title: Agonist-biased trafficking of somatostatin receptor 2A in enteric neurons.
abstract: Somatostatin (SST) 14 and SST 28 activate somatostatin 2A receptors (SSTR2A) on enteric neurons to control gut functions. SST analogs are treatments of neuroendocrine and bleeding disorders, cancer, and diarrhea, with gastrointestinal side effects of constipation, abdominal pain, and nausea. How endogenous agonists and drugs differentially regulate neuronal SSTR2A is unexplored. We evaluated SSTR2A trafficking in murine myenteric neurons and neuroendocrine AtT-20 cells by microscopy and determined whether agonist degradation by endosomal endothelin-converting enzyme 1 (ECE-1) controls SSTR2A trafficking and association with β-arrestins, key regulators of receptors. SST-14, SST-28, and peptide analogs (octreotide, lanreotide, and vapreotide) stimulated clathrin- and dynamin-mediated internalization of SSTR2A, which colocalized with ECE-1 in endosomes and the Golgi. After incubation with SST-14, SSTR2A recycled to the plasma membrane, which required active ECE-1 and an intact Golgi. SSTR2A activated by SST-28, octreotide, lanreotide, or vapreotide was retained within the Golgi and did not recycle. Although ECE-1 rapidly degraded SST-14, SST-28 was resistant to degradation, and ECE-1 did not degrade SST analogs. SST-14 and SST-28 induced transient interactions between SSTR2A and β-arrestins that were stabilized by an ECE-1 inhibitor. Octreotide induced sustained SSTR2A/β-arrestin interactions that were not regulated by ECE-1. Thus, when activated by SST-14, SSTR2A internalizes and recycles via the Golgi, which requires ECE-1 degradation of SST-14 and receptor dissociation from β-arrestins. After activation by ECE-1-resistant SST-28 and analogs, SSTR2A remains in endosomes because of sustained β-arrestin interactions. Therapeutic SST analogs are ECE-1-resistant and retain SSTR2A in endosomes, which may explain their long-lasting actions.
authors.affiliation: From the Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Peishen
authors.initials: P
authors.lastname: Zhao
authors.affiliation: From the Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Meritxell
authors.initials: M
authors.lastname: Canals
authors.affiliation: the Department of Surgery, University of California, San Francisco, San Francisco, California 94143.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Murphy
authors.affiliation: the Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, Massachusetts 02142, and.
authors.forename: Diana
authors.initials: D
authors.lastname: Klingler
authors.affiliation: the Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, San Francisco, California 94110.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Eriksson
authors.affiliation: the Department of Surgery, University of California, San Francisco, San Francisco, California 94143.
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Pelayo
authors.affiliation: the Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, Massachusetts 02142, and.
authors.forename: Markus
authors.initials: M
authors.lastname: Hardt
authors.affiliation: From the Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia,. Electronic address: Nigel.Bunnett@Monash.edu.
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Bunnett
authors.affiliation: From the Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia,. Electronic address: Daniel.Poole@Monash.edu.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Poole
mesh_terms: D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D017615:Enteric Nervous System / Q000378:metabolism*; D005260:Female; D005765:Gastrointestinal Agents / Q000494:pharmacology; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D008297:Male; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D015282:Octreotide / Q000493:pharmacokinetics; D021381:Protein Transport; D059748:Proteolysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017481:Receptors, Somatostatin / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D013004:Somatostatin / Q000235:genetics / Q000378:metabolism*; D053561:Somatostatin-28 / Q000235:genetics / Q000378:metabolism*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D005765:Gastrointestinal Agents; D017481:Receptors, Somatostatin; D000071557:beta-Arrestins; D013004:Somatostatin; D053561:Somatostatin-28; C093733:somatostatin receptor 2; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; C000606925:Ece1 protein, mouse; D000072396:Endothelin-Converting Enzymes; D015282:Octreotide
keywords: Arrestin; Endocytosis; Endothelin-converting Enzyme; Neurons; Neuropeptide; Receptor Recycling; Somatostatin
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