Ischemia activates actin depolymerizing factor: Role in proximal tubule microvillar actin alterations

Niles Schwartz, Melanie Hosford, Ruben M. Sandoval, Mark Wagner, Simon J. Atkinson, James Bamburg, Bruce Molitoris

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

Apical membrane of renal proximal tubule cells is extremely sensitive to ischemia, with structural alterations occurring within 5 min. These changes are felt secondary to actin cytoskeletal disruption, yet the mechanism responsible is unknown. Actin depolymerizing factor (ADF), a 19-kDa actin- binding protein, has recently been shown to play an important role in regulation of actin filament dynamics. Because ADF is known to mediate pH- dependent F-actin binding, depolymerization, and severing, and because ADF activation occurs by dephosphorylation, we questioned whether ADF played a role in microvilli microfilament disruption during ischemia. To test our hypothesis, we induced renal ischemia in the rat with the clamp model. Initial immunofluorescence and Western blot studies on cortical tissue documented the presence of ADF in proximal tubule cells. Under physiological conditions, ADF was distributed homogeneously throughout the cytoplasm, primarily in the Triton X-100-soluble fraction, and both phosphorylated (pADF) and nonphosphorylated forms were identified. During ischemia, marked alterations occurred. Intraluminal vesicle/bleb structures contained extremely high concentrations of ADF along with G-actin, but not F-actin. Western blot showed a rapidly occurring duration-dependent dephosphorylation of ADF. At 0-30 min of ischemia, total ADF levels were unchanged, whereas pADF decreased significantly to 72% and 19% of control levels, at 5 and 15 min, respectively. Urine collected under physiological conditions did not contain ADF or actin, whereas urine collected after 30 min of ischemia contained both ADF and actin. Reperfusion was associated with normalization of cellular pADF levels, pADF intracellular distribution, and repair of apical microvilli. These data suggest that activation of ADF during ischemia via dephosphorylation is, in part, responsible for apical actin disruption resulting in microvillar destruction and formation of intraluminal vesicles.

Original languageEnglish
JournalAmerican Journal of Physiology - Renal Physiology
Volume276
Issue number4 45-4
StatePublished - Apr 1999

Fingerprint

Destrin
Actins
Ischemia
Microvilli
Actin Cytoskeleton
Western Blotting
Urine
Microfilament Proteins
Proximal Kidney Tubule
Octoxynol
Blister

Keywords

  • Actin cytoskeleton
  • Acute renal failure
  • ATP depletion
  • Cofilin
  • LIM kinase
  • Renal proximal tubule cell

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

Ischemia activates actin depolymerizing factor : Role in proximal tubule microvillar actin alterations. / Schwartz, Niles; Hosford, Melanie; Sandoval, Ruben M.; Wagner, Mark; Atkinson, Simon J.; Bamburg, James; Molitoris, Bruce.

In: American Journal of Physiology - Renal Physiology, Vol. 276, No. 4 45-4, 04.1999.

Research output: Contribution to journalArticle

Schwartz, Niles ; Hosford, Melanie ; Sandoval, Ruben M. ; Wagner, Mark ; Atkinson, Simon J. ; Bamburg, James ; Molitoris, Bruce. / Ischemia activates actin depolymerizing factor : Role in proximal tubule microvillar actin alterations. In: American Journal of Physiology - Renal Physiology. 1999 ; Vol. 276, No. 4 45-4.
@article{46295989f4bc4778b0c78b1f6c419ced,
title = "Ischemia activates actin depolymerizing factor: Role in proximal tubule microvillar actin alterations",
abstract = "Apical membrane of renal proximal tubule cells is extremely sensitive to ischemia, with structural alterations occurring within 5 min. These changes are felt secondary to actin cytoskeletal disruption, yet the mechanism responsible is unknown. Actin depolymerizing factor (ADF), a 19-kDa actin- binding protein, has recently been shown to play an important role in regulation of actin filament dynamics. Because ADF is known to mediate pH- dependent F-actin binding, depolymerization, and severing, and because ADF activation occurs by dephosphorylation, we questioned whether ADF played a role in microvilli microfilament disruption during ischemia. To test our hypothesis, we induced renal ischemia in the rat with the clamp model. Initial immunofluorescence and Western blot studies on cortical tissue documented the presence of ADF in proximal tubule cells. Under physiological conditions, ADF was distributed homogeneously throughout the cytoplasm, primarily in the Triton X-100-soluble fraction, and both phosphorylated (pADF) and nonphosphorylated forms were identified. During ischemia, marked alterations occurred. Intraluminal vesicle/bleb structures contained extremely high concentrations of ADF along with G-actin, but not F-actin. Western blot showed a rapidly occurring duration-dependent dephosphorylation of ADF. At 0-30 min of ischemia, total ADF levels were unchanged, whereas pADF decreased significantly to 72{\%} and 19{\%} of control levels, at 5 and 15 min, respectively. Urine collected under physiological conditions did not contain ADF or actin, whereas urine collected after 30 min of ischemia contained both ADF and actin. Reperfusion was associated with normalization of cellular pADF levels, pADF intracellular distribution, and repair of apical microvilli. These data suggest that activation of ADF during ischemia via dephosphorylation is, in part, responsible for apical actin disruption resulting in microvillar destruction and formation of intraluminal vesicles.",
keywords = "Actin cytoskeleton, Acute renal failure, ATP depletion, Cofilin, LIM kinase, Renal proximal tubule cell",
author = "Niles Schwartz and Melanie Hosford and Sandoval, {Ruben M.} and Mark Wagner and Atkinson, {Simon J.} and James Bamburg and Bruce Molitoris",
year = "1999",
month = "4",
language = "English",
volume = "276",
journal = "American Journal of Physiology",
issn = "0193-1857",
publisher = "American Physiological Society",
number = "4 45-4",

