Vacuolar proteins play essential roles in plant physiology and development, but the factors and the machinery regulating their vesicle trafficking through the endomembrane compartments remain largely unknown. We and others have recently identified an evolutionarily conserved plant endosomal sorting complex required for transport (ESCRT)-associated protein apoptosis-linked gene-2 interacting protein X (ALIX), which plays canonical functions in the biogenesis of the multivesicular body/prevacuolar compartment (MVB/PVC) and in the sorting of ubiquitinated membrane proteins. In this study, we elucidate the roles and underlying mechanism of ALIX in regulating vacuolar transport of soluble proteins, beyond its conventional ESCRT function in eukaryotic cells. We show that ALIX colocalizes and physically interacts with the retromer core subunits Vps26 and Vps29 in planta. Moreover, double-mutant analysis reveals the genetic interaction of ALIX with Vps26 and Vps29 for regulating trafficking of soluble vacuolar proteins. Interestingly, depletion of ALIX perturbs membrane recruitment of Vps26 and Vps29 and alters the endosomal localization of vacuolar sorting receptors (VSRs). Taken together, ALIX functions as a unique retromer core subcomplex regulator by orchestrating receptor-mediated vacuolar sorting of soluble proteins.

Central European Institute of Technology Mendel University in Brno CZ 61300 Brno Czech Republic

Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology School of Life Sciences The Chinese University of Hong Kong Shatin New Territories Hong Kong China

Centro Nacional de Biotecnología Consejo Superior de Investigaciones Científicas Cantoblanco E 28049 Madrid Spain

Faculty of Science and Engineering Konan University Kobe 658 8501 Japan

Graduate School of Science Kyoto University Sakyo ku Kyoto 606 8502 Japan

Guangdong Provincial Key Laboratory of Biotechnology for Plant Development School of Life Sciences South China Normal University Guangzhou 510631 China

State Key Laboratory of Subtropical Silviculture Zhejiang A and F University 311300 Hangzhou China

The Chinese University of Hong Kong Shenzhen Research Institute Shenzhen 518057 China

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Proc Natl Acad Sci U S A. 2022 Jun 28;119(26):e2207055119. doi: 10.1073/pnas.2207055119. PubMed

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