id: MODULE:vasopressin_receptor_signaling title: Vasopressin receptor signaling — V1a/V1b Gq/11-phospholipase C coupling and the renal V2 Gs/ADCY6/cAMP/AKAP-anchored PKA pathway driving aquaporin-2 exocytosis and water reabsorption description: >- Arginine vasopressin (AVP), a neurohypophyseal nonapeptide hormone, acts through three G protein-coupled receptors that fall into two signalling classes. The V1a receptor (AVPR1A; vascular smooth muscle, liver, platelets, brain) and the V1b receptor (AVPR1B; anterior pituitary corticotrophs) couple to the Gq/11 alpha subunits GNAQ and GNA11, stimulating phospholipase C beta, inositol trisphosphate-driven calcium release and diacylglycerol/PKC signalling, which underlie vasoconstriction and pituitary ACTH release. The V2 receptor (AVPR2), on the basolateral membrane of renal collecting-duct principal cells, couples to the stimulatory G alpha subunit GNAS, which activates adenylyl cyclase type 6 (ADCY6), the dominant inner-medullary cyclase. cAMP activates protein kinase A, which is tethered to intracellular aquaporin-2 (AQP2)-bearing vesicles by the A-kinase anchoring protein AKAP18 (AKAP7) together with the cAMP phosphodiesterase PDE4D. PKA phosphorylates AQP2 at serine 256, which is required for the regulated exocytosis of AQP2 vesicles. The vesicles move through a RAB11A-positive recycling compartment with the motor myosin Vb (MYO5B) and its Rab11 adaptor RAB11FIP2, the Rap1 GTPase-activating protein SPA-1 (SIPA1) binds AQP2 and is required for its apical delivery, and the R-SNARE VAMP2 on the vesicle fuses with the apical Q-SNAREs SNAP23 and syntaxin-3 (or syntaxin-4). AQP2 water channels in the apical membrane then let water follow the osmotic gradient out of the tubular lumen, concentrating the urine. PKA also phosphorylates and activates PDE4D on the same vesicles, providing local negative feedback, and PKA-phosphorylated CREB drives AQP2 transcription. Loss-of-function mutations in AVPR2 or AQP2 cause nephrogenic diabetes insipidus. status: DRAFT scope: CONCRETE references: - id: PMID:1534149 title: Molecular cloning of the receptor for human antidiuretic hormone. reference_review: relevance: HIGH correctness: VERIFIED review_notes: >- PubMed-verified; cloning of human AVPR2 and statement of its adenylyl cyclase coupling. Also the source of AVPR2's IDA vasopressin receptor activity annotation in GOA. - id: PMID:8106369 title: Molecular cloning, sequencing, and functional expression of a cDNA encoding the human V1a vasopressin receptor. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:7929452 title: Molecular cloning and functional expression of a cDNA encoding the human V1b vasopressin receptor. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:9322919 title: "The human V3 pituitary vasopressin receptor: ligand binding profile and density-dependent signaling pathways." reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: >- Human V1b (V3) receptor stimulates phospholipase C; cAMP coupling appears only at high receptor density, so the Gq/PLC route is taken as the physiological coupling. - id: PMID:20864687 title: Adenylate cyclase 6 determines cAMP formation and aquaporin-2 phosphorylation and trafficking in inner medulla. reference_review: relevance: HIGH correctness: VERIFIED review_notes: Mouse Adcy6 knockout; fixes ADCY6 as the V2-coupled cyclase in the inner medulla. - id: PMID:9169447 title: Phosphorylation of serine 256 is required for cAMP-dependent regulatory exocytosis of the aquaporin-2 water channel. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:15037626 title: Identification of a novel A-kinase anchoring protein 18 isoform and evidence for its role in the vasopressin-induced aquaporin-2 shuttle in renal principal cells. reference_review: relevance: HIGH correctness: VERIFIED review_notes: >- Identifies the rat AKAP18delta splice variant on AQP2 vesicles; the human gene-product mapping to the long AKAP7 entry is a curator inference recorded in notes. - id: PMID:17135396 title: Compartmentalization of cAMP-dependent signaling by phosphodiesterase-4D is involved in the regulation of vasopressin-mediated water reabsorption in renal principal cells. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:8663227 title: Phosphorylation and activation of a cAMP-specific phosphodiesterase by the cAMP-dependent protein kinase. Involvement of serine 54 in the enzyme activation. reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Rat PDE4D3 biochemistry; establishes the PKA feedback activation mechanism, not its renal context. - id: PMID:17156409 title: A Role of myosin Vb and Rab11-FIP2 in the aquaporin-2 shuttle. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:15196935 title: Aquaporin-2 trafficking is regulated by PDZ-domain containing protein SPA-1. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:12186952 title: Functional involvement of VAMP/synaptobrevin-2 in cAMP-stimulated aquaporin 2 translocation in renal collecting duct cells. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:18505797 title: AQP2 exocytosis in the renal collecting duct -- involvement of SNARE isoforms and the regulatory role of Munc18b. reference_review: relevance: HIGH correctness: VERIFIED - id: PMID:8140421 title: Requirement of human renal water channel aquaporin-2 for vasopressin-dependent concentration of urine. reference_review: relevance: HIGH correctness: VERIFIED evidence: - source_id: PW:0000491 title: vasopressin signaling pathway statement: >- The module boundary follows the RGD Pathway Ontology overview diagram and record text, which draw Avp acting on Avpr1a (Gq alpha, phospholipase C beta, second messengers, calcium elevation, vasoconstriction) and on Avpr2 (Gs alpha, adenylyl cyclase, cAMP and the PKA pathway driving Aqp2 translocation and Aqp2 expression, and so water reabsorption), and name the human V1b receptor AVPR1B as the pituitary receptor. Derived through projects/RGD_PATHWAY_ONTOLOGY (pathways/PW_0000491.yaml). - source_id: PW:0000713 title: vasopressin signaling pathway via receptor type 2 statement: >- The V2 branch follows the RGD diagram for the receptor type 2 subpathway: Avpr2 to Gnas to Adcy6, ATP to cAMP, PKA compartmentalised by Akap7 with Pde4d on Aqp2-bearing vesicles, PKA phosphorylation of AQP2 serine 256 and of Pde4d, the Myo5b/Rab11a/Rab11fip2 trafficking machinery, the v-SNARE Vamp2 with the t-SNAREs Snap23 and syntaxin (3 or 4), and Sipa1 as an Aqp2-binding Rap1 GAP required for translocation. Derived through projects/RGD_PATHWAY_ONTOLOGY (pathways/PW_0000713.yaml). - source_id: GO:1904117 title: cellular response to vasopressin statement: >- Grounded in GO cellular response to vasopressin, the curated closeMatch for PW:0000491 (and broadMatch for PW:0000713) in the project's PW-GO SSSOM mapping. GO has no vasopressin receptor signaling pathway term, so the receptor branches are typed with the coupling-class terms GO:0007200 (V1a/V1b) and GO:0007189 (V2). - source_id: PMID:1534149 title: Molecular cloning of the receptor for human antidiuretic hormone. statement: >- The antidiuretic (V2) receptor stimulates adenylyl cyclase and promotes cAMP-mediated insertion of water pores into the