen.   In 1854, Rudolph Virchow performed iodine staining, normally used to...
The Proteasome01:13

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...

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Related Experiment Video

Updated: Jul 18, 2026

Purification and Aggregation of the Amyloid Precursor Protein Intracellular Domain
10:08

Purification and Aggregation of the Amyloid Precursor Protein Intracellular Domain

Published on: August 28, 2012

Amyloid beta/A4 precursor protein (APP) processing in lysosomes.

K Tagawa1, K Maruyama, S Ishiura

  • 1National Institute of Neuroscience, NCNP, Tokyo, Japan.

Annals of the New York Academy of Sciences
|December 31, 1992
PubMed
Summary

Cathepsin B acts as an enzyme in processing amyloid precursor protein (APP), potentially contributing to Alzheimer's disease pathogenesis by cleaving APP into specific fragments.

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Imaging the Intracellular Trafficking of APP with Photoactivatable GFP
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Saccharomyces cerevisiae Models of Alzheimer's Disease to Screen Genes, Mutations, and Chemicals Affecting Amyloid Beta Production by γ-Secretase
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Saccharomyces cerevisiae Models of Alzheimer's Disease to Screen Genes, Mutations, and Chemicals Affecting Amyloid Beta Production by γ-Secretase

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Last Updated: Jul 18, 2026

Purification and Aggregation of the Amyloid Precursor Protein Intracellular Domain
10:08

Purification and Aggregation of the Amyloid Precursor Protein Intracellular Domain

Published on: August 28, 2012

Imaging the Intracellular Trafficking of APP with Photoactivatable GFP
07:55

Imaging the Intracellular Trafficking of APP with Photoactivatable GFP

Published on: October 17, 2015

Saccharomyces cerevisiae Models of Alzheimer's Disease to Screen Genes, Mutations, and Chemicals Affecting Amyloid Beta Production by γ-Secretase
11:57

Saccharomyces cerevisiae Models of Alzheimer's Disease to Screen Genes, Mutations, and Chemicals Affecting Amyloid Beta Production by γ-Secretase

Published on: June 24, 2025

Area of Science:

  • Neuroscience
  • Biochemistry
  • Molecular Biology

Background:

  • Alzheimer's disease (AD) is linked to amyloid beta protein plaques.
  • Amyloid precursor protein (APP) processing is crucial in AD pathogenesis.

Purpose of the Study:

  • To investigate the role of cathepsin B as a potential secretase for APP.
  • To determine if lysosomal cathepsin B is involved in constitutive APP processing.

Main Methods:

  • Utilized APP-transfected COS-1 cells for experimental analysis.
  • Conducted digestion experiments to assess cathepsin B activity on APP.

Main Results:

  • Confirmed cathepsin B's involvement in constitutive APP processing.
  • Demonstrated cathepsin B cleavage of APP into 115 kDa and 9 kDa fragments.

Conclusions:

  • Lysosomal cathepsin B is identified as a candidate APP secretase.
  • The cleavage products suggest a role for cathepsin B in normal APP metabolism and potentially AD.