Somatostatin (SST), also known as somatotropin release-inhibiting factor (SRIF), is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Somatostatin has a wide distribution throughout the central nervous system (CNS) as well as in peripheral tissues, for example in the pituitary, pancreas and stomach. The various actions of somatostatin are mediated by a family of rhodopsin-like G protein-coupled receptors, which comprise of five distinct subtypes: Somatostatin receptor 1 (SSTR1), Somatostatin receptor 2 (SSTR2), Somatostatin receptor 3 (SSTR3), Somatostatin receptor 4 (SSTR4) and Somatostatin receptor 5 (SSTR5) [, , ]. These subtypes are widely expressed in many tissues [, , , , , ], and frequently multiple subtypes coexist in the same cell []. The somatostatin receptor subtypes also share common signalling pathways, such as the inhibition of adenylyl cyclase [, ], activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K+ channels (SSTR2, SSTR3, SSTR4, SSTR5) [, ], to voltage-dependent Ca2+ channels (SSTR1, SSTR2) [], to an Na+/H+ exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, SSTR2), phospholipase C (SSTR2, SSTR5), and phospholipase A2 (SSTR4) []. Amongst the wide spectrum of somatostatin effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2) [].This entry represents SSTR2. In humans has been found in high levels the brain, kidney and pituitary, with lower levels in the jejunum, pancreas, colon and liver. All five human somatostatin receptors expressed in COS-7 cells are coupled to activation of phosphoinositide (PI)-specific PLC-beta; and Ca2+ mobilisation via pertussis toxin-sensitive G protein(s) with an order of potency of SSTR5 >SSTR2 >SSTR3 >SSTR4 >SSTR1 [].
Somatostatin (SST), also known as somatotropin release-inhibiting factor (SRIF), is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Somatostatin has a wide distribution throughout the central nervous system (CNS) as well as in peripheral tissues, for example in the pituitary, pancreas and stomach. The various actions of somatostatin are mediated by a family of rhodopsin-like G protein-coupled receptors, which comprise of five distinct subtypes: Somatostatin receptor 1 (SSTR1), Somatostatin receptor 2 (SSTR2), Somatostatin receptor 3 (SSTR3), Somatostatin receptor 4 (SSTR4) and Somatostatin receptor 5 (SSTR5) [, , ]. These subtypes are widely expressed in many tissues [, , , , , ], and frequently multiple subtypes coexist in the same cell []. The somatostatin receptor subtypes also share common signalling pathways, such as the inhibition of adenylyl cyclase [, ], activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K+ channels (SSTR2, SSTR3, SSTR4, SSTR5) [, ], to voltage-dependent Ca2+ channels (SSTR1, SSTR2) [], to an Na+/H+ exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, SSTR2), phospholipase C (SSTR2, SSTR5), and phospholipase A2 (SSTR4) []. Amongst the wide spectrum of somatostatin effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2) [].This entry represents SSTR1 []. In humans, it is expressed at high levels in the jejunum and stomach, with lower levels in the pancreas, colon and kidney, but it is absent in the brain. Conversely, in rodent tissue, high levels are found in the brain, but are absent in peripheral tissues []. All five human somatostatin receptors expressed in COS-7 cells are coupled to activation of phosphoinositide (PI)-specific PLC-beta; and Ca2+ mobilisation via pertussis toxin-sensitive G protein(s) with an order of potency of SSTR5 >SSTR2 >SSTR3 >SSTR4 >SSTR1 [].
Somatostatin (SST), also known as somatotropin release-inhibiting factor (SRIF), is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Somatostatin has a wide distribution throughout the central nervous system (CNS) as well as in peripheral tissues, for example in the pituitary, pancreas and stomach. The various actions of somatostatin are mediated by a family of rhodopsin-like G protein-coupled receptors, which comprise of five distinct subtypes: Somatostatin receptor 1 (SSTR1), Somatostatin receptor 2 (SSTR2), Somatostatin receptor 3 (SSTR3), Somatostatin receptor 4 (SSTR4) and Somatostatin receptor 5 (SSTR5) [, , ]. These subtypes are widely expressed in many tissues [, , , , , ], and frequently multiple subtypes coexist in the same cell []. The somatostatin receptor subtypes also share common signalling pathways, such as the inhibition of adenylyl cyclase [, ], activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K+ channels (SSTR2, SSTR3, SSTR4, SSTR5) [, ], to voltage-dependent Ca2+ channels (SSTR1, SSTR2) [], to an Na+/H+ exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, SSTR2), phospholipase C (SSTR2, SSTR5), and phospholipase A2 (SSTR4) []. Amongst the wide spectrum of somatostatin effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2) [].This entry represents SST5R. It is expressed in range of tissues including the small intestine, heart, adrenal, cerebellum, pituitary, placenta and skeletal muscle. It is also expressed in pancreatic islets [], where somatostatin is a known regulator of insulin and glucagon secretion. All five human somatostatin receptors expressed in COS-7 cells have been shown to couple to activation of phosphoinositide (PI)-specific PLC-beta; and Ca2+ mobilisation via pertussis toxin-sensitive G protein(s) with an order of potency of SSTR5 >SSTR2 >SSTR3 >SSTR4 >SSTR1 [].
