👤 Yasaman Jami-Alahmadi

Patients with metabolic syndrome and heart failure (HF) often have accompanying kidney dysfunction, which was recently defined as cardiovascular-kidney-metabolic (CKM) syndrome. Prior metabolomics profiling of metabolic syndrome patients identified a plasma branched chain amino acid (BCAA) signature, and BCAAs themselves are elevated in the myocardium of patients with HF, potentially due to a defect in BCAA catabolic breakdown. The rate limiting step of BCAA catabolism is the decarboxylation by the enzyme branched chain ketoacid dehydrogenase (BCKDH), which is negatively regulated by BCKDH kinase (BCKDK or BDK), and BDK inhibitors improve metabolism and heart failure preclinically. Here, using two pre-clinical CKM models, the hyperphagic ZSF1 obese rat and the uninephrectomized SDT fatty rat with high salt drinking water, we applied unbiased proteomic, transcriptomic and metabolomic profiling to assess overall kidney gene expression and mitochondrial function. We show that BCAA catabolic impairment is associated with and may be causal to CKM and demonstrated impairment in BCAA catabolism within ZSF1 obese rat kidneys. In both CKM animal models, treatment with the BDK inhibitor BT2 improved urine protein content, kidney hypertrophy, and kidney pathology. Furthermore, coadministration of BT2 and the sodium-glucose cotransporter-2 inhibitor empagliflozin demonstrated additive effects to improve kidney parameters, kidney gene expression signatures, and kidney mitochondrial density and function. Our study suggests that in addition to its previously reported beneficial effects on metabolism and cardiac function, BDK inhibition may also improve kidney health and therefore could represent a new therapeutic avenue for CKM. Show less

The tripartite motif (TRIM) family of E3 ubiquitin ligases is well known for its roles in antiviral restriction and innate immunity regulation, in addition to many other cellular pathways. In particular, TRIM25-mediated ubiquitination affects both carcinogenesis and antiviral response. While individual substrates have been identified for TRIM25, it remains unclear how it regulates diverse processes. Here we characterized a mutation, R54P, critical for TRIM25 catalytic activity, which we successfully utilized to "trap" substrates. We demonstrated that TRIM25 targets proteins implicated in stress granule formation (G3BP1/2), nonsense-mediated mRNA decay (UPF1), nucleoside synthesis (NME1), and mRNA translation and stability (PABPC4). The R54P mutation abolishes TRIM25 inhibition of alphaviruses independently of the host interferon response, suggesting that this antiviral effect is a direct consequence of ubiquitination. Consistent with that, we observed diminished antiviral activity upon knockdown of several TRIM25-R54P specific interactors including NME1 and PABPC4. Our findings highlight that multiple substrates mediate the cellular and antiviral activities of TRIM25, illustrating the multi-faceted role of this ubiquitination network in modulating diverse biological processes. Show less