title: Somatostatin receptor desensitization in NG108-15 cells. A consequence of receptor sequestration.
abstract: In NG108-15 cells inhibition of both N-type calcium channel current and adenylyl cyclase by somatostatin (SRIF) was not sustained but rapidly desensitized in the continued presence of the drug. The degree and rate of desensitization were concentration-dependent, and the desensitization was homologous with respect to the delta-opioid receptor. We have been unable to obtain evidence for the involvement of G protein-coupled receptor kinases (GRKs) in this desensitization. SRIF-induced desensitization of N-type calcium channel currents was not reduced in cells stably overexpressing a dominant negative mutant of GRK2 or following intracellular dialysis with GRK2- and GRK3-blocking peptides or with heparin. Inhibitors of protein kinase A, protein kinase C, and protein kinase G were also without effect. In contrast, both the rate and degree of SRIF-induced desensitization were reduced by pretreatment with phenylarsine oxide or concanavalin A, both inhibitors of receptor endocytosis. Furthermore, SRIF-induced desensitization was enhanced by monensin, which prevents receptor recycling back to the plasma membrane. Similarly, SRIF-induced desensitization of adenylyl cyclase inhibition was not reduced in cells stably overexpressing dominant negative mutant GRK2 but was reduced in cells pretreated with the receptor endocytosis inhibitor hyperosmotic sucrose or concanavalin A. These data are consistent with the view that SRIF-induced desensitization in NG108-15 cells results from receptor internalization.
authors.affiliation: Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom.
authors.forename: V
authors.initials: V
authors.lastname: Beaumont
authors.forename: M B
authors.initials: MB
authors.lastname: Hepworth
authors.forename: J S
authors.initials: JS
authors.lastname: Luty
authors.forename: E
authors.initials: E
authors.lastname: Kelly
authors.forename: G
authors.initials: G
authors.lastname: Henderson
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D016466:CHO Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004705:Endocytosis; D011493:Protein Kinase C / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000819:agonists / Q000378:metabolism*; D011994:Recombinant Proteins / Q000819:agonists / Q000378:metabolism; D013004:Somatostatin / Q000494:pharmacology
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D002121:Calcium Channel Blockers; D017481:Receptors, Somatostatin; D011994:Recombinant Proteins; D013004:Somatostatin; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D006152:Cyclic GMP