Cholesterol depletion inhibits epidermal growth factor receptor transactivation by angiotensin II in vascular smooth muscle cells: role of cholesterol-rich microdomains and focal adhesions in angiotensin II signaling

Angiotensin II (Ang II) induces transactivation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for various signaling molecules in vascular smooth muscle cells (VSMCs). Cholesterol and sphingomyelin-enriched lipid rafts are plasma membrane microdomains that concentr...

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Bibliographic Details
Published in:The Journal of biological chemistry 2001-12, Vol.276 (51), p.48269-48275
Main Authors: Ushio-Fukai, M, Hilenski, L, Santanam, N, Becker, P L, Ma, Y, Griendling, K K, Alexander, R W
Format: Article
Language:English
Subjects:
Angiotensin II - physiology
Animals
beta-Cyclodextrins
Caveolin 1
Caveolins - metabolism
Cell Membrane - drug effects
Cell Membrane - metabolism
Cells, Cultured
Cholesterol - metabolism
Cyclodextrins - pharmacology
Enzyme Activation
Epidermal Growth Factor - physiology
ErbB Receptors - chemistry
ErbB Receptors - genetics
Fluorescent Antibody Technique
Male
Microscopy, Electron
Muscle, Smooth, Vascular - drug effects
Muscle, Smooth, Vascular - physiology
Muscle, Smooth, Vascular - ultrastructure
Phosphorylation
Protein Binding
Protein-Serine-Threonine Kinases
Proto-Oncogene Proteins - metabolism
Proto-Oncogene Proteins c-akt
Rats
Rats, Sprague-Dawley
Signal Transduction
Transcriptional Activation
Tyrosine - metabolism
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Summary:Angiotensin II (Ang II) induces transactivation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for various signaling molecules in vascular smooth muscle cells (VSMCs). Cholesterol and sphingomyelin-enriched lipid rafts are plasma membrane microdomains that concentrate various signaling molecules. Caveolae are specialized lipid rafts that are organized by the cholesterol-binding protein, caveolin, and have been shown to be associated with EGF-Rs. Angiotensin II stimulation promotes a rapid movement of AT(1) receptors to caveolae; however, their functional role in angiotensin II signaling has not been elucidated. Here we show that cholesterol depletion by beta-cyclodextrin disrupts caveolae structure and concomitantly inhibits tyrosine phosphorylation of the EGF-R and subsequent activation of protein kinase B (PKB)/Akt induced by angiotensin II. Similar inhibitory effects were obtained with other cholesterol-binding agents, filipin and nystatin. In contrast, EGF-R autophosphorylation and activation of Akt/PKB in response to EGF are not affected by cholesterol depletion. The early Ang II-induced upstream signaling events responsible for transactivation of the EGF-R, such as the intracellular Ca(2+) increase and c-Src activation, also remain intact. The EGF-R initially binds caveolin, but these two proteins rapidly dissociate following angiotensin II stimulation during the time when EGF-R transactivation is observed. The activated EGF-R is localized in focal adhesions together with tyrosine-phosphorylated caveolin. These findings suggest that 1) a scaffolding role of caveolin is essential for EGF-R transactivation by angiotensin II and 2) cholesterol-rich microdomains as well as focal adhesions are important signal-organizing compartments required for the spatial and temporal organization of angiotensin II signaling in VSMCs.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M105901200