Unique Pharmacology Research Articles

The Discovery, Preclinical, and Early Clinical Development of Potent and Selective GPR40 Agonists for the Treatment of Type 2 Diabetes Mellitus (LY2881835, LY2922083, and LY2922470).

The G protein-coupled receptor 40 (GPR40) also known as free fatty acid receptor 1 (FFAR1) is highly expressed in pancreatic, islet β-cells and responds to endogenous fatty acids, resulting in amplification of insulin secretion only in the presence of elevated glucose levels. Hypothesis driven structural modifications to endogenous FFAs, focused on breaking planarity and reducing lipophilicity, led to the identification of spiropiperidine and tetrahydroquinoline acid derivatives as GPR40 agonists with unique pharmacology, selectivity, and pharmacokinetic properties. Compounds 1 (LY2881835), 2 (LY2922083), and 3 (LY2922470) demonstrated potent, efficacious, and durable dose-dependent reductions in glucose levels along with significant increases in insulin and GLP-1 secretion during preclinical testing. A clinical study with 3 administered to subjects with T2DM provided proof of concept of 3 as a potential glucose-lowering therapy. This manuscript summarizes the scientific rationale, medicinal chemistry, preclinical, and early development data of this new class of GPR40 agonists.

New insights and evolving role of pegylated liposomal doxorubicin in cancer therapy

We herein review various pharmacological and clinical aspects of pegylated liposomal doxorubicin (PLD), the first nanomedicine to be approved for cancer therapy, and discuss the gap between its potent antitumor activity in preclinical studies and its comparatively modest achievements in clinical studies and limited use in clinical practice. PLD is a complex formulation of doxorubicin based on pharmaceutical nanotechnology with unique pharmacokinetic and pharmacodynamic properties. Its long circulation time with stable retention of the payload and its accumulation in tumors with high vascular permeability both result in important advantages over conventional chemotherapy. The ability of PLD to buffer a number of undesirable side effects of doxorubicin, including a major risk reduction in cardiac toxicity, is now well-established and confers a major added value in a number of disease conditions. PLD is approved for the treatment of ovarian cancer, breast cancer, multiple myeloma, and Kaposi sarcoma. In addition, clinically significant antitumor activity of PLD has been reported in a number of other cancer types, including lymphomas and soft tissue sarcomas. In spite of this, PLD has not replaced conventional doxorubicin in common applications such as the adjuvant and neoadjuvant treatment of breast cancer, and its use in the clinic has not become as widespread as one may have predicted. Exploiting the unique pharmacology of PLD, analyzing its selective biodistribution and homing to tumors in cancer patients with proper theranostic tools, and harnessing its complex interaction with the immune system, will lead to a more selective and rational use of PLD that may have great impact on future clinical results and may help realize its largely untapped potential.

Remifentanil tolerance and hyperalgesia: short-term gain, long-term pain?

The unique pharmacology of remifentanil makes it a popular intra-operative analgesic. Short-acting opioids like remifentanil have been associated with acute opioid tolerance and/or opioid-induced hyperalgesia, two phenomena which have different mechanisms and are pharmacologically distinct. Clinical studies show heterogeneity of remifentanil infusion regimens, durations of infusion, maintenance of anaesthesia, cumulative dose of remifentanil and pain measures, which makes it difficult to draw conclusions about the incidence of acute tolerance or hyperalgesia. However, it appears that intra-operative remifentanil infusion rates of above 0.25μg.kg-1 .min-1 are associated with higher postoperative opioid consumption, suggesting tolerance. Infusion rates greater than 0.2μg.kg-1 .min-1 are characterised by lower mechanical/pressure/cold/pain thresholds, which suggests hyperalgesia. The use of concurrent multimodal analgesia, especially N-methyl-D-aspartate receptor antagonists, may be an effective preventive strategy. The clinical significance and long-term consequences of these entities is still uncertain.

