Peroxisomal Ubiquitin-Protein Ligases Peroxin2 and Peroxin10 Have Distinct But Synergistic Roles in Matrix Protein Import and Peroxin5 Retrotranslocation in Arabidopsis. Issue 3 (11th September 2014)

• Record Type: Journal Article
• Authors: Burkhart, Sarah E.; Kao, Yun-Ting; Bartel, Bonnie
• Is Part Of: Plant physiology. Volume 166:Issue 3(2014)
• Page Start: 1329
• Page End: 1344
• Publication Date: 2014-09-11
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.114.247148
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Two Arabidopsis membrane peroxins contribute to peroxisomal matrix protein import via distinct roles in recycling and degrading a matrix receptor protein . Abstract: Peroxisomal matrix proteins carry peroxisomal targeting signals (PTS s), PTS 1 or PTS 2, and are imported into the organelle with the assistance of peroxin (PEX) proteins. From a microscopy-based screen to identify Arabidopsis ( Arabidopsis thaliana ) mutants defective in matrix protein degradation, we isolated unique mutations in PEX2 and PEX10, which encode ubiquitin-protein ligases anchored in the peroxisomal membrane. In yeast ( Saccharomyces cerevisiae ), PEX2, PEX10, and a third ligase, PEX12, ubiquitinate a peroxisome matrix protein receptor, PEX5, allowing the PEX1 and PEX6 ATP-hydrolyzing enzymes to retrotranslocate PEX5 out of the membrane after cargo delivery. We found that the pex2-1 and pex10-2 Arabidopsis mutants exhibited defects in peroxisomal physiology and matrix protein import. Moreover, the pex2-1 pex10-2 double mutant exhibited severely impaired growth and synergistic physiological defects, suggesting that PEX2 and PEX10 function cooperatively in the wild type. The pex2-1 lesion restored the unusually low PEX5 levels in the pex6-1 mutant, implicating PEX2 in PEX5 degradation when retrotranslocation is impaired. PEX5 overexpression altered pex10-2 but not pex2-1 defects, suggesting that PEX10 facilitates PEX5 retrotranslocation from the peroxisomal membrane. Although the pex2-1 pex10-2 double mutant displayed severe import defects of both PTS 1 and PTS 2 proteins into peroxisomes, both pex2-1 and pex10-2 single mutants exhibited clear import defects of PTS 1 proteins but apparently normal PTS 2 import. A similar PTS 1-specific pattern was observed in the pex4-1 ubiquitin-conjugating enzyme mutant. Our results indicate that Arabidopsis PEX2 and PEX10 cooperate to support import of matrix proteins into plant peroxisomes and suggest that some PTS 2 import can still occur when PEX5 retrotranslocation is slowed.