Title:Cathepsin B-A Neuronal Death Mediator in Alzheimer’s Disease Leading
to Neurodegeneration
Volume: 22
Issue: 15
Author(s): Anjali Sharma, Rayala Swetha, Nilesh Gajanan Bajad, Ankit Ganeshpurkar, Ravi Singh, Ashok Kumar and Sushil Kumar Singh*
Affiliation:
- Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
Keywords:
Cathepsin B, β-amyloid, pyroglutamate amyloid- β (PGlu-Aβ), neuroinflammation, regulated secretory pathway, humanized antibody, Alzheimer’s disease.
Abstract: The lysosomal cysteine protease enzyme, named Cathepsin B, mainly degrades the protein
and manages its average turnover in our body. The Cathepsin B active form is mostly present inside
the lysosomal part at a cellular level, providing the slightly acidic medium for its activation. Multiple
findings on Cathepsin B reveal its involvement in neurons’ degeneration and a possible role as a neuronal
death mediator in several neurodegenerative diseases. In this review article, we highlight the
participation of Cathepsin B in the etiology/progress of AD, along with various other factors. The enzyme
is involved in producing neurotoxic Aβ amyloid in the AD brain by acting as the β-secretase
enzyme in the regulated secretory pathways responsible for APP processing. Aβ amyloid accumulation
and amyloid plaque formation lead to neuronal degeneration, one of the prominent pathological
hallmarks of AD. Cathepsin B is also involved in the production of PGlu-Aβ, which is a truncated and
highly neurotoxic form of Aβ. Some of the findings also revealed that Cathepsin B specific gene deletion
decreases the level of PGlu-Aβ inside the brain of experimental mice. Therefore, neurotoxicity
might be considered a new pathological indication of AD due to the involvement of Cathepsin B. It
also damages neurons present in the CNS region by producing inflammatory responses and generating
mitochondrial ROS. However, Cathepsin B inhibitors, i.e., CA-074, can prevent neuronal death in AD
patients. The other natural inhibitors are also equally effective against neuronal damage with higher
selectivity. Its synthetic inhibitors are specific for their target; however, they lose their selectivity in
the presence of quite a few reducing agents. Therefore, a humanized monoclonal antibody is used as a
selective Cathepsin B inhibitor to overcome the problem experienced. The use of Cathepsin B for the
treatment of AD and other neurodegenerative diseases could be considered a rational therapeutic
target.