ABSTRACT
Circadian disruption influences metabolic health. Metabolism modulates circadian function. However, the mechanisms coupling circadian rhythms and metabolism remain poorly understood. Here, we report that cystathionine ß-synthase (CBS), a central enzyme in one-carbon metabolism, functionally interacts with the core circadian protein cryptochrome 1 (CRY1). In cells, CBS augments CRY1-mediated repression of the CLOCK/BMAL1 complex and shortens circadian period. Notably, we find that mutant CBS-I278T protein, the most common cause of homocystinuria, does not bind CRY1 or regulate its repressor activity. Transgenic CbsZn/Zn mice, while maintaining circadian locomotor activity period, exhibit reduced circadian power and increased expression of E-BOX outputs. CBS function is reciprocally influenced by CRY1 binding. CRY1 modulates enzymatic activity of the CBS. Liver extracts from Cry1-/- mice show reduced CBS activity that normalizes after the addition of exogenous wild-type (WT) CRY1. Metabolomic analysis of WT, CbsZn/Zn , Cry1-/- , and Cry2-/- samples highlights the metabolic importance of endogenous CRY1. We observed temporal variation in one-carbon and transsulfuration pathways attributable to CRY1-induced CBS activation. CBS-CRY1 binding provides a post-translational switch to modulate cellular circadian physiology and metabolic control.
Subject(s)
Circadian Clocks/genetics , Circadian Rhythm/genetics , Cryptochromes/genetics , Cystathionine beta-Synthase/genetics , Metabolome/genetics , Protein Processing, Post-Translational , ARNTL Transcription Factors/genetics , ARNTL Transcription Factors/metabolism , Amino Acid Sequence , Animals , CLOCK Proteins/genetics , CLOCK Proteins/metabolism , Cryptochromes/deficiency , Cystathionine beta-Synthase/metabolism , E-Box Elements , Female , HEK293 Cells , Humans , Male , Metabolic Networks and Pathways/genetics , Mice , Mice, Knockout , Mutation , Period Circadian Proteins/genetics , Period Circadian Proteins/metabolism , Protein Binding , Sequence Alignment , Sequence Homology, Amino Acid , Signal TransductionABSTRACT
Light is a very important environmental factor that governs many cellular responses in organisms. As a consequence, organisms possess different kinds of light-sensing photoreceptors to regulate their physiological variables and adapt to a given habitat. The cryptochrome/photolyase family (CPF) includes photoreceptors that perform different functions in different organisms. Photolyases repair ultraviolet-induced DNA damage by a process known as photoreactivation using photons absorbed from the blue end of the light spectrum. On the other hand, cryptochromes act as blue light circadian photoreceptors in plants and Drosophila to regulate growth and development. In mammals, cryptochromes have light-independent functions and are very important transcriptional regulators that act at the molecular level as negative transcriptional regulators of the circadian clock. In this review, we highlight current knowledge concerning the structural and functional relationships of CPF members.
