HSP-25 and HSP-90 stabilize Na,K-ATPase in cytoskeletal fractions of ischemic rat renal cortex.
BACKGROUND
We recently designed an in vitro system based on differential Triton-extractability of Na,K-ATPase from the cytoskeletal protein fraction isolated from rat renal cortex after renal ischemia. In the present study, we hypothesized that heat shock protein (HSP)-70, HSP-25 and HSP-90 work synergistically to stabilize the cytoskeletal anchorage of Na,K-ATPase.


METHODS
Cellular proteins were fractionated by differential centrifugation into cytoskeletal pellets (I-PEL) obtained early (exhibiting abnormally high Triton extractability of Na,K-ATPase) and non-cytoskeletal supernatants (R-SUP) obtained late (exhibiting high abundance of HSP) after renal ischemia. For assessment of the role of HSP-70, HSP-25 and HSP-90 upon in vitro re-compartmentalization, I-PEL was either incubated in R-SUP with/without HSP antibodies, or in buffer with/without HSPs at different titers and combinations. Effects were evaluated by changes of Triton extractability of Na,K-ATPase after co-incubation.


RESULTS
R-SUP was shown to contain significant amounts of HSP-70, HSP-25 and HSP-90. Incubation of I-PEL in R-SUP reduced Triton extractability of Na,K-ATPase. Addition of antibodies against each HSP significantly abolished these effects of R-SUP. Incubation of I-PEL with purified HSP-70, HSP-25 or HSP-90 each partly reproduced the effects of R-SUP, whereas the combination of all three HSP demonstrated a strong and more than additive effect on the cytoskeletal stabilization of Na,K-ATPase.


CONCLUSIONS
The molecular mechanisms responsible for postischemic re-compartmentalization of Na,K-ATPase in rat renal cortex likely involves interactions between HSP-70, HSP-25 and HSP-90, stress proteins known to be induced in the ischemic kidney.
Bidmon
Bettina
B
Kinderdialyse and Ludwig Boltzmann Institut, Department of Pediatrics, Universitätsklinik für Kinder und Jugendheilkunde, AKH Wien, Wien, Austria.
Endemann
Michaela
M
Müller
Thomas
T
Arbeiter
Klaus
K
Herkner
Kurt
K
Aufricht
Christoph
C
D058186:Acute Kidney Injury / Q000378:metabolism; D000818:Animals; D002458:Cell Fractionation; D003599:Cytoskeleton / Q000201:enzymology*; D055551:HSP27 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins; D007511:Ischemia / Q000378:metabolism*; D007672:Kidney Cortex / Q000201:enzymology*; D008297:Male; D009363:Neoplasm Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D055551:HSP27 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C486114:Hspb1 protein, rat; D009363:Neoplasm Proteins; D000254:Sodium-Potassium-Exchanging ATPase