J Integr Plant Biol ›› 2024, Vol. 66 ›› Issue (5): 1007-1023.DOI: 10.1111/jipb.13645

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  • 收稿日期:2023-12-06 接受日期:2024-02-27 出版日期:2024-05-01 发布日期:2024-05-31

A converged ubiquitin-proteasome pathway for the degradation of TOC and TOM tail-anchored receptors

Meijing Yang1, 2†, Shuai Chen3, 4†, Shey-Li Lim1, Lang Yang1, 2, Jia Yi Zhong1, Koon Chuen Chan1, Zhizhu Zhao1, Kam-Bo Wong4, 5, Junqi Wang2 and Boon Leong Lim1, 5, 6*   

  1. 1. School of Biological Sciences, University of Hong Kong, Pokfulam 999077, Hong Kong, China
    2. Department of Biology, Southern University of Science and Technology, Shenzhen 518055, China
    3. School of Biomedical Engineering, Shenzhen University, Shenzhen 518060, China
    4. School of Life Sciences, The Chinese University of Hong Kong, Shatin 999077, Hong Kong, China
    5. State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin 999077, Hong Kong, China
    6. HKU Shenzhen Institute of Research and Innovation, Shenzhen 518052, China
    †These authors contributed equally to this work.
    *Correspondence:Boon Leong Lim (bllim@hku.hk)
  • Received:2023-12-06 Accepted:2024-02-27 Online:2024-05-01 Published:2024-05-31

Abstract: In plants, thousands of nucleus-encoded proteins translated in the cytosol are sorted to chloroplasts and mitochondria by binding to specific receptors of the TOC (translocon on the outer chloroplast membrane) and the TOM (translocon on the outer mitochondrial membrane) complexes for import into those organelles. The degradation pathways for these receptors are unclear. Here, we discovered a converged ubiquitin-proteasome pathway for the degradation of Arabidopsis thaliana TOC and TOM tail-anchored receptors. The receptors are ubiquitinated by E3 ligase(s) and pulled from the outer membranes by the AAA+ adenosine triphosphatase CDC48, after which a previously uncharacterized cytosolic protein, transmembrane domain (TMD)-binding protein for tail-anchored outer membrane proteins (TTOP), binds to the exposed TMDs at the C termini of the receptors and CDC48, and delivers these complexes to the 26S proteasome.

Key words: 26S proteasome, CDC48, SP1, TOC, TOM, ubiquitination

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