luminal membrane of collecting tubule cells. supporting_text: >- which binds to specific receptors on renal collecting tubule cells, stimulates adenylyl cyclase and promotes the cyclic AMP-mediated incorporation of water pores into the luminal surface of these cells. - source_id: PMID:8140421 title: Requirement of human renal water channel aquaporin-2 for vasopressin-dependent concentration of urine. statement: Human genetic evidence that AQP2 is the obligatory effector of V2 antidiuresis. supporting_text: Thus, aquaporin-2 is essential for vasopressin-dependent concentration of urine. notes: >- Derived from the RGD Pathway Ontology diagrams PW:0000491 (vasopressin signaling pathway) and PW:0000713 (its receptor type 2 branch) through the RGD_PATHWAY_ONTOLOGY project. Both PW ids are listed as evidence because the module covers both. The other PW subpathways linked from the PW:0000491 diagram are not claimed: PW:0000712 (receptor type 1 branch) has no separate RGD record in the project and its content is the V1 variant here; the generic PW:0000227 (Galphas), PW:0000229 (Galphaq) and PW:0000543 (PKA) pathways are represented by reference to modules/gpcr_camp_pka_signaling.yaml and modules/gpcr_plc_calcium_pkc_signaling.yaml. All 17 RGD-curated human genes (ADCY6 AKAP7 AQP2 AVP AVPR1A AVPR1B AVPR2 GNA11 GNAQ GNAS MYO5B PDE4D RAB11A RAB11FIP2 SIPA1 SNAP23 VAMP2) are modelled. Three proteins not on the RGD gene list are added because the RGD text names their step and the step has no enzyme otherwise: PRKACA (the PKA catalytic subunit that phosphorylates AQP2 Ser256; PKA is drawn only as a pathway node) and the syntaxins STX3 and STX4 ("syntaxin (3 or 4)" in the PW:0000713 text). Molecular functions come from each protein's experimental (or, where none exists, IBA/TAS) GO annotations in QuickGO and from the primary literature, verified against go-basic releases/2026-07-26. Receptor variant set. The root module has one shared part (the AVP ligand) and a variant_set on receptor coupling class, mirroring modules/dopamine_receptor_signaling.yaml and modules/acetylcholine_signaling.yaml. V1 receptors: AVPR1A and AVPR1B both carry IDA vasopressin receptor activity (GO:0005000) and couple via pertussis-toxin-insensitive Gq/11 to phospholipase C (PMID:8106369, PMID:7929452, PMID:9322919); GNAQ and GNA11 carry G protein activity (GO:0003925) as their reviewed core function. No cached paper assays the human V1 receptors with GNAQ or GNA11 by name, so the Gq/11 assignment rests on the PTX-insensitive PLC coupling plus the RGD diagram's Gq alpha node; downstream PLC beta, IP3/calcium and DAG/PKC are included by reference to gpcr_plc_calcium_pkc_signaling#plc_beta_activation, not re-modelled. Vasoconstriction, hepatic glycogenolysis, platelet and behavioural effects of V1a and ACTH release by V1b are physiological outputs of other cell types and are left as prose. AVPR1B can couple to cAMP at very high expression (PMID:9322919); this is treated as an overexpression effect, not a separate branch. V2 receptor: AVPR2 (GO:0005000 IDA PMID:1534149; GO:0007189 IDA) couples to GNAS (P63092, Gs alpha short form, as in the GO-CAM) and ADCY6. ADCY6 rather than the generic module's ADCY5 is the cyclase because the RGD diagram names Adcy6 and Adcy6-null mice lose dDAVP-stimulated inner-medullary cAMP (PMID:20864687). AVP as ligand, not as a pathway participant. Per the CLAUDE.md substrate/participant rule, AVP is given its molecular function only: neuropeptide hormone activity (GO:0005184, IDA; a child of hormone activity and receptor ligand activity). It is not given cellular response to vasopressin, which is the response of the target cell to AVP, nor the receptor-signalling process terms; no human AVP row in GOA carries them either. The curated GO-CAM gomodel:67e5e74400004286 models AVP (the Arg-vasopressin chain P01185-PRO_0000020515) the same way: an extracellular hormone activity that directly positively regulates AVPR2 vasopressin receptor activity and has AVPR2 as input, part of renal water absorption (GO:0070295, a physiological process rather than the signalling pathway). The module annoton uses the parent accession P01185 with that chain noted. AQP2 is a participant, not merely a PKA substrate or a vesicle cargo. AQP2 has two roles in this module and the two are treated differently. As the phosphoacceptor of PKA and the cargo of the regulated vesicles it is an input: it is listed as a PKA target and is not annotated to exocytosis or to the signalling pathway, since cargo does none of the work of vesicle transport or fusion. As the apical water channel, it does the work of the module's output step itself: water channel activity (GO:0015250, EXP/IMP; nonfunctional NDI mutants in PMID:8140421) moves water across the apical membrane, which is the transport step of renal water absorption. That passes the "does the gene do any of the work" test (it is the channel, not a substrate of one), so the AQP2 annoton is a leaf effector with GO:0015250 and process GO:0070295 renal water absorption. Comparator check: GO:0070295 in human GOA is carried by AVPR2 (IDA) and HAS2/HYAL2, while AQP2 carries renal water homeostasis (GO:0003091, IMP) and water transport (GO:0006833, IDA/IMP) but not GO:0070295. Since AQP2 is itself the channel that carries out the transport, the module asserts GO:0070295 on the AQP2 annoton and records the absence from GOA as a possible curation gap rather than evidence against the role. PKA and the AKAP18/PDE4D compartment. The generic cAMP/PKA cascade is not re-modelled: the cyclase and PKA tiers point at modules/gpcr_camp_pka_signaling.yaml by module_ref (adenylyl_cyclase_activation and pka_creb_output), and the CREB-driven transcription of AQP2 that both RGD records describe is covered by that module's PKA/CREB node rather than duplicated here. What is specific to this pathway, and therefore modelled, is the vesicle compartment: AKAP18 anchors PKA on AQP2-bearing vesicles with PDE4D (PMID:15037626, PMID:17135396), PKA phosphorylates AQP2 Ser256 to permit exocytosis (PMID:9169447) and phosphorylates PDE4D to activate it (PMID:8663227, PMID:17135396), giving local negative feedback on cAMP. Gene-product caveats: the AQP2-vesicle AKAP is the rat AKAP18delta splice variant, and human AKAP7 has two reviewed entries (O43687 alpha/beta and Q9P0M2 gamma) neither of which is the delta isoform, so the annoton uses the main human AKAP7 entry O43687 and the isoform mismatch is recorded as a knowledge gap. Its function is taken as GO:0035591 signaling adaptor activity, the core function in the AKAP7 gene review, rather than the GOA row GO:0051018 protein kinase A binding, which is a protein-binding descendant and says less about the role; the review's own evidence is for cardiac CaV1.2 anchoring, not the AQP2 vesicle, which is why the renal claim is carried by the vesicle-specific papers here. PRKACA is the PKA exemplar with cAMP-dependent protein kinase activity (GO:0004691); the RGD diagrams draw PKA only as a pathway node, so no specific catalytic subunit is named by RGD. Trafficking machinery. The recycling step is modelled as one part with four annotons: RAB11A (G protein activity GO:0003925, IDA, as