Microtubules regulate angiotensin II type 1 receptor and Rac1 localization in caveolae/lipid rafts: role in redox signaling.
OBJECTIVE
Microtubules are important in signal transduction temporal-spatial organization. Full expression of angiotensin II (Ang II) signaling in vascular smooth muscle cells (VSMCs) is dependent on the reactive oxygen species (ROS) derived from nicotinamide-adenine dinucleotide phosphate (NAD(P)H) oxidase and the dynamic association of the Ang II type 1 receptor (AT1R) with caveolae/lipid rafts. Translocation of the small GTPase Rac1 to the plasma membrane is an essential step for activation of NAD(P)H oxidase; however, its precise localization in the plasma membrane after agonist stimulation and how it is targeted are unknown. We hypothesized that microtubules are involved in regulating multiphasic Ang II signaling events in VSMC.


RESULTS
We show that Ang II promotes Rac1 and AT1R trafficking into caveolae/lipid rafts, which is blocked by disruption of microtubules with nocodazole. As a consequence, nocodazole significantly inhibits Ang II-stimulated H2O2 production, its downstream ROS-dependent epidermal growth factor receptor transactivation, Akt phosphorylation, and vascular hypertrophy without affecting Rac1 activation or ROS-independent extracellular signal-regulated kinase 1/2 phosphorylation.


CONCLUSIONS
These results suggest that proper Rac1 and AT1R trafficking into caveolae/lipid rafts requires the integrity of microtubules and provide insight into the essential role of microtubules for the spatial-temporal organization of ROS-dependent and caveolae/lipid rafts-dependent AT(1)R signaling linked to vascular hypertrophy.
Zuo
Lian
L
Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Ga 30322, USA.
Ushio-Fukai
Masuko
M
Hilenski
Lula L
LL
Alexander
R Wayne
RW
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000166:cytology; D021941:Caveolae / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006984:Hypertrophy; D021962:Membrane Microdomains / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017382:Reactive Oxygen Species; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D004815:Epidermal Growth Factor; D006861:Hydrogen Peroxide; D066246:ErbB Receptors; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020830:rac1 GTP-Binding Protein; D015739:Nocodazole