Abstract 13362: STIM1 and STIM2 are Required in Smooth Muscle Development and Function
STIM1 and STIM2 control Ca2+ signaling in several cell types by activating the store operated Ca2+ entry (SOCE). Whereas their role and functions are well studied in immune cells, their role in vascular smooth muscle cells (SMC) remains unknown. We hypothesize that STIM proteins play a crucial role in controlling the Ca2+ signaling in SMC. Hence, STIM are required for SMC normal function and development. To investigate the physiological function of STIM proteins in SMC we generate a smooth muscle-specific STIM1 knockout and STIM1/STIM2- double knockout mouse (SM-STIM1 KO and SM-STIM1/2 DKO) using the Cre-lox technology. STIM deletion was confirmed by western blot and the Cre tissue-distribution was confirmed using a double-fluorescent reporter mice. Vascular reactivity, an important index of smooth muscle function, was studied by wire myography, while proliferative index and intracellular Ca2+ measurements were done in aortic SMC isolated from STIM1 KO and WT mice, NFAT translocation was studied in SMC infected with NFAT-GFP adenovirus. The STIM1/2-DKO was lethal right after birth, while the SM-STIM1 KO mice were vital. However, STIM1 KO mice showed growth retardation and a reduced lifespan. The contractile response to phenylephrine was significantly blunted in aortic rings isolated from SM-STIM KO mice (21.2±10.3% less than WT littermate, p<0.05). Fura-2 loaded SMC from SM-STIM1 KO exhibited a reduced SOCE associated with an impaired Ca2+ entry in response to serum or PDGF stimulation. Consistently, loss of STIM1 was associated with a significantly reduced SMC proliferation response (40.5±8.3%, p<0.05). Finally, simultaneous recording of intracellular Ca2+ and NFAT-GFP showed that in STIM1-KO SMC, NFAT translocation to the nucleus was significantly reduced compared to the WT SMC. Taken together our data demonstrate that: 1) expression of STIM1 and STIM2 in SMC is required for normal mouse development; 2) STIM1 deletion results in impaired vascular reactivity and SMC proliferation; 3) these physiologic actions of STIM1 are likley related to changes in calcium signaling. Our work may help to understand the role of STIM1 in vascular patholgies associated with SMC dysfunction.
- © 2011 by American Heart Association, Inc.