CRY1 ve CBS Etkilesimin Sirkadyen Ritim ve Metabolizma Uzerindeki Iki Yonlu Etkisi

Circadian clock controls the physiology and behavior in order to synchronize them to 24-hr rhythm. Synchronization of physiological events in our body both prevents us from diseases and helps us to overcome the existing problems. Unlike the central clock located in the SCN (suprachiasmatic nucleus) which is regulated by light, peripheral clocks either regulated by central clock or by feeding cues. Despite the many efforts have been done in the field to understand how transcription and translation is controlled by circadian clock, they are not enough to explain the oscillation of 50% of the metabolites. There is little known about how circadian clock molecular machinery controls metabolism or post-translational regulations of core clock components to regulate metabolically-important proteins. Here we characterize a novel molecular interaction between one of the negative arm proteins of circadian clock (CRY1) and an important metabolic enzyme CBS (cystathionine-beta-synthase). Mutations resulting loss-of-function of CBS causes a multi-systemic disorder called homocystinuria. Physical interaction of these two proteins provides bi-directional regulation of both circadian rhythm and metabolism. Other than transcriptional repressor role of CRY1, as a novel post-translational regulatory mechanism, it binds to CBS and regulates metabolism by favoring oligomerization and increasing the activity of it. On the other hand, wild type CBS, but not disease-causing mutant CBS, binds to CRY1 and enhances the repressor activity. Additionally, we also analyzed the effect of mutant CBS which causes homocystinuria in humans. CBS-I278T cannot form oligomers and thus, doesn't have any enzyme activity. This single mutation blocks the interaction of CRY1 and CBS. We verified the physiologic importance of this interaction by performing untargeted metabolomics screen in Cry1-/- and Cbs-/- liver samples and analyzed the significantly affected pathways. Strikingly, Cry1-/- affects the same pathways that are affected by Cbs-/-. These pathways are transsulfuration pathway, lysine, arginine and proline metabolisms and urea cycle. Our results provide better understanding about how circadian clock and metabolism regulate each other at post-translational level, with direct protein-protein interactions. We anticipate that our results will provide new circadian perspective to treat CBS-caused homocystinuria disease.