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Browsing by Subject "Ganglia, Spinal"
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Item Inhibition of the Ubc9 E2 SUMO-conjugating enzyme-CRMP2 interaction decreases NaV1.7 currents and reverses experimental neuropathic pain(Lippincott, Williams & Wilkins, 2018-10) François-Moutal, Liberty; Dustrude, Erik T.; Wang, Yue; Brustovetsky, Tatiana; Dorame, Angie; Ju, Weina; Moutal, Aubin; Perez-Miller, Samantha; Brustovetsky, Nickolay; Gokhale, Vijay; Khanna, May; Khanna, Rajesh; Pharmacology and Toxicology, School of MedicineWe previously reported that destruction of the small ubiquitin-like modifier (SUMO) modification site in the axonal collapsin response mediator protein 2 (CRMP2) was sufficient to selectively decrease trafficking of the voltage-gated sodium channel NaV1.7 and reverse neuropathic pain. Here, we further interrogate the biophysical nature of the interaction between CRMP2 and the SUMOylation machinery, and test the hypothesis that a rationally designed CRMP2 SUMOylation motif (CSM) peptide can interrupt E2 SUMO-conjugating enzyme Ubc9-dependent modification of CRMP2 leading to a similar suppression of NaV1.7 currents. Microscale thermophoresis and amplified luminescent proximity homogeneous alpha assay revealed a low micromolar binding affinity between CRMP2 and Ubc9. A heptamer peptide harboring CRMP2's SUMO motif, also bound with similar affinity to Ubc9, disrupted the CRMP2-Ubc9 interaction in a concentration-dependent manner. Importantly, incubation of a tat-conjugated cell-penetrating peptide (t-CSM) decreased sodium currents, predominantly NaV1.7, in a model neuronal cell line. Dialysis of t-CSM peptide reduced CRMP2 SUMOylation and blocked surface trafficking of NaV1.7 in rat sensory neurons. Fluorescence dye-based imaging in rat sensory neurons demonstrated inhibition of sodium influx in the presence of t-CSM peptide; by contrast, calcium influx was unaffected. Finally, t-CSM effectively reversed persistent mechanical and thermal hypersensitivity induced by a spinal nerve injury, a model of neuropathic pain. Structural modeling has now identified a pocket-harboring CRMP2's SUMOylation motif that, when targeted through computational screening of ligands/molecules, is expected to identify small molecules that will biochemically and functionally target CRMP2's SUMOylation to reduce NaV1.7 currents and reverse neuropathic pain.Item Prostaglandin E2 enhances bradykinin-stimulated release of neuropeptides from rat sensory neurons in culture(Society for Neuroscience, 1994-08) Vasko, MR; Campbell, WB; Waite, KJ; Pharmacology and Toxicology, School of MedicineProstaglandins are known to enhance the inflammatory and nociceptive actions of other chemical mediators of inflammation such as bradykinin. One possible mechanism for this sensitizing action is that prostanoids augment the release of neuroactive substances from sensory neurons. To initially test this hypothesis, we examined whether selected prostaglandins could enhance the resting or bradykinin-evoked release of immunoreactive substance P (iSP) and/or immunoreactive calcitonin gene-related peptide (iCGRP) from sensory neurons in culture. Bradykinin alone causes a concentration-dependent increase in the release of iSP and iCGRP from isolated sensory neurons, and this action is abolished in the absence of extracellular calcium. Pretreating the neurons with PGE2 (10 nM to 1 microM) potentiates the bradykinin-evoked release of both iSP and iCGRP by approximately two-to fourfold. At these concentrations, PGE2 alone did not significantly alter peptide release. Exposing the cultures to 1 microM PGF2 alpha is ineffective in altering either resting or bradykinin-evoked peptide release. Sensory neurons in culture contain cyclooxygenase-like immunoreactivity suggesting that the enzyme that converts arachidonic acid to prostaglandins is present. In addition, pretreating cultures with 14C-arachidonic acid yields radiolabeled eicosanoids that cochromatograph with known prostaglandin standards. Preexposing cultures to indomethacin abolishes the production of prostaglandins and attenuates the bradykinin-stimulated release of iSP and iCGRP. This implies that the synthesis of prostaglandins contributes to the bradykinin-evoked release of peptides. The augmentation of bradykinin-induced release of iSP and iCGRP by PGE2 may be one mechanism to account for the inflammatory and hyperalgesic actions of this eicosanoid.Item Regulation of Voltage-Gated Ca2+ Currents by Ca2+/Calmodulin-dependent Protein Kinase II in Resting Sensory Neurons(Elsevier, 2014-09) Kostic, Sandra; Pan, Bin; Guo, Yuan; Yu, Hongwei; Sapunar, Damir; Kwok, Wai-Meng; Hudmon, Andy; Wu, Hsiang-En; Hogan, Quinn H.; Department of Biochemistry and Molecular Biology, IU School of MedicineCalcium/calmodulin-dependent protein kinase II (CaMKII) is recognized as a key element in encoding depolarization activity of excitable cells into facilitated voltage-gated Ca2+ channel (VGCC) function. Less is known about the participation of CaMKII in regulating VGCCs in resting cells. We examined constitutive CaMKII control of Ca2+ currents in peripheral sensory neurons acutely isolated from dorsal root ganglia (DRGs) of adult rats. The small molecule CaMKII inhibitor KN-93 (1.0μM) reduced depolarization-induced ICa by 16 – 30% in excess of the effects produced by the inactive homolog KN-92. The specificity of CaMKII inhibition on VGCC function was shown by efficacy of the selective CaMKII blocking peptide autocamtide-2-related inhibitory peptide in a membrane-permeable myristoylated form, which also reduced VGCC current in resting neurons. Loss of VGCC currents is primarily due to reduced N-type current, as application of mAIP selectively reduced N-type current by approximately 30%, and prior N-type current inhibition eliminated the effect of mAIP on VGCCs, while prior block of L-type channels did not reduce the effect of mAIP on total ICa. T-type currents were not affected by mAIP in resting DRG neurons. Transduction of sensory neurons in vivo by DRG injection of an adeno-associated virus expressing AIP also resulted in a loss of N-type currents. Together, these findings reveal a novel molecular adaptation whereby sensory neurons retain CaMKII support of VGCCs despite remaining quiescent.