AQP2 is necessary for vasopressin- and forskolin-mediated filamentous actin depolymerization in renal epithelial cells

Yui, Naofumi; Lu, Hua; Bouley, Richard; Brown, Dennis

doi:10.1242/bio.2011042

Cited by 32 publications

(36 citation statements)

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“…These observations support an "actin-driven transport" model for apical AQP2 trafficking (48). Recently AQP2 was shown to "catalyze" F-actin depolymerization, thus taking an active role in its own trafficking (37). Until now, direct observation of vasopressin-induced dynamic changes of apical F-actin has not been visualized in live, polarized collecting duct cells that express endogenous AQP2, and the molecular components involved have been largely missing.…”

Section: Discussionmentioning

confidence: 56%

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Quantitative apical membrane proteomics reveals vasopressin-induced actin dynamics in collecting duct cells

Loo

Chen

Wang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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In kidney collecting duct cells, filamentous actin (F-actin) depolymerization is a critical step in vasopressin-induced trafficking of aquaporin-2 to the apical plasma membrane. However, the molecular components of this response are largely unknown. Using stable isotope-based quantitative protein mass spectrometry and surface biotinylation, we identified 100 proteins that showed significant abundance changes in the apical plasma membrane of mouse cortical collecting duct cells in response to vasopressin. Fourteen of these proteins are involved in actin cytoskeleton regulation, including actin itself, 10 actin-associated proteins, and 3 regulatory proteins. Identified were two integral membrane proteins (Clmn, Nckap1) and one actin-binding protein (Mpp5) that link F-actin to the plasma membrane, five F-actin end-binding proteins (Arpc2, Arpc4, Gsn, Scin, and Capzb) involved in F-actin reorganization, and two actin adaptor proteins (Dbn1, Lasp1) that regulate actin cytoskeleton organization. There were also protease (Capn1), protein kinase (Cdc42bpb), and Rho guanine nucleotide exchange factor 2 (Arhgef2) that mediate signal-induced F-actin changes. Based on these findings, we devised a live-cell imaging method to observe vasopressininduced F-actin dynamics in polarized mouse cortical collecting duct cells. In response to vasopressin, F-actin gradually disappeared near the center of the apical plasma membrane while consolidating laterally near the tight junction. This F-actin peripheralization was blocked by calcium ion chelation. Vasopressin-induced apical aquaporin-2 trafficking and forskolin-induced water permeability increase were blocked by F-actin disruption. In conclusion, we identified a vasopressin-regulated actin network potentially responsible for vasopressin-induced apical F-actin dynamics that could explain regulation of apical aquaporin-2 trafficking and water permeability increase.V asopressin regulates aquaporin-2 (AQP2) and osmotic water transport in the collecting duct by regulating total AQP2 protein abundance and AQP2 trafficking to and from the apical plasma membrane of principal cells (1). Understanding these regulatory mechanisms at the molecular level is important to the ultimate understanding of the pathophysiology of multiple water balance disorders (2). This goal is abetted by the methods of molecular systems biology (proteomics and transcriptomics), which not only reveal "parts lists" for collecting duct cells but also can identify what biological and molecular processes are regulated by vasopressin. These proteomic and transcriptomic data have been made publicly available in databases (3). Many of these studies have focused on whole cells (4-6), whereas several analyzed subcellular fractions (7-12). Analysis of subcellular fractions is technically demanding, but it has the benefit of identifying low abundance proteins with important functions. To identify proteins potentially involved in apical AQP2 trafficking, we previously used NHS-based surface biotinylation coupled to streptavidin...

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Section: Discussionmentioning

confidence: 56%

“…The P values were obtained using Fisher's exact test against all transcripts expressed in mpkCCD cells (4). (31,(36)(37)(38)(39)(40)(41)(42)(43). Furthermore, inhibition of Rho, a small GTPase protein involved in actin polymerization (44), results in AQP2 membrane localization (36,38,42,45).…”

Section: Discussionmentioning

confidence: 99%

Quantitative apical membrane proteomics reveals vasopressin-induced actin dynamics in collecting duct cells

Loo

Chen

Wang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…This actin barrier physically prevents the fusion of AQP2-containing vesicles with the apical plasma membrane. Conversely, upon dehydration and the release of the hormone vasopressin, the actin barrier is depolymerized (4,33). Thus, water homeostasis requires equilibrium between AQP2 vesicles that are sequestered in the cytoplasm by the actin barrier and active water pores fused to the apical membranes.…”

Section: Resultsmentioning

confidence: 99%

“…Vasopressin induces PKA phosphorylation of serine 256 on AQP2 and stimulates its translocation from intracellular vesicles to the apical membranes of cells lining the collecting ducts. Reabsorption of water through the kidney preserves fluid balance and results in more concentrated urine (3,4). Conversely, when an animal ingests excess water, decreased plasma osmolality inhibits vasopressin release, and AQP2 is recovered from the apical membrane by endocytosis.…”

