title: Met receptor tyrosine kinase signals through a cortactin-Gab1 scaffold complex, to mediate invadopodia.
abstract: Invasive carcinoma cells form actin-rich matrix-degrading protrusions called invadopodia. These structures resemble podosomes produced by some normal cells and play a crucial role in extracellular matrix remodeling. In cancer, formation of invadopodia is strongly associated with invasive potential. Although deregulated signals from the receptor tyrosine kinase Met (also known as hepatocyte growth factor are linked to cancer metastasis and poor prognosis, its role in invadopodia formation is not known. Here we show that stimulation of breast cancer cells with the ligand for Met, hepatocyte growth factor, promotes invadopodia formation, and in aggressive gastric tumor cells where Met is amplified, invadopodia formation is dependent on Met activity. Using both GRB2-associated-binding protein 1 (Gab1)-null fibroblasts and specific knockdown of Gab1 in tumor cells we show that Met-mediated invadopodia formation and cell invasion requires the scaffold protein Gab1. By a structure-function approach, we demonstrate that two proline-rich motifs (P4/5) within Gab1 are essential for invadopodia formation. We identify the actin regulatory protein, cortactin, as a direct interaction partner for Gab1 and show that a Gab1-cortactin interaction is dependent on the SH3 domain of cortactin and the integrity of the P4/5 region of Gab1. Both cortactin and Gab1 localize to invadopodia rosettes in Met-transformed cells and the specific uncoupling of cortactin from Gab1 abrogates invadopodia biogenesis and cell invasion downstream from the Met receptor tyrosine kinase. Met localizes to invadopodia along with cortactin and promotes phosphorylation of cortactin. These findings provide insights into the molecular mechanisms of invadopodia formation and identify Gab1 as a scaffold protein involved in this process.
authors.affiliation: Department of Biochemistry, McGill University, Montréal Québec H3A 1Y6,  Canada.
authors.forename: Charles V
authors.initials: CV
authors.lastname: Rajadurai
authors.forename: Serhiy
authors.initials: S
authors.lastname: Havrylov
authors.forename: Kossay
authors.initials: K
authors.lastname: Zaoui
authors.forename: Richard
authors.initials: R
authors.lastname: Vaillancourt
authors.forename: Matthew
authors.initials: M
authors.lastname: Stuible
authors.forename: Monica
authors.initials: M
authors.lastname: Naujokas
authors.forename: Dongmei
authors.initials: D
authors.lastname: Zuo
authors.forename: Michel L
authors.initials: ML
authors.lastname: Tremblay
authors.forename: Morag
authors.initials: M
authors.lastname: Park
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D045744:Cell Line, Tumor; D002465:Cell Movement; D005260:Female; D006801:Humans; D009361:Neoplasm Invasiveness; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism*; D011554:Pseudopodia / Q000201:enzymology / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C098587:GAB1 protein, human; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met