Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vasopressin acts on renal collecting duct cells to stimulate translocation of aquaporin-2 (AQP2)-containing membrane vesicles from throughout the cytoplasm to the apical region. The vesicles fuse with the plasma membrane to increase water permeability. To identify the intracellular membrane compartments that contain AQP2, we carried out LC-MS/MS-based proteomic analysis of immunoisolated AQP2-containing intracellular vesicles from rat inner medullary collecting duct. Immunogold electron microscopy and immunoblotting confirmed heavy AQP2 labeling of immunoisolated vesicles. Vesicle proteins were separated by SDS-PAGE followed by in-gel trypsin digestion in consecutive gel slices and identification by LC-MS/MS. Identification of Rab GTPases 4, 5, 18, and 21 (associated with early endosomes); Rab7 (late endosomes); and Rab11 and Rab25 (recycling endosomes) indicate that a substantial fraction of intracellular AQP2 is present in endosomal compartments. In addition, several endosome-associated SNARE proteins were identified including syntaxin-7, syntaxin-12, syntaxin-13, Vti1a, vesicle-associated membrane protein 2, and vesicle-associated membrane protein 3. Rab3 was not found, however, either by mass spectrometry or immunoblotting, suggesting a relative lack of AQP2 in secretory vesicles. Additionally, we identified markers of the trans-Golgi network, components of the exocyst complex, and several motor proteins including myosin 1C, non-muscle myosins IIA and IIB, myosin VI, and myosin IXB. Beyond this, identification of multiple endoplasmic reticulum-resident proteins and ribosomal proteins indicated that a substantial fraction of intracellular AQP2 is present in rough endoplasmic reticulum. These results show that AQP2-containing vesicles are heterogeneous and that intracellular AQP2 resides chiefly in endosomes, trans-Golgi network, and rough endoplasmic reticulum.
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PMID:Large scale protein identification in intracellular aquaporin-2 vesicles from renal inner medullary collecting duct. 1590 45

In the renal collecting duct, vasopressin controls transport of water and solutes via regulation of membrane transporters such as aquaporin-2 (AQP2) and the epithelial urea transporter UT-A. To discover proteins potentially involved in vasopressin action in rat kidney collecting ducts, we enriched membrane "raft" proteins by harvesting detergent-resistant membranes (DRMs) of the inner medullary collecting duct (IMCD) cells. Proteins were identified and quantified with LC-MS/MS. A total of 814 proteins were identified in the DRM fractions. Of these, 186, including several characteristic raft proteins, were enriched in the DRMs. Immunoblotting confirmed DRM enrichment of representative proteins. Immunofluorescence confocal microscopy of rat IMCDs with antibodies to DRM proteins demonstrated heterogeneity of raft subdomains: MAL2 (apical region), RalA (predominant basolateral labeling), caveolin-2 (punctate labeling distributed throughout the cells), and flotillin-1 (discrete labeling of large intracellular structures). The DRM proteome included GPI-anchored, doubly acylated, singly acylated, cholesterol-binding, and integral membrane proteins (IMPs). The IMPs were, on average, much smaller and more hydrophobic than IMPs identified in non-DRM-enriched IMCD. The content of serine 256-phosphorylated AQP2 was greater in DRM than in non-DRM fractions. Vasopressin did not change the DRM-to-non-DRM ratio of most proteins, whether quantified by tandem mass spectrometry (LC-MS/MS, n=22) or immunoblotting (n=6). However, Rab7 and annexin-2 showed small increases in the DRM fraction in response to vasopressin. In accord with the long-term goal of creating a systems-level analysis of transport regulation, this study has identified a large number of membrane-associated proteins expressed in the IMCD that have potential roles in vasopressin action.
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PMID:Large-scale quantitative LC-MS/MS analysis of detergent-resistant membrane proteins from rat renal collecting duct. 1859 8

Aquaporin-2 (AQP2) is a vasopressin-regulated water channel protein responsible for osmotic water reabsorption by kidney collecting ducts. In response to vasopressin, AQP2 traffics from intracellular vesicles to the apical plasma membrane of collecting duct principal cells, where it increases water permeability and, hence, water reabsorption. Despite continuing efforts, gaps remain in our knowledge of vasopressin-regulated AQP2 trafficking. Here, we studied the functions of two retromer complex proteins, small GTPase Rab7 and vacuolar protein sorting 35 (Vps35), in vasopressin-induced AQP2 trafficking in a collecting duct cell model (mpkCCD cells). We showed that upon vasopressin removal, apical AQP2 returned to Rab5-positive early endosomes before joining Rab11-positive recycling endosomes. In response to vasopressin, Rab11-associated AQP2 trafficked to the apical plasma membrane before Rab5-associated AQP2 did so. Rab7 knockdown resulted in AQP2 accumulation in early endosomes and impaired vasopressin-induced apical AQP2 trafficking. In response to vasopressin, Rab7 transiently colocalized with Rab5, indicative of a role of Rab7 in AQP2 sorting in early endosomes before trafficking to the apical membrane. Rab7-mediated apical AQP2 trafficking in response to vasopressin required GTPase activity. When Vps35 was knocked down, AQP2 accumulated in recycling endosomes under vehicle conditions and did not traffic to the apical plasma membrane in response to vasopressin. We conclude that Rab7 and Vps35 participate in AQP2 sorting in early endosomes under vehicle conditions and apical membrane trafficking in response to vasopressin.
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PMID:Rab7 involves Vps35 to mediate AQP2 sorting and apical trafficking in collecting duct cells. 3208 68

Aquaporin-2 (AQP2) is a vasopressin-regulated water channel protein responsible for water reabsorption by the kidney collecting ducts. Under control conditions, most AQP2 resides in the recycling endosomes of principal cells, where it answers to vasopressin with trafficking to the apical plasma membrane to increase water reabsorption. Upon vasopressin withdrawal, apical AQP2 retreats to the early endosomes before joining the recycling endosomes for the next vasopressin stimulation. Prior studies have demonstrated a role of AQP2 S269 phosphorylation in reducing AQP2 endocytosis, thereby prolonging apical AQP2 retention. Here, we studied where in the cells S269 was phosphorylated and dephosphorylated in response to vasopressin versus withdrawal. In mpkCCD collecting cells, vacuolar protein sorting 35 knockdown slowed vasopressin-induced apical AQP2 trafficking, resulting in AQP2 accumulation in the recycling endosomes where S269 was phosphorylated. Rab7 knockdown, which impaired AQP2 trafficking from the early to recycling endosomes, reduced vasopressin-induced S269 phosphorylation. Rab5 knockdown, which impaired AQP2 endocytosis, did not affect vasopressin-induced S269 phosphorylation. Upon vasopressin withdrawal, S269 was not dephosphorylated in Rab5 knockdown cells. In contrast, S269 dephosphorylation upon vasopressin withdrawal was completed in Rab7 or vacuolar protein sorting 35 knockdown cells. We conclude that S269 is dephosphorylated during Rab5-mediated AQP2 endocytosis before AQP2 joins the recycling endosomes upon vasopressin withdrawal. While in the recycling endosomes, AQP2 can be phosphorylated at S269 in response to vasopressin before apical trafficking.
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PMID:Intracellular location of aquaporin-2 serine 269 phosphorylation and dephosphorylation in kidney collecting duct cells. 3279 72