Physiological mechanism by which acetyl CoA carboxylase is regulated

Off-target effects of psychoactive drugs revealed by genome-wide assays in yeast

To better understand off-target effects of widely prescribed psychoactive drugs, we performed a comprehensive series of chemogenomic screens using the budding yeast Saccharomyces cerevisiae as a model system. Because the known human targets of these drugs do not exist in yeast, we could employ the yeast gene deletion collections and parallel fitness profiling to explore potential off-target effects in a genome-wide manner. Among 214 tested, documented psychoactive drugs, we identified 81 compounds that inhibited wild-type yeast growth and were thus selected for genome-wide fitness profiling. Many of these drugs had a propensity to affect multiple cellular functions. The sensitivity profiles of half of the analyzed drugs were enriched for core cellular processes such as secretion, protein folding, RNA processing, and chromatin structure. Interestingly, fluoxetine (Prozac) interfered with establishment of cell polarity, cyproheptadine (Periactin) targeted essential genes with chromatin-remodeling roles, while paroxetine (Paxil) interfered with essential RNA metabolism genes, suggesting potential secondary drug targets. We also found that the more recently developed atypical antipsychotic clozapine (Clozaril) had no fewer off-target effects in yeast than the typical antipsychotics haloperidol (Haldol) and pimozide (Orap). Our results suggest that model organism pharmacogenetic studies provide a rational foundation for understanding the off-target effects of clinically important psychoactive agents and suggest a rational means both for devising compound derivatives with fewer side effects and for tailoring drug treatment to individual patient genotypes.

Short-term regulation of acetyl CoA carboxylase: is the key enzyme in long-chain fatty acid synthesis regulated by an existing physiological mechanism?

Acetyl CoA carboxylase, the rate-limiting enzyme in regulating fatty acid synthesis, is thought to be controlled by allosteric effectors, its state of aggregation, covalent modulation and protein inhibitors. It is still obscure whether citrate, a positive allosteric effector, and long-chain fatty acyl CoA esters, negative allosteric effectors, function physiologically to regulate acetyl CoA carboxylase activity. New evidence from several laboratories reveals that the covalent phosphorylation may not involve regulation of acetyl CoA carboxylase activity. Protein inhibitors from liver cytosol and a peptide from fat cells were found to regulate acetyl CoA carboxylase both in vivo and in vitro. Coenzyme A, guanosine 5-monophosphate and phosphatidylinositol 4,5-bisphosphate may have an indirect effect, but certainly no direct involvement, on carboxylase activity.