High affinity complexes of pannexin channels and L-type calcium channel splice-variants in human lung: Possible role in clevidipine-induced dyspnea relief in acute heart failure

Clevidipine, a dihydropyridine (DHP) analogue, lowers blood pressure (BP) by inhibiting l-type calcium channels (CaV1.2; gene CACNA1C) predominantly located in vascular smooth muscle (VSM). However, clinical observations suggest that clevidipine acts by a more complex mechanism. Clevidipine more potently reduces pulmonary vascular resistance (PVR) than systemic vascular resistance and its spectrum of effects on PVR are not shared by other DHPs. Clevidipine has potent spasmolytic effects in peripheral arteries at doses that are sub-clinical for BP lowering and, in hypertensive acute heart failure, clevidipine, but not other DHPs, provides dyspnea relief, partially independent of BP reduction. These observations suggest that a molecular variation in CaV1.2 may exist which confers unique pharmacology to different DHPs. We sequenced CACNA1C transcripts from human lungs and measured their affinity for clevidipine. Human lung tissue contains CACNA1C mRNA with many different splice variations. CaV1.2 channels with a specific combination of variable exons showed higher affinity for clevidipine, well below the concentration associated with BP reduction. Co-expression with pannexin 1 further increased the clevidipine affinity for this CaV1.2 splice variant. A high-affinity splice variant of CaV1.2 in combination with pannexin 1 could underlie the selective effects of clevidipine on pulmonary arterial pressure and on dyspnea. Research in ContextClevidipine lowers blood pressure by inhibiting calcium channels in vascular smooth muscle. In patients with acute heart failure, clevidipine was shown to relieve breathing problems. This was only partially related to the blood pressure lowering actions of clevidipine and not conferred by another calcium channel inhibitor. We here found calcium channel variants in human lung that are more selectively inhibited by clevidipine, especially when associated with pannexin channels. This study gives a possible mechanism for clevidipine's relief of breathing problems and supports future clinical trials testing the role of clevidipine in the treatment of acute heart failure.

Pimavanserin: An Inverse Agonist Antipsychotic Drug.

Approximately all clinically useful antipsychotic drugs have known activity as dopamine receptor antagonists, but many of these drugs also are inverse agonists at the serotonin-2A (5HT2A) receptor. Pimavanserin is an inverse agonist at the 5HT2A receptor, with a lower binding affinity at the serotonin-2C receptor and sigma 1 receptor, but no significant binding to dopamine or other receptors. Because of its unique pharmacology, pimavanserin was approved for the treatment of psychosis associated with Parkinson's disease, and it has a low risk for exacerbating motor symptoms compared to standard antipsychotic medications. Whether pimavanserin can treat psychotic symptoms in schizophrenia, psychotic depression, psychotic mania, delirium, or drug-induced psychosis, is not known. Based on its inverse agonist effect at 5HT2A receptors, pimavanserin may have potential for treating symptoms associated with the use of hallucinogen drugs and for treating akathisia associated with antipsychotic medications. [Journal of Psychosocial Nursing and Mental Health Services, 54 (6), 21-24.].

Azilsartan: from bench to bedside

Renin-angiotensin-aldosterone system inhibitors are commonly used to control blood pressure (BP) because of their excellent efficacy and tolerability profiles. Oral azilsartan, an angiotensin receptor blocker (ARB), is indicated for the treatment of adults with essential hypertension. This article reviews the unique structure, pharmacology, therapeutic efficacy, and tolerability of azilsartan in this patient population. Azilsartan has shown higher affinity, a more potent inhibitory effect, and slower dissociation from angiotensin receptor II type I than other ARBs in in vitro studies. In several phase III randomized, double-blind, controlled clinical trials, oral azilsartan 40 or 80 mg once daily, as monotherapy or in combination therapy with chlorthalidone, hydrochlorothiazide, or amlodipine, provided superior BP control to control therapy. In head-to-head clinical studies, azilsartan at its highest therapeutic dose of 80 mg/day provided a BP reduction that was superior to that with olmesartan at its highest therapeutic dose of 40 mg/day. The safety and tolerability of azilsartan was similar to that of placebo and other ARBs. Apart from reducing BP, azilsartan also exhibited pleiotropic effects in in vitro studies. Future studies are needed to prove the role of azilsartan in cardiometabolic diseases.

