Calcium dependence of integrity of the actin cytoskeleton of proximal tubule cell microvilli.
To better define the role of Ca2+ in pathophysiological alterations of the proximal tubule microvillus actin cytoskeleton, we studied freshly isolated tubules in which intracellular free Ca2+ was equilibrated with highly buffered, precisely defined medium Ca2+ levels using a combination of the metabolic inhibitor, antimycin, and the ionophore, ionomycin, in the presence of glycine, to prevent lethal membrane damage and resulting nonspecific changes. Increases of Ca2+ to > or = 10 microM were sufficient to initiate concurrent actin depolymerization, fragmentation of F-actin into forms requiring high-speed centrifugation for recovery, redistribution of villin to sedimentable fractions, and structural microvillar damage consisting of severe swelling and fragmentation of actin cores. These observations implicate Ca(2+)-dependent, villin-mediated actin cytoskeletal disruption in tubule cell microvillar damage under conditions conceivably present during pathophysiological states. However, despite prior evidence for cytosolic free Ca2+ increases of the same order of magnitude and similar structural microvillar alterations, Ca(2+)- and villin-mediated events did not appear to account for the initial microvillar damage that occurs during ATP depletion induced by antimycin alone or hypoxia.
Sogabe
K
K
Department of Internal Medicine, University of Michigan, Ann Arbor, USA.
Roeser
N F
NF
Davis
J A
JA
Nurko
S
S
Venkatachalam
M A
MA
Weinberg
J M
JM
D000199:Actins / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D003851:Deoxyribonucleases / Q000494:pharmacology; D004338:Drug Combinations; D005260:Female; D005998:Glycine / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000502:physiology* / Q000648:ultrastructure*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008871:Microvilli / Q000502:physiology / Q000648:ultrastructure; D010590:Phalloidine; D011817:Rabbits; D012235:Rhodamines; D013194:Staining and Labeling
D000199:Actins; D003598:Cytoskeletal Proteins; D004338:Drug Combinations; D012235:Rhodamines; C032456:antimycin; D010590:Phalloidine; D015759:Ionomycin; D000968:Antimycin A; D007770:L-Lactate Dehydrogenase; D003851:Deoxyribonucleases; D002118:Calcium; D005998:Glycine