bims-ciryme 2024-05-26 papers

J Clin Endocrinol Metab. 2024 May 23. pii: dgae350. [Epub ahead of print]

Characterising 24-h skeletal muscle gene expression alongside metabolic & endocrine responses under diurnal conditions.

Harry A Smith, Iain Templeman, Max Davis, Tommy Slater, David J Clayton, Ian Varley, Lewis J James, Benita Middleton, Jonathan D Johnston, Leonidas G Karagounis, Kostas Tsintzas, Dylan Thompson, Javier T Gonzalez, Jean-Philippe Walhin, James A Betts.

CONTEXT: Skeletal muscle plays a central role in the storage, synthesis, and breakdown of nutrients, yet little research has explored temporal responses of this human tissue, especially with concurrent measures of systemic biomarkers of metabolism.
OBJECTIVE: To characterise temporal profiles in skeletal muscle expression of genes involved in carbohydrate metabolism, lipid metabolism, circadian clocks, and autophagy and descriptively relate them to systemic metabolites and hormones during a controlled laboratory protocol.
METHODS: Ten healthy adults (9M/1F, mean ± SD: age: 30 ± 10 y; BMI: 24.1 ± 2.7 kg·m-2) rested in the laboratory for 37 hours with all data collected during the final 24 hours of this period (i.e., 0800-0800 h). Participants ingested hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 2200-0700 h. Blood samples were collected hourly for endocrine and metabolite analyses, with muscle biopsies occurring every 4 h from 1200 h to 0800 h the following day to quantify gene expression.
RESULTS: Plasma insulin displayed diurnal rhythmicity peaking at 1804 h. Expression of skeletal muscle genes involved in carbohydrate metabolism (Name - Acrophase; GLUT4 - 1440 h; PPARGC1A -1613 h; HK2 - 1824 h) and lipid metabolism (FABP3 - 1237 h; PDK4 - 0530 h; CPT1B - 1258 h) displayed 24 h rhythmicity that reflected the temporal rhythm of insulin. Equally, circulating glucose (0019 h), NEFA (0456 h), glycerol (0432 h), triglyceride (2314 h), urea (0046 h), CTX (0507 h) and cortisol concentrations (2250 h) also all displayed diurnal rhythmicity.
CONCLUSION: Diurnal rhythms were present in human skeletal muscle gene expression as well systemic metabolites and hormones under controlled diurnal conditions. The temporal patterns of genes relating to carbohydrate and lipid metabolism alongside circulating insulin are consistent with diurnal rhythms being driven in part by the diurnal influence of cyclic feeding and fasting.

Keywords: Circadian rhythms; Diurnal; Gene expression; Glucose; Lipids; Skeletal muscle

DOI: https://doi.org/10.1210/clinem/dgae350

J Biol Chem. 2024 May 20. pii: S0021-9258(24)01892-1. [Epub ahead of print] 107391

Hierarchical and scaffolded phosphorylation of two degrons controls PER2 stability.

Joel Celio Francisco, David M Virshup.

The duration of the transcription-repression cycles that give rise to mammalian circadian rhythms is largely determined by the stability of the PERIOD protein, the rate-limiting components of the molecular clock. The degradation of PERs is tightly regulated by multisite phosphorylation by Casein Kinase 1 (CK1δ/ε). In this phosphoswitch, phosphorylation of a PER2 degron (Degron 2, D2) causes degradation, while phosphorylation of the PER2 Familial Advanced Sleep Phase (FASP) domain blocks CK1 activity on the degron, stabilizing PER2. However, this model and many other studies of PER2 degradation do not include the second degron of PER2 that is conserved in PER1, termed Degron 1, D1. We examined how these two degrons contribute to PER2 stability, affect the balance of the phosphoswitch, and how they are differentiated by CK1. Using PER2-luciferase fusions and real-time luminometry, we investigated the contribution of both D2 and of CK1-PER2 binding. We find that D1, like D2, is a substrate of CK1 but that D1 plays only a 'backup' role in PER2 degradation. Notably, CK1 bound to a PER1:PER2 dimer protein can phosphorylate PER1 D1 in trans. This scaffolded phosphorylation provides additional levels of control to PER stability and circadian rhythms.

Keywords: Casein Kinase 1; Period; circadian rhythms; phosphoswitch; scaffolded phosphorylation; sleep disorder

DOI: https://doi.org/10.1016/j.jbc.2024.107391

EMBO J. 2024 May 22.

Circadian regulation of macromolecular complex turnover and proteome renewal.

Estere Seinkmane, Anna Edmondson, Sew Y Peak-Chew, Aiwei Zeng, Nina M Rzechorzek, Nathan R James, James West, Jack Munns, David Cs Wong, Andrew D Beale, John S O'Neill.

Although costly to maintain, protein homeostasis is indispensable for normal cellular function and long-term health. In mammalian cells and tissues, daily variation in global protein synthesis has been observed, but its utility and consequences for proteome integrity are not fully understood. Using several different pulse-labelling strategies, here we gain direct insight into the relationship between protein synthesis and abundance proteome-wide. We show that protein degradation varies in-phase with protein synthesis, facilitating rhythms in turnover rather than abundance. This results in daily consolidation of proteome renewal whilst minimising changes in composition. Coupled rhythms in synthesis and turnover are especially salient to the assembly of macromolecular protein complexes, particularly the ribosome, the most abundant species of complex in the cell. Daily turnover and proteasomal degradation rhythms render cells and mice more sensitive to proteotoxic stress at specific times of day, potentially contributing to daily rhythms in the efficacy of proteasomal inhibitors against cancer. Our findings suggest that circadian rhythms function to minimise the bioenergetic cost of protein homeostasis through temporal consolidation of protein turnover.

Keywords: Circadian; Proteostasis; Ribosome; SILAC

DOI: https://doi.org/10.1038/s44318-024-00121-5