LB-S&T-08 EFFICACY AND SAFETY OF A NEW HERBAL FORMULA (KBMSI-2) IN THE TREATMENT OF ERECTILE DYSFUNCTION: A RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED CLINICAL TRIAL

castration-resistant prostate cancer (CRPC) emphasizes the continued importance of the AR signaling axis in the disease. Despite the use of this new generation of therapies, some men with CRPC do not respond and resistance to these therapies typically develops for those that do. Mechanisms attributed to the emergence of this non-responsive CRPC include the expression of ligand binding domain (LBD)-null constitutively active splice variants of the AR (AR-SV), hyperactive AR, and others. These AR-SV expressing CRPCs require alternate approaches to inhibit both the full length and AR-SVs. The objective of this work is to develop selective androgen receptor degraders (SARDs) that degrade all forms of the AR and provide advanced treatment options to men with CRPC. METHODS: AR ligand binding, transactivation, fluorescence polarization, and Western blot assays were performed to screen novel SARDs. Prostate cancer cell line gene expression, proliferation, cell line and patient-derived xenografts (PDX) were performed to evaluate the efficacy of SARDs. Molecular mechanistic studies were performed to understand the mechanism of action. RESULTS: A novel series of highly potent SARDs with unique pharmacology have been discovered. These compounds selectively bind to the LBD, inhibit, and degrade the AR at nanomolar concentrations. The SARDs degrade AR-V7 and other variants that lack the LBD and inhibit the proliferation of ARand AR-SVdependent PCa cells with potencies better than that of comparators. SARDs robustly inhibit the growth of the LNCaP androgen-dependent prostate cancer (PCa) xenograft, the 22RV1 CRPC xenograft, and ARand AR-SVpositive CRPC patient-derived xenografts (PDX). 22RV1 and PDX Pr-3001 are dependent on AR-SV expression and the observed inhibition of growth is indicative of the SARDs0 ability to inhibit the AR-SV activity in vivo. Quenching of the steady-state fluorescence spectrum supports an interaction between the SARDs and the AR activation function domain (AF-1), making these molecules first-in-class dual-interacting AR antagonists and degraders. Ongoing studies are revealing the mechanism of action for these SARDs. CONCLUSIONS: Novel highly potent SARDs that interact with both the AF-1 and LBD of the AR were discovered and characterized as a potential next-generation treatment option for CRPC.

Adenosine Triphosphate-Sensitive Potassium Currents in Heart Disease and Cardioprotection.

The subunit makeup of the family of adenosine triphosphate-sensitive potassium channel (KATP) channels is more complex and labile than thought. The growing association of Kir6.1 and SUR2 variants with specific cardiovascular electrical and contractile derangements and the clear association with Cantu syndrome establish the importance of appropriate activity in normal function of the heart and vasculature. Further studies of such patients will reveal new mutations in KATP subunits and perhaps in proteins that regulate KATP synthesis, trafficking, or location, all of which may ultimately benefit therapeutically from the unique pharmacology of KATP channels.

A Molecular Mechanism for Sequential Activation of a G Protein-Coupled Receptor

Ligands targeting G protein-coupled receptors (GPCRs) are currently classified as either orthosteric, allosteric, or dualsteric/bitopic. Here, we introduce a new pharmacological concept for GPCR functional modulation: sequential receptor activation. A hallmark feature of this is a stepwise ligand binding mode with transient activation of a first receptor site followed by sustained activation of a second topographically distinct site. We identify 4-CMTB (2-(4-chlorophenyl)-3-methyl-N-(thiazol-2-yl)butanamide), previously classified as a pure allosteric agonist of the free fatty acid receptor 2, as the first sequential activator and corroborate its two-step activation in living cells by tracking integrated responses with innovative label-free biosensors that visualize multiple signaling inputs in real time. We validate this unique pharmacology with traditional cellular readouts, including mutational and pharmacological perturbations along with computational methods, and propose a kinetic model applicable to the analysis of sequential receptor activation. We envision this form of dynamic agonism as a common principle of nature to spatiotemporally encode cellular information.

Bupropion: a systematic review and meta-analysis of effectiveness as an antidepressant.

