In today’s sleep and circadian rhythm journal club, we discussed a follow-up to a previously published study from a January issue of PNAS. In the current and previous studies, a massive team of scientists and robots screened thousands (literally, about 60,000) of compounds to identify those that alter circadian rhythmicity in various cell lines with luciferase-expressing genes, namely Per2 and Bmal1. While the previous paper focused on many classes of compounds, the present study focused on one: carbazole derivatives. After a very thorough array of molecular assays, it was found that this class of compounds (KL001) gates circadian rhythmicity by means of interacting with constituents of the molecular circadian clock, particularly the negative transcription factor CRY. And the amount of specificity for CRY is very strong as shown in this immunoblot in which there is little KL001 binding to the positive transcriptional factors Clock and Bmal1.
In order to illustrate a public health relevance, it was also found that KL001 modulates gluconeogenesis in the liver. This was examined by measuring changes in the expression of gluconeogenesis-related genes (ones that I vaguely recall from a bioenergetics course that I took in graduate school) in the absence or presence of glucagon which is the hormone released from the pancreas that is responsible for initiating gluconeogenesis. The marked change in gene expression in the presence of glucagon and/or KL001 is documented below. While this compound does have the potential to evolve in to a weight loss drug, the likelihood of it being so is basically none. Why else would this information have been published?
Hirota T, Lee JW, St John PC, Sawa M, Iwaisako K, Noguchi T, Pongsawakul PY, Sonntag T, Welsh DK, Brenner DA, Doyle FJ 3rd, Schultz PG, & Kay SA (2012). Identification of small molecule activators of cryptochrome. Science (New York, N.Y.), 337 (6098), 1094-7 PMID: 22798407