A pump-independent function of the Na,K-ATPase is required for epithelial junction function and tracheal tube-size control

Paul, Sarah M.; Palladino, Michael J.; Beitel, Greg J.

doi:10.1242/dev.02710

Cited by 99 publications

(129 citation statements)

References 46 publications

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“…Epithelial junction formation and tracheal tube-size control in Drosophila require a pump-independent function of the Na þ /K þ -ATPase. 35 The catalytic a-subunits of this pump and the closely related H þ /K þ -ATPase interact with ankyrin, a cytoskeletal protein implicated in epithelial junction formation. 36 Linking the cytoskeleton to specialized areas of the plasma membrane may thus be a feature shared among several members of the P-type ATPase superfamily.…”

Section: Discussionmentioning

confidence: 99%

A flippase-independent function of ATP8B1, the protein affected in familial intrahepatic cholestasis type 1, is required for apical protein expression and microvillus formation in polarized epithelial cells

et al. 2010

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Mutations in ATP8B1 cause familial intrahepatic cholestasis type 1, a spectrum of disorders characterized by intrahepatic cholestasis, reduced growth, deafness, and diarrhea. ATP8B1 belongs to the P 4 P-type adenosine triphosphatase (ATPase) family of putative aminophospholipid translocases, and loss of aminophospholipid asymmetry in the canalicular membranes of ATP8B1-deficient liver cells has been proposed as the primary cause of impaired bile salt excretion. To explore the origin of the hepatic and extrahepatic symptoms associated with ATP8B1 deficiency, we investigated the impact of ATP8B1 depletion on the domain-specific aminophospholipid translocase activities and polarized organization of polarized epithelial Caco-2 cells. Caco-2 cells were stably transfected with short hairpin RNA constructs to block ATP8B1 expression. Aminophospholipid translocase activity was assessed using spin-labeled phospholipids. The polarized organization of these cells was determined by pulse-chase analysis, cellfractionation, immunocytochemistry, and transmission electron microscopy. ATP8B1 was abundantly expressed in the apical membrane of Caco-2 cells, and its expression was markedly induced during differentiation and polarization. Blocking ATP8B1 expression by RNA interference (RNAi) affected neither aminophospholipid transport nor the asymmetrical distribution of aminophospholipids across the apical bilayer. Nonetheless, ATP8B1-depleted Caco-2 cells displayed profound perturbations in apical membrane organization, including a disorganized apical actin cytoskeleton, a loss in microvilli, and a posttranscriptional defect in apical protein expression. Conclusion: Our findings point to a critical role of ATP8B1 in apical membrane organization that is unrelated to its presumed aminophospholipid translocase activity, yet potentially relevant for the development of cholestasis and the manifestation of extrahepatic features associated with ATP8B1 deficiency.

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Section: Discussionmentioning

confidence: 99%

A flippase-independent function of ATP8B1, the protein affected in familial intrahepatic cholestasis type 1, is required for apical protein expression and microvillus formation in polarized epithelial cells

et al. 2010

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“…Pump activity is not required for this regulation because pump-dead CATP-1 rescues the developmental delay in catp-1 mutants. The Drosophila Na + /K + ATPase also has a pumpindependent function in epithelial and septate junction formation (Paul et al, 2007;Paul et al, 2003). This function in cell junction appears to be conserved in vertebrates because the rat α1 isoform can rescue all junctional defects in Drosophila Atpα-null mutants.…”

Section: Pump Activity-independent Regulation Of Ach Signaling By Na mentioning

confidence: 99%

Na+/K+ ATPase regulates the expression and localization of acetylcholine receptors in a pump activity-independent manner

