The somatostatin somatotropin release-inhibiting factor (SRIF) receptor subtypes sst(2A) and sst(5) are frequently coexpressed in SRIF-responsive cells, including endocrine pituitary cells. We previously demonstrated that sst(2A) and sst(5) exhibit different subcellular localizations and regulation of cell surface expression, although they have similar signaling properties. We investigated here whether sst(2A) and sst(5) functionally interact in cells coexpressing the two receptor subtypes. We stimulated both transfected cells stably expressing sst(2A) alone (CHO-sst(2A)) or together with sst(5) (CHO-sst(2A+5)) and the pituitary cell line AtT20, which endogenously expresses the two receptor subtypes, with either the nonselective agonist D-Trp(8)-SRIF-14 or the sst(2)-selective agonist L-779,976. In CHO-sst(2A) cells, stimulation with either ligand resulted in the loss of approximately 75\% of cell surface SRIF binding sites and massive internalization of sst(2A) receptors. The cells were desensitized to subsequent stimulation with D-Trp(8)-SRIF-14, which failed to inhibit forskolin-evoked cAMP accumulation. Similarly, in CHO-sst(2A+5) and AtT20 cells, D-Trp(8)-SRIF-14 induced the loss of 60-70\% of SRIF binding sites as well as massive sst(2A) endocytosis. By contrast, in cells expressing both sst(2A) and sst(5), selective stimulation of sst(2A) with L-779,976 resulted in only 20-40\% loss of cell surface binding and markedly reduced sst(2A) internalization. Consequently, whereas CHO-sst(2A+5) and AtT20 cells stimulated with D-Trp(8)-SRIF-14 were desensitized to a second stimulation with the same agonist, cells prestimulated with L-779,976 were not desensitized to subsequent D-Trp(8)-SRIF-14 stimulation. These findings indicate that the presence of sst(5) in the same cells modulates trafficking and cell surface regulation of sst(2A) and cellular desensitization to the effects of SRIF.
%0 Journal Article
%1 sharif_coexpression_2007
%A Sharif, Nadder
%A Gendron, Louis
%A Wowchuk, Julia
%A Sarret, Philippe
%A Mazella, Jean
%A Beaudet, Alain
%A Stroh, Thomas
%D 2007
%J Endocrinology
%K Amides Animals Cricetinae Cricetulus Cyclic_{AMP} Endocytosis Forskolin Indoles Iodine_Radioisotopes Mice Protein_Transport Radioligand_Assay Receptors Signal_Transduction Somatostatin Transfection {CHO}_Cells
%N 5
%P 2095--2105
%R 10.1210/en.2006-1266
%T Coexpression of somatostatin receptor subtype 5 affects internalization and trafficking of somatostatin receptor subtype 2
%U http://www.ncbi.nlm.nih.gov/pubmed/17272399
%V 148
%X The somatostatin somatotropin release-inhibiting factor (SRIF) receptor subtypes sst(2A) and sst(5) are frequently coexpressed in SRIF-responsive cells, including endocrine pituitary cells. We previously demonstrated that sst(2A) and sst(5) exhibit different subcellular localizations and regulation of cell surface expression, although they have similar signaling properties. We investigated here whether sst(2A) and sst(5) functionally interact in cells coexpressing the two receptor subtypes. We stimulated both transfected cells stably expressing sst(2A) alone (CHO-sst(2A)) or together with sst(5) (CHO-sst(2A+5)) and the pituitary cell line AtT20, which endogenously expresses the two receptor subtypes, with either the nonselective agonist D-Trp(8)-SRIF-14 or the sst(2)-selective agonist L-779,976. In CHO-sst(2A) cells, stimulation with either ligand resulted in the loss of approximately 75\% of cell surface SRIF binding sites and massive internalization of sst(2A) receptors. The cells were desensitized to subsequent stimulation with D-Trp(8)-SRIF-14, which failed to inhibit forskolin-evoked cAMP accumulation. Similarly, in CHO-sst(2A+5) and AtT20 cells, D-Trp(8)-SRIF-14 induced the loss of 60-70\% of SRIF binding sites as well as massive sst(2A) endocytosis. By contrast, in cells expressing both sst(2A) and sst(5), selective stimulation of sst(2A) with L-779,976 resulted in only 20-40\% loss of cell surface binding and markedly reduced sst(2A) internalization. Consequently, whereas CHO-sst(2A+5) and AtT20 cells stimulated with D-Trp(8)-SRIF-14 were desensitized to a second stimulation with the same agonist, cells prestimulated with L-779,976 were not desensitized to subsequent D-Trp(8)-SRIF-14 stimulation. These findings indicate that the presence of sst(5) in the same cells modulates trafficking and cell surface regulation of sst(2A) and cellular desensitization to the effects of SRIF.
