Role of circadian CLOCK signaling in cellular senescence.

The circadian rhythm is a key biological mechanism that aligns organisms' physiological processes with Earth's 24-h light-dark cycle, crucial for cellular and tissue homeostasis. Disruption of this system is linked to accelerated aging and age-related diseases. Central to circadian regulation is the CLOCK protein, which controls gene transcription related to tissue homeostasis, cellular senescence, and DNA repair. Research reveals CLOCK's dual role: in normal cells, it supports rejuvenation by activating DNA repair factors like XPA and modulating metabolism; in tumor cells, CLOCK signaling is often hijacked by oncogenic drivers like c-MYC and Pdia3, which inhibit telomere shortening / cellular senescence, thereby fostering uncontrolled proliferation and tumorigenesis. Additionally, gut microbiota-derived aryl hydrocarbon receptor (AhR) signals can disrupt the CLOCK-BMAL1 complex, affecting circadian rhythms. CLOCK also interacts with mTOR and NF-κB pathways to regulate autophagy and mitigate harmful secretions impacting tissue function. This review examines the molecular links between CLOCK and cellular senescence, drawing from animal and human studies, to highlight CLOCK's role in aging and its potential as a target for anti-aging therapies.