Opioids are first-line drugs for moderate to severe acute pain and cancer pain. However, these medications are associated with severe side effects, and whether they are efficacious in treatment of chronic nonmalignant pain remains controversial. Medications that act through alternative molecular mechanisms are critically needed. Antagonists of α9α10 nicotinic acetylcholine receptors (nAChRs) have been proposed as an important nonopioid mechanism based on studies demonstrating prevention of neuropathology after trauma-induced nerve injury. However, the key α9α10 ligands characterized to date are at least two orders of magnitude less potent on human vs. rodent nAChRs, limiting their translational application. Furthermore, an alternative proposal that these ligands achieve their beneficial effects by acting as agonists of GABA B receptors has caused confusion over whether blockade of α9α10 nAChRs is the fundamental underlying mechanism. To address these issues definitively, we developed RgIA4, a peptide that exhibits high potency for both human and rodent α9α10 nAChRs, and was at least 1,000-fold more selective for α9α10 nAChRs vs. all other molecular targets tested, including opioid and GABA B receptors. A daily s.c. dose of RgIA4 prevented chemotherapy-induced neuropathic pain in rats. In wild-type mice, oxaliplatin treatment produced cold allodynia that could be prevented by RgIA4. Additionally, in α9 KO mice, chemotherapy-induced development of cold allodynia was attenuated and the milder, temporary cold allodynia was not relieved by RgIA4. These findings establish blockade of α9-containing nAChRs as the basis for the efficacy of RgIA4, and that α9-containing nAChRs are a critical target for prevention of chronic cancer chemotherapyinduced neuropathic pain.pain | chemotherapy | alpha9 | nicotinic

Angiotensin signaling promotes interactions between AKAP150, PKC, and TRPV4 channels to form signaling domains that control Ca2+ influx into arterial myocytes.

TRPV2 is a member of the transient receptor potential family of ion channels involved in chemical and thermal pain transduction. Unlike the related TRPV1 channel, TRPV2 does not appear to bind either calmodulin or ATP in its N-terminal ankyrin repeat domain. In addition, it does not contain a calmodulin-binding site in the distal C-terminal region, as has been proposed for TRPV1. We have found that TRPV2 channels transiently expressed in F-11 cells undergo Ca 2ϩ -dependent desensitization, similar to the other TRPVs, suggesting that the mechanism of desensitization may be conserved in the subfamily of TRPV channels. TRPV2 desensitization was not altered in whole-cell recordings in the presence of calmodulin inhibitors or on coexpression of mutant calmodulin but was sensitive to changes in

For Cys-loop ligand-gated ion channels (LGIC), the protein movements that couple neurotransmitter binding to channel gating are not well known. The pre-M1 region, which links the extracellular agonist-binding domain to the channel-containing transmembrane domain, is in an ideal position to transduce binding site movements to gating movements. A cluster of cationic residues in this region is observed in all LGIC subunits, and in particular, an arginine residue is absolutely conserved. We mutated charged pre-M1 residues in the GABA A receptor ␣ 1 (K219, R220, K221) and ␤ 2 (K213, K215, R216) subunits to cysteine and expressed the mutant subunits with wild-type ␤ 2 or ␣ 1 in Xenopus oocytes. Cysteine substitution of ␤ 2 R216 abolished channel gating by GABA without altering the binding of the GABA agonist [3 H]muscimol, indicating that this residue plays a key role in coupling GABA binding to gating. Tethering thiol-reactive methanethiosulfonate (MTS) reagents onto ␣ 1 K219C, ␤ 2 K213C, and ␤ 2 K215C increased maximal GABA-activated currents, suggesting that structural perturbations of the pre-M1 regions affect channel gating. GABA altered the rates of sulfhydryl modification of ␣ 1 K219C, ␤ 2 K213C, and ␤ 2 K215C, indicating that the pre-M1 regions move in response to channel activation. A positively charged MTS reagent modified ␤ 2 K213C and ␤ 2 K215C significantly faster than a negatively charged reagent, and GABA activation eliminated modification of ␤ 2 K215C by the negatively charged reagent. Overall, the data indicate that the pre-M1 region is part of the structural machinery coupling GABA binding to gating and that the transduction of binding site movements to channel movements is mediated, in part, by electrostatic interactions.