INTRACELLULAR TRANSDUCING MECHANISMS COUPLED TO BRAIN SOMATOSTATIN RECEPTORS

doi:10.1006/phrs.1996.0042

Pharmacological Research

Volume 33, Issue 6, June 1996, Pages 297-305

https://doi.org/10.1006/phrs.1996.0042 Get rights and content

Abstract

This review systematically analyses recent knowledge of the biology of somatostatin receptors. Indeed, since the molecular cloning of five somatostatin receptors in 1992, a growing bulk of scientific data has been produced regarding the cell type localization, the physiological role and the biochemical intracellular pathways activated by the single somatostatin receptors.

The aim of this review is to present all these data, also discussing the conflicting evidence that has been reported, to further stimulate research efforts in the field.

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Cited by (14)

Somatostatin receptor subtype 2A expression in the rat retina
1999, Neuroscience
Somatostatin is mainly expressed by sparsely occurring amacrine and interplexiform cells in the retina. In this study, we characterized the expression and cellular localization of one of the somatostatin subtype (sst) receptors, sst_2A, in the rat retina. The presence of sst_2A receptor messenger RNA in retinal extracts was demonstrated by reverse transcription–polymerase chain reaction using specific primers to detect the sst₂ receptor and its isoforms, sst_2A and sst_2B. Specific sst_2A receptor immunoreactivity was mainly localized to the plasma membrane of several neuronal cell types. In the outer retina, immunoreactivity was localized to cone photoreceptors, horizontal cells, and rod and cone bipolar cells. Double-label experiments showed the co-localization of sst_2A receptor and protein kinase C (α and β), a rod bipolar cell marker, and of sst_2A receptor and Calbindin-D_28k, a horizontal cell marker. In the inner retina, sst_2A receptor immunoreactivity occurred in tyrosine hydroxylase-positive amacrine cells; most were of medium to large size.
These findings indicate that somatostatin may act at a distance, in a paracrine manner, on several cell types that express the sst_2A receptor, and therefore exert a broad modulatory influence on both scotopic and photopic visual pathways.
Molecular cloning and pharmacological characterization of a somatostatin receptor subtype in the gymnotiform fish Apteronotus albifrons
1999, General and Comparative Endocrinology
The actions of the various forms of somatostatin (SRIF), including those of the tetradecapeptide SRIF₁₄, are mediated by specific receptors. In mammals, five subtypes of SRIF receptors, termed sst_1–5, have been cloned. Using a combination of reverse transcriptase-polymerase chain reaction and genomic library screening in the gymnotiform fish Apteronotus albifrons, a gene encoding the first-known nonmammalian SRIF receptor has been isolated. The deduced amino acid sequence displays 59% identity with the human sst₃ receptor protein; hence, the gene is termed “Apteronotus sst₃.” The predicted protein consists of 494 amino acid residues exhibiting a putative seven-transmembrane domain topology typical of G protein-coupled receptors. A signal corresponding to the Apteronotus sst₃ receptor was detected in brain after amplification of poly(A)⁺-RNA by reverse transcriptase-polymerase chain reaction, but not by Northern blot analysis or in situ hybridization, suggesting a low level of expression. Membranes prepared from CCL39 cells stably expressing the Apteronotus sst₃ receptor gene bound [¹²⁵I][Leu⁸, $d$ -Trp²²,¹²⁵ I-Tyr²⁵]SRIF₂₈ with high affinity and in a saturable manner (B_max = 4470 fmol/mg protein; pK_D = 10.5). SRIF₁₄ and various synthetic SRIF receptor agonists produced a dose-dependent inhibition of radioligand binding, with the following rank order of potency: SRIF₁₄ ≈ SRIF₂₈ > BIM 23052 > octreotide > BIM 23056. Under low stringency conditions, an Apteronotus sst₃ probe hybridized to multiple DNA fragments in HindIII or EcoRI digests of A. albifrons DNA, indicating that the Apteronotus sst₃ receptor is a member of a larger family of Apteronotus SRIF receptors.
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Regular ArticleINTRACELLULAR TRANSDUCING MECHANISMS COUPLED TO BRAIN SOMATOSTATIN RECEPTORS

Abstract

Regular Article
INTRACELLULAR TRANSDUCING MECHANISMS COUPLED TO BRAIN SOMATOSTATIN RECEPTORS