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Endothelial calreticulin and its role in vascular function
Author(s) -
Biwer Lauren,
Good Miranda,
Sonkusare Swapnil,
Isakson Brant
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.955.3
Subject(s) - calreticulin , endoplasmic reticulum , ryanodine receptor , biology , calcium binding protein , vascular smooth muscle , microbiology and biotechnology , medicine , endocrinology , calcium , smooth muscle
Myoendothelial junctions (MEJ) are projections from endothelial cells (EC) that make contact with neighboring smooth muscle cells (SMC) and are the anatomical hallmarks of resistance arteries. MEJ also exhibit presence of endoplasmic reticulum (ER), as evidenced from the ER retention signal –KDEL immunostaining and the live ER tracker (glibenclamide) in holes of the internal elastic lamina. Within the ER, calreticulin is a calcium binding protein that can bind approximately 50% of ER calcium and we found it was significantly enriched in the non lipid‐raft fraction of the MEJ in vitro . Due to the importance of ER calcium signals at the MEJ in controlling vascular tone, we investigated the in vivo role of calreticulin in the endothelium and the MEJ. We generated a tamoxifen inducible, endothelial specific calreticulin floxed mouse. To confirm knockdown of calreticulin in the EC, we digested diaphragm skeletal muscle to obtain microvascular EC from mice injected with peanut oil or tamoxifen. Live cells were stained with CD31 antibody (to mark EC), CD45 (to exclude leukocytes), fixed and permeabilized, and stained with calreticulin. We saw a significant decrease in the percentage of CD31+, Calreticulin+ cells after tamoxifen injection, indicating less EC were expressing calreticulin in our knockout mouse. In calreticulin mice with and without tamoxifen, we could not identify any basal change in blood pressure as measured by radiotelemetry. However, after acute injection of 0.1mg/kg PE, the rapid and significant increase in blood pressure seen in control mice was significantly blunted in mice lacking EC calreticulin. Because of this, we used pressure myography on isolated resistance arteries from mice (both third order mesenteric arteries and thoracodorsal arteries) lacking EC calreticulin and found them to have less constriction to PE dose response curves. In order to determine if this blunted response is due to less agonist‐induced ER calcium release, we also measured calcium transients at MEJs of intact resistance arteries. In summary, calreticulin in the EC appears to play an important role in the regulation of vascular tone and blood pressure, possibly through its actions at the ER in MEJs. We hypothesize calreticulin's presence at the MEJ may be to mediate ER calcium release and provide the negative feedback that occurs upon SMC stimulation with PE. Support or Funding Information American Heart Association National Institute of Health