The project aims to understand how unique signatures of Ca[2+] mediated by STIM proteins control the proliferation of vascular smooth muscle cells (VSMC). Ca[2+] signals play a crucial role in not only controlling vascular contraction but also in regulating the growth and proliferation smooth muscle cells. The work examines the function of two crucial proteins, STIM1 and STIM2, that sense changes in the Ca[2+] within the SR lumen of VSMCS, and through a highly coordinated translocation process, move into small specialized junctions between the SR and PM. STIM proteins directly activate Ca[2+] channels in the PM and hence control Ca[2+] entry into VSMCS. The project has two specific aims:
Aim 1 : To examine the distinct functional roles of STIM1 and STIM2 proteins in mediating Ca[2+] signals in VSMCs. These studies will test the hypothesis that the STIM2 phenotype in VSMCs from SM-STIM1-KO animals has a ?Ca[2+] signature response? important in mediating distinct physiological differences in VSMC proliferation. The experimental approach to test this hypothesis utilizes a combination of live cellular imaging, expression of dominant negative channel proteins, electrophysiology, and novel Ca[2+] probes to assess the functional roles of STIM-mediated Ca[2+] signals in VSMCs and examines: (a) the ?temporal Ca[2+] signature? of Ca[2+] signals in VSMCs from SM-STIM1- KO mice. (b) the ?spatial Ca[2+] signature? of Ca[2+] signals in VSMCs from SM-STIM1-KO mice: and (c) how luminal SR levels reflect the STIM-mediated Ca[2+] signature in VSMCs.
Aim 2 : To determine how STIM-induced Ca[2+] signature responses regulate proliferative pathways in VSMCs. The hypothesis to be tested is that STIM-specific Ca[2+] entry signals control gene expression and proliferative VSMC responses through the calcineurin/NFAT axis.
The aims are to determine (a) how STIM proteins control expression of components of the calcineurin NFAT pathway in proliferative VSMC.;(b) (b) STIM-mediated Ca[2+] signaling occurs during mitogenic stimulation;(c) how STIM proteins control the NFAT translocation/gene expression pathway.
Significance of this work. The role of SOCE in physiology and pathophysiology is just emerging, STIM1 involvement in the cell proliferation is a novel observation and the spatiotemporal interplay mechanisms underlying the SMC dysfunctions are still largely unknown. Define the distinct roles of STIM1 vs. STIM2 will provide new insights in the STIM proteins regulation and may spawn new investigational initiatives into a wider view of the etiopathology and therapeutic management of vascular occlusive diseases. The connection between STIM-mediated calcium entry/NFAT VSMC proliferation may aid in developing strategies for pharmacologically modulating the pathways targeting STIM which, in turn, can control the proliferation rate and therefore control or prevent proliferative vascular smooth muscle diseases.
|Wang, Xizhuo; Wang, Youjun; Zhou, Yandong et al. (2014) Distinct Orai-coupling domains in STIM1 and STIM2 define the Orai-activating site. Nat Commun 5:3183|
|Mancarella, Salvatore; Potireddy, Santhi; Wang, Youjun et al. (2013) Targeted STIM deletion impairs calcium homeostasis, NFAT activation, and growth of smooth muscle. FASEB J 27:893-906|
|Mancarella, Salvatore; Wang, Youjun; Deng, Xiaoxiang et al. (2011) Hypoxia-induced acidosis uncouples the STIM-Orai calcium signaling complex. J Biol Chem 286:44788-98|