ATAD3A oligomerization causes neurodegeneration by coupling mitochondrial fragmentation and bioenergetics defects.

Mitochondrial fragmentation and bioenergetic failure manifest in Huntington's disease (HD), a fatal neurodegenerative disease. The factors that couple mitochondrial fusion/fission with bioenergetics and their impacts on neurodegeneration however remain poorly understood. Our proteomic analysis identifies mitochondrial protein ATAD3A as an interactor of mitochondrial fission GTPase, Drp1, in HD. Here we show that, in HD, ATAD3A dimerization due to deacetylation at K135 residue is required for Drp1-mediated mitochondrial fragmentation. Disturbance of ATAD3A steady state impairs mtDNA maintenance by disrupting TFAM/mtDNA binding. Blocking Drp1/ATAD3A interaction with a peptide, DA1, abolishes ATAD3A oligomerization, suppresses mitochondrial fragmentation and mtDNA lesion, and reduces bioenergetic deficits and cell death in HD mouse- and patient-derived cells. DA1 treatment reduces behavioral and neuropathological phenotypes in HD transgenic mice. Our findings demonstrate that ATAD3A plays a key role in neurodegeneration by linking Drp1-induced mitochondrial fragmentation to defective mtDNA maintenance, suggesting that DA1 might be useful for developing HD therapeutics.

Interventions Targeting Glucocorticoid-Krüppel-like Factor 15-Branched-Chain Amino Acid Signaling Improve Disease Phenotypes in Spinal Muscular Atrophy Mice.

The circadian glucocorticoid-Krüppel-like factor 15-branched-chain amino acid (GC-KLF15-BCAA) signaling pathway is a key regulatory axis in muscle, whose imbalance has wide-reaching effects on metabolic homeostasis. Spinal muscular atrophy (SMA) is a neuromuscular disorder also characterized by intrinsic muscle pathologies, metabolic abnormalities and disrupted sleep patterns, which can influence or be influenced by circadian regulatory networks that control behavioral and metabolic rhythms. We therefore set out to investigate the contribution of the GC-KLF15-BCAA pathway in SMA pathophysiology of Taiwanese Smn-/-;SMN2 and Smn2B/- mouse models. We thus uncover substantial dysregulation of GC-KLF15-BCAA diurnal rhythmicity in serum, skeletal muscle and metabolic tissues of SMA mice. Importantly, modulating the components of the GC-KLF15-BCAA pathway via pharmacological (prednisolone), genetic (muscle-specific Klf15 overexpression) and dietary (BCAA supplementation) interventions significantly improves disease phenotypes in SMA mice. Our study highlights the GC-KLF15-BCAA pathway as a contributor to SMA pathogenesis and provides several treatment avenues to alleviate peripheral manifestations of the disease. The therapeutic potential of targeting metabolic perturbations by diet and commercially available drugs could have a broader implementation across other neuromuscular and metabolic disorders characterized by altered GC-KLF15-BCAA signaling.

Low-protein diet supplemented with ketoacids reduces the severity of renal disease in 5/6 nephrectomized rats: a role for KLF15.

Dietary protein restriction is an important treatment for chronic kidney disease. Herein, we tested the effect of low-protein or low-protein plus ketoacids (KA) diet in a remnant kidney model. Rats with a remnant kidney were randomized to receive normal protein diet (22%), low-protein (6%) diet (LPD), or low-protein (5%) plus KA (1%) diet for 6 months. Protein restriction prevented proteinuria, decreased blood urea nitrogen levels, and renal lesions; however, the LPD retarded growth and decreased serum albumin levels. Supplementation with KA corrected these abnormalities and provided superior renal protection compared with protein restriction alone. The levels of Kruppel-like factor-15 (KLF15), a transcription factor shown to reduce cardiac fibrosis, were decreased in remnant kidneys. Protein restriction, which increased KLF15 levels in the normal kidney, partially recovered the levels of KLF15 in remnant kidney. The expression of KLF15 in mesangial cells was repressed by oxidative stress, transforming growth factor-ß, and tumor necrosis factor (TNF)-α. The suppressive effect of TNF-α on KLF15 expression was mediated by TNF receptor-1 and nuclear factor-κB. Overexpression of KLF15 in mesangial and HEK293 cells significantly decreased fibronectin and type IV collagen mRNA levels. Furthermore, KLF15 knockout mice developed glomerulosclerosis following uninephrectomy. Thus, KLF15 may be an antifibrotic factor in the kidney, and its decreased expression may contribute to the progression of kidney disease.

The Krüppel-like factor KLF2 inhibits peroxisome proliferator-activated receptor-gamma expression and adipogenesis.

Obesity is an important public health problem associated with a number of disease states such as diabetes and arteriosclerosis. As such, an understanding of the mechanisms governing adipose tissue differentiation and function is of considerable importance. We recently reported that the Krüppel-like zinc finger transcription factor KLF15 can induce adipocyte maturation and GLUT4 expression. In this study, we identify that a second family member, KLF2/Lung Krüppel-like factor (LKLF), as a negative regulator of adipocyte differentiation. KLF2 is highly expressed in adipose tissue, and studies in cell lines and primary cells demonstrate that KLF2 is expressed in preadipocytes but not mature adipocytes. Constitutive overexpression of KLF2 but not KLF15 potently inhibits peroxisome proliferator-activated receptor-gamma (PPARgamma) expression with no effect on the upstream regulators C/EBPbeta and C/EBPdelta. However, the expression of C/EBPalpha and SREBP1c/ADD1 (adipocyte determination and differentiation factor-1/sterol regulatory element-binding protein-1), two factors that feedback in a positive manner to enhance PPARgamma function, was also markedly reduced. In addition, transient transfection studies show that KLF2 directly inhibits PPARgamma2 promoter activity (70% inhibition; p < 0.001). Using a combination of promoter mutational analysis and gel mobility shift assays, we have identified a binding site within the PPARgamma2 promoter, which mediates this inhibitory effect. These data identify a novel role for KLF2 as a negative regulator of adipogenesis.