in the curated FIP3-Rab11 GO-CAM), its effector RAB11FIP2 (small GTPase binding GO:0031267), the actin-based motor MYO5B (microfilament motor activity GO:0000146) and SIPA1/SPA-1 (GTPase activator activity GO:0005096, EXP), with PMID:17156409 for the myosin Vb/Rab11/Rab11-FIP2 requirement and PMID:15196935 for the SPA-1 requirement. SIPA1 was flagged for checking in the task: it is retained, because its role is directly supported (it binds AQP2, its Rap1GAP-dead mutant and constitutively active Rap1 block apical trafficking, and trafficking is impaired in Spa-1-null mice) and the activity asserted is its own experimentally established Rap1 GAP activity, not a vasopressin-specific invention. RAB11FIP2's GO:0031267 rests on IEA plus IPI protein-kinase and Rab11 interaction rows rather than a direct-assay GTPase-binding annotation, which is noted here rather than hidden. The fusion step keeps the vesicle R-SNARE VAMP2 (SNAP receptor activity GO:0005484) and the apical Q-SNAREs SNAP23 and syntaxin-3/syntaxin-4 as a variant set, with the generic zippering/fusion mechanism left to modules/snare_fusion_cycle.yaml. VAMP3 and Munc18b (PMID:18505797) are named in the literature but are not on either RGD gene list and are left out; syntaxin-3 and syntaxin-4 are included because the PW:0000713 text names "syntaxin (3 or 4)" even though neither has an RGD gene link on the diagram. Deliberately outside the module. Vasopressin biosynthesis, processing and axonal transport (modelled by the curated GO-CAM gomodel:69729a3800003304) are upstream ligand supply. Vasoconstriction, pituitary ACTH release, platelet and behavioural effects are downstream physiology of the V1 arm in other cell types. AQP3 and AQP4, the constitutive basolateral exit route for the water that AQP2 admits, are not on either RGD gene list and are mentioned only here. The calcium-dependent, cAMP-dependent but PKA-independent route to AQP2 translocation that both RGD records mention is recorded as a knowledge gap, not asserted, because neither record names the mediating gene products. knowledge_gaps: - gap_statement: >- Which human AKAP7 gene product performs the AQP2-vesicle PKA anchoring that the rat AKAP18delta splice variant was shown to perform is not established. boundary: >- The module grounds the anchoring step on the main human AKAP7 entry O43687; the experiments (PMID:15037626, PMID:17135396) used rat AKAP18delta, which corresponds to no reviewed human isoform entry. gap_kind: - BIOLOGY status: OPEN significance: >- Determines whether the human AQP2 shuttle uses an AKAP7 splice variant, a different AKAP, or several redundantly. resolution: >- Isoform-resolved proteomics and isoform-specific knockdown of AKAP7 variants in human collecting-duct principal cells, with AQP2 surface delivery as the readout. - gap_statement: >- The mechanism of the cAMP-dependent but PKA-independent, calcium-mediated route to AQP2 translocation, and which proteins carry it, is unresolved. boundary: >- Only the PKA-dependent Ser256 route is modelled; no alternative effector branch is asserted. gap_kind: - BIOLOGY status: OPEN significance: >- If a parallel route exists, AQP2 delivery is not strictly PKA-gated and the V2 branch has an effector tier the module does not represent. resolution: >- Identify the cAMP effector (for example an Epac/Rap arm) and test AQP2 surface delivery in principal cells with PKA inhibited and calcium clamped. module: id: vasopressin_receptor_signaling label: Vasopressin receptor signaling (V1a/V1b Gq and renal V2 Gs/AQP2 branches) module_type: SIGNALING_PATHWAY concepts: - preferred_term: cellular response to vasopressin term: id: GO:1904117 label: cellular response to vasopressin description: >- The target-cell response to arginine vasopressin through its three G protein-coupled receptors; GO has no vasopressin receptor signaling pathway term, so the coupling-class terms GO:0007200 and GO:0007189 type the two branches. context: taxa: - preferred_term: Homo sapiens term: id: NCBITaxon:9606 label: Homo sapiens description: >- Members are grounded on the human proteins; the RGD diagrams are rat curation and several key trafficking experiments are rat or rat-derived collecting-duct lines. cellular_components: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane description: Receptors, G proteins and the cyclase act at the plasma membrane. - preferred_term: cytosol term: id: GO:0005829 label: cytosol description: PKA, the anchored phosphodiesterase and the trafficking machinery act in the cytosol. parts: - order: 1 role: vasopressin ligand supply to the receptors node: id: avp_ligand label: Arginine vasopressin as receptor ligand module_type: REGULATORY_STEP description: >- AVP is released from the neurohypophysis and reaches the receptors as an extracellular hormone. Its molecular function is receptor ligand activity; the signalling and response processes belong to the receiving cell, not to the hormone. annotons: - id: avp_hormone label: AVP neuropeptide hormone activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AVP (Arg-vasopressin chain of the AVP-neurophysin 2-copeptin precursor) term: id: UniProtKB:P01185 label: Vasopressin-neurophysin 2-copeptin description: >- The active ligand is the cleaved Arg-vasopressin chain (UniProtKB:P01185-PRO_0000020515), the entity used by the curated GO-CAM. function: preferred_term: neuropeptide hormone activity term: id: GO:0005184 label: neuropeptide hormone activity targets: - preferred_term: AVPR2 (V2 receptor) term: id: UniProtKB:P30518 label: Vasopressin V2 receptor - preferred_term: AVPR1A (V1a receptor) term: id: UniProtKB:P37288 label: Vasopressin V1a receptor locations: - preferred_term: extracellular region term: id: GO:0005576 label: extracellular region role_description: >- The hormone that occupies the receptors. No process role is asserted: AVP performs none of the steps of the signalling pathway it triggers, and no human AVP annotation in GOA carries the receptor-signalling or cellular-response terms. gocam_associations: - model: gomodel:67e5e74400004286 activity: gomodel:67e5e74400004286/67e5e74400004322 title: "AVPR2 -mediated signaling G-alpha-s (\"stimulatory\", activating adenylate cyclase) following activation by vasopressin (AVP) (Human)." description: >- The curated model types the Arg-vasopressin chain with hormone activity (GO:0005179, the parent of the term used here) in the extracellular region, directly positively regulating AVPR2 and part of renal water absorption; it gives the hormone no signalling-pathway process. - order: 2 role: receptor subtype branches and their G protein coupling node: id: vaso_receptor_branches label: Vasopressin receptor branches module_type: SIGNALING_PATHWAY description: >- The three vasopressin receptors split into a Gq/11-phospholipase C class (V1a, V1b) and a Gs-adenylyl cyclase class (V2). Both are real alternatives in the organism, expressed in different tissues, so they are modelled as a variant set on coupling class rather than as sequential parts. variant_sets: - id: vaso_receptor_coupling label: Vasopressin receptor coupling class axis: receptor subtype and G protein coupling class selection: ONE_OR_MORE notes: >- V1a (vascular smooth muscle, liver, platelets, brain) and V1b (anterior pituitary) signal through Gq/11 and phospholipase C; V2 (collecting-duct principal cells) signals through Gs, adenylyl cyclase and cAMP. A cell can express more than one, so one or more variants satisfy the set. variants: - id: v1_gq_branch label: V1a/V1b receptors -> Gq/11 -> phospholipase C module_type: SIGNALING_PATHWAY description: >- AVP-occupied V1a or V1b receptors activate the Gq/11 alpha subunits, which stimulate phospholipase C beta; the resulting IP3/calcium and DAG/PKC signalling is the generic Gq cascade and is included by reference. concepts: - preferred_term: phospholipase C-activating G protein-coupled receptor signaling pathway term: id: GO:0007200 label: phospholipase C-activating G protein-coupled receptor signaling pathway parts: - order: 1 role: V1 receptor and Gq/11 activation node: id: v1_receptor_activation label: V1a/V1b receptors activate G alpha q/11 module_type: REGULATORY_STEP description: >- Both V1-class receptors couple to phospholipase C through a pertussis-toxin-insensitive (Gq/11) route. GNAQ and GNA11 are the alpha subunits; no cached experiment pairs the human V1 receptors with a named Gq paralog, so either satisfies the step. annotons: - id: gnaq_v1 label: GNAQ G protein activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: GNAQ (G alpha q) term: id: UniProtKB:P50148 label: Guanine nucleotide-binding protein G(q) subunit alpha function: preferred_term: G protein activity term: id: GO:0003925 label: G protein activity processes: - preferred_term: phospholipase C-activating G protein-coupled receptor signaling pathway term: id: GO:0007200 label: phospholipase C-activating G protein-coupled receptor signaling pathway locations: - preferred_term: cytoplasmic side of plasma membrane term: id: GO:0009898 label: cytoplasmic side of plasma membrane role_description: >- GTP-bound G alpha q transducer of the V1 receptors; its reviewed core function is G protein activity (IDA). - id: gna11_v1 label: GNA11 G protein activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: GNA11 (G alpha 11) term: id: UniProtKB:P29992 label: Guanine nucleotide-binding protein subunit alpha-11 function: preferred_term: G protein activity term: id: GO:0003925 label: G protein activity processes: - preferred_term: phospholipase C-activating G protein-coupled receptor signaling pathway term: id: GO:0007200 label: phospholipase C-activating G protein-coupled receptor signaling pathway locations: - preferred_term: cytoplasmic side of plasma membrane term: id: GO:0009898 label: cytoplasmic side of plasma membrane role_description: >- The second Gq-class alpha subunit; redundant with GNAQ for this step in the RGD diagram's Gq alpha node. variant_sets: - id: v1_receptor_members label: V1-class vasopressin receptors axis: receptor paralog selection: ONE_OR_MORE notes: >- AVPR1A and AVPR1B are the two V1-class receptors. They share the Gq/PLC coupling but occupy different tissues, so either (or both) satisfies this step. variants: - id: avpr1a_variant label: Vasopressin V1a receptor (AVPR1A) module_type: REGULATORY_STEP annotons: - id: avpr1a_receptor label: AVPR1A vasopressin receptor activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AVPR1A (V1a) term: id: UniProtKB:P37288 label: Vasopressin V1a receptor function: preferred_term: vasopressin receptor activity term: id: GO:0005000 label: vasopressin receptor activity targets: - preferred_term: GNAQ (G alpha q) term: id: UniProtKB:P50148 label: Guanine nucleotide-binding protein G(q) subunit alpha processes: - preferred_term: phospholipase C-activating G protein-coupled receptor signaling pathway term: id: GO:0007200 label: phospholipase C-activating G protein-coupled receptor signaling pathway locations: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane role_description: >- Vascular smooth muscle, liver, platelet and brain receptor; its calcium-mobilising output underlies vasoconstriction. evidence: - source_id: PMID:8106369 statement: >- The cloned human V1a receptor binds AVP with high affinity and couples to phospholipase C through a pertussis-toxin-insensitive (Gq-class) route. supporting_text: >- Measurement of AVP-induced inositol phosphate production and calcium mobilization confirmed that the expressed V1a AVP receptor is coupled to phospholipase C via a pertussis toxin-insensitive pathway. - id: avpr1b_variant label: Vasopressin V1b receptor (AVPR1B) module_type: REGULATORY_STEP annotons: - id: avpr1b_receptor label: AVPR1B vasopressin receptor activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AVPR1B (V1b, also called V3) term: id: UniProtKB:P47901 label: Vasopressin V1b receptor function: preferred_term: vasopressin receptor activity term: id: GO:0005000 label: vasopressin receptor activity targets: - preferred_term: GNAQ (G alpha q) term: id: UniProtKB:P50148 label: Guanine nucleotide-binding protein G(q) subunit alpha processes: - preferred_term: phospholipase C-activating G protein-coupled receptor signaling pathway term: id: GO:0007200 label: phospholipase C-activating G protein-coupled receptor signaling pathway locations: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane role_description: >- Pituitary receptor whose calcium signal drives ACTH release; the least characterised of the three, and the one the PW:0000491 record says is not drawn on the diagram. evidence: - source_id: PMID:7929452 statement: >- The human V1b receptor mediates pituitary hormone release through phosphatidylinositol hydrolysis and calcium mobilisation, and its expression is pituitary-restricted. supporting_text: >- Release is mediated by the V1b receptor through the mobilization of intracellular Ca2+ by phosphatidylinositol hydrolysis. - source_id: PMID:9322919 statement: >- AVP stimulates phospholipase C through the human V1b/V3 receptor; cAMP coupling appears only at the highest receptor densities. supporting_text: >- AVP triggered stimulation of phospholipase C in CHO-V3 cells (partially sensitive to treatment with pertussis toxin) with a potency directly proportional to receptor density. - order: 2 role: phospholipase C beta effector cascade node: id: v1_plc_effector label: PLC beta hydrolysis of PIP2 (shared Gq effector) description: >- Included by reference to the PLC beta step of the generic Gq-PLC-calcium-PKC module; the downstream IP3/calcium and DAG/PKC steps are in that same module and are not duplicated here. module_ref: gpcr_plc_calcium_pkc_signaling#plc_beta_activation connections: - source: v1_receptor_activation target: v1_plc_effector connection_type: POSITIVELY_REGULATES description: >- GTP-bound Gq/11 downstream of the V1 receptors stimulates phospholipase C beta, the entry point of the generic Gq cascade. - id: v2_gs_branch label: V2 receptor -> Gs -> ADCY6 -> cAMP/PKA -> AQP2 exocytosis and water reabsorption module_type: SIGNALING_PATHWAY description: >- In collecting-duct principal cells the V2 receptor activates Gs and adenylyl cyclase 6; cAMP activates PKA anchored with PDE4D on AQP2-bearing vesicles; PKA phosphorylation of AQP2 Ser256 permits exocytosis of the vesicles through a Rab11/myosin Vb recycling route