HER2 carboxyl-terminal fragments regulate cell migration and cortactin phosphorylation.
A group of breast cancer patients with a higher probability of developing metastasis expresses a series of carboxyl-terminal fragments (CTFs) of the tyrosine kinase receptor HER2. One of these fragments, 611-CTF, is a hyperactive form of HER2 that constitutively establishes homodimers maintained by disulfide bonds, making it an excellent model to study overactivation of HER2 during tumor progression and metastasis. Here we show that expression of 611-CTF increases cell motility in a variety of assays. Since cell motility is frequently regulated by phosphorylation/dephosphorylation, we looked for phosphoproteins mediating the effect of 611-CTF using two alternative proteomic approaches, stable isotope labeling with amino acids in cell culture and difference gel electrophoresis, and found that the latter is particularly well suited to detect changes in multiphosphorylated proteins. The difference gel electrophoresis screening identified cortactin, a cytoskeleton-binding protein involved in the regulation of cell migration, as a phosphoprotein probably regulated by 611-CTF. This result was validated by characterizing cortactin in cells expressing this HER2 fragment. Finally, we showed that the knockdown of cortactin impairs 611-CTF-induced cell migration. These results suggest that cortactin is a target of 611-CTF involved in the regulation of cell migration and, thus, in the metastatic behavior of breast tumors expressing this CTF.
García-Castillo
Jesús
J
Medical Oncology Research Program, Vall d'Hebron University Hospital, Passeig Vall d'Hebron 119-129, 08035 Barcelona, Spain.
Pedersen
Kim
K
Angelini
Pier-Davide
PD
Bech-Serra
Joan Josep
JJ
Colomé
Núria
N
Cunningham
Matthew Paul
MP
Parra-Palau
Josep Lluis
JL
Canals
Francesc
F
Baselga
José
J
Arribas
Joaquín
J
D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement; D051356:Cortactin / Q000737:chemistry*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry*; D015398:Signal Transduction
D051356:Cortactin; D010455:Peptides; D010750:Phosphoproteins; D018719:Erb-b2 Receptor Tyrosine Kinases