Doi

Iwasaki

2008

Molecular and Cellular Neuroscience

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Na + /K + ATPase is a plasma membrane-localized sodium pump that maintains the ion gradients between the extracellular and intracellular environments, which in turn controls the cellular resting membrane potential. Recent evidence suggests that the pump is also localized at synapses and regulates synaptic efficacy. However, its precise function at the synapse is unknown. Here we show that two mutations in the α subunit of the eat-6 Na + /K + ATPase in Caenorhabditis elegans dramatically increase the sensitivity to acetylcholine (Ach) agonists and alter the localization of nicotinic Ach receptors at the neuromuscular junction (NMJ). These defects can be rescued by mutated EAT-6 proteins which lack its pump activity, suggesting the presence of a novel function for Ach signaling. The Na + /K + ATPase accumulates at postsynaptic sites and appears to surround Ach receptors to maintain rigid clusters at the NMJ. Our findings suggest a critical pump activityindependent, allele -specific role for Na + /K + ATPase on postsynaptic organization and synaptic efficacy.

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“…Indeed, the ␤ 2 subunit of the Na,KATPase was first described as an adhesion protein in glial cells (AMOG) in the rat brain (12). Specific isoforms of the Na,KATPase play a crucial role in intercellular junction formation in a Drosophila tracheal epithelium (9,10,18). The ␤ 1 subunit of the Na,K-ATPase is necessary for normal intercellular adhesion in MDCK cells, a cell line with characteristics of the distal renal tubule (11,19).…”

mentioning

confidence: 99%

Inverse Correlation between the Extent of N-Glycan Branching and Intercellular Adhesion in Epithelia

Vagin

Tokhtaeva

Yakubov

et al. 2008

Journal of Biological Chemistry

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The majority of cell adhesion molecules are N-glycosylated, but the role of N-glycans in intercellular adhesion in epithelia remains ill-defined. Reducing N-glycan branching of cellular glycoproteins by swainsonine, the inhibitor of N-glycan processing, tightens and stabilizes cell-cell junctions as detected by a 3-fold decrease in the paracellular permeability and a 2-3-fold increase in the resistance of the adherens junction proteins to extraction by non-ionic detergent. In addition, exposure of cells to swainsonine inhibits motility of MDCK cells. Mutagenic removal of N-glycosylation sites from the Na,K-ATPase ␤ 1 subunit impairs cell-cell adhesion and decreases the effect of swainsonine on the paracellular permeability of the cell monolayer and also on detergent resistance of adherens junction proteins, indicating that the extent of N-glycan branching of this subunit is important for intercellular adhesion. The N-glycans of the Na,K-ATPase ␤ 1 subunit and E-cadherin are less complex in tight renal epithelia than in the leakier intestinal epithelium. The complexity of the N-glycans linked to these proteins gradually decreases upon the formation of a tight monolayer from dispersed MDCK cells. This correlates with a cell-cell adhesion-induced increase in expression of GnT-III (stops N-glycan branching) and a decrease in expression of GnTs IVC and V (promote N-glycan branching) as detected by realtime quantitative PCR. Consistent with these results, partial silencing of the gene encoding GnT-III increases branching of N-glycans linked to the Na,K-ATPase ␤ 1 subunit and other glycoproteins and results in a 2-fold increase in the paracellular permeability of MDCK cell monolayers. These results suggest epithelial cells can regulate tightness of cell junctions via remodeling of N-glycans, including those linked to the Na,K-ATPase ␤ 1 -subunit.

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A pump-independent function of the Na,K-ATPase is required for epithelial junction function and tracheal tube-size control

Cited by 99 publications

References 46 publications

A flippase-independent function of ATP8B1, the protein affected in familial intrahepatic cholestasis type 1, is required for apical protein expression and microvillus formation in polarized epithelial cells

A flippase-independent function of ATP8B1, the protein affected in familial intrahepatic cholestasis type 1, is required for apical protein expression and microvillus formation in polarized epithelial cells

Na+/K+ ATPase regulates the expression and localization of acetylcholine receptors in a pump activity-independent manner

Inverse Correlation between the Extent of N-Glycan Branching and Intercellular Adhesion in Epithelia

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