Selective interactions of spinophilin with the C-terminal domains of the δ- and μ-opioid receptors and G proteins differentially modulate opioid receptor signaling

Previous studies have shown that the intracellular domains of opioid receptors serve as platforms for the formation of a multi-component signaling complex consisting of various interacting partners (Leontiadis et al., 2009, Cell Signal. 21, 1218-1228; Georganta et al., 2010, Neuropharmacology, 59(3), 139-148). In the present study we demonstrate that spinophilin a dendritic-spine enriched scaffold protein associates with δ- and μ-opioid receptors (δ-ΟR, μ-OR) constitutively in HEK293 an interaction that is altered upon agonist administration and enhanced upon forskolin treatment for both μ-OR and δ-ΟR. Spinophilin association with the opioid receptors is mediated via the third intracellular loop and a conserved region of the C-terminal tails. The portion of spinophilin responsible for interaction with the δ-OR and μ-OR is narrowed to a region encompassing amino acids 151-444. Spinophilin, RGS4, Gα and Gβγ subunits of G proteins form a multi-protein complex using specific regions of spinophilin and a conserved amino acid stretch of the C-terminal tails of both δ-μ-ORs. Expression of spinophilin in HEK293 cells potentiated DPDPE-mediated adenylyl-cyclase inhibition of δ-OR leaving unaffected the levels of cAMP accumulation mediated by the μ-OR. Moreover, measurements of extracellular signal regulated kinase (ERK1,2) phosphorylation indicated that the presence of spinophilin attenuated agonist-driven ERK1,2 phosphorylation mediated upon activation of the δ-OR but not the μ-OR. Collectively, these findings suggest that spinophilin associates with both δ- and μ-ΟR and G protein subunits in HEK293 cells participating in a multimeric signaling complex that displays a differential regulatory role in opioid receptor signaling.     

Mechanistic studies of the modulation of cleavage activity of topoisomerase I by DNA adducts of mono- and bi-functional PtII complexes

Using electrophoresis and replication mapping, we show that the presence of DNA adducts of bifunctional antitumor cisplatin or monodentate [PtCl(dien)]Cl (dien = diethylenetriamine) in the substrate DNA inhibits eukaryotic topoisomerase 1 (top1) action, the adducts of cisplatin being more effective. The presence of camptothecin in the samples of platinated DNA markedly enhances effects of Pt–DNA adducts on top1 activity. Interestingly, the effects of Pt–DNA adducts on the catalytic activity of top1 in the presence of camptothecin differ depending on the sequence context. A multiple metallation of the short nucleotide sequences on the scissile strand, immediately downstream of the cleavage site impedes the cleavage by top1. On the other hand, DNA cleavage by top1 at some cleavage sites which were not platinated in their close proximity is notably enhanced as a consequence of global platination of DNA. We suggest that this enhancement of DNA cleavage by top1 may consist in its inability to bind to other cleavage sites platinated in their close neighborhood; thus, more molecules of top1 may become available for cleavage at the sites where top1 normally cleaves and where platination does not interfere.     

Psychophysiological Responses of Female Headache Sufferers and Controls Using a Picture-Viewing Paradigm

Despite the advancement of the biopsychosocial model, the interrelationship between behavioral, emotional, and physiological factors in tension-type headache (TTH) remains unclear. Using a picture-viewing paradigm, the present study investigated differences between females with TTH and controls on physiological reactivity, affective valence and arousal, and oral motor habits. In addition, the concordance between EMG activity and self-reported oral habits (i.e., proprioceptive awareness) and EMG activity and self-reported affect (i.e., affective coherence) were measured using within-subject correlations per individual and then compared between groups. Data were analyzed for 27 TTH sufferers and 27 controls who completed a questionnaire packet followed by a psychophysiological assessment consisting of 3 phases (adaptation, scheduled-viewing, recovery) with EMG activity recorded continuously at 3 sites (frontalis, corrugator, zygomatic). During the scheduled-viewing phase, participants were presented with 24 pictures designed to elicit positive, neutral, and negative affect. Compared to controls, the headache group reported elevations in pain, oral habits, and stress across the 3 phases of the assessment, along with elevations in arousal while viewing the pictures. There were no significant differences between the groups in EMG activity while viewing the pictures. Analyses on concordance revealed partial evidence for poor proprioceptive awareness and affective coherence among the headache group, although the correlations were not significantly different than the control group. These findings suggest that arousal, stress perception, and oral habits may play a role in the pathophysiology of TTH and that within-subject designs should be tested further against group designs when measuring psychophysiological concordance.     

Enhanced nuclear proteomics

Nuclear proteomics provides an opportunity to examine protein effectors that contribute to cellular phenotype. Both the quality and sensitivity of gel-based nuclear proteomics are limited, however, by the over-representation of histones in the protein mixture. These highly charged proteins overshadow rare species and interfere with IEF. A nuclear isolation and protein extraction procedure, tested on human embryonic stem cells, is reported that effectively isolates intact nuclei and then depletes the sample of histones by taking advantage of their ability to form an insoluble complex with DNA at lower pH (even under denaturing conditions). Ubiquitous histones and abundant nuclear actin, are depleted up to 99 +/- 0.02 and 42 +/- 5%, respectively. This technique greatly improves electrofocusing efficacy and nearly doubles the number of detected protein spots. This approach to nuclear protein isolation for 2-D PAGE opens the door to better investigation of nuclear protein dynamics.