Circadian modulation of proteasome activity and accumulation of oxidized protein in human embryonic kidney HEK 293 cells and primary dermal fibroblasts

Abstract

The circadian system orchestrates the timing of physiological processes of an organism living in daily environmental changes. Disruption of circadian rhythmicity has been shown to result in increased oxidative stress and accelerated aging. The circadian regulation of antioxidant defenses suggests that other redox homeostasis elements such as oxidized protein degradation by the proteasome, could also be modulated by the circadian clock. Hence, we have investigated whether proteasome activities and oxidized protein levels would exhibit circadian rhythmicity in synchronized cultured mammalian cells and addressed the mechanisms underlying this process. Using synchronized human embryonic kidney HEK 293 cells and primary dermal fibroblasts, we have shown that the levels of carbonylated protein and proteasome activity vary rhythmically following a 24h period. Such a modulation of proteasome activity is explained, at least in part, by the circadian expression of both Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and the proteasome activator PA28αβ. HEK 293 cells showed an increased susceptibility to oxidative stress coincident with the circadian-dependent lower activity of the proteasome. Finally, in contrast to young fibroblasts, no circadian modulation of the proteasome activity and carbonylated protein levels was evidenced in senescent fibroblasts. This paper reports a novel role of the circadian system for regulating proteasome function. In addition, the observation that proteasome activity is modulated by the circadian clock opens new avenues for both the cancer and the aging fields, as exemplified by the rhythmic resistance of immortalized cells to oxidative stress and loss of rhythmicity of proteasome activity in senescent fibroblasts.

Diurnal Rhythms Spatially and Temporally Organize Autophagy

“…Low-amplitude rhythms in proteasome activity were demonstrated in immortalized tissue culture cells using model peptide substrates ( Desvergne et al, 2016 ). We asked whether similar rhythms in proteasomal activity could be detected in mouse liver and, if so, what temporal relationship exists between autophagic and proteasomal activity.…”

Adaptive homeostasis and the free radical theory of ageing

“…At the same time, Nrf2 nuclear translocation and transcriptional binding to Electrophile Responsive Elements (EpRE’s), also called Antioxidant Response Elements (ARE’s) within the upstream regulatory regions of many target genes [52] (including those encoding 20S Proteasome subunits) [41], leads to de novo synthesis and further elevation of the available 20S Proteasome pool [41, 168]. Collectively, these events ensure that the cell has both an immediate (minutes) and long-term (hours) source of available and functionally competent 20S Proteasome, with these responses appearing as an in-phase mediated process [169].…”

Redox biology and the interface between bioenergetics, autophagy and circadian control of metabolism

“…These observations suggest that that there is tissue-specific control of protein synthesis, in terms of time-of-day-dependent oscillations. Although little is known regarding daily oscillations in protein degradation, evidence exists in support of the concept that both proteasome activity and autophagy likely exhibit 24-hr rhythms [195, 196]. In the latter case, histologic and biochemical approaches suggest increased autophagic flux in the liver and heart during the sleep phase [197].…”