New quality control discovered in yeast peroxisomes

Finding and breaking down defective proteins

For the first time, the researchers have identified and molecularly characterized the RADAR pathway (“Receptor Accumulation and Degradation in the Absence of Recycling”) in baker’s yeast. This mechanism ensures that import receptors that are defective or no longer functional are specifically recognized, tagged, and degraded. “This prevents faulty proteins from interfering with the function of peroxisomes,” explains Ralf Erdmann, Chair of the Department of Systems Biochemistry at Ruhr University Bochum.

At the core of the RADAR pathway is the AAA-ATPase Cdc48p, which orchestrates the degradation process together with its cofactors Ufd1p and Npl4p, as well as the AAA-ATPase Msp1p. The researchers demonstrated that Cdc48p extracts defective import receptors from the peroxisomal membrane, enabling their subsequent degradation by the proteasome. Thus, the RADAR pathway resembles the well-characterized ERAD system (Endoplasmic Reticulum-Associated Degradation), which fulfills a comparable quality control function in the endoplasmic reticulum. 

Contribution to cell health

“Our results show that peroxisomes possess a specialized quality control mechanism that prevents malfunctions and supports cellular health,” explains Erdmann. “This discovery represents a major step forward in understanding peroxisomal quality control and the role of Cdc48p in cellular protein surveillance.” Because peroxisomes play a central role in human metabolism and the RADAR pathway is conserved in humans, these findings offer new insights into the fundamental mechanisms of cellular homeostasis and protein quality control.