Subtype-selective expression of the five somatostatin receptors (hSSTR1-5) in human pancreatic islet cells: a quantitative double-label immunohistochemical analysis.

Abstract

We have developed a panel of rabbit polyclonal antipeptide antibodies against the five human somatostatin receptor subtypes (hSSTR1-5) and used them to analyze the pattern of expression of hSSTR1-5 in normal human islet cells by quantitative double-label confocal fluorescence immunocytochemistry. All five hSSTR subtypes were variably expressed in islets. The number of SSTR immunopositive cells showed a rank order of SSTR1 > SSTR5 > SSTR2 > SSTR3 > SSTR4. SSTR1 was strongly colocalized with insulin in all beta-cells. SSTR5 was also an abundant isotype, being colocalized in 87% of beta-cells. SSTR2 was found in 46% of beta-cells, whereas SSTR3 and SSTR4 were relatively poorly expressed. SSTR2 was strongly colocalized with glucagon in 89% of alpha-cells, whereas SSTR5 and SSTR1 colocalized with glucagon in 35 and 26% of alpha-cells, respectively. SSTR3 was detected in occasional alpha-cells, and SSTR4 was absent. SSTR5 was preferentially expressed in 75% of SST-positive cells and was the principal delta-cell SSTR subtype, whereas SSTR1-3 were colocalized in only a few delta-cells, and SSTR4 was absent. These studies reveal predominant expression of SSTR1, SSTR2, and SSTR5 in human islets. Beta-cells, alpha-cells, and delta-cells each express multiple SSTR isoforms, beta-cells being rich in SSTR1 and SSTR5, alpha-cells in SSTR2, and delta-cells in SSTR5. Although there is no absolute specificity of any SSTR for an islet cell type, SSTR1 is beta-cell selective, and SSTR2 is alpha-cell selective. SSTR5 is well expressed in beta-cells and delta-cells and moderately well expressed in alpha-cells, and thereby it lacks the islet cell selectivity displayed by SSTR1 and SSTR2. Subtype-selective SSTR expression in islet cells could be the basis for preferential insulin suppression by SSTR1-specific ligands and of glucagon inhibition by SSTR2-selective compounds.

Localization of Niemann–Pick C1 protein in astrocytes: Implications for neuronal degeneration in Niemann– Pick type C disease

“…Astrocytes have been implicated in the delivery of glucose and lactate to neurons (19) and are known to play an important role in the uptake and recycling of neuronally released glutamate (20). In this respect it is of interest that glutamine synthetase in human cerebral cortical astrocytes is localized in a manner that closely resembles the perisynaptic astrocytic localization of NPC1 in this study (16).…”

“…Confocal Microscopy. Human fetal astrocytes were grown on glass coverslips, fixed in 4% paraformaldehyde, and processed for double-label fluorescence colocalization of NPC1 and LAMP2 (a marker for late endosomes and lysosomes) (8,15) by using NPC1-C primary antibody (1:400) with rhodamine-conjugated anti-rabbit IgG secondary antibody (1:100) or mouse monoclonal anti-human LAMP2 IgG primary antibody (1:250) and fluorescein-conjugated goat anti-mouse IgG (1:100) (8,13,16). The fluorescent images were visualized on a Zeiss LSM410 confocal microscope equipped with an Argon͞Krypton laser.…”

Expression of the gene for a membrane-bound fatty acid receptor in the pancreas and islet cell tumours in humans: evidence for GPR40 expression in pancreatic beta cells and implications for insulin secretion

“…TaqMan analysis revealed that levels of GPR40 mRNA expression in pancreatic islets were 20-fold higher than those in the pancreas in the same individuals. Notably, the mRNA level of the GPR40 gene in isolated islets was comparable to those of genes encoding GLP1R, ABCC8 (SUR1) and SSTRs, all of which are abundantly expressed in human pancreatic islets [13][14][15][16].…”

“…We measured mRNA expression of the GPR40 gene as well as genes encoding sulfonylurea receptor 1 (ABCC8, previously known as SUR1) [13], glucagon-like peptide 1 receptor (GLP1R) [14,15] and somatostatin receptor (SSTR) 3 and 5 [16] using the following method. Total RNA was extracted using the Qiagen RNeasy Mini Kit (Qiagen, Hilden, Germany) [17].…”

Could 68Ga-somatostatin analogues be an important alternative to 18F-DOPA PET/CT in pediatrics?

“…The aim of the study was to validate the use of 68 Ga-DOTANOC as effective and widely available alternative to 18 F-DOPA in CHI. Although, somatostatin analogues (e.g., 68 Ga-DOTANOC) with high affinity to the somatostatin receptor (SSTR) subtypes 2, 3, and 5, should be taken up by the endocrine cells of the islets of Langerhans expressing all SSTR subtypes [11], only little information is available in the literature regarding the usefulness of radiolabelled somatostatin analogues in CHI [12,13]. Indeed, this is the first and well-conducted comparison of such radiotracers in CHI.…”