and SNARE-mediated fusion with the apical membrane, where AQP2 then conducts water out of the tubular lumen. concepts: - preferred_term: adenylate cyclase-activating G protein-coupled receptor signaling pathway term: id: GO:0007189 label: adenylate cyclase-activating G protein-coupled receptor signaling pathway - preferred_term: renal water absorption term: id: GO:0070295 label: renal water absorption context: cellular_components: - preferred_term: apical plasma membrane term: id: GO:0016324 label: apical plasma membrane description: >- The destination of the AQP2 vesicles and the membrane across which water is reabsorbed; the receptor itself is basolateral. parts: - order: 1 role: V2 receptor and Gs activation node: id: v2_receptor_activation label: AVPR2 activates G alpha s module_type: REGULATORY_STEP description: >- AVP-occupied V2 receptor acts as a guanine nucleotide exchange factor for Gs; G alpha s-GTP then stimulates adenylyl cyclase. annotons: - id: avpr2_receptor label: AVPR2 vasopressin receptor activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AVPR2 (V2) term: id: UniProtKB:P30518 label: Vasopressin V2 receptor function: preferred_term: vasopressin receptor activity term: id: GO:0005000 label: vasopressin receptor activity targets: - preferred_term: GNAS (G alpha s) term: id: UniProtKB:P63092 label: Guanine nucleotide-binding protein G(s) subunit alpha isoforms short processes: - preferred_term: adenylate cyclase-activating G protein-coupled receptor signaling pathway term: id: GO:0007189 label: adenylate cyclase-activating G protein-coupled receptor signaling pathway - preferred_term: renal water absorption term: id: GO:0070295 label: renal water absorption locations: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane role_description: >- The antidiuretic receptor on the basolateral membrane of collecting-duct principal cells; loss-of-function mutations cause X-linked nephrogenic diabetes insipidus. evidence: - source_id: PMID:1534149 statement: >- The cloned human antidiuretic hormone receptor is a GPCR that stimulates adenylyl cyclase and drives cAMP-mediated insertion of water pores into the luminal membrane. supporting_text: >- which binds to specific receptors on renal collecting tubule cells, stimulates adenylyl cyclase and promotes the cyclic AMP-mediated incorporation of water pores into the luminal surface of these cells. gocam_associations: - model: gomodel:67e5e74400004286 activity: gomodel:67e5e74400004286/67e5e74400004287 title: "AVPR2 -mediated signaling G-alpha-s (\"stimulatory\", activating adenylate cyclase) following activation by vasopressin (AVP) (Human)." description: >- Same gene and molecular function (GO:0005000) at the plasma membrane, part of GO:0007189 nested in GO:0070295 renal water absorption, with AVP as input and GNAS downstream. - id: gnas_v2 label: GNAS G protein activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: GNAS (G alpha s, short isoforms) term: id: UniProtKB:P63092 label: Guanine nucleotide-binding protein G(s) subunit alpha isoforms short function: preferred_term: G protein activity term: id: GO:0003925 label: G protein activity targets: - preferred_term: ADCY6 (adenylyl cyclase 6) term: id: UniProtKB:O43306 label: Adenylate cyclase type 6 processes: - preferred_term: adenylate cyclase-activating G protein-coupled receptor signaling pathway term: id: GO:0007189 label: adenylate cyclase-activating G protein-coupled receptor signaling pathway locations: - preferred_term: cytoplasmic side of plasma membrane term: id: GO:0009898 label: cytoplasmic side of plasma membrane role_description: >- The stimulatory G alpha subunit named by the RGD diagram and used by the curated GO-CAM; its GTP-bound form activates ADCY6. gocam_associations: - model: gomodel:67e5e74400004286 activity: gomodel:67e5e74400004286/67e5e74400004289 title: "AVPR2 -mediated signaling G-alpha-s (\"stimulatory\", activating adenylate cyclase) following activation by vasopressin (AVP) (Human)." description: >- Same gene and molecular function (GO:0003925) on the cytoplasmic side of the plasma membrane, directly positively regulating the ADCY6 activity. - order: 2 role: cAMP generation by adenylyl cyclase 6 node: id: v2_adcy6 label: ADCY6 produces cAMP module_type: REACTION description: >- ADCY6 is the dominant adenylyl cyclase of the renal inner medulla and the isoform named by the RGD diagram; it converts ATP to cAMP when activated by G alpha s. The generic cyclase tier of the Gs-GPCR motif lives in modules/gpcr_camp_pka_signaling.yaml (adenylyl_cyclase_activation), which uses ADCY5; this node states the renal isoform instead. annotons: - id: adcy6_cyclase label: ADCY6 adenylate cyclase activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: ADCY6 (adenylyl cyclase 6) term: id: UniProtKB:O43306 label: Adenylate cyclase type 6 function: preferred_term: adenylate cyclase activity term: id: GO:0004016 label: adenylate cyclase activity products: - preferred_term: 3',5'-cyclic AMP processes: - preferred_term: adenylate cyclase-activating G protein-coupled receptor signaling pathway term: id: GO:0007189 label: adenylate cyclase-activating G protein-coupled receptor signaling pathway locations: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane role_description: >- Generates the cAMP that activates vesicle-anchored PKA; without it the inner medulla cannot mount a vasopressin cAMP response. evidence: - source_id: PMID:20864687 statement: >- AC6 is the most abundant inner-medullary cyclase and its loss abolishes the dDAVP-stimulated cAMP rise and AQP2 phosphorylation and trafficking. supporting_text: >- levels of AC6 mRNA, the most highly expressed AC isoform in the inner medulla, inversely correlate with fluid intake - source_id: PMID:20864687 statement: >- AC6-null mice have less inner-medullary cAMP, less phospho-AQP2 and a lower urine osmolality. supporting_text: >- mice lacking AC6 had lower levels of inner medullary cAMP, reduced abundance of phosphorylated AQP2 (at both serine-256 and serine-269), and lower urine osmolality than wild-type mice. gocam_associations: - model: gomodel:67e5e74400004286 activity: gomodel:67e5e74400004286/67e5e74400004291 title: "AVPR2 -mediated signaling G-alpha-s (\"stimulatory\", activating adenylate cyclase) following activation by vasopressin (AVP) (Human)." description: >- Same gene and molecular function (GO:0004016) with cAMP (CHEBI:17489) as output, downstream of the GNAS activity in GO:0007189. - order: 3 role: generic cAMP/PKA activation and CREB-driven AQP2 expression node: id: v2_camp_pka_interface label: cAMP activation of PKA and CREB output description: >- Included by reference to the generic Gs-GPCR cAMP/PKA module, which models cAMP binding the PKA regulatory subunits, release of the catalytic subunits and PKA phosphorylation of CREB. Both RGD records note that PKA-phosphorylated CREB drives transcription of AQP2; that transcriptional arm is covered there rather than duplicated here. module_ref: gpcr_camp_pka_signaling#pka_creb_output - order: 4 role: AKAP18-anchored PKA on AQP2 vesicles phosphorylates AQP2 Ser256 node: id: v2_vesicle_pka_compartment label: AKAP18/PKA/PDE4D compartment on