Somatostatin (SST), also known as somatotropin release-inhibiting factor (SRIF), is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Somatostatin has a wide distribution throughout the central nervous system (CNS) as well as in peripheral tissues, for example in the pituitary, pancreas and stomach. The various actions of somatostatin are mediated by a family of rhodopsin-like G protein-coupled receptors, which comprise of five distinct subtypes: Somatostatin receptor 1 (SSTR1), Somatostatin receptor 2 (SSTR2), Somatostatin receptor 3 (SSTR3), Somatostatin receptor 4 (SSTR4) and Somatostatin receptor 5 (SSTR5) [, , ]. These subtypes are widely expressed in many tissues [, , , , , ], and frequently multiple subtypes coexist in the same cell []. The somatostatin receptor subtypes also share common signalling pathways, such as the inhibition of adenylyl cyclase [, ], activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K+ channels (SSTR2, SSTR3, SSTR4, SSTR5) [, ], to voltage-dependent Ca2+ channels (SSTR1, SSTR2) [], to an Na+/H+ exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, SSTR2), phospholipase C (SSTR2, SSTR5), and phospholipase A2 (SSTR4) []. Amongst the wide spectrum of somatostatin effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2) [].This entry represents SSTR4. It is present in high levels in the pituitary, but is less abundant in the brain and peripheral tissues [, , ]. All five human somatostatin receptors expressed in COS-7 cells are coupled to activation of phosphoinositide (PI)-specific PLC-beta; and Ca2+ mobilisation via pertussis toxin-sensitive G protein(s) with an order of potency of SSTR5 >SSTR2 >SSTR3 >SSTR4 >SSTR1 [].
Somatostatin (SST), also known as somatotropin release-inhibiting factor (SRIF), is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. Somatostatin has a wide distribution throughout the central nervous system (CNS) as well as in peripheral tissues, for example in the pituitary, pancreas and stomach. The various actions of somatostatin are mediated by a family of rhodopsin-like G protein-coupled receptors, which comprise of five distinct subtypes: Somatostatin receptor 1 (SSTR1), Somatostatin receptor 2 (SSTR2), Somatostatin receptor 3 (SSTR3), Somatostatin receptor 4 (SSTR4) and Somatostatin receptor 5 (SSTR5) [, , ]. These subtypes are widely expressed in many tissues [, , , , , ], and frequently multiple subtypes coexist in the same cell []. The somatostatin receptor subtypes also share common signalling pathways, such as the inhibition of adenylyl cyclase [, ], activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K+ channels (SSTR2, SSTR3, SSTR4, SSTR5) [, ], to voltage-dependent Ca2+ channels (SSTR1, SSTR2) [], to an Na+/H+ exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, SSTR2), phospholipase C (SSTR2, SSTR5), and phospholipase A2 (SSTR4) []. Amongst the wide spectrum of somatostatin effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2) [].This entry represents SSTR3. It is widely distributed in mouse brain, with high levels in the forebrain, hippocampus and amygdala; moderate levels are also present in the substantia nigra. All five human somatostatin receptors expressed in COS-7 cells are coupled to activation of phosphoinositide (PI)-specific PLC-beta; and Ca2+ mobilisation via pertussis toxin-sensitive G protein(s) with an order of potency of SSTR5 >SSTR2 >SSTR3 >SSTR4 >SSTR1 []. Inhibition of angiogenesis has been shown to be via the SSTR3, and involves the inhibition of MAPK and endothelial nitric oxide synthase (eNOS) activity [].
