Harvey, C. | Search bioRxiv

bioRxiv2018

Dissection of yeast pleiotropic drug resistance regulation reveals links between cell cycle regulation and control of drug pump expression

Eukaryotes utilize a highly-conserved set of drug efflux transporters to confer pleiotropic drug resistance (PDR). Despite decades of effort interrogating this process, multiple aspects of the PDR process, in particular PDR regulation, remain mysterious. In order to interrogate the regulation of this critical process, we have developed a small-molecule responsive biosensor that couples PDR transcriptional induction to growth rate in Saccharomyces cerevisiae. We applied this system to genome-wide screens for potential PDR regulators using the homozygous diploid deletion collection. These screens identified and characterized a series of genes with significant but previously uncharacterized roles in the modulation of the yeast PDR in addition to recapitulating previously-known factors involved in PDR regulation. Furthermore, we demonstrate that disruptions of the mitotic spindle checkpoint assembly lead to elevated PDR response in response to exposure to certain compounds. These results not only establish our biosensor system as a viable tool to investigate PDR in high-throughput, but also uncovers novel control mechanisms governing PDR response and a previously uncharacterized link between this process and cell cycle regulation.\n\nSignificancePleiotropic drug resistance (PDR) is a conserved mechanism by which cells utilize membrane bound pumps to transport chemicals out of the cell. Here, we develop a growth-based biosensor system in yeast that enables high-throughput identification of factors that transcriptionally regulate PDR. Among the novel PDR regulators identified here, we show that spindle assembly checkpoint (SAC) proteins, which are important for cell cycle regulation, inhibit hyperactivation of PDR upon drug treatment. This result provides insights into PDR regulation, as well as potential targets for therapeutic intervention, particularly in chemoresistant cancers where the cell cycle regulation is often disrupted.

genetics↗

bioRxiv2017

Prefrontal cortex regulates amygdala response to threat in trait anxiety

BackgroundHighly co-morbid mood and anxiety disorders are associated with aberrant fronto-limbic signalling during emotional processing. Animal models suggest that hypoactive prefrontal cortex weakens top-down control of limbic structures, causing heightened limbic and behavioural reactivity to negative information. Here we tested for this causal mechanism in human trait anxiety. We reasoned that if dorsolateral prefrontal cortex controls amygdala response to affective information, then stimulation of that brain region should reduce the hyperactive amygdala threat responsivity seen in trait anxiety.\n\nMethodsUsing a within-subjects design, sixteen high-trait anxious females received active and sham transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex, in counterbalanced order, with sessions timed to be at least one month apart. Each session was followed immediately by a functional magnetic resonance imaging (fMRI) scan during which participants performed an attentional task with threat-related distractors.\n\nResultsAs predicted, compared to sham stimulation, active prefrontal cortex stimulation reduced amygdala threat reactivity and simultaneously increased activity in cortical regions associated with attentional control and improved task accuracy.\n\nConclusionsThese results demonstrate a causal role for impoverished frontal regulation of amygdaloid function in attentional capture by threat in trait anxiety. The finding that prefrontal stimulation reduces amygdala threat reactivity acutely indicates a neurocognitive mechanism that could contribute to tDCS treatment effects in affective disorders.

neuroscience↗