The Sigma-2 Receptor and Progesterone Receptor Membrane Component 1 are Different Binding Sites Derived From Independent Genes.

The sigma-2 receptor (S2R) is a potential therapeutic target for cancer and neuronal diseases. However, the identity of the S2R has remained a matter of debate. Historically, the S2R has been defined as (1) a binding site with high affinity to 1,3-di-o-tolylguanidine (DTG) and haloperidol but not to the selective sigma-1 receptor ligand (+)-pentazocine, and (2) a protein of 18-21 kDa, as shown by specific photolabeling with [(3)H]-Azido-DTG and [(125)I]-iodoazido-fenpropimorph ([(125)I]-IAF).

Sigma Receptor Binding Assays.

Sigma receptors, both Sigma-1(S1R) and Sigma-2 (S2R), are small molecule-regulated, primarily endoplasmic reticulum (ER) membrane-associated sites. A number of drugs bind to sigma receptors, including the antipsychotic haloperidol and (+)-pentazocine, an opioid analgesic. Sigma receptors are implicated in many central nervous system disorders, in particular Alzheimer's disease and conditions associated with motor control, such as Amyotrophic Lateral Sclerosis (ALS).

Biochemical Pharmacology of the Sigma-1 Receptor.

The sigma-1 receptor (S1R) is a 223 amino acid two transmembrane (TM) pass protein. It is a non-ATP-binding nonglycosylated ligand-regulated molecular chaperone of unknown three-dimensional structure. The S1R is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes with broad functions that regulate cellular calcium homeostasis and reduce oxidative stress.

Endothelial protective genes induced by statin are mimicked by ERK5 activation as triggered by a drug combination of FTI-277 and GGTI-298.

Background: Statins are potent inhibitors of cholesterol biosynthesis and are clinically beneficial in preventing cardiovascular diseases, however, the therapeutic utility of these drugs is limited by myotoxicity. Here, we explored the mechanism of statin-mediated activation of ERK5 in the human endothelium with the goal of identifying compounds that confer endothelial protection but are nontoxic to muscle.

Methods: An ERK5-one hybrid luciferase reporter transfected into COS-7 cells with pharmacological and molecular manipulations dissected the signaling pathway leading to statin activation of ERK5.

The oligomeric states of the purified sigma-1 receptor are stabilized by ligands.

Sigma-1 receptor (S1R) is a mammalian member of the ERG2 and sigma-1 receptor-like protein family (pfam04622). It has been implicated in drug addiction and many human neurological disorders, including Alzheimer and Parkinson diseases and amyotrophic lateral sclerosis. A broad range of synthetic small molecules, including cocaine, (+)-pentazocine, haloperidol, and small endogenous molecules such as N,N-dimethyltryptamine, sphingosine, and steroids, have been identified as regulators of S1R.

Noncompetitive inhibition of indolethylamine-N-methyltransferase by N,N-dimethyltryptamine and N,N-dimethylaminopropyltryptamine.

Indolethylamine-N-methyltransferase (INMT) is a Class 1 transmethylation enzyme known for its production of N,N-dimethyltryptamine (DMT), a hallucinogen with affinity for various serotonergic, adrenergic, histaminergic, dopaminergic, and sigma-1 receptors. DMT is produced via the action of INMT on the endogenous substrates tryptamine and S-adenosyl-l-methionine (SAM). The biological, biochemical, and selective small molecule regulation of INMT enzyme activity remain largely unknown.

Photoaffinity labeling of the sigma-1 receptor with N-[3-(4-nitrophenyl)propyl]-N-dodecylamine: evidence of receptor dimers.

The sigma-1 receptor is a ligand-regulated endoplasmic reticulum (ER) resident chaperone involved in the maintenance of cellular homeostasis. Coupling of the sigma-1 receptor with various ER and/or plasma membrane ion channels is associated with its ability to regulate the locomotor activity and cellular proliferation produced in response to sigma-1 receptor ligands. A number of endogenous small molecules bind to the sigma-1 receptor and have been shown to regulate its activity; these include progesterone, N,N-dimethyltryptamine, d-erythro-sphingosine, and/or other endogenous lipids.

The ligand binding region of the sigma-1 receptor: studies utilizing photoaffinity probes, sphingosine and N-alkylamines.

The sigma-1 receptor is a 26 kDa endoplasmic reticulum resident membrane protein that has been shown to have chaperone activity in addition to its promiscuous binding to pharmacological agents. Ligand binding domain(s) of the sigma-1 receptor have been identified using the E. coli expressed and purified receptor protein and novel radioiodinated azido photoaffinity probes followed by proteolytic and chemical cleavage strategies.

