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

Background: Mitochondrial damage with overproduction of mitochondrial reactive oxygen species (mtROS) and apoptosis is a hallmark of acute kidney injury (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 following AKI. Methods: We analyzed DDR1 localization in kidneys of patients with AKI and mice following ischemia reperfusion-induced AKI. To determine whether mitochondrial DDR1 (mitDDR1) 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 upon collagen stimulation; the steps involved in DDR1 mitochondrial translocation; and the contribution of mitDDR1 in regulating mtROS production and apoptosis. Results: mitDDR1 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 non-canonical pathway whereby activated DDR1 translocates to the mitochondria to promote oxidative stress and cell apoptosis.