Bupropion has been used as an antidepressant for over 20 years, though its licence for such use varies and it is typically a third- or fourth-line agent. It has a unique pharmacology, inhibiting the reuptake of noradrenaline and dopamine, potentially providing pharmacological augmentation to more common antidepressants such as selective serotonergic reuptake inhibitors (SSRIs). This systematic review and meta-analysis identified 51 studies, dividing into four categories: bupropion as a sole antidepressant, bupropion coprescribed with another antidepressant, bupropion in 'other' populations (e.g. bipolar depression, elderly populations) and primary evaluation of side effects. Methodologically more robust trials support the superiority of bupropion over placebo, and most head-to-head antidepressant trials showed an equivalent effectiveness, though some of these are hindered by a lack of a placebo arm. Most work on the coprescribing of bupropion with another antidepressant supports an additional effect, though many are open-label trials. Several large multi-medication trials, most notably STAR*D, also support a therapeutic role for bupropion; in general, it demonstrated similar effectiveness to other medications, though this literature highlights the generally low response rates in refractory cohorts. Effectiveness has been shown in 'other' populations, though there is an overall dearth of research. Bupropion is generally well tolerated, it has very low rates of sexual dysfunction, and is more likely to cause weight loss than gain. Our findings support the use of bupropion as a sole or coprescribed antidepressant, particularly if weight gain or sexual dysfunction are, or are likely to be, significant problems. However there are notable gaps in the literature, including less information on treatment naïve and first presentation depression, particularly when one considers the ever-reducing rates of response in more refractory illness. There are some data to support bupropion targeting specific symptoms, but insufficient information to reliably inform such prescribing, and it remains uncertain whether bupropion pharmacodynamically truly augments other drugs.

Probing Binding Interactions of Agonists with the α6β2 Nicotinic Acetylcholine Receptor

The nicotinic acetylcholine receptor (nAChR) is a ligand gated ion channel and a member of the Cys-loop family, which also contains receptors for serotonin, glycine, and GABA. There are twelve known neuronal subunits which pentamerize in different combinations to form various subtypes, each with a unique function, pharmacology and distribution in the brain. The α6β2-containing subtypes are found mainly in dopaminergic neurons and are thus important targets in the study of Parkinson's disease and addiction. Advanced knowledge of the binding site, which sits at the interface of α6 and β2, could lead toward design of agonists that specifically target this subtype. The α6L9'sβ2_(LFM/AAQA)L9's (α6β2‡) construct enabled heterologous expression and activation of a pure and stoichiometrically controlled population of α6β2 receptors in X. laevis oocytes. Currents were high enough in the α6β2‡ system to tolerate nonsense suppression-based non-canonical amino acid mutagenesis, which allowed for structure function studies between the receptor and several agonists. Initial structure-function studies probed for a cation-π interaction between agonists and the indole side chain of α6 TrpB. This is accomplished using an analog-tryptophan series whereby the negative electrostatic potential on the surface the indole ring was incrementally decreased via electron-withdrawing substituents such as fluorine and measuring the effect that has on binding. Results show that ACh makes a cation-π interaction, but surprisingly nicotine and TC-299423 do not. However, the latter two agonists do make a hydrogen bond interaction with the carbonyl of TrpB. This conclusion was made by substituting the adjacent amino acid with an alpha-hydroxy acid and measuring the corresponding shift in binding due to that amide-to-ester backbone mutation. The result was further quantified for nicotine in a double-mutant cycle analysis utilizing N’-methylnicotinium, which showed the interaction to have a coupling energy of ∼2 kcal/mol.

The Biochemical Toxin Arsenal from Ant Venoms.

