Small‐molecule inhibition of MuRF1 attenuates skeletal muscle atrophy and dysfunction in cardiac cachexia

Abstract

BackgroundMuscle ring finger 1 (MuRF1) is a muscle‐specific ubiquitin E3 ligase activated during clinical conditions associated with skeletal muscle wasting. Yet, there remains a paucity of therapeutic interventions that directly inhibit MuRF1 function, particularly in vivo. The current study, therefore, developed a novel compound targeting the central coiled coil domain of MuRF1 to inhibit muscle wasting in cardiac cachexia.MethodsWe identified small molecules that interfere with the MuRF1–titin interaction from a 130 000 compound screen based on Alpha Technology. A subset of nine prioritized compounds were synthesized and administrated during conditions of muscle wasting, that is, to C2C12 muscle cells treated with dexamethasone and to mice treated with monocrotaline to induce cardiac cachexia.ResultsThe nine selected compounds inhibited MuRF1–titin complexation with IC50 values <25 μM, of which three were found to also inhibit MuRF1 E3 ligase activity, with one further showing low toxicity on cultured myotubes. This last compound, EMBL chemical core ID#704946, also prevented atrophy in myotubes induced by dexamethasone and attenuated fibre atrophy and contractile dysfunction in mice during cardiac cachexia. Proteomic and western blot analyses showed that stress pathways were attenuated by ID#704946 treatment, including down‐regulation of MuRF1 and normalization of proteins associated with apoptosis (BAX) and protein synthesis (elF2B‐delta). Furthermore, actin ubiquitinylation and proteasome activity was attenuated.ConclusionsWe identified a novel compound directed to MuRF1's central myofibrillar protein recognition domain. This compound attenuated in vivo muscle wasting and contractile dysfunction in cardiac cachexia by protecting de novo protein synthesis and by down‐regulating apoptosis and ubiquitin‐proteasome‐dependent proteolysis.

Small‐molecule‐mediated chemical knock‐down of MuRF1/MuRF2 and attenuation of diaphragm dysfunction in chronic heart failure

“…C57/BL6 female mice ( n = 70) underwent an MI to induce CHF or sham surgery, where a surgical silk suture ligated the left anterior descending coronary artery (LAD) as previously described . One week after LAD ligation, echocardiography was performed to confirm MI, and only mice with a large infarct [left ventricular ejection fraction (LVEF) <20%] were subsequently randomized into either receiving normal chow (CHF, n = 11) or chow supplemented with compound (0.1% of compound ID#704946, CHF + 704946, n = 12) as recently described . Sham animals that underwent surgery but where the LAD was not ligated served as controls and were fed normal chow (sham, n = 15).…”

“…We recently described a small molecule (compound ID#704946, molecular weight 490 Da) that inhibited MuRF1 expression/activity in vivo and was able to attenuate skeletal muscle atrophy and dysfunction in mice treated with monocrotaline to induce right ventricular hypertrophy and subsequent cardiac cachexia . In that earlier study, the compound ID#704946 was given 1 week before monocrotaline treatment was initiated, complicating the interpretation of therapeutic applicability.…”

Myricanol rescues dexamethasone‐induced muscle dysfunction via a sirtuin 1‐dependent mechanism

“…Two muscle specific ubiquitin E3 ligases, muscle atrophy F‐box (atrogin‐1) and muscle ring finger 1 (MuRF1), are critical determinants of muscle atrophy . Inhibition of MuRF1 attenuates muscle atrophy . Autophagy is critical to trigger mitochondrial fragmentation in GC‐induced muscle atrophy .…”

MicroRNAs in muscle wasting

“…1 The mature miR binds to its target mRNAs leading to a blocked translation or degradation thereby providing the cell with a post-transcriptional control of gene expression. 7 The related proteins MuRF-2 and MuRF-3 bind to microtubules and are implicated in sarcomere formation with evident functional redundancy, which has proven to be important for the maintenance of skeletal muscle, as double knockout mice lead to myopathy, reduced fore generation, and fibre type shift. 4 MyomiRs comprise a group of miRs, who display an enriched expression in skeletal muscle including miR-1, miR-133a, miR-133b, miR-206, miR-208, miR-208b, miR-486, and miR-499.…”