Characterization of interactions of 4-nitrophenylpropyl-N-alkylamine with ς receptors.

Sigma receptors are small membrane proteins implicated in a number of pathophysiological conditions, including drug addiction, psychosis, and cancer; thus, small molecule inhibitors of sigma receptors have been proposed as potential pharmacotherapeutics for these diseases. We previously discovered that endogenous monochain N-alkyl sphingolipids, including d-erythro-sphingosine, sphinganine, and N,N-dimethylsphingosine, bind to the sigma-1 receptor at physiologically relevant concentrations [Ramachandran, S., et al.

In vitro interaction of tubulin with the photoreceptor cGMP phosphodiesterase gamma-subunit.

The alpha and beta tubulins compose the microtubule cytoskeleton which is involved in many cellular processes such as vesicular transport. The photoreceptor cells in the retina are neurons specialized for phototransduction. Here we report a novel interaction between tubulin and the photoreceptor cGMP phosphodiesterase (PDE6) gamma subunit (PDE gamma).

Synthesis and characterization of N,N-dialkyl and N-alkyl-N-aralkyl fenpropimorph-derived compounds as high affinity ligands for sigma receptors.

The sigma-1 receptor is a unique non-opioid, non-PCP binding site that has been implicated in many different pathophysiological conditions including psychosis, drug addiction, retinal degeneration and cancer. Based on the structure of fenpropimorph, a high affinity (K(i)=0.005 nM)(1) sigma-1 receptor ligand and strong inhibitor of the yeast sterol isomerase (ERG2), we previously deduced a basic sigma-1 receptor pharmacophore or chemical backbone composed of a phenyl ring attached to a di-substituted nitrogen atom via an alkyl chain.

The sigma1 receptor interacts with N-alkyl amines and endogenous sphingolipids.

The sigma1 receptor is distinguished for its ability to bind various pharmacological agents including drugs of abuse such as cocaine and methamphetamine. Some endogenous ligands have been identified as putative sigma1 receptor regulators. High affinity ligands for the sigma1 receptor contain a nitrogen atom connected to long alkyl chains.

Probing the steroid binding domain-like I (SBDLI) of the sigma-1 receptor binding site using N-substituted photoaffinity labels.

Radioiodinated photoactivatable photoprobes can provide valuable insights regarding protein structure. Previous work in our laboratory showed that the cocaine derivative and photoprobe 3-[ (125)I]iodo-4-azidococaine ([ (125)I]IACoc) binds to the sigma-1 receptor with 2-3 orders of magnitude higher affinity than cocaine [Kahoun, J. R.

Juxtaposition of the steroid binding domain-like I and II regions constitutes a ligand binding site in the sigma-1 receptor.

sigma-1 receptors represent unique binding sites that are capable of interacting with a wide range of compounds to mediate different cellular events. The composition of the ligand binding site of this receptor is unclear, since no NMR or crystal structures are available. Recent studies in our laboratory using radiolabeled photoreactive ligands suggested that the steroid binding domain-like I (SBDLI) (amino acids 91-109) and the steroid binding domain-like II (SBDLII) (amino acids 176-194) regions are involved in forming the ligand binding site(s) ( Chen, Y.

Identification of regions of the sigma-1 receptor ligand binding site using a novel photoprobe.

sigma Receptors, once considered a class of opioid receptors, are now regarded as a unique class of receptors that contain binding sites for a wide range of ligands, including the drug 1-N(2',6'-dimethylmorpholino)3-(4-t-butylpropylamine) (fenpropimorph), a yeast sterol isomerase inhibitor. Because fenpropimorph has high-binding affinity to the sigma-1 receptor, we have synthesized a series of fenpropimorph-like derivatives with varying phenyl ring substituents and have characterized their binding affinities to the sigma-1 receptor. In addition, we have synthesized a carrier-free, radioiodinated fenpropimorph-like photoaffinity label, 1-N-(2',6'-dimethyl-morpholino)-3-(4-azido-3-[(125)I]iodo-phenyl)propane ([(125)I]IAF), which covalently derivatized the sigma-1 receptor (25.

A valid method of laparoscopic simulation training and competence assessment.

Background: The purpose of our study was to evaluate the construct validity of laparoscopic technical performance measures and the face validity of three laparoscopic simulations.

Materials And Methods: Subjects (N = 27) of varying levels of surgical experience performed three laparoscopic simulations, representing appendectomy (LA), cholecystectomy (LC), and inguinal hemiorrhaphy (LH). Five laparoscopic surgeons, blinded to the identity of the subjects, rated the subjects on procedural competence on a binary scale and in four skills categories on a 5-point scale: clinical judgment, dexterity, serial/simultaneous complexity, and spatial orientation.