Ants (Formicidae) represent a taxonomically diverse group of hymenopterans with over 13,000 extant species, the majority of which inject or spray secretions from a venom gland. The evolutionary success of ants is mostly due to their unique eusociality that has permitted them to develop complex collaborative strategies, partly involving their venom secretions, to defend their nest against predators, microbial pathogens, ant competitors, and to hunt prey. Activities of ant venom include paralytic, cytolytic, haemolytic, allergenic, pro-inflammatory, insecticidal, antimicrobial, and pain-producing pharmacologic activities, while non-toxic functions include roles in chemical communication involving trail and sex pheromones, deterrents, and aggregators. While these diverse activities in ant venoms have until now been largely understudied due to the small venom yield from ants, modern analytical and venomic techniques are beginning to reveal the diversity of toxin structure and function. As such, ant venoms are distinct from other venomous animals, not only rich in linear, dimeric and disulfide-bonded peptides and bioactive proteins, but also other volatile and non-volatile compounds such as alkaloids and hydrocarbons. The present review details the unique structures and pharmacologies of known ant venom proteinaceous and alkaloidal toxins and their potential as a source of novel bioinsecticides and therapeutic agents.

Long Receptor Residence Time of C26 Contributes to Super Agonist Activity at the Human β2 Adrenoceptor.

Super agonists produce greater functional responses than endogenous agonists in the same assay, and their unique pharmacology is the subject of increasing interest and debate. We propose that receptor residence time and the duration of receptor signaling contribute to the pharmacology of super agonism. We have further characterized the novel β2 adrenoceptor agonist C26 (7-[(R)-2-((1R,2R)-2-benzyloxycyclopentylamino)-1-hydroxyethyl]-4-hydroxybenzothiazolone), which displays higher intrinsic activity than the endogenous ligand adrenaline in cAMP accumulation, β-arrestin-2 recruitment, and receptor internalization assays. C26 recruited β-arrestin-2, and internalized the Green Fluorescent Protein (GFP)-taggedβ2 adrenoceptor at a slow rate, with half-life (t1/2) values of 0.78 ± 0.1 and 0.78 ± 0.04 hours, respectively. This was compared with 0.31 ± 0.04 and 0.34 ± 0.01 hours for adrenaline-mediated β-arrestin-2 recruitment and GFP-β2 internalization, respectively. The slower rate for C26 resulted in levels of β-arrestin-2 recruitment increasing up to 4-hour agonist incubation, at which point the intrinsic activity was determined to be 124.3 ± 0.77% of the adrenaline response. In addition to slow functional kinetics, C26 displayed high affinity with extremely slow receptor dissociation kinetics, giving a receptor residence half-life of 32.7 minutes at 37°C, which represents the slowest dissociation rate we have observed for any β2 adrenoceptor agonist tested to date. In conclusion, we propose that the gradual accumulation of long-lived active receptor complexes contributes to the increased intrinsic activity of C26 over time. This highlights the need to consider the temporal aspects of agonist binding and signaling when characterizing ligands as super agonists.

Paclitaxel Through the Ages of Anticancer Therapy: Exploring Its Role in Chemoresistance and Radiation Therapy.

Paclitaxel (Taxol®) is a member of the taxane class of anticancer drugs and one of the most common chemotherapeutic agents used against many forms of cancer. Paclitaxel is a microtubule-stabilizer that selectively arrests cells in the G2/M phase of the cell cycle, and found to induce cytotoxicity in a time and concentration-dependent manner. Paclitaxel has been embedded in novel drug formulations, including albumin and polymeric micelle nanoparticles, and applied to many anticancer treatment regimens due to its mechanism of action and radiation sensitizing effects. Though paclitaxel is a major anticancer drug which has been used for many years in clinical treatments, its therapeutic efficacy can be limited by common encumbrances faced by anticancer drugs. These encumbrances include toxicities, de novo refraction, and acquired multidrug resistance (MDR). This article will give a current and comprehensive review of paclitaxel, beginning with its unique history and pharmacology, explore its mechanisms of drug resistance and influence in combination with radiation therapy, while highlighting current treatment regimens, formulations, and new discoveries.

Synthesis and Pharmacological Characterization of C4-(Thiotriazolyl)-substituted-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylates. Identification of (1R,2S,4R,5R,6R)-2-Amino-4-(1H-1,2,4-triazol-3-ylsulfanyl)bicyclo[3.1.0]hexane-2,6-dicarboxylic Acid (LY2812223), a Highly Potent, Functionally Selective mGlu2 Receptor Agonist.

