An alternative mitophagy pathway mediated by Rab9 protects the heart against ischemia
Toshiro Saito, … , Mondira Kundu, Junichi Sadoshima
Toshiro Saito, … , Mondira Kundu, Junichi Sadoshima
Published December 4, 2018
Citation Information: J Clin Invest. 2019;129(2):802-819. https://doi.org/10.1172/JCI122035.
View: Text | PDF
Research Article Cardiology Cell biology

An alternative mitophagy pathway mediated by Rab9 protects the heart against ischemia

Abstract

Energy stress, such as ischemia, induces mitochondrial damage and death in the heart. Degradation of damaged mitochondria by mitophagy is essential for the maintenance of healthy mitochondria and survival. Here, we show that mitophagy during myocardial ischemia was mediated predominantly through autophagy characterized by Rab9-associated autophagosomes, rather than the well-characterized form of autophagy that is dependent on the autophagy-related 7 (Atg) conjugation system and LC3. This form of mitophagy played an essential role in protecting the heart against ischemia and was mediated by a protein complex consisting of unc-51 like kinase 1 (Ulk1), Rab9, receptor-interacting serine/thronine protein kinase 1 (Rip1), and dynamin-related protein 1 (Drp1). This complex allowed the recruitment of trans-Golgi membranes associated with Rab9 to damaged mitochondria through S179 phosphorylation of Rab9 by Ulk1 and S616 phosphorylation of Drp1 by Rip1. Knockin of Rab9 (S179A) abolished mitophagy and exacerbated the injury in response to myocardial ischemia, without affecting conventional autophagy. Mitophagy mediated through the Ulk1/Rab9/Rip1/Drp1 pathway protected the heart against ischemia by maintaining healthy mitochondria.

Authors

Toshiro Saito, Jihoon Nah, Shin-ichi Oka, Risa Mukai, Yoshiya Monden, Yasuhiro Maejima, Yoshiyuki Ikeda, Sebastiano Sciarretta, Tong Liu, Hong Li, Erdene Baljinnyam, Diego Fraidenraich, Luke Fritzky, Peiyong Zhai, Shizuko Ichinose, Mitsuaki Isobe, Chiao-Po Hsu, Mondira Kundu, Junichi Sadoshima

×

Figure 8

Pharmacological inhibition of Rip1 impairs mitophagy during starvation in the heart.

Options: View larger image (or click on image) Download as PowerPoint
Pharmacological inhibition of Rip1 impairs mitophagy during starvation i...
(A) CMs transduced with DsRed-Mito (green) were stained with rabbit anti-Rip1 antibody and/or mouse anti-GFP and anti-YFP antibodies, and in vivo protein-protein interaction (red dots) between Rip1 and YFP-Rab9 was detected with secondary proximity probes, Anti-Rabbit-PLUS, and Anti-Mouse MINUS using the Duolink In Situ PLA Detection Kit. Scale bars: 10 μm; original magnification, ×5 (enlarged insets). Arrows indicate the PLA signal close to the mitochondria. (B) Representative immunoblots showing phosphorylation of Drp1 in the presence or absence of 7-Cl-O-Nec-1 during glucose deprivation (GD) in CMs. (C) WT/Mito-Keima–Tg mice were subjected to 48 hours of starvation. The effect of 7-Cl-O-Nec-1 on mitophagy in the heart was examined. Either control inhibitor or 7-Cl-O-Nec-1 (1.80 μg/g BW) was injected i.p. twice during the 48-hour starvation period. Representative images and a summary are shown (n = 3 per group). Scale bars: 50 μm; original magnification, ×3 (enlarged insets). Error bars represent the SEM. #P < 0.05 versus control (unpaired Student’s t test). Nec-1, 7-Cl-O-Nec-1.