tailieunhanh - Báo cáo khoa học: Intracellular degradation of somatostatin-14 following somatostatin-receptor 3-mediated endocytosis in rat insulinoma cells

Somatostatin receptor (SSTR) endocytosis influences cellular responsiveness to agonist stimulation and somatostatin receptor scintigraphy, a common diagnostic imaging technique. Recently, we have shown that SSTR1 is dif-ferentially regulated in the endocytic and recycling pathway of pancreatic cells after agonist stimulation. | ễFEBS Journal Intracellular degradation of somatostatin-14 following somatostatin-receptor 3-mediated endocytosis in rat insulinoma cells Dirk Roosterman1 Nicole E. I. Brune2 Oliver J. Kreuzer2 Micha Feld1 Sylvia Pauser1 Kim Zarse2 Martin Steinhoff1 and Wolfgang Meyerhof2 1 Department of Dermatology IZKF Munster and Ludwig Boltzmann Institute for Celland Immunobiology of the Skin Germany 2 Department of Molecular Genetics German Institute of Human Nutrition Potsdam-Rehbruecke Nuthetal Germany Keywords endocytosis G-protein-coupled receptor neuropeptide proteolysis somatostatin Correspondence D. Roosterman Department of Dermatology and IZKF Munster Von-Esmarch-Strasse 58 D-48148 Munster Germany Fax 49 0251 8357452 Tel 49 0251 8352932 E-mail roosterman@ Received 27 March 2008 revised 20 June 2008 accepted 23 July 2008 doi Somatostatin receptor SSTR endocytosis influences cellular responsiveness to agonist stimulation and somatostatin receptor scintigraphy a common diagnostic imaging technique. Recently we have shown that SSTR1 is differentially regulated in the endocytic and recycling pathway of pancreatic cells after agonist stimulation. Additionally SSTR1 accumulates and releases internalized somatostatin-14 SST-14 as an intact and biologically active ligand. We also demonstrated that SSTR2A was sequestered into early endosomes whereas internalized SST-14 was degraded by endosomal peptidases and not routed into lysosomal degradation. Here we examined the fate of peptide agonists in rat insulinoma cells expressing SSTR3 by biochemical methods and confocal laser scanning microscopy. We found that 125I Tyr11-SST-14 rapidly accumulated in intracellular vesicles where it was degraded in an ammonium chloride-sensitive manner. In contrast 125I Tyr1-octreotide accumulated and was released as an intact peptide. Rhodamine-B-labeled SST-14 however was rapidly internalized into endosome-like vesicles and fluorescence signals colocalized