AQP2-bearing vesicles module_type: REGULATORY_STEP description: >- What is specific to the AQP2 shuttle is where PKA acts: an AKAP18 (AKAP7) scaffold holds PKA, and PDE4D, on the AQP2-bearing vesicles, so that the cAMP signal is decoded locally. PKA phosphorylation of AQP2 serine 256 is the licence for regulated exocytosis. annotons: - id: akap7_anchor label: AKAP18 (AKAP7) anchoring of PKA on AQP2 vesicles participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AKAP7 (AKAP18) term: id: UniProtKB:O43687 label: A-kinase anchor protein 7 isoforms alpha and beta function: preferred_term: signaling adaptor activity term: id: GO:0035591 label: signaling adaptor activity targets: - preferred_term: PRKACA (PKA catalytic subunit alpha) term: id: UniProtKB:P17612 label: cAMP-dependent protein kinase catalytic subunit alpha - preferred_term: PDE4D term: id: UniProtKB:Q08499 label: 3',5'-cyclic-AMP phosphodiesterase 4D processes: - preferred_term: positive regulation of cAMP/PKA signal transduction term: id: GO:0141163 label: positive regulation of cAMP/PKA signal transduction locations: - preferred_term: cytoplasmic vesicle membrane term: id: GO:0030659 label: cytoplasmic vesicle membrane role_description: >- Places PKA (and PDE4D) on the AQP2 vesicle, so the kinase reaches its substrate and the local cAMP level is set by a co-anchored phosphodiesterase. The activity is adaptor binding; the shuttle is its consequence. evidence: - source_id: PMID:15037626 statement: >- The AKAP18delta splice variant sits on the same intracellular vesicles as AQP2 and PKA and is recruited with AQP2 to the plasma membrane on AVP stimulation. supporting_text: >- Within the particulate fraction, AKAP18delta was identified on the same intracellular vesicles as AQP2 and PKA. - source_id: PMID:15037626 statement: PKA anchoring by AKAPs is a prerequisite for the AQP2 shuttle. supporting_text: >- The tethering of PKA to subcellular compartments by protein kinase A anchoring proteins (AKAPs) is a prerequisite for the AQP2 shuttle. - source_id: PMID:17135396 statement: >- AKAP18delta on AQP2-bearing vesicles interacts directly with PDE4D and PKA. supporting_text: >- AKAP18delta, which is located on AQP2-bearing vesicles, directly interacts with PDE4D and PKA. - id: prkaca_aqp2_kinase label: PKA phosphorylation of AQP2 serine 256 participant: selector_type: GENE_PRODUCT gene_product: preferred_term: PRKACA (PKA catalytic subunit alpha) term: id: UniProtKB:P17612 label: cAMP-dependent protein kinase catalytic subunit alpha function: preferred_term: cAMP-dependent protein kinase activity term: id: GO:0004691 label: cAMP-dependent protein kinase activity targets: - preferred_term: AQP2 (serine 256) term: id: UniProtKB:P41181 label: Aquaporin-2 - preferred_term: PDE4D (feedback substrate) term: id: UniProtKB:Q08499 label: 3',5'-cyclic-AMP phosphodiesterase 4D processes: - preferred_term: endosome to plasma membrane protein transport term: id: GO:0099638 label: endosome to plasma membrane protein transport locations: - preferred_term: cytoplasmic vesicle membrane term: id: GO:0030659 label: cytoplasmic vesicle membrane role_description: >- The kinase of the pathway. RGD draws PKA only as a pathway node, so the catalytic exemplar PRKACA is supplied here; the phosphosite (AQP2 Ser256) is the licensing step for regulated exocytosis. evidence: - source_id: PMID:9169447 statement: >- AQP2 serine 256 is required for cAMP-dependent regulated exocytosis: the S256A mutant is neither phosphorylated nor delivered to the surface, and gives no cAMP-stimulated water permeability. supporting_text: >- Our results indicated that serine 256 of AQP2 is necessary for regulatory exocytosis and that cAMP-responsive redistribution of AQP2 may be regulated by phosphorylation of AQP2. - source_id: PMID:17135396 statement: PKA and PDE4D are both located on AQP2-bearing vesicles. supporting_text: >- PKA and cAMP-specific phosphodiesterase-4D (PDE4D) are located on AQP2-bearing vesicles. - order: 5 role: Rab11/myosin Vb recycling of AQP2 vesicles toward the apical membrane node: id: v2_aqp2_recycling label: AQP2 vesicle recycling machinery module_type: REGULATORY_STEP description: >- AQP2 cycles through a RAB11A-positive recycling compartment. The motor myosin Vb, recruited through RAB11A and the Rab11 adaptor RAB11FIP2, and the AQP2-binding Rap1 GAP SPA-1 (SIPA1) are each required for apical delivery. annotons: - id: rab11a_recycling label: RAB11A G protein activity on AQP2 vesicles participant: selector_type: GENE_PRODUCT gene_product: preferred_term: RAB11A term: id: UniProtKB:P62491 label: Ras-related protein Rab-11A function: preferred_term: G protein activity term: id: GO:0003925 label: G protein activity targets: - preferred_term: RAB11FIP2 term: id: UniProtKB:Q7L804 label: Rab11 family-interacting protein 2 - preferred_term: MYO5B (myosin Vb) term: id: UniProtKB:Q9ULV0 label: Unconventional myosin-Vb processes: - preferred_term: endosome to plasma membrane protein transport term: id: GO:0099638 label: endosome to plasma membrane protein transport locations: - preferred_term: recycling endosome term: id: GO:0055037 label: recycling endosome role_description: >- The vesicular receptor for the myosin Vb motor; its GTP-bound form recruits RAB11FIP2 and myosin Vb to AQP2-bearing vesicles. evidence: - source_id: PMID:17156409 statement: Rab11 is present on AQP2-bearing vesicles. supporting_text: Rab11 was found on AQP2-bearing vesicles. gocam_associations: - model: gomodel:654d809000002780 activity: gomodel:654d809000002780/654d809000002794 title: Early endosome to recycling endosome transport by the FIP3-Rab11 complex (Human) description: >- Same gene and molecular function (GO:0003925) in a curated endosomal recycling model; that model uses the FIP3 (RAB11FIP3) adaptor, where the AQP2 shuttle uses RAB11FIP2. - id: rab11fip2_adaptor label: RAB11FIP2 linkage of Rab11 to myosin Vb participant: selector_type: GENE_PRODUCT gene_product: preferred_term: RAB11FIP2 (Rab11-FIP2) term: id: UniProtKB:Q7L804 label: Rab11 family-interacting protein 2 function: preferred_term: small GTPase binding term: id: GO:0031267 label: small GTPase binding processes: - preferred_term: endosome to plasma membrane protein transport term: id: GO:0099638 label: endosome to plasma membrane protein transport locations: - preferred_term: recycling endosome term: id: GO:0055037 label: recycling endosome role_description: >- Binds both Rab11 and the myosin Vb tail; the C2-deleted mutant traps AQP2 in a Rab11 compartment and abolishes the shuttle. evidence: - source_id: PMID:17156409 statement: >- Dominant-negative myosin Vb tail and Rab11-FIP2 lacking the C2 domain trap AQP2 in a Rab11 compartment and abolish the shuttle, in a Rab11-binding-dependent way. supporting_text: >- This effect was dependent on binding of myosin Vb tail and Rab11-FIP2-DeltaC2 to Rab11. - id: myo5b_motor label: Myosin Vb motor activity in AQP2 recycling participant: selector_type: GENE_PRODUCT gene_product: preferred_term: MYO5B (myosin Vb) term: id: UniProtKB:Q9ULV0 label: Unconventional myosin-Vb function: preferred_term: microfilament motor activity term: id: GO:0000146 label: microfilament motor activity