Activation of the c-Met receptor complex in fibroblasts drives invasive cell behavior by signaling through transcription factor STAT3.
c-Met is the receptor for hepatocyte growth factor/scatter factor (HGF/SF). It mediates multiple cellular responses in development and adult life, and c-Met hyperactivity is associated with malignant transformation of cells and the acquisition of metastatic properties. Signal transducer and activator of transcription 3 (STAT3) has been shown to contribute to c-Met-mediated cell motility and is, thus, potentially involved in the control of invasive cell behavior. We have functionally reconstituted c-Met-dependent signal transduction in fibroblasts with the aim of studying Met-driven cell invasiveness and the role of STAT3 in this phenomenon. Activation of the system was achieved by means of a hybrid receptor comprising the extracellular domain of the nerve growth factor (NGF) receptor TrkA, the cytoplasmic part of c-Met and a C-terminally fused blue fluorescent protein (BFP). In addition, a GFP-tagged derivative of adaptor protein Gab1 was expressed. NGF-stimulation of mouse fibroblasts expressing tagged versions of both Trk-Met and Gab1 with NGF resulted in anchorage-independent growth and enhanced invasiveness. By freeze-fracture cytochemistry and electron microscopy, we were able to visualize the ligand-induced formation of multivalent receptor complex assemblies within the cell membrane. NGF-stimulation of the heterologous receptor system evoked activation of STAT3 as evidenced by tyrosine phosphorylation and the formation of STAT3 clusters at the cell membrane. siRNA-mediated ablation of STAT3 expression resulted in a drastic reduction of c-Met-driven invasiveness, indicating an important role of STAT3 in the control of this particularly relevant property of transformed cells.
Cramer
Alexander
A
Institute of Biochemistry I, Friedrich Schiller University Jena, Nonnenplan 2, 07743 Jena, Germany.
Kleiner
Sandra
S
Westermann
Martin
M
Meissner
Anja
A
Lange
Anika
A
Friedrich
Karlheinz
K
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D003260:Contact Inhibition; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts; D051379:Mice; D005810:Multigene Family; D041681:NIH 3T3 Cells; D019859:Proto-Oncogene Proteins c-met / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019859:Proto-Oncogene Proteins c-met