Identification of orthosteric mGlu(2/3) receptor agonists capable of discriminating between individual mGlu2 and mGlu3 subtypes has been highly challenging owing to the glutamate-site sequence homology between these proteins. Herein we detail the preparation and characterization of a series of molecules related to (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate 1 (LY354740) bearing C4-thiotriazole substituents. On the basis of second messenger responses in cells expressing other recombinant human mGlu2/3 subtypes, a number of high potency and efficacy mGlu2 receptor agonists exhibiting low potency mGlu3 partial agonist/antagonist activity were identified. From this, (1R,2S,4R,5R,6R)-2-amino-4-(1H-1,2,4-triazol-3-ylsulfanyl)bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 14a (LY2812223) was further characterized. Cocrystallization of 14a with the amino terminal domains of hmGlu2 and hmGlu3 combined with site-directed mutation studies has clarified the underlying molecular basis of this unique pharmacology. Evaluation of 14a in a rat model responsive to mGlu2 receptor activation coupled with a measure of central drug disposition provides evidence that this molecule engages and activates central mGlu2 receptors in vivo.

Palonosetron in the prevention of chemotherapy-induced nausea and vomiting: an evidence-based review of safety, efficacy, and place in therapy.

Introduction: The second-generation 5-hydroxytryptamine-3 (5-HT3) receptor antagonist palonosetron is effective in the prevention of chemotherapy-induced nausea and vomiting (CINV) associated with highly and moderately emetogenic chemotherapy (HEC and MEC, respectively). In addition, palonosetron has been the first and, at present, the only 5-HT3 receptor antagonist to have a specific indication for the prevention of delayed CINV associated with MEC. The unique pharmacology of this antagonist is thought to partly explain its improved efficacy against delayed symptoms.Aims: To review the evidence underlying the use of palonosetron in preventing CINV.Evidence review: A recent meta-analysis consistently showed that palonosetron significantly increases the control of both emesis and nausea during the acute and delayed phases after single-day HEC or MEC. Consistent with these findings from trials that did not include an neurokinin-1 (NK-1) receptor antagonist, randomized controlled trials recently showed that a triple combination with palonosetron achieves significantly better control of delayed CINV, particularly delayed nausea, in patients undergoing HEC or the high-risk combination of an anthracycline and cyclophosphamide (AC). Evidence from randomized studies also supports palonosetron as a valuable option to reduce the total corticosteroid dose administered in patients undergoing multiple cycles of MEC or AC chemotherapy. Additional benefits of palonosetron include the lack of a warning on cardiac safety and no known clinically significant drug–drug interactions.Place in therapy and conclusion: Evidence currently available indicates that palonosetron significantly adds to the clinician’s ability to effectively control CINV in patients undergoing HEC or MEC. It is recommended in the international guidelines for the prevention of CINV caused by MEC. The high safety profile and the opportunity to reduce the total corticosteroid dose with no loss in efficacy against delayed CINV should also contribute to a wider use of palonosetron in clinical practice.

The Noscapine Chronicle: A Pharmaco-Historic Biography of the Opiate Alkaloid Family and its Clinical Applications.

Given its manifold potential therapeutic applications and amenability to modification, noscapine is a veritable "Renaissance drug" worthy of commemoration. Perhaps the only facet of noscapine's profile more astounding than its versatility is its virtual lack of side effects and addictive properties, which distinguishes it from other denizens of Papaver somniferum. This review intimately chronicles the rich intellectual and pharmacological history behind the noscapine family of compounds, the length of whose arms was revealed over decades of patient scholarship and experimentation. We discuss the intriguing story of this family of nontoxic alkaloids, from noscapine's purification from opium at the turn of the 19th century in Paris to the recent torrent of rationally designed analogs with tremendous anticancer potential. In between, noscapine's unique pharmacology; impact on cellular signaling pathways, the mitotic spindle, and centrosome clustering; use as an antimalarial drug and cough suppressant; and exceptional potential as a treatment for polycystic ovarian syndrome, strokes, and diverse malignancies are catalogued. Seminal experiments involving some of its more promising analogs, such as amino-noscapine, 9-nitronoscapine, 9-bromonoscapine, and reduced bromonoscapine, are also detailed. Finally, the bright future of these oftentimes even more exceptional derivatives is described, rounding out a portrait of a truly remarkable family of compounds.