processes: - preferred_term: endosome to plasma membrane protein transport term: id: GO:0099638 label: endosome to plasma membrane protein transport locations: - preferred_term: recycling endosome term: id: GO:0055037 label: recycling endosome role_description: >- Actin-based motor of the AQP2 recycling route; colocalises with AQP2 intracellularly at rest and at the plasma membrane after AVP. evidence: - source_id: PMID:17156409 statement: >- Myosin Vb is the motor of AQP2 recycling and myosin Vb- and Rab11-FIP2-dependent recycling is an integral part of the shuttle. supporting_text: >- we identified myosin Vb as a motor protein involved in AQP2 recycling and show that myosin Vb- and Rab11-FIP2-dependent recycling of AQP2 is an integral part of the AQP2 shuttle. - id: sipa1_rap1_gap label: SPA-1 (SIPA1) Rap1 GAP activity in AQP2 trafficking participant: selector_type: GENE_PRODUCT gene_product: preferred_term: SIPA1 (SPA-1) term: id: UniProtKB:Q96FS4 label: Signal-induced proliferation-associated protein 1 function: preferred_term: GTPase activator activity term: id: GO:0005096 label: GTPase activator activity targets: - preferred_term: RAP1A term: id: UniProtKB:P62834 label: Ras-related protein Rap-1A processes: - preferred_term: Rap protein signal transduction term: id: GO:0032486 label: Rap protein signal transduction - preferred_term: protein localization to plasma membrane term: id: GO:0072659 label: protein localization to plasma membrane locations: - preferred_term: cytosol term: id: GO:0005829 label: cytosol role_description: >- Binds AQP2 through its PDZ domain and keeps Rap1 activity low; the GAP-dead mutant, constitutively active Rap1, and Spa-1 deficiency all block apical AQP2 delivery. Its own GAP activity is experimentally established, so the role is a participation claim, not a guess. evidence: - source_id: PMID:15196935 statement: SPA-1 binds AQP2 directly and is required for its trafficking. supporting_text: >- Our results show that SPA-1 directly binds to AQP2 and regulates at least in part AQP2 trafficking. - source_id: PMID:15196935 statement: >- The Rap1GAP activity is the relevant function: the GAP-dead SPA-1 mutant and constitutively active Rap1 both inhibit apical AQP2 trafficking. supporting_text: >- AQP2 trafficking to the apical membrane was inhibited by the SPA-1 mutant lacking Rap1GAP activity and by the constitutively active mutant of Rap1. - order: 6 role: SNARE-mediated fusion of AQP2 vesicles with the apical membrane node: id: v2_aqp2_fusion label: VAMP2/SNAP23/syntaxin fusion of AQP2 vesicles module_type: REGULATORY_STEP description: >- The vesicle R-SNARE VAMP2 pairs with apical Q-SNAREs (SNAP23 with syntaxin-3 or syntaxin-4) to fuse AQP2 vesicles with the apical membrane. The generic zippering and disassembly mechanism is in modules/snare_fusion_cycle.yaml and is not duplicated. annotons: - id: vamp2_rsnare label: VAMP2 vesicle R-SNARE participant: selector_type: GENE_PRODUCT gene_product: preferred_term: VAMP2 (synaptobrevin-2) term: id: UniProtKB:P63027 label: Vesicle-associated membrane protein 2 function: preferred_term: SNAP receptor activity term: id: GO:0005484 label: SNAP receptor activity processes: - preferred_term: vesicle fusion term: id: GO:0006906 label: vesicle fusion - preferred_term: exocytosis term: id: GO:0006887 label: exocytosis locations: - preferred_term: cytoplasmic vesicle membrane term: id: GO:0030659 label: cytoplasmic vesicle membrane role_description: >- The R-SNARE on AQP2 vesicles; cleaving it with tetanus neurotoxin abolishes cAMP-stimulated AQP2 delivery to the surface. evidence: - source_id: PMID:12186952 statement: >- Tetanus neurotoxin cleavage of synaptobrevin-2 abolishes cAMP-stimulated AQP2 targeting to the plasma membrane in renal collecting-duct cells. supporting_text: >- TeNT treatment in intact CD8 cells completely abolished cAMP-stimulated AQP2 targeting to the plasma membrane - source_id: PMID:18505797 statement: >- Knockdown of VAMP2 (with VAMP3, Stx3 and SNAP23) strongly inhibits AQP2 fusion at the apical membrane. supporting_text: >- Taken together these findings propose VAMP2, VAMP3, Stx3 and SNAP23 as the complementary set of SNAREs responsible for AQP2-vesicle fusion into the apical membrane - id: snap23_qsnare label: SNAP23 apical Q-SNARE participant: selector_type: GENE_PRODUCT gene_product: preferred_term: SNAP23 (SNAP-23) term: id: UniProtKB:O00161 label: Synaptosomal-associated protein 23 function: preferred_term: SNAP receptor activity term: id: GO:0005484 label: SNAP receptor activity processes: - preferred_term: vesicle fusion term: id: GO:0006906 label: vesicle fusion - preferred_term: exocytosis term: id: GO:0006887 label: exocytosis locations: - preferred_term: apical plasma membrane term: id: GO:0016324 label: apical plasma membrane role_description: >- The Qbc-SNARE of the apical acceptor complex, contributing two SNARE motifs; its core function in the SNAP23 gene review is this zippering/fusogenic activity. evidence: - source_id: PMID:18505797 statement: >- SNAP23 is associated with the apical plasma membrane, forms complexes with Stx3 and the vesicle R-SNAREs, and its knockdown inhibits AQP2 fusion. supporting_text: >- Both VAMP2 and VAMP3 were associated with immunoisolated AQP2 vesicles, whereas syntaxin 3 (Stx3), SNAP23 and Munc18 were associated with the apical plasma membrane. variant_sets: - id: aqp2_syntaxin_choice label: Apical syntaxin partner axis: Q-SNARE (syntaxin) paralog selection: ONE_OR_MORE notes: >- The PW:0000713 record names "syntaxin (3 or 4)". Syntaxin-3 is the partner identified on the apical membrane in AQP2-vesicle fusion experiments; syntaxin-4 is retained as the alternative named by RGD. Neither has an RGD gene link on the diagram. variants: - id: stx3_variant label: Syntaxin-3 (STX3) module_type: REGULATORY_STEP annotons: - id: stx3_qsnare label: STX3 apical syntaxin participant: selector_type: GENE_PRODUCT gene_product: preferred_term: STX3 (syntaxin-3) term: id: UniProtKB:Q13277 label: Syntaxin-3 function: preferred_term: SNAP receptor activity term: id: GO:0005484 label: SNAP receptor activity processes: - preferred_term: vesicle fusion term: id: GO:0006906 label: vesicle fusion locations: - preferred_term: apical plasma membrane term: id: GO:0016324 label: apical plasma membrane role_description: >- The apical Qa-SNARE shown to form complexes with VAMP2/VAMP3, SNAP23 and Munc18b in collecting-duct cells. evidence: - source_id: PMID:18505797 statement: Stx3 forms the AQP2-relevant SNARE complexes and is required for AQP2 fusion. supporting_text: >- Co-immunoprecipitation experiments indicated that Stx3 forms complexes with VAMP2, VAMP3, SNAP23 and Munc18b. - id: stx4_variant label: Syntaxin-4 (STX4) module_type: REGULATORY_STEP annotons: - id: stx4_qsnare label: STX4 apical syntaxin (alternative) participant: selector_type: GENE_PRODUCT gene_product: preferred_term: STX4 (syntaxin-4) term: id: UniProtKB:Q12846 label: Syntaxin-4 function: preferred_term: SNAP receptor activity term: id: GO:0005484 label: SNAP receptor activity processes: - preferred_term: vesicle fusion term: id: GO:0006906 label: vesicle fusion locations: - preferred_term: plasma membrane