title: Pharmacological characterization of a recombinant, fluorescent somatostatin receptor agonist.
abstract: Somatostatin (SST) is a peptide neurotransmitter/hormone found in several mammalian tissue types. Apart from its natural importance, labeled SST/analogues are utilized in clinical applications such as targeting/diagnosis of neuroendocrine tumors. We report on the development and characterization of a novel, recombinant, fluorescent somatostatin analogue that has potential to elucidate somatostatin-activated cell signaling. SST was genetically fused with a monomeric-red fluorescent protein (mRFP) as the fluorescent label. The attachment of SST to mRFP had no detectable effect on its fluorescent properties. This analogue's potency to activate the endogenous and transfected somatostatin receptors was characterized using assays of membrane potential and Ca(2+) mobilization and immunocytochemistry. SST-mRFP was found to be an effective somatostatin receptor agonist, able to trigger the membrane hyperpolarization, mobilization of the intracellular Ca(2+) and receptor-ligand internalization in cells expressing somatostatin receptors. This complex represents a novel optical reporter due to its red emission spectral band suitable for in vivo imaging and tracking of the somatostatin receptor signaling pathways, affording higher resolution and sensitivity than those of the state-of-the-art radiolabeling bioassays.
authors.affiliation: MQ Biofocus Research Centre, Macquarie University, Sydney, NSW 2109, Australia.
authors.forename: Varun K A
authors.initials: VK
authors.lastname: Sreenivasan
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Stremovskiy
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Kelf
authors.forename: Marika
authors.initials: M
authors.lastname: Heblinski
authors.forename: Ann K
authors.initials: AK
authors.lastname: Goodchild
authors.forename: Mark
authors.initials: M
authors.lastname: Connor
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Deyev
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Zvyagin
mesh_terms: D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D005453:Fluorescence; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D008969:Molecular Sequence Data; D015202:Protein Engineering / Q000379:methods; D017481:Receptors, Somatostatin / Q000819:agonists* / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology*; D013004:Somatostatin / Q000235:genetics* / Q000494:pharmacology; D000097573:Red Fluorescent Protein
chemical_list: D002118:Calcium; D008164:Luminescent Proteins; D017481:Receptors, Somatostatin; D011994:Recombinant Proteins; D013004:Somatostatin; D000097573:Red Fluorescent Protein; C106140:somatostatin receptor sst2A