How do cells regulate the degradation of misfolded proteins?

Cells have intricate mechanisms in place to regulate the degradation of misfolded proteins and maintain protein quality control. Proper protein folding is crucial for cellular function, and misfolded proteins can lead to various diseases and cellular malfunctions.

Protein Quality Control Mechanisms

Cells employ several pathways to identify and target defective proteins for degradation:

1. Ubiquitin-Proteasome System

The ubiquitin-proteasome system tags misfolded proteins with ubiquitin molecules, marking them for degradation by the proteasome. The proteasome is a cellular complex that breaks down proteins into smaller peptides.

2. Chaperone-Mediated Autophagy

In this process, chaperone proteins recognize misfolded proteins and transport them to lysosomes for degradation. Lysosomes contain enzymes that break down proteins into their constituent amino acids for recycling.

3. Cellular Stress Response

During cellular stress, such as heat shock or oxidative stress, cells upregulate protein quality control pathways to manage the increased load of misfolded proteins.

Overall, these quality control pathways play a critical role in maintaining proteostasis and preventing the accumulation of toxic misfolded proteins that can lead to diseases like Alzheimer's and Parkinson's.