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Role of Rac1 in A2B Adenosine Receptor and Epac1 signaling to Extracellular Signal‐Regulated Kinase in human endothelial cells
Author(s) -
Olah Mark,
Miller Lauren
Publication year - 2012
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.26.1_supplement.663.1
Subject(s) - forskolin , rac1 , microbiology and biotechnology , nadph oxidase , rac gtp binding proteins , signal transduction , adenosine , biology , chemistry , receptor , biochemistry , reactive oxygen species
Endothelial cell proliferation is required for angiogenesis. Our laboratory has previously shown that activation of the A2B adenosine receptor (A2BAR) through the cAMP effector Epac1 activates extracellular signal‐regulated kinase (ERK1/2), a key protein for endothelial cell proliferation. Presently, we hypothesize that the small GTPase Rac1 is involved in signaling from the A2BAR and Epac1 to ERK1/2 activation. In human microvascular endothelial cells (HMVEC), the Rac inhibitor NSC23766 diminished ERK1/2 activation by the A2BAR agonist 5‐N‐ethylcarboxamidoadenosine (NECA) and forskolin by 61.7 ± 10.4% and 60.3 ± 7.9%, respectively. Targeting of Rac1 with siRNA reduced NECA‐ and forskolin‐induced ERK1/2 stimulation. NECA, forskolin and a direct activator of Epac1 each promoted an ~2.2‐fold stimulation of Rac1 as assessed in a Rac1‐specific pull‐down assay. Knockdown of Epac1 with siRNA reduced NECA‐ and forskolin‐stimulated Rac1 activation by 65.4 ± 9.0% and 78.6 ± 10.1% respectively. A putative downstream target of Rac1 in HMVEC is NADPH oxidase with production of reactive oxygen species a possible mediator of ERK1/2 activation. The NADPH oxidase inhibitor diphenyleneiodonium reduced ERK1/2 activation by NECA and forskolin by 55.6 ± 7.1% and 78.5 ± 6.6%, respectively. These results indicate that the A2BAR activates ERK1/2 in endothelial cells via an Epac1‐Rac1‐NADPH oxidase signaling cassette.