CLOCK promotes 3T3‐L1 cell proliferation via Wnt signaling

Abstract

Circadian genes control most of the physiological functions including cell cycle. Cell proliferation is a critical factor in the differentiation of progenitor cells. However, the role of Clock gene in the regulation of cell cycle via wingless-type (Wnt) pathway and the relationship between Clock and adipogenesis are unclear. We found that the circadian locomotor output cycles kaput (Clock) regulated the proliferation and the adipogenesis of 3T3-L1 preadipocytes. We found that Clock attenuation inhibited the viability of 3T3-L1 preadipocytes in the cell counting kit 8. The expression of c-Myc and Cyclin D1 decreased dramatically in 3T3-L1 when Clock was silenced with short interfering RNA and was also decreased in fat tissue and adipose tissue-derived stem cells of Clock D19 mice. Clock directly controls the expression of the components of Wnt signal transduction pathway, which was verified by serum shock, chromatin immunoprecipitation, Western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, IWR-1, a Wnt signal pathway inhibitor, inhibited the cell cycle promotion by CLOCK, which was detected by cell viability assay, flow cytometry, and qRT-PCR. Therefore, CLOCK transcription control of Wnt signaling promotes cell cycle progression in 3T3-L1 preadipocytes. Clock inhibited the adipogenesis on day 2 in 3T3-L1 cells via Oil Red O staining and qRT-PCR detection and probably related to cellular differentiation. These data provide evidence that the circadian gene Clock regulates the proliferation of preadipocytes and affects adipogenesis. V C 2016 IUBMB Life, 68(7):557-568, 2016

Social Isolation Modulates CLOCK Protein and Beta-Catenin Expression Pattern in Gonadotropin-Inhibitory Hormone Neurons in Male Rats

“…The relation between CLOCK and β-catenin in neuronal cells has not been elucidated by any other studies. Given that β-catenin has been predicted to have an E-box (CACGTG) binding site on its promoter, it is certainly possible that CLOCK may drive β-catenin expression directly via binding to the E-box in liver cells ( 47 ). This appears to explain the reduction of β-catenin fluctuations in relation to the reduction of CLOCK fluctuations as observed in our results, as well as the increase in CLOCK expression corresponding to a rise in nuclear β-catenin levels.…”

Melatonin promotes circadian rhythm‐induced proliferation through Clock/histone deacetylase 3/c‐Myc interaction in mouse adipose tissue

“…Melatonin and its oscillation influence several circadian biological rhythms through controlling the transcription and translation of clock genes in peripheral adipose tissues . There are multiple factors connecting the cell cycle and the circadian clock . Circadian locomotor output cycle kaput (Clock) combines with brain and muscle aryl hydrocarbon receptor nuclear translocator‐like 1 (Bmal1) to form a heterodimer.…”

Clock represses preadipocytes adipogenesis via GILZ

“…And PPAR‐γ mRNA rhythmicity is abolished in epigonadal fat of clock mutant mice (Kennaway, Owens, Voultsios, & Wight, ). Furthermore, we found downregulated Clock affect the early stage of adipogenesis of 3T3‐L1 cells (Zhu et al, ). However, studies revealing that Clock affects adipogenesis, thereby contributing to fat phenotype are yet lacking.…”