term: id: GO:0005886 label: plasma membrane role_description: >- The alternative plasma-membrane syntaxin named by the RGD record; detected in AQP2-expressing collecting-duct cells, with no direct assay of its requirement for AQP2 fusion in the cached papers. evidence: - source_id: PMID:12186952 statement: >- Syntaxin-4 is one of the SNARE homologs present in the AQP2-expressing collecting-duct cell line. supporting_text: >- RT-PCR and western blot analysis confirmed the presence of the SNARE homologs VAMP/synaptobrevin-2, syntaxin-1, syntaxin-4 and SNAP-23 in CD8 cells. - order: 7 role: apical AQP2 water channel conducts the reabsorbed water node: id: v2_aqp2_water_transport label: AQP2 water channel activity at the apical membrane module_type: REACTION description: >- Once in the apical membrane, AQP2 is the channel that conducts water out of the tubular lumen along the osmotic gradient; this is the output of the whole branch, and AQP2 performs it itself. annotons: - id: aqp2_channel label: AQP2 water channel activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: AQP2 (aquaporin-2) term: id: UniProtKB:P41181 label: Aquaporin-2 function: preferred_term: water channel activity term: id: GO:0015250 label: water channel activity processes: - preferred_term: renal water absorption term: id: GO:0070295 label: renal water absorption - preferred_term: water transport term: id: GO:0006833 label: water transport locations: - preferred_term: apical plasma membrane term: id: GO:0016324 label: apical plasma membrane role_description: >- The effector of the pathway. AQP2 is also the PKA substrate and the vesicle cargo, but those are input roles; the activity asserted here is its own channel activity, which does the transport step of renal water absorption. Nonfunctional AQP2 causes autosomal recessive nephrogenic diabetes insipidus. evidence: - source_id: PMID:8140421 statement: >- Compound heterozygous AQP2 mutations in recessive nephrogenic diabetes insipidus produce nonfunctional water channels, so AQP2 is essential for vasopressin-dependent urine concentration. supporting_text: >- Functional expression studies in Xenopus oocytes revealed that each mutation resulted in nonfunctional water channel proteins. Thus, aquaporin-2 is essential for vasopressin-dependent concentration of urine. - source_id: PMID:8140421 statement: >- V2 receptor occupancy leads to insertion of water channels into the apical membrane of collecting-duct principal cells. supporting_text: >- Binding of vasopressin to its V2 receptor leads to the insertion of water channels in apical membranes of principal cells in collecting ducts. - order: 8 role: PDE4D termination of the local cAMP signal optional: true node: id: v2_pde4d_termination label: PDE4D hydrolysis of vesicle-local cAMP module_type: REGULATORY_STEP description: >- PDE4D, anchored with PKA on the same AQP2 vesicles, hydrolyses the local cAMP; PKA phosphorylation activates it, so the branch carries its own negative feedback and the water-permeability response is self-limiting. annotons: - id: pde4d_pde label: PDE4D cAMP phosphodiesterase activity participant: selector_type: GENE_PRODUCT gene_product: preferred_term: PDE4D term: id: UniProtKB:Q08499 label: 3',5'-cyclic-AMP phosphodiesterase 4D function: preferred_term: 3',5'-cyclic-AMP phosphodiesterase activity term: id: GO:0004115 label: 3',5'-cyclic-AMP phosphodiesterase activity substrates: - preferred_term: 3',5'-cyclic AMP processes: - preferred_term: negative regulation of adenylate cyclase-activating G protein-coupled receptor signaling pathway term: id: GO:0106072 label: negative regulation of adenylate cyclase-activating G protein-coupled receptor signaling pathway locations: - preferred_term: cytoplasmic vesicle membrane term: id: GO:0030659 label: cytoplasmic vesicle membrane role_description: >- Sets the local cAMP concentration on AQP2 vesicles; inhibiting PDE4 with rolipram raises anchored PKA activity and enhances the shuttle, while PKA-activated PDE4D reduces osmotic water permeability. evidence: - source_id: PMID:17135396 statement: >- Inhibiting PDE4 raises AKAP-tethered PKA activity on AQP2 vesicles and enhances the shuttle and water permeability. supporting_text: >- The selective PDE4 inhibitor rolipram increases AKAP-tethered PKA activity on AQP2-bearing vesicles and enhances the AQP2 shuttle and thereby the osmotic water permeability. - source_id: PMID:17135396 statement: >- At the plasma membrane PDE4D is activated by PKA phosphorylation and reduces osmotic water permeability, closing the feedback loop. supporting_text: >- Here PDE4D is activated through PKA phosphorylation and reduces the osmotic water permeability. - source_id: PMID:8663227 statement: >- PKA phosphorylation of PDE4D3 serine 54 is what activates the enzyme, the mechanism of this feedback step. supporting_text: >- While substitution of serine 13 with alanine did not affect the activation by PKA, substitution of Ser54 completely suppressed the kinase activation. connections: - source: v2_receptor_activation target: v2_adcy6 connection_type: POSITIVELY_REGULATES description: AVP-occupied AVPR2 activates GNAS, whose GTP-bound form stimulates ADCY6. - source: v2_adcy6 target: v2_camp_pka_interface connection_type: PROVIDES_INPUT_FOR description: cAMP made by ADCY6 activates PKA (generic cAMP/PKA module). - source: v2_camp_pka_interface target: v2_vesicle_pka_compartment connection_type: PROVIDES_INPUT_FOR description: >- The activated kinase acts in the AKAP18-defined vesicle compartment, where its substrate AQP2 is. - source: v2_vesicle_pka_compartment target: v2_aqp2_recycling connection_type: POSITIVELY_REGULATES description: >- Phosphorylation of AQP2 Ser256 licenses the regulated exocytic route through the Rab11/myosin Vb recycling compartment. - source: v2_aqp2_recycling target: v2_aqp2_fusion connection_type: PRECEDES chaining_status: NOT_APPLICABLE chaining_note: >- Vesicle transport step followed by a membrane-fusion step; there is no CoA or other small-molecule intermediate for the reaction-chaining check to match. description: Recycling delivers AQP2 vesicles to the apical membrane, where the SNAREs fuse them. - source: v2_aqp2_fusion target: v2_aqp2_water_transport connection_type: PRECEDES chaining_status: NOT_APPLICABLE chaining_note: >- Fusion inserts the channel; the following step is transmembrane water transport, with no acyl-carrier intermediate to chain. description: Fusion puts AQP2 in the apical membrane, where it conducts water. - source: v2_pde4d_termination target: v2_camp_pka_interface connection_type: NEGATIVELY_REGULATES description: >- Vesicle-anchored PDE4D hydrolyses the local cAMP, terminating PKA activation. - source: v2_vesicle_pka_compartment target: v2_pde4d_termination connection_type: POSITIVELY_REGULATES description: >- PKA phosphorylates PDE4D (serine 54 in PDE4D3), activating it; this is the negative-feedback arm of the branch. connections: - source: avp_ligand target: vaso_receptor_branches connection_type: POSITIVELY_REGULATES description: >- Extracellular AVP occupies and activates the receptors of both coupling classes; the hormone itself performs no step of the downstream pathway.