Discoidin Domain Receptor 1 Translocation to the Mitochondria Promotes Oxidative Stress and Apoptosis in Acute Kidney Injury

KEY POINTS: Discoidin domain receptor 1 (DDR1) translocated to the mitochondria of proximal tubule cells after AKI. DDR1 contributed to AKI by promoting the production of mitochondrial reactive oxygen species and cell apoptosis. Mechanistically, DDR1 translocated to mitochondria by interacting with Hsp60 and promoted oxidative stress by regulating phosphorylation of p66Shc. BACKGROUND: Mitochondrial damage with overproduction of mitochondrial reactive oxygen species (mtROS) and apoptosis is a hallmark of AKI. Discoidin domain receptor 1 (DDR1) is a collagen receptor tyrosine kinase that contributes to AKI. Mass spectrometry analysis of DDR1-interacting proteins identified several mitochondrial proteins, suggesting that DDR1 associated with mitochondria. Thus, we analyzed whether DDR1 translocated to mitochondria and promoted mitochondrial dysfunction after AKI. METHODS: We analyzed DDR1 localization in kidneys of patients with AKI and mice after ischemia/reperfusion-induced AKI. To determine whether mitochondrial DDR1 (mtDDR1) regulated mitochondrial functions, we generated kidney cells expressing wild-type or a kinase dead DDR1. Then, we investigated the location of wild-type or mutated DDR1 on collagen stimulation, the steps involved in DDR1 mitochondrial translocation, and the contribution of mtDDR1 in regulating mtROS production and apoptosis. RESULTS: mtDDR1 was detected in injured human and mice kidneys, and collagen-activated DDR1 translocated to the mitochondria where it increased mtROS production and tubule cell apoptosis. Collagen-activated DDR1 translocated to the outer membrane of mitochondria through its association with the chaperone mtHsp60 and induced oxidative stress and apoptosis by promoting tyrosine phosphorylation of p66Shc, a regulator of the cellular redox state and apoptosis. Moreover, cells expressing a kinase dead DDR1, treated with a DDR1 inhibitor, or expressing p66Shc mutated in the DDR1-targeted phosphorylation sites had reduced mtROS and apoptosis. CONCLUSIONS: We describe a novel noncanonical pathway whereby activated DDR1 translocates to the mitochondria to promote oxidative stress and cell apoptosis.