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 language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Renal Fluid and Electrolyte Physiology |
| Volume | 263 |
| Issue number | 3 32-3 |
| State | Published - Sep 1992 |
| Externally published | Yes |
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Keywords
- 1,6-diphenyl-1,3,5-hexatriene polarization
- Actin
- Fodrin
- Membrane fluidity
- Uvomorulin
ASJC Scopus subject areas
- Physiology
Cite this
Cytoskeleton disruption and apical redistribution of proximal tubule Na+-K+-ATPase during ischemia. / Molitoris, Bruce; Dahl, Rolf; Geerdes, Alison.
In: American Journal of Physiology - Renal Fluid and Electrolyte Physiology, Vol. 263, No. 3 32-3, 09.1992.Research output: Contribution to journal › Article
}
TY - JOUR
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
KW - Actin
KW - Fodrin
KW - Membrane fluidity
KW - Uvomorulin
UR - http://www.scopus.com/inward/record.url?scp=0026784859&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0026784859&partnerID=8YFLogxK
M3 - Article
VL - 263
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0193-1857
IS - 3 32-3
ER -