Circadian period is compensated for repressor protein turnover rates in single cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 121; no. 34; p. e2404738121
• Main Authors: Gabriel, Christian H, Del Olmo, Marta, Rizki Widini, Arunya, Roshanbin, Rashin, Woyde, Jonas, Hamza, Ebrahim, Gutu, Nica-Nicoleta, Zehtabian, Amin, Ewers, Helge, Granada, Adrian, Herzel, Hanspeter, Kramer, Achim
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 20.08.2024
• Subjects: Animals; Biological clocks; Circadian Clocks - physiology; Circadian rhythm; Circadian Rhythm - physiology; Circadian rhythms; Cryptochromes - genetics; Cryptochromes - metabolism; Fluctuations; Fluorescence; Heterogeneity; Humans; Mammalian cells; Mathematical models; Metabolism; Mice; Period 1 protein; Period Circadian Proteins - genetics; Period Circadian Proteins - metabolism; Protein Stability; Protein turnover; Proteins; Repressor Proteins - genetics; Repressor Proteins - metabolism; Single-Cell Analysis; Turnover rate; metabolic compensation; circadian rhythms; single-cell imaging; fluorescence microscopy; protein degradation
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2404738121

Most mammalian cells have molecular circadian clocks that generate widespread rhythms in transcript and protein abundance. While circadian clocks are robust to fluctuations in the cellular environment, little is known about the mechanisms by which the circadian period compensates for fluctuating metabolic states. Here, we exploit the heterogeneity of single cells both in circadian period and a metabolic parameter-protein stability-to study their interdependence without the need for genetic manipulation. We generated cells expressing key circadian proteins (CRYPTOCHROME1/2 (CRY1/2) and PERIOD1/2 (PER1/2)) as endogenous fusions with fluorescent proteins and simultaneously monitored circadian rhythms and degradation in thousands of single cells. We found that the circadian period compensates for fluctuations in the turnover rates of circadian repressor proteins and uncovered possible mechanisms using a mathematical model. In addition, the stabilities of the repressor proteins are circadian phase dependent and correlate with the circadian period in a phase-dependent manner, in contrast to the prevailing model.