Clustered Mitochondrial Homolog Inhibition by Lipocalin-2 Orchestrates Mitochondrial Disruption and Contributes to Kidney Disease

KEY POINTS: Lipocalin-2 inhibited clustered mitochondrial homolog (CLUH) activity and caused mitochondrial dysfunction. Loss of CLUH in kidneys triggered metabolic reprogramming and impaired mitochondrial structure. CLUH expression decreased with kidney injury and correlated with kidney function decline in patients. BACKGROUND: Lipocalin-2 (LCN2) is a secreted protein involved in transporting hydrophobic molecules, regulating antibacterial responses and iron homeostasis. LCN2 expression increases after kidney damage and participates in CKD onset. We previously identified LCN2 as a regulator of mitochondrial dysfunction in renal tubular cells. This study aims to better understand LCN2's role in mitochondrial dysfunction and kidney pathology. METHODS: LCN2 interactome was studied using mass spectrometry. The impact of LCN2 on clustered mitochondrial homolog (CLUH) activity was explored by immunofluorescence, Western blot, quantitative PCR, and RNA-immunoprecipitation. The role of CLUH on mitochondrial function in kidney was evaluated by RNAseq, metabolomics, electron microscopy, and immunochemistry using transgenic mice. RESULTS: We characterized LCN2 interactome and identified CLUH in a multiprotein complex with LCN2. CLUH regulates mitochondrial homeostasis by binding mRNAs of nuclear-encoded mitochondrial proteins and promoting their translation. We demonstrated that LCN2 inhibited CLUH activity, leading to perinuclear mitochondrial clustering. We showed that CLUH was expressed in renal tubular cells and that its expression and activity decreased, while LCN2 expression increased after kidney injury leading to CKD. In human CKD patients, CLUH expression was inversely correlated with kidney lesions and kidney failure. CLUH genetic deletion in kidney nephron induced mitochondrial dysfunction and a subsequent interstitial fibrosis and kidney loss of function. CONCLUSIONS: This study shows that LCN2 forms a complex with CLUH and inhibits its activity, leading to perinuclear mitochondrial clustering. CLUH loss of function in renal tubular cells is associated with mitochondrial dysfunction and fibrosis, and in humans, CLUH expression inversely correlates with kidney lesions and loss of function.