TBK1 adaptor AZI2/NAP1 regulates NDP52-driven mitochondrial autophagy

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

doi:10.1016/j.jbc.2024.107775

TBK1 adaptor AZI2/NAP1 regulates NDP52-driven mitochondrial autophagy

J Biol Chem. 2024 Sep 12:107775. doi: 10.1016/j.jbc.2024.107775. Online ahead of print.

Authors

Ryu Endo¹, Hiroki Kinefuchi¹, Momoha Sawada¹, Reika Kikuchi¹, Waka Kojima¹, Noriyuki Matsuda¹, Koji Yamano²

Affiliations

¹ Department of Biomolecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
² Department of Biomolecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan. Electronic address: kojibiom@tmd.ac.jp.

PMID: 39276928
DOI: 10.1016/j.jbc.2024.107775

Abstract

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.