AVPR1B

AVPR1B is a Gq/11-coupled vasopressin receptor that functions as a critical mediator of hypothalamic-pituitary-adrenal (HPA) axis activation and paracrine hormone signaling in the endocrine pancreas. In anterior pituitary corticotrophs, AVPR1B mediates arginine vasopressin (AVP)-stimulated ACTH release, and its genetic knockout or pharmacological antagonism significantly attenuates plasma ACTH and corticosterone responses to acute stress (PMID:20846299, PMID:23580725). AVPR1B is dramatically upregulated in corticotropinomas—an effect potentiated by USP8 mutations that enhance AVPR1B promoter activity—where it drives desmopressin-stimulated ACTH hypersecretion, intracellular Ca²⁺ mobilization, and cell proliferation (PMID:23884782, PMID:35451730). In pancreatic islets, AVPR1B is expressed exclusively in alpha cells, where its activation by AVP stimulates glucagon secretion that promotes glucose-dependent insulin release from beta cells through a paracrine GLP-1R-dependent mechanism (PMID:39217353).

1. 2008 Medium

   The question of where in the brain AVPR1B acts to regulate anxiety was addressed by showing that dorsal hippocampal AVPR1B mediates anxiety-like behavior, establishing region-specific functional roles for vasopressin receptor subtypes.

   Evidence Intra-hippocampal microinfusion of selective AVPR1B antagonist (SSR 149415) with elevated plus-maze and shock-probe behavioral tests in rats

   PMID:18508119

   Open questions at the time

   • Single lab finding; independent replication in additional behavioral paradigms needed
   • Downstream signaling cascades in hippocampal neurons not characterized
   • Whether dorsal hippocampal AVPR1B affects HPA axis feedback remains untested
2. 2010 High

   The necessity of AVPR1B for stress-induced HPA axis activation was established by demonstrating that both genetic knockout and pharmacological antagonism of Avpr1b markedly reduce ACTH and corticosterone responses to acute stress.

   Evidence Avpr1b knockout mice and selective V1bR antagonist treatment with plasma ACTH/corticosterone measurement across restraint and forced-swim stress paradigms

   PMID:20846299

   Open questions at the time

   • Whether AVPR1B is required for chronic stress responses not addressed
   • Intracellular signaling pathway (Gq, Ca²⁺, PKC) in corticotrophs not dissected in vivo
3. 2013 High

   AVPR1B was identified as the key receptor mediating desmopressin-induced ACTH hypersecretion in human corticotropinomas, explaining why the desmopressin stimulation test selectively detects Cushing's disease: AVPR1B is massively overexpressed in corticotropinomas relative to normal pituitary.

   Evidence qRT-PCR for receptor expression, primary corticotropinoma cell cultures with desmopressin stimulation, ACTH secretion assays, intracellular Ca²⁺ imaging, and AVPR1B antagonist blockade; corroborated by V1bR antagonist Nelivaptan reducing heat-stress-induced ACTH in rats

   PMID:23580725 PMID:23884782

   Open questions at the time

   • Mechanism driving AVPR1B upregulation in tumors was not yet identified
   • Whether AVPR1B-mediated proliferation is sufficient for tumorigenesis remains unknown
4. 2022 Medium

   A mechanism for AVPR1B overexpression in corticotropinomas was revealed: recurrent USP8 mutations enhance AVPR1B promoter activity, linking a frequent somatic driver mutation to the receptor upregulation underlying desmopressin responsiveness.

   Evidence Dual-luciferase reporter assay comparing mutant vs. wild-type USP8 effects on Avpr1b promoter activity; qRT-PCR and immunohistochemistry in tumor samples

   PMID:35451730

   Open questions at the time

   • Single-lab reporter assay; independent validation and identification of the transcription factor intermediaries needed
   • Whether USP8-driven AVPR1B upregulation is necessary and sufficient for desmopressin sensitivity in vivo not shown
   • The direct USP8 substrate linking deubiquitination to AVPR1B promoter activation is unidentified
5. 2024 Medium

   AVPR1B function was extended beyond the pituitary and brain by showing it is the exclusive vasopressin receptor in pancreatic alpha cells, where it triggers glucagon release that drives paracrine GLP-1R-dependent insulin secretion from beta cells.

   Evidence Single-cell transcriptomics for receptor localization; islet vs. isolated beta-cell insulin secretion assays; V1bR, GLP-1R, and GCGR selective antagonist experiments

   PMID:39217353

   Open questions at the time

   • Single-lab finding; in vivo confirmation of AVP/AVPR1B-glucagon-GLP-1R axis in glucose homeostasis needed
   • Physiological relevance under fasting vs. fed states not delineated
   • Whether AVPR1B in alpha cells contributes to diabetes pathophysiology is unexplored

• The structural basis of AVPR1B selective agonism/antagonism, the full downstream signaling network in corticotrophs (beyond Ca²⁺ mobilization), and the therapeutic potential of AVPR1B-targeted therapy in Cushing's disease and metabolic disorders remain to be established.
• No high-resolution structure of AVPR1B in complex with ligand or G protein is available
• Complete Gq/Ca²⁺/PKC signaling cascade in corticotrophs not mapped
• Clinical efficacy of selective AVPR1B antagonists in Cushing's disease not demonstrated