Dataset Information

Chemical Systems Biology Reveals Mechanisms of Dissociated Glucocorticoid Receptor Signaling

ABSTRACT: Glucocorticoids display remarkable anti-inflammatory activity, but their use is limited by undesirable on-target effects including insulin resistance and skeletal muscle atrophy. We used a chemical systems biology approach called Ligand Class Analysis (LCA) to examine ligands designed to alter the receptor through distinct structural mechanisms. These ligands displayed a full range of activity profiles, providing the variance required to identify ligand-specific gene expression and transcriptional coregulator interaction patterns that were highly predictive of their effects on myocyte glucose disposal and protein balance. Anti-inflammatory effects were linked to inhibition of glucose disposal in skeletal muscle but not to muscle atrophy. This approach successfully predicted dissociated activity in vivo, identifying compounds that were muscle sparing or anabolic for protein balance and mitochondrial potential. LCA defines the mechanistic links between the ligand-receptor interface and the physiological outcomes of the ligands, a general approach that can be applied to any ligand-regulated allosteric signaling system.

ORGANISM(S): Mus musculus

PROVIDER: GSE149453 | GEO | 2020/09/08

REPOSITORIES: GEO

ACCESS DATA

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

Project description:In skeletal muscle, the pattern of electrical activity regulates the expression of proteins involved in synaptic transmission, contraction and metabolism. Disruptions in electrical activity, resulting from prolonged bed-rest, cast-immobilization or trauma, inevitably lead to muscle atrophy. The mechanisms that regulate muscle atrophy are poorly understood, but it seems likely that changes in gene expression play a key role in initiating and maintaining a muscle atrophy program. Previously, we found that Runx1, a transcription factor previously termed AML1, was substantially induced in muscle following denervation. More recently, we sought to determine whether this increase in Runx1 expression may be causally related to the morphological changes in skeletal muscle that accompany muscle disuse, notably muscle atrophy. We found that Runx1 is indeed required to sustain muscle and to minimize atrophy following denervation. Experiments described here are designed to identify the genes that are regulated by Runx1 in skeletal muscle with the particular goal of identifying genes that regulate muscle atrophy. We propose to use microarray analysis to identify genes, expressed in skeletal muscle, that are mis-regulated in mice lacking Runx1. We inactivated runx1 selectively in skeletal muscle and found that denervated myofibers in mutant mice atrophy far more (90% atrophy) than in wild-type mice (30% atrophy). We therefore reason that Runx1 activates and/or represses genes that are required to sustain muscle and to minimize atrophy. We generated MCK::cre; runx1f/- and runx1f/- control mice. In normal mice, an increase in runx1 expression is detected by two days after denervation and is maximal by five days after denervation. Muscle atrophy is first evident between one and two weeks after denervation. As we wish to avoid detecting global changes in gene expression that are associated with late stages of muscle atrophy, we plan to denervate muscle for three or five days and to compare gene expression in dissected innervated and denervated muscles from mutant and control mice. We will generate thirty samples for comparison-5 replicates per condition: Samples 1-3 from runx1f/- control mice. (1) innervated tibialis anterior muscles (TA); (2) 3-day-denervated TA; (3) 5-day-denervated TA. Samples 4-6 from MCK::cre; runx1f/- mice. (4) innervated TA; (5) 3-day-denervated TA; (6) 5-day-denervated TA. We obtain sufficient total RNA (10 micrograms) from each dissected muscle to avoid pooling samples. We will analyze adult mice of the same age (~six weeks after birth; most will be littermates) and sex-male. It is difficult to anticipate how many genes will be identified in this screen, as few target genes for Runx1 have been identified in any cell type and none in skeletal muscle. Moreover, although we would prefer to focus our attention on genes that are strongly dependent upon Runx1 expression (e.g. more than 5-fold difference in expression in wild-type and mutant mice), we do not know the extent to which target gene expression will depend upon Runx1. For these reasons, in these experiments, we will analyze expression from five âidenticalâ samples, so that we can be confident that even small (e.g. three-fold) differences in expression can be reliably determined. Importantly, in order to confirm results obtained from the microarray data, we will use other assays (RNase protection) to measure RNA expression of candidate genes in innervated and denervated muscles of wild-type and mutant mice.

Project description:Skeletal muscle atrophy is dictated by the balance between protein synthesis and protein breakdown, known as proteostasis. With advanced age, muscle atrophy contributes to development of co-morbidities, loss of strength and independence, and all-cause mortality. Aging also coincides with the accumulation of senescent cells within skeletal muscle that produce inflammatory products, known as the senescence associated secretory phenotype. Previously, we found that a metformin + leucine (MET+LEU) combination treatment had synergistic effects in aged mice to improve skeletal muscle structure and function during disuse atrophy. Therefore, the objective of this study was to determine the mechanisms by which MET+LEU exhibits muscle atrophy protection in vitro and if this occurs through cellular senescence. C2C12 myoblasts differentiated into myotubes were used to determine MET+LEU mechanisms during serum-deprivation (SD) atrophy. Single myofibers were isolated from aged (22-23 mo) C57Bl6/J mice, and human primary myoblasts were extracted from a healthy older adult donor. 25 + 125 µM MET+LEU treatment increased differentiation of myotubes and prevented SD induced atrophy. Low concentration (0.1 + 0.5 µM) MET+LEU had unique effects to prevent myotube atrophy and cause transcriptional reprogramming compared to individual therapies. SD increased inflammatory and cellular senescence pathways that was reversed with MET+LEU treatment. SD resulted in dysregulated proteostasis that was rescued with MET+LEU, and proteasome inhibition with MG-132 also rescued myotube atrophy. Cellular senescence transcriptional pathways and markers increased by SD were reversed with MET+LEU treatment, and dasatinib + quercetin (D+Q) senolytic treatment prevented myotube atrophy similar to MET+LEU. In aged myofibers, MET+LEU prevented SD atrophy, and in human primary myotubes MET+LEU prevented reductions in myonuclei fusion. These data provide evidence that MET+LEU has muscle cell intrinsic properties to prevent atrophy by reversing senescence and improving proteostasis

Dataset Information

Chemical Systems Biology Reveals Mechanisms of Dissociated Glucocorticoid Receptor Signaling

Dataset's files

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets