Phosphorylation of smooth muscle 22α facilitates angiotensin II-induced ROS production via activation of the PKCδ-P47phox axis through release of PKCδ and actin dynamics and is associated with hypertrophy and hyperplasia of vascular smooth muscle cells in vitro and in vivo.
BACKGROUND
We have demonstrated that smooth muscle (SM) 22α inhibits cell proliferation via blocking Ras-ERK1/2 signaling in vascular smooth muscle cells (VSMCs) and in injured arteries. The recent study indicates that SM22α disruption can independently promote arterial inflammation through activation of reactive oxygen species (ROS)-mediated NF-κB pathways. However, the mechanisms by which SM22α controls ROS production have not been characterized.


OBJECTIVE
To investigate how SM22α disruption promotes ROS production and to characterize the underlying mechanisms.


RESULTS
ROS level was measured by dihydroethidium staining for superoxide and TBA assay for malondialdehyde, respectively. We showed that downregulation and phosphorylation of SM22α were associated with angiotensin (Ang) II-induced increase in ROS production in VSMCs of rats and human. Ang II induced the phosphorylation of SM22α at Serine 181 in an Ang II type 1 receptor-PKCδ pathway-dependent manner. Phosphorylated SM22α activated the protein kinase C (PKC)δ-p47phox axis via 2 distinct pathways: (1) disassociation of PKCδ from SM22α, and in turn binding to p47phox, in the early stage of Ang II stimulation; and (2) acceleration of SM22α degradation through ubiquitin-proteasome, enhancing PKCδ membrane translocation via induction of actin cytoskeletal dynamics in later oxidative stress. Inhibition of SM22α phosphorylation abolished the Ang II-activated PKCδ-p47phox axis and inhibited the hypertrophy and hyperplasia of VSMCs in vitro and in vivo, accompanied with reduction of ROS generation.


CONCLUSIONS
These findings indicate that the disruption of SM22α plays pivotal roles in vascular oxidative stress. PKCδ-mediated SM22α phosphorylation is a novel link between actin cytoskeletal remodeling and oxidative stress and may be a potential target for the development of new therapeutics for cardiovascular diseases.
Department of Biochemistry and Molecular Biology, College of Basic Medicine, Hebei Medical University, No. 361, Zhongshan East Rd, Shijiazhuang, 050017, China.
Pin
P
Lv
Sui-Bing
SB
Miao
Ya-Nan
YN
Shu
Li-Hua
LH
Dong
George
G
Liu
Xiao-Li
XL
Xie
Min
M
Gao
Yu-Can
YC
Wang
Ya-Juan
YJ
Yin
Xiao-Juan
XJ
Wang
Mei
M
Han
D000199:Actins / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006965:Hyperplasia; D006984:Hypertrophy; D008297:Male; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019255:NADPH Oxidases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D051745:Protein Kinase C-delta / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*
D000199:Actins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D017382:Reactive Oxygen Species; C051615:transgelin; D000804:Angiotensin II; D049452:Green Fluorescent Proteins; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D051745:Protein Kinase C-delta