Cytoskeleton disruption and apical redistribution of proximal tubule Na+-K+-ATPase during ischemia

Bruce Molitoris, Rolf Dahl, Alison Geerdes

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131 Citations (Scopus)

Abstract

The polar distribution of Na+-K+-ATPase to the basolateral membrane of proximal tubule cells is essential for the efficient and vectorial reabsorption of Na+ and may be dependent on the formation of a metabolically stable, detergent-insoluble complex of Na+-K+-ATPase with the actin membrane cytoskeleton. The present studies utilized immunocytochemical techniques to demonstrate and quantify the apical redistribution of Na+-K+-ATPase during mild ischemia (15 min) that occurred in proximal (1.3 ± 0.9 vs. 4.5 ± 1.1 particles/100 μm surface membrane, P <0.01) but not distal tubule cells. Treatment of control apical membranes with 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A2C), a fluidizing agent, markedly increased membrane fluidity without any effect on Na+-K+-ATPase activity. In brush-border membrane vesicles isolated after ischemia, however, A2C further increased an already elevated Na+-K+-ATPase activity. During ischemia, total cellular Na+-K+-ATPase activity remained unaltered, but the Triton X-100-soluble (noncytoskeleton associated) fraction of Na+-K+-ATPase increased significantly following 15 and 30 min. There was a corresponding decrease in the Triton X-100-insoluble fraction of Na+-K+-ATPase, with the ratio of detergent-soluble to -insoluble Na+-K+-ATPase increasing from 13 ± 2 to 32 ± 5% (P <0.01) during 30 min of ischemia. Western blot analysis of the Triton X-100-soluble fraction, following 30 min of ischemic injury, revealed the presence of Na+-K+-ATPase, actin, fodrin, and uvomorulin. However, in a fraction highly enriched for Na+-K+-ATPase, neither actin, fodrin, nor uvomorulin was detected. Taken together, these data suggest that in proximal tubule cells, as in Madin-Darby canine kidney cells, Na+-K+-ATPase exists primarily in a cytoskeletal-associated form. During ischemic injury, the actin cytoskeleton is disrupted, and Na+-K+-ATPase dissociates from the actin cortical cytoskeleton and is then free to redistribute to the apical membrane in proximal but not distal tubule cells.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume263
Issue number3 32-3
StatePublished - Sep 1992
Externally publishedYes

Fingerprint

Cytoskeleton
Ischemia
Membranes
Octoxynol
Actin Cytoskeleton
Cadherins
Detergents
sodium-translocating ATPase
Actins
Membrane Fluidity
Madin Darby Canine Kidney Cells
Wounds and Injuries
Microvilli
Western Blotting

Keywords

  • 1,6-diphenyl-1,3,5-hexatriene polarization
  • Actin
  • Fodrin
  • Membrane fluidity
  • Uvomorulin

ASJC Scopus subject areas

  • Physiology

Cite this

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title = "Cytoskeleton disruption and apical redistribution of proximal tubule Na+-K+-ATPase during ischemia",
abstract = "The polar distribution of Na+-K+-ATPase to the basolateral membrane of proximal tubule cells is essential for the efficient and vectorial reabsorption of Na+ and may be dependent on the formation of a metabolically stable, detergent-insoluble complex of Na+-K+-ATPase with the actin membrane cytoskeleton. The present studies utilized immunocytochemical techniques to demonstrate and quantify the apical redistribution of Na+-K+-ATPase during mild ischemia (15 min) that occurred in proximal (1.3 ± 0.9 vs. 4.5 ± 1.1 particles/100 μm surface membrane, P <0.01) but not distal tubule cells. Treatment of control apical membranes with 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A2C), a fluidizing agent, markedly increased membrane fluidity without any effect on Na+-K+-ATPase activity. In brush-border membrane vesicles isolated after ischemia, however, A2C further increased an already elevated Na+-K+-ATPase activity. During ischemia, total cellular Na+-K+-ATPase activity remained unaltered, but the Triton X-100-soluble (noncytoskeleton associated) fraction of Na+-K+-ATPase increased significantly following 15 and 30 min. There was a corresponding decrease in the Triton X-100-insoluble fraction of Na+-K+-ATPase, with the ratio of detergent-soluble to -insoluble Na+-K+-ATPase increasing from 13 ± 2 to 32 ± 5{\%} (P <0.01) during 30 min of ischemia. Western blot analysis of the Triton X-100-soluble fraction, following 30 min of ischemic injury, revealed the presence of Na+-K+-ATPase, actin, fodrin, and uvomorulin. However, in a fraction highly enriched for Na+-K+-ATPase, neither actin, fodrin, nor uvomorulin was detected. Taken together, these data suggest that in proximal tubule cells, as in Madin-Darby canine kidney cells, Na+-K+-ATPase exists primarily in a cytoskeletal-associated form. During ischemic injury, the actin cytoskeleton is disrupted, and Na+-K+-ATPase dissociates from the actin cortical cytoskeleton and is then free to redistribute to the apical membrane in proximal but not distal tubule cells.",
keywords = "1,6-diphenyl-1,3,5-hexatriene polarization, Actin, Fodrin, Membrane fluidity, Uvomorulin",
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T1 - Cytoskeleton disruption and apical redistribution of proximal tubule Na+-K+-ATPase during ischemia

