Premium
Actin association and stimulus‐specific activation of ERK1/2 in smooth muscle cells are regulated at the level of ERK1/2 scaffolds
Author(s) -
Vetterkind Susanne,
Poythress Ransom,
Lin Qian Qian,
Morgan Kathleen G
Publication year - 2013
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.27.1_supplement.729.7
Subject(s) - iqgap1 , microbiology and biotechnology , phosphorylation , actin , kinase , chemistry , scaffold protein , stimulation , protein kinase c , actin cytoskeleton , signal transduction , cytoskeleton , biology , endocrinology , biochemistry , cell
In smooth muscle, the extracellular signal regulated kinases 1 and 2 (ERK1/2) contextually regulate contraction or proliferation. Here, we test the hypothesis that ERK1/2 scaffolds regulate the intracellular localization and consequently, stimulus‐specific outcomes of ERK1/2 activation. SiRNA against the ERK1/2 scaffold IQGAP1 impairs phorbol ester induced ERK1/2 phosphorylation, but has no effect on basal or serum induced ERK1/2 phosphorylation in A7r5 smooth muscle cells. IP experiments show that ERK1/2 associates with both, IQGAP1 and kinase suppressor of ras‐1 under unstimulated conditions and dissociates upon serum stimulation. However, only IQGAP1 remains associated with ERK1/2 after phorbol ester stimulation. Immunofluorescence imaging and proximity ligation assays show that phorbol ester induced actin binding of phospho‐ERK1/2 is reduced after siRNA knock down of either IQGAP1 or caveolin‐1 (CaV). Interestingly, actin binding of total ERK1/2 is impaired by IQGAP1 siRNA, but not CaV siRNA. Simultaneous knock down of IQGAP1 and CaV reduces phorbol ester induced phospho‐ ERK1/2 to the same degree as IQGAP1 or CaV knock down alone, indicating that these two scaffolds act in the same ERK1/2 activation pathway. In summary, our results show that ERK1/2 scaffolds control distinct ERK1/2 pools and modulate the outcome of ERK1/2 activation in a stimulus‐specific manner. Support: HL080003, HL086655.