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2017 ; 8
(34
): 56490-56505
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Proteolytic cleavages in the extracellular domain of receptor tyrosine kinases by
membrane-associated serine proteases
#MMPMID28915606
Chen LM
; Chai KX
Oncotarget
2017[Aug]; 8
(34
): 56490-56505
PMID28915606
show ga
The epithelial extracellular membrane-associated serine proteases matriptase,
hepsin, and prostasin are proteolytic modifying enzymes of the extracellular
domain (ECD) of the epidermal growth factor receptor (EGFR). Matriptase also
cleaves the ECD of the vascular endothelial growth factor receptor 2 (VEGFR2) and
the angiopoietin receptor Tie2. In this study we tested the hypothesis that these
serine proteases may cleave the ECD of additional receptor tyrosine kinases
(RTKs). We co-expressed the proteases in an epithelial cell line with Her2, Her3,
Her4, insulin receptor (INSR), insulin-like growth factor I receptor (IGF-1R),
the platelet-derived growth factor receptors (PDGFRs) ? and ?, or nerve growth
factor receptor A (TrkA). Western blot analysis was performed to detect the
carboxyl-terminal fragments (CTFs) of the RTKs. Matriptase and hepsin were found
to cleave the ECD of all RTKs tested, while TMPRSS6/matriptase-2 cleaves the ECD
of Her4, INSR, and PDGFR ? and ?. Prostasin was able to cleave the ECD of Her3
and PDGFR?. Matriptase cleaves phosphorylated Her2 at Arg558 and Arg599 and the
Arg599 cleavage produces a CTF not recognized by the monoclonal antibody
trastuzumab/Herceptin. Her2 cleavages by matriptase can be inhibited by the
hepatocyte growth factor activator inhibitor 1 (HAI-1) in the MDA-MB-231 human
breast cancer cells. Matriptase silencing in the Her2, matriptase, and HAI-1
triple-positive SKBR3 human breast cancer cells enhanced Her2 protein
down-regulation induced by a sustained exposure to phorbol 12-myristate
13-acetate (PMA), which down-regulated matriptase protein. The novel Her2
cleavage and expression regulation mechanisms mediated by matriptase may have
potential impacts in Her2-targeting therapies.