What are the human protein degradation pathways?

The main protein degradation pathways in the human body include the ubiquitin-proteasome system, autophagy pathway, and rough endoplasmic reticulum pathway.

1. Ubiquitin-Proteasome System

The ubiquitin-proteasome system accounts for approximately 80% of total protein degradation. In this pathway, ubiquitin—a small protein—binds to target proteins destined for degradation, forming a ubiquitin-protein complex that is subsequently degraded by the proteasome.

2. Autophagy Pathway

Autophagy is a cellular self-degradation process that removes aged, damaged, or abnormal proteins within the cell. In this pathway, targeted proteins are enclosed within structures called autophagosomes, which then fuse with lysosomes for degradation.

3. Rough Endoplasmic Reticulum Pathway

The rough endoplasmic reticulum is a membrane system within the cell that packages proteins marked for degradation into vesicles, which are subsequently delivered to lysosomes for breakdown.

In summary, the human body employs various protein degradation pathways that play distinct roles under different conditions, collectively maintaining protein homeostasis.