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Biomedical subjects

M Wheatley

Publications and source records attributed to M Wheatley.

83 records · Page 5Linked to original sources
PubMed1987

Muscarinic acetylcholine receptors: structure, function subtypes and therapeutic perspectives.

Structural and binding studies on the purified rat forebrain muscarinic acetylcholine receptor (mAChR) are consistent with the idea that the receptor is structurally analogous to rhodopsin. We propose that it consists of a short, glycosylated N-terminus, followed by seven transmembrane helices, joined by extra-membranous loops. The transmembrane helices make up a substantial proportion of the molecule. Two peptides, one of which is glycosylated, and therefore close to the N-terminal part of the molecule are labelled on acidic residues by the irreversible antagonist, [3H]-PrBCM, and may thus form part of the ligand binding site. The conformational flexibility of the mAChR, and hence its ability to bind rigid selective ligands such as pirenzepine is strongly affected by the oxidation state of key cysteine residues. The molecule is proposed to terminate in a cytoplasmic C-terminal tail, which participates, together with the cytoplasmic loops, in the recognition of GTP-binding proteins. The C-terminus is susceptible to proteolytic attack, and shows evidence of sequence homology to the C-terminus of the beta-adrenergic receptor.

Animals↗
PubMed1986

Soluble and membrane-bound muscarinic acetylcholine receptors.

Three muscarinic acetylcholine receptor subtypes may be defined on the basis of functional and binding studies using selective antagonists. The subtypes may be solubilized in a stable form in digitonin. In solution, the subclasses still exhibit different structure-binding relationships but these have been perturbed by solubilization. The binding of the selective antagonist, pirenzepine, to the purified cortical receptor is complex and similar to that found in membranes. The muscarinic receptor subclasses thus appear to be different molecular entities. Possible explanations for the molecular heterogeneity are discussed. It has also been possible to solubilize receptor-GTP binding protein complexes which have higher sedimentation coefficients (13.4 S) than the apparently monomeric receptor (11.6 S).

Animals↗
PubMed1984

Reconstitution of solubilised brain D2 dopamine receptors into phospholipid vesicles.

D2 dopamine receptors have been solubilised from bovine caudate nucleus using cholate/sodium chloride in the presence of soyabean phospholipid. Reconstitution of the receptors into soyabean phospholipid vesicles has been achieved by dialysis to remove detergent and salt. The receptors are truly reconstituted as judged by sedimentation, electron microscopy, heat stability and analysis on sucrose density gradients. The ligand-binding properties of the reconstituted receptors resemble those of the solubilised preparation.

Animals↗
PubMed1984

Improvement in conditions for solubilisation and characterisation of brain D2 dopamine receptors using various detergents.

A series of detergents of varying chemical properties has been tested for solubilisation of bovine caudate nucleus D2 dopamine receptors using [3H]spiperone binding to assay the solubilised sites. The properties of the lysophosphatidylcholine (LPC)- and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulphonate (CHAPS)-solubilised preparations are described in detail. The preparations are truly solubilised, and sucrose density gradient and gel filtration data are reported. Specific [3H]spiperone binding in the LPC-solubilised preparation assayed at 4 degrees C is solely to D2 dopamine receptors. If the assay temperature is raised to 25 degrees C, the amount of specific [3H]spiperone binding is largely unchanged, but it forms a greater proportion of the total [3H]spiperone binding owing to a reduction in nonstereospecific (spirodecanone) [3H]spiperone binding at the higher temperature. The effect of raising the assay temperature is important as it enables more precise determinations of specific [3H]spiperone binding to be made. Part of the specific [3H]spiperone binding at 25 degrees C is to solubilised S2 serotonin receptors in addition to D2 dopamine receptors. Good correlations are observed between the affinities for binding of ligands to the solubilised D2 receptors and corresponding data obtained on membrane-bound receptors. Agonist binding in LPC-solubilised preparations is insensitive to guanine nucleotides. It is speculated that the spirodecanone sites represent, in part, proteolysed or damaged D2 dopamine, or S2 serotonin, receptors. In the CHAPS-solubilised preparation the pharmacological profile of [3H]spiperone binding is unclear when assayed at 4 degrees C, but in assays at 25 degrees C a clear serotonin S2 receptor component of specific [3H]spiperone binding can be discerned.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Glycosylation of G-protein-coupled receptors for hormones central to normal reproductive functioning: its occurrence and role.

Many hormones that are central to normal reproductive functioning mediate their physiological effects by activating a receptor which belongs to the large family of G-protein-coupled receptors (GPCR). Members of this family of receptor proteins are usually glycosylated on extracellular domains. In recent years the role of this glycosylation in cell surface expression/protein folding, ligand recognition and receptor-effector coupling has been investigated. This review summarises current knowledge of the role of glycosylation in the functioning of the receptors for gonadotrophin-releasing hormone (GnRH), luteinizing hormone/human chorionic gonadotrophin (LH/HCG), follicle stimulating hormone (FSH), oxytocin (OT) and vasopressin (AVP).

Animals↗