Caveolin-1 and Hsp70 interaction in microdissected proximal tubules from spontaneously hypertensive rats as an effect of Losartan.
BACKGROUND
Caveolin is required to traffic the AT1 receptor through the exocytic pathway. The chaperone Hsp70 regulates a diverse set of signaling pathways via their interactions with proteins.


METHODS
Here we examined the AT1 receptor antagonist Losartan effect on caveolin-1 and Hsp70 protein association in spontaneously hypertensive rat (SHR) proximal tubules. Hsp70 involvement in Losartan oxidative stress regulation was also studied. Five-week-old SHRs were randomized for receiving Losartan (40 mg/kg per day) (SHRLos) or no treatment (SHRH2O) during 6 weeks. Wistar-Kyoto rats (WKY) were normotensive controls.


RESULTS
By western blotting, the relative abundance of caveolin-1 was two-fold higher in microdissected proximal tubule membrane fractions from treated SHRs vs. WKYH2O. Hsp70 membrane translocation was demonstrated in SHRLos through out the up-regulation of Hsp70 expression in microdissected proximal tubule membrane fractions when compared with WKYH2O (P < 0.001). Conversely, decreased Hsp70 protein levels were shown in microdissected proximal tubule cytosol fraction from SHRLos (P < 0.01). Interaction between caveolin-1 and Hsp70 was further determined by coimmunoprecipitation and by immunofluorescence co-localization in SHRLos proximal tubule membranes. After membrane translocation of Hsp70, the decreased NADPH oxidase activity (RFU/microprot per min incubation) near controls demonstrated on microdissected proximal tubule membranes from SHRLos vs. SHRH2O (P < 0.01) was reversed by the preincubation with anti-Hsp70 antibody. In addition, interaction between Hsp70 and Nox4 was determined by the coimmunoprecipitation strategy showing that membrane overexpression of Hsp70 was associated with decreased Nox4 after Losartan treatment in SHRs.


CONCLUSIONS
After Losartan administration interaction of caveolin-1 and Hsp70 was shown in SHR proximal tubules. Translocation of Hsp70 to proximal tubule membranes in SHRLos might exert a cytoprotective effect by down-regulation of NADPH subunits Nox4.
Bocanegra
Victoria
V
IMBECU-CONICET (National Council of Scientific and Technical Research of Argentina), Argentina.
Manucha
Walter
W
Peña
Marcelo Rodríguez
MR
Cacciamani
Valeria
V
Vallés
Patricia G
PG
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D051242:Caveolin 1 / Q000502:physiology*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006973:Hypertension / Q000188:drug therapy* / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D019808:Losartan / Q000494:pharmacology*; D042282:Microdissection; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR; D017382:Reactive Oxygen Species / Q000378:metabolism
D047228:Angiotensin II Type 1 Receptor Blockers; D000975:Antioxidants; D051242:Caveolin 1; D018840:HSP70 Heat-Shock Proteins; D017382:Reactive Oxygen Species; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498911:Nox4 protein, rat; D019808:Losartan