}

TY - JOUR

T1 - Ischemia activates actin depolymerizing factor

T2 - Role in proximal tubule microvillar actin alterations

AU - Schwartz, Niles

AU - Hosford, Melanie

AU - Sandoval, Ruben M.

AU - Wagner, Mark

AU - Atkinson, Simon J.

AU - Bamburg, James

AU - Molitoris, Bruce

PY - 1999/4

Y1 - 1999/4

N2 - Apical membrane of renal proximal tubule cells is extremely sensitive to ischemia, with structural alterations occurring within 5 min. These changes are felt secondary to actin cytoskeletal disruption, yet the mechanism responsible is unknown. Actin depolymerizing factor (ADF), a 19-kDa actin- binding protein, has recently been shown to play an important role in regulation of actin filament dynamics. Because ADF is known to mediate pH- dependent F-actin binding, depolymerization, and severing, and because ADF activation occurs by dephosphorylation, we questioned whether ADF played a role in microvilli microfilament disruption during ischemia. To test our hypothesis, we induced renal ischemia in the rat with the clamp model. Initial immunofluorescence and Western blot studies on cortical tissue documented the presence of ADF in proximal tubule cells. Under physiological conditions, ADF was distributed homogeneously throughout the cytoplasm, primarily in the Triton X-100-soluble fraction, and both phosphorylated (pADF) and nonphosphorylated forms were identified. During ischemia, marked alterations occurred. Intraluminal vesicle/bleb structures contained extremely high concentrations of ADF along with G-actin, but not F-actin. Western blot showed a rapidly occurring duration-dependent dephosphorylation of ADF. At 0-30 min of ischemia, total ADF levels were unchanged, whereas pADF decreased significantly to 72% and 19% of control levels, at 5 and 15 min, respectively. Urine collected under physiological conditions did not contain ADF or actin, whereas urine collected after 30 min of ischemia contained both ADF and actin. Reperfusion was associated with normalization of cellular pADF levels, pADF intracellular distribution, and repair of apical microvilli. These data suggest that activation of ADF during ischemia via dephosphorylation is, in part, responsible for apical actin disruption resulting in microvillar destruction and formation of intraluminal vesicles.

AB - Apical membrane of renal proximal tubule cells is extremely sensitive to ischemia, with structural alterations occurring within 5 min. These changes are felt secondary to actin cytoskeletal disruption, yet the mechanism responsible is unknown. Actin depolymerizing factor (ADF), a 19-kDa actin- binding protein, has recently been shown to play an important role in regulation of actin filament dynamics. Because ADF is known to mediate pH- dependent F-actin binding, depolymerization, and severing, and because ADF activation occurs by dephosphorylation, we questioned whether ADF played a role in microvilli microfilament disruption during ischemia. To test our hypothesis, we induced renal ischemia in the rat with the clamp model. Initial immunofluorescence and Western blot studies on cortical tissue documented the presence of ADF in proximal tubule cells. Under physiological conditions, ADF was distributed homogeneously throughout the cytoplasm, primarily in the Triton X-100-soluble fraction, and both phosphorylated (pADF) and nonphosphorylated forms were identified. During ischemia, marked alterations occurred. Intraluminal vesicle/bleb structures contained extremely high concentrations of ADF along with G-actin, but not F-actin. Western blot showed a rapidly occurring duration-dependent dephosphorylation of ADF. At 0-30 min of ischemia, total ADF levels were unchanged, whereas pADF decreased significantly to 72% and 19% of control levels, at 5 and 15 min, respectively. Urine collected under physiological conditions did not contain ADF or actin, whereas urine collected after 30 min of ischemia contained both ADF and actin. Reperfusion was associated with normalization of cellular pADF levels, pADF intracellular distribution, and repair of apical microvilli. These data suggest that activation of ADF during ischemia via dephosphorylation is, in part, responsible for apical actin disruption resulting in microvillar destruction and formation of intraluminal vesicles.

KW - Actin cytoskeleton

KW - Acute renal failure

KW - ATP depletion

KW - Cofilin

KW - LIM kinase

KW - Renal proximal tubule cell

UR - http://www.scopus.com/inward/record.url?scp=0032941377&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032941377&partnerID=8YFLogxK

M3 - Article

C2 - 10198413

AN - SCOPUS:0032941377

VL - 276

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0193-1857

IS - 4 45-4

ER -