Rapid Nongenomic Action of Aldosterone on Protein Expressions of Hsp90(αandβ) and pc-Src in Rat Kidney

Abstract

Previousin vitrostudies indicated that aldosterone nongenomically phosphorylates epidermal growth factor receptor (EGFR) through activation of upstream signals, heat shock protein 90β(Hsp90β), and cytosolic (c)-Src kinase. We demonstrated that aldosterone rapidly elevates EGFR phosphorylation in rat kidney. There are noin vivodata regarding renal Hsp90(αandβ) and phosphorylated (p)c-Src protein expressions. The present study further investigates the expressions of these proteins. Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (Aldo: 150 μg/kg BW). After 30 minutes, abundances and localizations of these proteins were determined. Aldosterone enhanced renal Hsp90βprotein abundance (P<0.001), but Hsp90αand pc-Src protein levels remained unaltered. Expression of Hsp90(αandβ) was induced prominently in the proximal convoluted tubules (PCTs). Activation of Hsp90αwas observed in vascular and outer medulla regions, whereas Hsp90βwas induced in the cortex. Immunoreactivity of pc-Src was elevated in PCT with obvious staining at the luminal membrane. Thisin vivostudy is the first to demonstrate that aldosterone nongenomically elevates Hsp90(αandβ) protein expressions in rat kidney. Aldosterone had no effect on pc-Src protein levels but modulated localization. These results indicate that aldosterone regulates upstream mediators of EGFR transactivationin vivo.