@article{sharif_coexpression_2007,
abstract = {The somatostatin [somatotropin release-inhibiting factor {(SRIF)]} receptor subtypes {sst(2A)} and sst(5) are frequently coexpressed in {SRIF-responsive} cells, including endocrine pituitary cells. We previously demonstrated that {sst(2A)} and sst(5) exhibit different subcellular localizations and regulation of cell surface expression, although they have similar signaling properties. We investigated here whether {sst(2A)} and sst(5) functionally interact in cells coexpressing the two receptor subtypes. We stimulated both transfected cells stably expressing {sst(2A)} alone {(CHO-sst(2A))} or together with sst(5) {(CHO-sst(2A+5))} and the pituitary cell line {AtT20}, which endogenously expresses the two receptor subtypes, with either the nonselective agonist {[D-Trp(8)]-SRIF-14} or the sst(2)-selective agonist L-779,976. In {CHO-sst(2A)} cells, stimulation with either ligand resulted in the loss of approximately 75\% of cell surface {SRIF} binding sites and massive internalization of {sst(2A)} receptors. The cells were desensitized to subsequent stimulation with {[D-Trp(8)]-SRIF-14}, which failed to inhibit forskolin-evoked {cAMP} accumulation. Similarly, in {CHO-sst(2A+5)} and {AtT20} cells, {[D-Trp(8)]-SRIF-14} induced the loss of 60-70\% of {SRIF} binding sites as well as massive {sst(2A)} endocytosis. By contrast, in cells expressing both {sst(2A)} and sst(5), selective stimulation of {sst(2A)} with L-779,976 resulted in only 20-40\% loss of cell surface binding and markedly reduced {sst(2A)} internalization. Consequently, whereas {CHO-sst(2A+5)} and {AtT20} cells stimulated with {[D-Trp(8)]-SRIF-14} were desensitized to a second stimulation with the same agonist, cells prestimulated with L-779,976 were not desensitized to subsequent {[D-Trp(8)]-SRIF-14} stimulation. These findings indicate that the presence of sst(5) in the same cells modulates trafficking and cell surface regulation of {sst(2A)} and cellular desensitization to the effects of {SRIF.}},
added-at = {2011-08-03T17:38:07.000+0200},
author = {Sharif, Nadder and Gendron, Louis and Wowchuk, Julia and Sarret, Philippe and Mazella, Jean and Beaudet, Alain and Stroh, Thomas},
biburl = {https://www.bibsonomy.org/bibtex/2c971d92ea4f53dc6eb2af0e45207f282/crc_chus},
doi = {10.1210/en.2006-1266},
interhash = {edc4d63208a10a9c52abd77048f33ee3},
intrahash = {c971d92ea4f53dc6eb2af0e45207f282},
issn = {0013-7227},
journal = {Endocrinology},
keywords = {Amides Animals Cricetinae Cricetulus Cyclic_{AMP} Endocytosis Forskolin Indoles Iodine_Radioisotopes Mice Protein_Transport Radioligand_Assay Receptors Signal_Transduction Somatostatin Transfection {CHO}_Cells},
month = may,
note = {{PMID:} 17272399},
number = 5,
pages = {2095--2105},
timestamp = {2011-08-03T21:10:04.000+0200},
title = {Coexpression of somatostatin receptor subtype 5 affects internalization and trafficking of somatostatin receptor subtype 2},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17272399},
volume = 148,
year = 2007
}