Katsiarimpa Anthi, Muñoz Alfonso, Kalinowska Kamila, Uemura Tomohiro, Rojo Enrique, Isono Erika
Department of Plant Systems Biology, Technische Universität München, D-85354,Freising, Germany.
Plant Cell Physiol. 2014 Apr;55(4):727-36. doi: 10.1093/pcp/pcu019. Epub 2014 Jan 30.
Post-translational modification by ubiquitin plays a key role in the regulation of endocytic degradation in which ubiquitinated plasma membrane cargos are transported to the vacuole for degradation dependent on the ESCRT (endosomal sorting complex required for transport) machinery. Arabidopsis AMSH3 (ASSOCIATED MOLECULE WITH THE SH3 DOMAIN OF STAM 3) is a deubiquitinating enzyme that interacts with at least two subunits of the ESCRT-III machinery, VPS2.1 and VPS24.1. amsh3 null mutation causes seedling lethality, and amsh3 null mutants show defects in multiple intracellular trafficking pathways. In this study, we further analyzed the amsh3 mutant phenotype and showed that amsh3 accumulates membrane-associated ubiquitinated proteins, supporting the indication that AMSH3 functions in ubiquitin-mediated endocytic degradation. In accordance with this, an enzymatic inactive variant of AMSH3 inhibits the AvrPtoB-dependent endocytic degradation of CERK1 (CHITIN ELICITOR RECEPTOR KINASE 1). Furthermore, we showed that the interaction of AMSH3 with ESCRT-III is important for its function in planta. Together, our data indicate the importance of AMSH3 and the AMSH3-ESCRT-III interaction for deubiquitination and degradation of ubiquitinated membrane substrates in plants.
泛素介导的翻译后修饰在胞吞降解调控中起关键作用，在此过程中，泛素化的质膜货物被转运至液泡进行降解，这一过程依赖于ESCRT（转运所需的内体分选复合体）机制。拟南芥AMSH3（与STAM 3的SH3结构域相关的分子）是一种去泛素化酶，它与ESCRT-III机制的至少两个亚基VPS2.1和VPS24.1相互作用。amsh3基因敲除突变导致幼苗致死，且amsh3基因敲除突变体在多个细胞内运输途径中表现出缺陷。在本研究中，我们进一步分析了amsh3突变体表型，发现amsh3积累了与膜相关的泛素化蛋白，这支持了AMSH3在泛素介导的胞吞降解中发挥作用的观点。与此一致的是，AMSH3的酶活性失活变体抑制了CERK1（几丁质激发子受体激酶1）的AvrPtoB依赖性胞吞降解。此外，我们表明AMSH3与ESCRT-III的相互作用对其在植物中的功能很重要。总之，我们的数据表明AMSH3以及AMSH3-ESCRT-III相互作用对植物中泛素化膜底物的去泛素化和降解具有重要意义。