AU - Molitoris, Bruce

AU - Dahl, Rolf

AU - Geerdes, Alison

PY - 1992/9

Y1 - 1992/9

N2 - The polar distribution of Na+-K+-ATPase to the basolateral membrane of proximal tubule cells is essential for the efficient and vectorial reabsorption of Na+ and may be dependent on the formation of a metabolically stable, detergent-insoluble complex of Na+-K+-ATPase with the actin membrane cytoskeleton. The present studies utilized immunocytochemical techniques to demonstrate and quantify the apical redistribution of Na+-K+-ATPase during mild ischemia (15 min) that occurred in proximal (1.3 ± 0.9 vs. 4.5 ± 1.1 particles/100 μm surface membrane, P <0.01) but not distal tubule cells. Treatment of control apical membranes with 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A2C), a fluidizing agent, markedly increased membrane fluidity without any effect on Na+-K+-ATPase activity. In brush-border membrane vesicles isolated after ischemia, however, A2C further increased an already elevated Na+-K+-ATPase activity. During ischemia, total cellular Na+-K+-ATPase activity remained unaltered, but the Triton X-100-soluble (noncytoskeleton associated) fraction of Na+-K+-ATPase increased significantly following 15 and 30 min. There was a corresponding decrease in the Triton X-100-insoluble fraction of Na+-K+-ATPase, with the ratio of detergent-soluble to -insoluble Na+-K+-ATPase increasing from 13 ± 2 to 32 ± 5% (P <0.01) during 30 min of ischemia. Western blot analysis of the Triton X-100-soluble fraction, following 30 min of ischemic injury, revealed the presence of Na+-K+-ATPase, actin, fodrin, and uvomorulin. However, in a fraction highly enriched for Na+-K+-ATPase, neither actin, fodrin, nor uvomorulin was detected. Taken together, these data suggest that in proximal tubule cells, as in Madin-Darby canine kidney cells, Na+-K+-ATPase exists primarily in a cytoskeletal-associated form. During ischemic injury, the actin cytoskeleton is disrupted, and Na+-K+-ATPase dissociates from the actin cortical cytoskeleton and is then free to redistribute to the apical membrane in proximal but not distal tubule cells.

AB - The polar distribution of Na+-K+-ATPase to the basolateral membrane of proximal tubule cells is essential for the efficient and vectorial reabsorption of Na+ and may be dependent on the formation of a metabolically stable, detergent-insoluble complex of Na+-K+-ATPase with the actin membrane cytoskeleton. The present studies utilized immunocytochemical techniques to demonstrate and quantify the apical redistribution of Na+-K+-ATPase during mild ischemia (15 min) that occurred in proximal (1.3 ± 0.9 vs. 4.5 ± 1.1 particles/100 μm surface membrane, P <0.01) but not distal tubule cells. Treatment of control apical membranes with 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A2C), a fluidizing agent, markedly increased membrane fluidity without any effect on Na+-K+-ATPase activity. In brush-border membrane vesicles isolated after ischemia, however, A2C further increased an already elevated Na+-K+-ATPase activity. During ischemia, total cellular Na+-K+-ATPase activity remained unaltered, but the Triton X-100-soluble (noncytoskeleton associated) fraction of Na+-K+-ATPase increased significantly following 15 and 30 min. There was a corresponding decrease in the Triton X-100-insoluble fraction of Na+-K+-ATPase, with the ratio of detergent-soluble to -insoluble Na+-K+-ATPase increasing from 13 ± 2 to 32 ± 5% (P <0.01) during 30 min of ischemia. Western blot analysis of the Triton X-100-soluble fraction, following 30 min of ischemic injury, revealed the presence of Na+-K+-ATPase, actin, fodrin, and uvomorulin. However, in a fraction highly enriched for Na+-K+-ATPase, neither actin, fodrin, nor uvomorulin was detected. Taken together, these data suggest that in proximal tubule cells, as in Madin-Darby canine kidney cells, Na+-K+-ATPase exists primarily in a cytoskeletal-associated form. During ischemic injury, the actin cytoskeleton is disrupted, and Na+-K+-ATPase dissociates from the actin cortical cytoskeleton and is then free to redistribute to the apical membrane in proximal but not distal tubule cells.

KW - 1,6-diphenyl-1,3,5-hexatriene polarization

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KW - Fodrin

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KW - Uvomorulin

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VL - 263

JO - American Journal of Physiology

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