Optimized deep-targeted proteotranscriptomic profiling reveals unexplored Conus toxin diversity and novel cysteine frameworks

Cone snails are predatory marine gastropods characterized by a sophisticated venom apparatus responsible for the biosynthesis and delivery of complex mixtures of cysteine-rich toxin peptides. These conotoxins fold into small highly structured frameworks, allowing them to potently and selectively interact with heterologous ion channels and receptors. Approximately 2,000 toxins from an estimated number of >70,000 bioactive peptides have been identified in the genus Conus to date. Here, we describe a high-resolution interrogation of the transcriptomes (available at www.ddbj.nig.ac.jp) and proteomes of the diverse compartments of the Conus episcopatus venom apparatus. Using biochemical and bioinformatic tools, we found the highest number of conopeptides yet discovered in a single Conus specimen, with 3,305 novel precursor toxin sequences classified into 9 known superfamilies (A, I1, I2, M, O1, O2, S, T, Z), and identified 16 new superfamilies showing unique signal peptide signatures. We were also able to depict the largest population of venom peptides containing the pharmacologically active C-C-CC-C-C inhibitor cystine knot and CC-C-C motifs (168 and 44 toxins, respectively), as well as 208 new conotoxins displaying odd numbers of cysteine residues derived from known conotoxin motifs. Importantly, six novel cysteine-rich frameworks were revealed which may have novel pharmacology. Finally, analyses of codon usage bias and RNA-editing processes of the conotoxin transcripts demonstrate a specific conservation of the cysteine skeleton at the nucleic acid level and provide new insights about the origin of sequence hypervariablity in mature toxin regions.

α7 and β2 Nicotinic Acetylcholine Receptor Subunits Form Heteromeric Receptor Complexes that Are Expressed in the Human Cortex and Display Distinct Pharmacological Properties

The existence of α7β2 nicotinic acetylcholine receptors (nAChRs) has recently been demonstrated in both the rodent and human brain. Since α7-containing nAChRs are promising drug targets for schizophrenia and Alzheimer’s disease, it is critical to determine whether α7β2 nAChRs are present in the human brain, in which brain areas, and whether they differ functionally from α7 nAChR homomers. We used α-bungarotoxin to affinity purify α7-containing nAChRs from surgically excised human temporal cortex, and found that α7 subunits co-purify with β2 subunits, indicating the presence of α7β2 nAChRs in the human brain. We validated these results by demonstrating co-purification of β2 from wild-type, but not α7 or β2 knock-out mice. The pharmacology and kinetics of human α7β2 nAChRs differed significantly from that of α7 homomers in response to nAChR agonists when expressed in Xenopus oocytes and HEK293 cells. Notably, α7β2 heteromers expressed in HEK293 cells display markedly slower rise and decay phases. These results demonstrate that α7 subunits in the human brain form heteromeric complexes with β2 subunits, and that human α7β2 nAChR heteromers respond to nAChR agonists with a unique pharmacology and kinetic profile. α7β2 nAChRs thus represent an alternative mechanism for the reported clinical efficacy of α7 nAChR ligands.

In-vivo pharmacology of Trace-Amine Associated Receptor 1

Trace-amines (TAs) are endogenous amines that are implicated in several physiological processes including modulation of aminergic neurotransmission. These compounds exert their effect by activating a class of G protein-coupled receptors termed Trace-Amine Associated Receptors (TAARs), where TAAR1 is the only human receptor that has been shown to bind endogenous TAs. Most of the studies have focused on studying the role of TAAR1 on modulation of the dopamine transmission. These studies indicate that TAAR1 is a negative regulator of dopamine transmission making TAAR1 a novel target for neuropsychiatric disorders that arises from dopamine dysfunction such as schizophrenia. This review discusses the unique pharmacology of TAAR1 with the major focus on the physiological role of TAAR1 and its modulation of dopamine transmission.