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confidence: 99%

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

Whiting

Ogier

Forbush

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Filtration through the kidney eliminates toxins, manages electrolyte balance, and controls water homeostasis. Reabsorption of water from the luminal fluid of the nephron occurs through aquaporin-2 (AQP2) water pores in principal cells that line the kidney-collecting duct. This vital process is impeded by formation of an "actin barrier" that obstructs the passive transit of AQP2 to the plasma membrane. Bidirectional control of AQP2 trafficking is managed by hormones and signaling enzymes. We have discovered that vasopressin-independent facets of this homeostatic mechanism are under the control of A-Kinase Anchoring Protein 220 (AKAP220; product of the Akap11 gene). CRISPR/Cas9 gene editing and imaging approaches show that loss of AKAP220 disrupts apical actin networks in organoid cultures. Similar defects are evident in tissue sections from AKAP220-KO mice. Biochemical analysis of AKAP220-null kidney extracts detected reduced levels of active RhoA GTPase, a well-known modulator of the actin cytoskeleton. Fluorescent imaging of kidney sections from these genetically modified mice revealed that RhoA and AQP2 accumulate at the apical surface of the collecting duct. Consequently, these animals are unable to appropriately dilute urine in response to overhydration. We propose that membrane-proximal signaling complexes constrained by AKAP220 impact the actin barrier dynamics and AQP2 trafficking to ensure water homeostasis. yet only approximately 1.5 L of urine is excreted. The majority of this water is reabsorbed from the luminal fluid of the nephron (1). Regulated water reabsorption in response to dehydration occurs through aquaporin-2 (AQP2) water pores in the principal cells of the collecting duct (2). This is stimulated by the hormone arginine vasopressin (AVP). Vasopressin induces PKA phosphorylation of serine 256 on AQP2 and stimulates its translocation from intracellular vesicles to the apical membranes of cells lining the collecting ducts. Reabsorption of water through the kidney preserves fluid balance and results in more concentrated urine (3, 4). Conversely, when an animal ingests excess water, decreased plasma osmolality inhibits vasopressin release, and AQP2 is recovered from the apical membrane by endocytosis. This renders the collecting duct impermeable to water, thereby diverting excess water through the ureter to the bladder.Not surprisingly, defects in AQP2 trafficking have pathophysiological outcomes. For example, nephrogenic diabetes insipidus (NDI) is associated with impaired vasopressin signaling to AQP2 (5-8). Symptoms include excessive thirst, excretion of a large volume of dilute urine, and electrolyte imbalances, including hypernatremia (1, 5). Hereditary forms of this disease appear in patients with inactivating mutations in the V2 vasopressin receptor (V2R) or AQP2 (9-12). Thus, understanding the molecular mechanisms that govern bidirectional control of AQP2 location may lead to new therapeutic approaches for the treatment of NDI.Although the enzymes and effector proteins that govern AQP2 in...

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“…Some studies have shown that actin and actin-associated proteins interact with AQP2 to regulate its trafficking (91,130). We have found that VP treatment depolymerizes actin only in cells that express AQP2, implying that the water channel somehow catalyzes this process (146). Indeed, a phosphorylation-dependent interaction between AQP2 and the actin-binding protein tropomyosin 5b may be at least partially responsible for this effect (90).…”

Section: Statins Mobilize Aqp2 Trafficking and Increase Urinary Concementioning

confidence: 75%

New insights into the dynamic regulation of water and acid-base balance by renal epithelial cells

Brown

Bouley

Păunescu

et al. 2012

American Journal of Physiology-Cell Physiology

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Maintaining tight control over body fluid and acid-base homeostasis is essential for human health and is a major function of the kidney. The collecting duct is a mosaic of two cell populations that are highly specialized to perform these two distinct processes. The antidiuretic hormone vasopressin (VP) and its receptor, the V2R, play a central role in regulating the urinary concentrating mechanism by stimulating accumulation of the aquaporin 2 (AQP2) water channel in the apical membrane of collecting duct principal cells. This increases epithelial water permeability and allows osmotic water reabsorption to occur. An understanding of the basic cell biology/physiology of AQP2 regulation and trafficking has informed the development of new potential treatments for diseases such as nephrogenic diabetes insipidus, in which the VP/V2R/AQP2 signaling axis is defective. Tubule acidification due to the activation of intercalated cells is also critical to organ function, and defects lead to several pathological conditions in humans. Therefore, it is important to understand how these "professional" proton-secreting cells respond to environmental and cellular cues. Using epididymal proton-secreting cells as a model system, we identified the soluble adenylate cyclase (sAC) as a sensor that detects luminal bicarbonate and activates the vacuolar proton-pumping ATPase (V-ATPase) via cAMP to regulate tubular pH. Renal intercalated cells also express sAC and respond to cAMP by increasing proton secretion, supporting the hypothesis that sAC could function as a luminal sensor in renal tubules to regulate acid-base balance. This review summarizes recent advances in our understanding of these fundamental processes. aquaporin 2; vacuolar ATPase; intercalated cell; principal cell; kidney; epididymis IT HAS BEEN KNOWN FOR MANY years that the major functions of collecting duct principal cells and intercalated cells (Fig. 1) can be regulated by the recycling of aquaporin 2 (AQP2) and the vacuolar H ϩ -ATPase (V-ATPase), respectively, between cytoplasmic vesicles and the plasma membrane (1,26,28,40,54,67,85,142). A considerable amount of the earlier data illuminating these processes was generated using readily accessible model epithelial systems such as the toad urinary bladder (48,83,140) and the turtle bladder (3,127,128), in which cellular function and morphology could be correlated with measurements of water flux and acid-base transport. More recently, a variety of in vitro cell culture models have replaced the toad bladder as an experimental system for water channel trafficking and function. This review will show how cell cultures have provided novel and important information on aquaporin 2 trafficking that has been translatable to the in vivo situation and has allowed the development of strategies to bypass the vasopressin (VP)/vasopressin type 2 receptor (V2R) signaling axis that is defective in nephrogenic diabetes insipidus (NDI). We will go on to demonstrate how the epididymis and vas deferens (from the male reproductive tract) ha...

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AQP2 is necessary for vasopressin- and forskolin-mediated filamentous actin depolymerization in renal epithelial cells

Cited by 32 publications

References 42 publications

Quantitative apical membrane proteomics reveals vasopressin-induced actin dynamics in collecting duct cells

Quantitative apical membrane proteomics reveals vasopressin-induced actin dynamics in collecting duct cells

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

New insights into the dynamic regulation of water and acid-base balance by renal epithelial cells

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