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Mechanotransduction properties of the cytoplasmic tail of PECAM‐1
Author(s) -
Snyder Jessica L.,
McBeath Elena,
Thomas Tamlyn N.,
Chiu Yi Jen,
Clark Robert L.,
Fujiwara Keigi
Publication year - 2017
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/boc.201600079
Subject(s) - phosphorylation , mechanotransduction , cytoplasm , microbiology and biotechnology , biology , tyrosine phosphorylation , tyrosine , biophysics , cell signaling , signal transduction , biochemistry
Background Information Vascular endothelial cells (ECs) are a well‐known cell system used in the study of mechanobiology. Using cultured ECs, we found that platelet EC adhesion molecule 1 (PECAM‐1, CD31), a cell adhesion protein localised to regions of EC–EC contact, was rapidly tyrosine phosphorylated in ECs exposed to shear or cyclic stretch. Src‐homology 2 domain‐containing protein tyrosine phosphatase 2 (SHP2) binds phosphorylated PECAM‐1 and activates the extracellular signal‐regulated kinase1/2 (ERK1/2) signalling cascade, a known flow‐activated signalling pathway. Results Although PECAM‐1 tyrosine phosphorylation is characterised in ECs exposed to fluid shear stress, it is less well demonstrated in the cells stretched cyclically. Thus, we first show that PECAM‐1 is tyrosine‐phosphorylated in ECs cyclically stretched. We hypothesise that when an external force is applied to a monolayer of ECs, the force is directly transmitted to PECAM‐1 which is then stretched and phosphorylation sites in its cytoplasmic domain are exposed and phosphorylated. This hypothesis requires the presence of any stretchable structure within the PECAM‐1 cytoplasmic domain. Force spectroscopy measurements were performed with a construct containing cytoplasmic PECAM‐1 domains inserted between I27 motifs, a recombinant string of the structural elements from titin. This strategy allowed us to identify the events in which a single molecule is being pulled and to detect the unravelling of the cytoplasmic domain of PECAM‐1 by force. The response by PECAM‐1 to mechanical loading was heterogeneous but with magnitudes as high as or higher than the naturally force bearing I27 domains. Conclusions The PECAM‐1 cytoplasmic domain has a structure that can be unfolded by externally applied force and this unfolding of PECAM‐1 may be necessary for its phosphorylation, the first step of PECAM‐1 mechanosignalling. Significance When EC monolayers are mechanically stimulated, the PECAM‐1 found at EC contacts is phosphorylated. We have proposed that under these conditions, the cytoplasmic domain of PECAM‐1 is unfolded, which then exposes a phosphorylation site, allowing it to be accessed. The stretch induced unfolding is essential to this model of PECAM‐1 mechanosignalling. In this study, we investigate whether the cytoplasmic domain of PECAM‐1 has a stretchable structure, and the results are in line with our hypothesis.