Abstract 15370: Non-Genomic Action of Aldosterone in VSMC Requires Translocation of Mineralocorticoid Receptor to the Caveolae in the Plasma-Membrane and Subsequent Trans-Activation of Angiotensin II Type1 Receptor and its Downstream Tyrosine Kinase Pyk2/ROS/MAPKs Pathway
Aldosterone (Aldo), known as a Na-sensitive hypertensive hormone, also promotes inflammation/fibrosis in the cardiovascular system. Aldo binds to mineralocorticoid receptor (MR) and Aldo-bound MR translocates into the nucleus to initiate transcription of Na channel-mRNA in an hour, whereas inflammatory action of Aldo is initiated in a few minutes after stimulation, independently of transcription. Mechanism of such non-genomic action has not been fully clarified, although tyrosine kinase Src/ROS/MAPKs have been shown to be initially involved. Caveolae is a micro-domain with low fluidity in the plasma-membrane where signaling molecules are highly accumulated and activated. Caveolin is an essential molecule to form the caveolae structure. We here show that caveolae transmits the aldosterone non-genomic signaling.
Methods and Results: Primary-cultured VSMC was stimulated with Aldo (100 nM) and molecular association and sub-cellular localization was analyzed by immunoprecipitation and immunostaining. In a few minutes after stimulation with Aldo, Aldo-associated MR increasingly bound to HSP90 and, surprisingly, Aldo/MR/HSP90 complex was recruited to the Caveolae in the plasma-membrane by HSP90-binding to Caveolin−1. Subsequently, tyrosine kinases c-Src and PYK2 were recruited to HSP90 and mutually activated. Activated PYK2 stimulate ROS/MAPKs. PYK2-deficiency abolished ROS/MAPK activation by Aldo. Treatment with MR inhibitor and siRNA-mediated knockdown of HSP90 abolished activation of PYK2/ROS/MAPKs. SiRNA-mediated knockdown of caveolin-1 and disruption of caveolae by cholesterol depletion abolished translocation of MR to the plasma-membrane and activation of PYK2/ROS/MAPKs. Furthermore, Aldo increased the association between caveolin-1 and Angiotensin-II Type1 Receptor(AT1-R) and treatment with AT1-R blocker or AT1-R-deficiency abolished activation of PYK2/ROS/MAPK by Aldo.
Conclusions: Translocation of MR to the caveolae and subsequent trans-activation of AT1-R is essential for the non-genomic action by Aldo.
- © 2010 by American Heart Association, Inc.