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Background: Single residue substitutions in sarcomeric proteins cause most inherited cardiomyopathies. Results: Mutant ␣-tropomyosins cause multiple functional alterations in actin affinity and Ca 2ϩ sensitivity. Conclusion: Mutants follow distinct mechanisms to change Ca 2ϩ sensitivity. Significance: Fluorescence assays to measure changes in troponin C conformation may provide a simple platform for preliminary high throughput screening of modulatory small molecules to treat inherited cardiomyopathies.

These results demonstrate that the MSO target glutamine synthetase is required for the early steps of the cytokine response to endotoxins, and that its pharmacological inhibition may be exploited to treat inflammation.

BackgroundThe glutamine synthetase inhibitor methionine sulfoximine (MSO), shown previously to prevent death caused by an inflammatory liver response in mice, was tested on in vitro production of cytokines by mouse peritoneal macrophages triggered with lipopolysaccharide (LPS).ResultsMSO significantly reduced the production of Interleukin 6 (IL-6) and Tumor Necrosis Factor Alpha (TNFα) at 4 and 6 h after LPS-treatment. This reduction did not result from decreased transcription of IL-6 and TNFα genes, and therefore appeared to result from post-transcriptional inhibition of synthesis of these cytokines. MSO treatment did not inhibit total protein synthesis and did not reduce the production of a third LPS-triggered cytokine CXCL1, so the effect was not a toxic or global downregulation of the LPS response. The anti-inflammatory effects of a glutamine synthetase inhibitor were seen even though the medium contained abundant (2 mM) glutamine, suggesting that the target for this activity was not glutamine synthetase. In agreement with this hypothesis, the L,R isomer of MSO, which does not inhibit glutamine synthetase and was previously thought to be inert, both significantly reduced IL-6 secretion in isolated macrophages and increased survival in a mouse model for inflammatory liver failure.ConclusionsOur findings provide evidence for a novel target of MSO. Future attempts to identify the additional target would therefore also provide a target for therapies to treat diseases involving damaging cytokine responses.