Gγ7 proteins contribute to coupling of nociceptin/orphanin FQ peptide (NOP) opioid receptors and voltage-gated Ca(2+) channels in rat stellate ganglion neurons

Betulinic acid, derived from the desert lavender Hyptis emoryi, attenuates paclitaxel-, HIV-, and nerve injury-associated peripheral sensory neuropathy via block of N- and T-type calcium channels

The Federal Pain Research Strategy recommended development of nonopioid analgesics as a top priority in its strategic plan to address the significant public health crisis and individual burden of chronic pain faced by >100 million Americans. Motivated by this challenge, a natural product extracts library was screened and identified a plant extract that targets activity of voltage-gated calcium channels. This profile is of interest as a potential treatment for neuropathic pain. The active extract derived from the desert lavender plant native to southwestern United States, when subjected to bioassay-guided fractionation, afforded 3 compounds identified as pentacyclic triterpenoids, betulinic acid (BA), oleanolic acid, and ursolic acid. Betulinic acid inhibited depolarization-evoked calcium influx in dorsal root ganglion (DRG) neurons predominantly through targeting low-voltage-gated (Cav3 or T-type) and CaV2.2 (N-type) calcium channels. Voltage-clamp electrophysiology experiments revealed a reduction of Ca, but not Na, currents in sensory neurons after BA exposure. Betulinic acid inhibited spontaneous excitatory postsynaptic currents and depolarization-evoked release of calcitonin gene-related peptide from lumbar spinal cord slices. Notably, BA did not engage human mu, delta, or kappa opioid receptors. Intrathecal administration of BA reversed mechanical allodynia in rat models of chemotherapy-induced peripheral neuropathy and HIV-associated peripheral sensory neuropathy as well as a mouse model of partial sciatic nerve ligation without effects on locomotion. The broad-spectrum biological and medicinal properties reported, including anti-HIV and anticancer activities of BA and its derivatives, position this plant-derived small molecule natural product as a potential nonopioid therapy for management of chronic pain.

Pharmacological Assays for Investigating the NOP Receptor

The nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) is a G protein-coupled receptor involved in the regulation of several physiological functions and pathological conditions. Thus, researchers from academia and industry are pursuing NOP to discover and study novel pharmacological entities. In a multidisciplinary effort of pharmacologists, medicinal chemists, and molecular and structural biologists the mechanisms of NOP activation and inhibition have been, at least partially, disentangled. Here, we review the in vitro methodologies employed, which have contributed to our understanding of this target. We hope this chapter guides the reader through the mostly established assay platforms to investigate NOP pharmacology, and gives some hints taking advantage from what has already illuminated the function of other GPCRs. We analyzed the pharmacological results obtained with a large panel of NOP ligands investigated in several assays including receptor binding, stimulation of GTPγS binding, decrease of cAMP levels, calcium flux stimulation via chimeric G proteins, NOP/G protein and NOP/β-arrestin interaction, label-free assays such as dynamic mass redistribution, and bioassays such as the electrically stimulated mouse vas deferens.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Gγ identity dictates efficacy of Gβγ signaling and macrophage migration

G protein βγ subunit (Gβγ) is a major signal transducer and controls processes ranging from cell migration to gene transcription. Despite having significant subtype heterogeneity and exhibiting diverse cell- and tissue-specific expression levels, Gβγ is often considered a unified signaling entity with a defined functionality. However, the molecular and mechanistic basis of Gβγ's signaling specificity is unknown. Here, we demonstrate that Gγ subunits, bearing the sole plasma membrane (PM)-anchoring motif, control the PM affinity of Gβγ and thereby differentially modulate Gβγ effector signaling in a Gγ-specific manner. Both Gβγ signaling activity and the migration rate of macrophages are strongly dependent on the PM affinity of Gγ. We also found that the type of C-terminal prenylation and five to six pre-CaaX motif residues at the PM-interacting region of Gγ control the PM affinity of Gβγ. We further show that the overall PM affinity of the Gβγ pool of a cell type is a strong predictor of its Gβγ signaling-activation efficacy. A kinetic model encompassing multiple Gγ types and parameterized for empirical Gβγ behaviors not only recapitulated experimentally observed signaling of Gβγ, but also suggested a Gγ-dependent, active-inactive conformational switch for the PM-bound Gβγ, regulating effector signaling. Overall, our results unveil crucial aspects of signaling and cell migration regulation by Gγ type-specific PM affinities of Gβγ.