Yeast functional analysis: Identification of two essential genes involved in ER to Golgi trafficking
TRAFFIC
Authors: Belgareh-Touze, N; Corral-Debrinski, M; Launhardt, H; Galan, JM; Munder, T; Le Panse, S; Haguenauer-Tsapis, R
Abstract
We screened for genes potentially involved in the secretory and vacuolar pathways a collection of 61 yeast strains, each bearing an essential orphan gene regulated by the tetO(7) -CYC1 promoter that can be down-regulated by doxycycline. After down-regulating the expression of these genes, we performed systematic Western blot analysis for markers of the secretory and vacuolar pathways that undergo post-translational modifications in their intracellular trafficking. Accumulation of protein precursors, revealed by Western immunoblot analysis, indicates defects in the secretory pathway or in associated biochemical modifications. After screening the whole collection, we identified two genes involved in ER to Golgi trafficking: RER2 , a cis -prenyl transferase, and USE1 , the function of which was unknown. We demonstrated that repression of USE1 also leads to BiP secretion, and therefore likely affects retrograde, in addition to anterograde, ER to Golgi trafficking. The collection also includes two essential genes involved in intracellular trafficking that were conveniently repressed without resulting growth or trafficking defects.
ELK1 Transcription Factor Linked to Dysregulated Striatal Mu Opioid Receptor Signaling Network and OPRM1 Polymorphism in Human Heroin Abusers
BIOLOGICAL PSYCHIATRY
Authors: Sillivan, Stephanie E.; Whittard, John D.; Jacobs, Michelle M.; Ren, Yanhua; Mazloom, Amin R.; Caputi, Francesca F.; Horvath, Monika; Keller, Eva; Ma'ayan, Avi; Pan, Ying-Xian; Chiang, Lillian W.; Hurd, Yasmin L.
Abstract
Background: Abuse of heroin and prescription opiate medications has grown to disturbing levels. Opioids mediate their effects through mu opioid receptors (MOR), but minimal information exists regarding MOR-related striatal signaling relevant to the human condition. The striatum is a structure central to reward and habitual behavior and neurobiological changes in this region are thought to underlie the pathophysiology of addiction disorders. Methods: We examined molecular mechanisms related to MOR in postmortem human brain striatal specimens from a homogenous European Caucasian population of heroin abusers and control subjects and in an animal model of heroin self-administration. Expression of ets-like kinase 1 (ELK1) was examined in relation to polymorphism of the MOR gene OPRM1 and drug history. Results: A characteristic feature of heroin abusers was decreased expression of MOR and extracellular regulated kinase signaling networks, concomitant with dysregulation of the downstream transcription factor ELK1. Striatal ELK1 in heroin abusers associated with the polymorphism rs2075572 in OPRM1 in a genotype dose-dependent manner and correlated with documented history of heroin use, an effect reproduced in an animal model that emphasizes a direct relationship between repeated heroin exposure and ELK1 dysregulation. A central role of ELK1 was evidenced by an unbiased whole transcriptome microarray that revealed similar to 20% of downregulated genes in human heroin abusers are ELK1 targets. Using chromatin immune precipitation, we confirmed decreased ELK1 promoter occupancy of the target gene Use1. Conclusions: ELK1 is a potential key transcriptional regulatory factor in striatal disturbances associated with heroin abuse and relevant to genetic mutation of OPRM1.