bims-mitpro 2024-09-22 papers

Issue of 2024–09–22
two papers selected by
Andreas Kohler, Umeå University

J Biol Chem. 2024 Sep 12. pii: S0021-9258(24)02276-2. [Epub ahead of print] 107775

TBK1 adaptor AZI2/NAP1 regulates NDP52-driven mitochondrial autophagy.

Ryu Endo, Hiroki Kinefuchi, Momoha Sawada, Reika Kikuchi, Waka Kojima, Noriyuki Matsuda, Koji Yamano.

Damaged mitochondria are selectively eliminated in a process called mitophagy. PINK1 and Parkin amplify ubiquitin signals on damaged mitochondria, which are then recognized by autophagy adaptors to induce local autophagosome formation. NDP52 and OPTN, two essential mitophagy adaptors, facilitate de novo synthesis of pre-autophagosomal membranes near damaged mitochondria by linking ubiquitinated mitochondria and ATG8 family proteins and by recruiting core autophagy initiation components. The multifunctional serine/threonine kinase TBK1 also plays important roles in mitophagy. OPTN directly binds TBK1 to form a positive feedback loop for isolation membrane expansion. TBK1 is also thought to indirectly interact with NDP52; however, its role in NDP52-driven mitophagy remains largely unknown. Here, we focused on two TBK1 adaptors, AZI2/NAP1 and TBKBP1/SINTBAD, that are thought to mediate the TBK1-NDP52 interaction. We found that both AZI2 and TBKBP1 are recruited to damaged mitochondria during Parkin-mediated mitophagy. Further, a series of AZI2 and TBKBP1 knockout constructs combined with an OPTN knockout showed that AZI2, but not TBKBP1, impacts NDP52-driven mitophagy. In addition, we found that AZI2 at S318 is phosphorylated during mitophagy, the impairment of which slightly inhibits mitochondrial degradation. These results suggest that AZI2, in concert with TBK1, plays an important role in NDP52-driven mitophagy.

Keywords: autophagy; mitochondria; mitophagy; polyubiquitin chain; serine/threonine protein kinase

DOI: https://doi.org/10.1016/j.jbc.2024.107775

Plant Commun. 2024 Sep 13. pii: S2590-3462(24)00529-7. [Epub ahead of print] 101133

Jasmonic acid plays an important role in mediating retrograde signaling under mitochondrial translational stress to balance plant growth and defense.

Jiahao Li, Guolong Yu, Xinyuan Wang, Chaocheng Guo, Yudong Wang, Xu Wang.

Proper mitochondrial function is crucial to plant growth and development. Inhibition of mitochondrial translation leads to mitochondrial proteotoxic stress, which triggers a protective transcriptional response that regulates nuclear gene expression, commonly referred to as the mitochondrial unfolded protein response (UPRmt). Although UPRmt has been extensively studied in yeast and mammals, very little is known about UPRmt in plants. Here, we show that mitochondrial translational stress inhibits plant growth and development by inducing jasmonic acid (JA) biosynthesis and signaling. The inhibitory effect of mitochondrial translational stress on plant growth was alleviated in JA signaling defective mutants coi1-2, myc2, and myc234. Genetic analysis indicates that Arabidopsis mitochondrial ribosomal protein L1 (MRPL1), a key factor in UPRmt, regulates plant growth in a CORONATINE-INSENSITIVE1 (COI1)-dependent manner. Moreover, under mitochondrial translational stress, MYC2 showed direct binding to G-boxes in the ETHYLENE RESPONSE FACTOR 109 (ERF109) promoter. The induction of ERF109 expression enhances hydrogen peroxide (H2O2) production, which acts as a feedback loop to inhibit root growth. In addition, mutation of MRPL1 increases JA accumulation, reduces plant growth, and enhances biotic stress resistance. Overall, our findings reveal that JA plays an important role in mediating retrograde signaling under mitochondrial translational stress to balance plant growth and defense.

Keywords: ERF109; hydrogen peroxide; jasmonic acid; mitochondrial retrograde signaling; mitochondrial translational stress; mitochondrial unfolded protein response

DOI: https://doi.org/10.1016/j.xplc.2024.101133