Odorant-binding proteins (OBPs) represent a highly abundant class of proteins secreted in the nasal mucus by the olfactory neuroepithelium. These proteins display binding affinity for a variety of odorant molecules, thereby assuming the role of carrier during olfactory perception. However, no specific interaction between OBP and olfactory receptors (ORs) has yet been shown and early events in olfaction remain so far poorly understood at a molecular level. Two human ORs, OR 17-209 and OR 17-210, were fused to a Green Fluorescent Protein and stably expressed in COS-7 cell lines. Interaction with OBP was investigated using a highly purified radioiodinated porcine OBP (pOBP) preparation, devoid of any ligand in its binding cavity. No specific binding of the pOBP tracer could be detected with OR 17-209. In contrast, OR 17-210 exhibited specific saturable binding (K-d = 9.48 nM) corresponding to the presence of a single class of high-affinity binding sites (B-max = 65.8 fmol/mg prot). Association and dissociation kinetics further confirmed high-affinity interaction between pOBP and OR 17-210. Autoradiographic studies of labeled pOBP to newborn. mouse slices revealed the presence of multiple specific binding sites located mainly in olfactory tissue but also in several other peripheral tissues. Our data thus demonstrate a high-affinity interaction between OBP and OR, indicating that under physiological conditions, ORs may be specifically associated with an OBP partner in the absence of odorant. This provides further evidence of a novel role for OBP in the mechanism of olfactory perception.

The expression of the 3 currently known neurotensin receptors was studied in human cancer cells of prostatic, colonic or pancreatic origin by means of RT‐PCR analysis and binding experiments. All the cells selected for this work have been shown to exhibit a growth response to neurotensin. We found that the 7 transmembrane domain, levocabastine insensitive receptor (NTR1) is expressed in most but not all of the cells studied whereas the 7 transmembrane domain, levocabastine sensitive receptor (NTR2) is present in none of these cells. The 100 kDa‐type I neurotensin receptor (NTR3) is expressed in all the cells assayed. Moreover, we demonstrated that neurotensin can stimulate the growth of CHO cells stably transfected with the NTR3. Taken together, our results strongly suggest that the NTR3 subtype could be involved in the growth response of human cancer cells to neurotensin. © 2001 Wiley‐Liss, Inc.

Internalization of G protein-coupled receptors is crucial for resensitization of phosphorylation-desensitized receptors, but also for their long term desensitization through sequestration. To elucidate the mechanisms regulating cell surface availability of the somatostatin (SRIF) receptor subtype sst5, we characterized its internalization properties in transfected COS-7 cells using biochemical, confocal microscopic, and electron microscopic techniques. Our results demonstrated rapid and efficient sequestration of specifically bound [125I]Tyr0-D-Trp8-SRIF (up to 45% of bound radioactivity). Combined immunocytochemical detection of sst5 and visualization of a fluorescent SRIF analog by confocal microscopy revealed that whereas the internalized ligand progressively clustered toward the cell center with time, immunoreactive receptors remained predominantly associated with the plasma membrane. The preservation of cell surface receptors was confirmed by binding experiments on whole cells revealing a lack of saturability of [125I]Tyr0-D-Trp8-SRIF binding at 37 C. Binding was rendered saturable by the drug monensin, showing that receptor recycling played a key role in the preservation of cell surface receptors. Electron microscopy demonstrated that in addition to receptor recycling, internalization of receptor-ligand complexes triggered a massive recruitment of sst5 receptor molecules from intracellular stores to the membrane. This combination of recycling and recruitment of spare receptors may protect sst5 from long term down-regulation through sequestration and, therefore, facilitate extended SRIF signaling.

Annals of the New York Academy of SciencesVolume 885, Issue 1 p. 455-458 Ligand Binding Profile and Effects of Melanin-Concentrating Hormone on Fish and Mammalian Skin Cells T. SUPLY, T. SUPLY Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorB. CARDINAUD, B. CARDINAUD Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorS. KANAMORI, S. KANAMORI Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorC. DAL FARRRA, C. DAL FARRRA Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorS. RICOIS, S. RICOIS Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorJ. L. NAHON, Corresponding Author J. L. NAHON Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France Address for correspondence: J. L. Nahon, I.P.M.C.-CNRS UPR 411, 660 route des Lucioles, Sophia-Atinpolis, 06560 Valbonne, France. 33 4 93 95 787 53 (voice); 33 4 93 95 77 08 (fax); Nahonjl@ipmc.cnrs.fr (e-mail).Search for more papers by this author T. SUPLY, T. SUPLY Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorB. CARDINAUD, B. CARDINAUD Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorS. KANAMORI, S. KANAMORI Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorC. DAL FARRRA, C. DAL FARRRA Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorS. RICOIS, S. RICOIS Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, FranceSearch for more papers by this authorJ. L. NAHON, Corresponding Author J. L. NAHON Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UPR411, 660 route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France Address for correspondence: J. L. Nahon, I.P.M.C.-CNRS UPR 411, 660 route des Lucioles, Sophia-Atinpolis, 06560 Valbonne, France. 33 4 93 95 787 53 (voice); 33 4 93 95 77 08 (fax); Nahonjl@ipmc.cnrs.fr (e-mail).Search for more papers by this author First published: 06 February 2006 https://doi.org/10.1111/j.1749-6632.1999.tb08711.xCitations: 5Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume885, Issue1CUTANEOUS NEUROIMMUNOMODULATION THE PROOPIOMELANOCORTIN SYSTEMOctober 1999Pages 455-458 RelatedInformation

1999 abstracts the viiith espid european society for the study and prevention of infant death conference

The inhibitory effect of the neuropeptide somatostatin on the expression of growth hormone was measured by quantitative polymerase chain reaction in the pituitary cell line AtT-20. We demonstrate that this effect is dependent on the internalization of somatostatin-receptor complexes and that it is totally independent from the peptide-induced inhibition of adenylate cyclase. Indeed, the inhibitory effect of the peptide on growth hormone mRNA levels was totally insensitive to pertussis toxin treatment but was totally abolished under conditions which block somatostatin receptor internalization. Comparative confocal microscopic imaging of fluorescent somatostatin sequestration and fluorescence immunolabeling of sst1, sst2A, and sst5 receptors suggests that sst2A is most probably responsible of the inhibitory effect of somatostatin on growth hormone expression.