Related Experiment Video

Updated: Sep 28, 2026

Cell-Based Drug Screening for Inhibitors of Autophagy Related 4B Cysteine Peptidase
09:51

Cell-Based Drug Screening for Inhibitors of Autophagy Related 4B Cysteine Peptidase

Published on: June 30, 2023

Cathepsin A regulates chaperone-mediated autophagy through cleavage of the lysosomal receptor

Ana Maria Cuervo1, Linda Mann, Erik J Bonten

  • 1Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. amcuervo@aecom.yu.edu

The EMBO Journal
|December 31, 2002
PubMed

Insights

Protective protein/cathepsin A (PPCA) degrades the lysosome-associated membrane protein type 2a (lamp2a), a key receptor for chaperone-mediated autophagy (CMA). This finding reveals a new role for PPCA

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Protective protein/cathepsin A (PPCA) is a multifunctional lysosomal protein with known roles in targeting and protecting glycosidases.
  • The physiological function of PPCA's serine carboxypeptidase activity remains largely unknown.
  • Lysosome-associated membrane protein type 2a (lamp2a) is the sole receptor for chaperone-mediated autophagy (CMA) and its levels regulate CMA activity.

Purpose of the Study:

  • To elucidate the physiological function of PPCA's protease activity.
  • To investigate the role of PPCA in the regulation of chaperone-mediated autophagy (CMA).
  • To determine the relationship between PPCA and lamp2a in the lysosome.

Main Methods:

  • Enzyme activity assays to assess PPCA's carboxypeptidase function.
  • Western blotting and immunofluorescence to quantify lamp2a levels and localization.
  • Cellular assays to measure chaperone-mediated autophagy (CMA) flux.
  • Co-immunoprecipitation to study PPCA-lamp2a interactions.

Main Results:

  • PPCA protease activity directly triggers the degradation of lamp2a.
  • Cells lacking functional PPCA exhibit reduced lamp2a degradation, leading to increased lamp2a levels and elevated CMA rates.
  • Restoration of PPCA activity normalized lamp2a degradation and CMA flux.
  • PPCA was found to associate with lamp2a on the lysosomal membrane and cleave it.

Conclusions:

  • The proteolytic activity of PPCA is essential for regulating lamp2a levels at the lysosomal membrane.
  • PPCA acts as a key regulator of chaperone-mediated autophagy (CMA) by controlling the degradation of its receptor, lamp2a.
  • This study defines a novel function for the multifunctional protein PPCA beyond its previously known roles.

More Related Videos

Exploring the Regulation of Lipid Droplet Catabolism through Lipophagy07:20

Exploring the Regulation of Lipid Droplet Catabolism through Lipophagy

Published on: January 31, 2025

The Lactate Dehydrogenase Sequestration Assay — A Simple and Reliable Method to Determine Bulk Autophagic Sequestration Activity in Mammalian Cells09:34

The Lactate Dehydrogenase Sequestration Assay — A Simple and Reliable Method to Determine Bulk Autophagic Sequestration Activity in Mammalian Cells

Published on: July 27, 2018

Related Concept Videos

Delivery Pathways to the Lysosome01:36

Delivery Pathways to the Lysosome

Eukaryotic cells use different mechanisms to eliminate toxic waste obsolete and worn-out substances. Lysosomes play a pivotal role in this, and hence, these substances are carried to the lysosome from other parts of the cell and extracellular space through different pathways. The most elaborately studied pathways to the lysosome are the endocytic pathways.
Endocytosis
In endocytosis, the cell membrane takes up macromolecules and particles from the surrounding medium. Clathrin-mediated...
Autophagy01:27

Autophagy

Autophagy is a self-digesting process by which a cell protects itself from threats both within and outside the cell, ranging from abnormal proteins to invading bacteria. In this process, obsolete components of the cell and invading microbes are degraded by hydrolytic enzymes active in an acidic environment of the lysosomal lumen.
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
Autophagic Cell Death01:18

Autophagic Cell Death

Christian de Duve discovered “autophagy,” a process in which cellular components are engulfed by membrane-bound organelles called autophagosomes. The autophagosomes then fuse with lysosomes to digest the enclosed contents. Autophagy is generally activated in cells to prevent cell death. However, cell death is triggered when the damage is beyond repair.
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and pro-apoptotic...
Cellular Injury V: Apoptosis and Autophagy01:22

Cellular Injury V: Apoptosis and Autophagy

Cells respond to damage and stress through highly coordinated processes that decide whether they survive or undergo controlled self-destruction. Two major pathways involved in this regulation are apoptosis, a type of programmed cell death, and autophagy, a survival mechanism that helps cells adapt to adverse conditions.ApoptosisApoptosis removes aged or injured cells to maintain tissue balance. During this process, the cell shrinks, chromatin condenses and fragments, and membrane-bound...
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst 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. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...