Heterogeneity of signal transduction at the subcellular level: microsphere-based focal EGF receptor activation and stimulation of Shc translocation.
Epidermal growth factor receptor (EGFR, erbB1) activation and translocation of the Shc adaptor protein to activated receptors were analyzed at the subcellular level by dual-label immunofluorescence and confocal laser scanning microscopy in conjunction with a new microsphere-based protocol. In the Quantitative Microsphere Recruitment Assay (QMRA) introduced here, epidermal growth factor-coated 1 microm diameter microspheres were distributed over the surface of adherent tissue culture cells expressing the receptor. High-resolution confocal microscopy of a fusion construct of the receptor and the green fluorescent protein expressed in Chinese hamster ovary cells demonstrated that engulfment and internalization of the microspheres occurred rapidly within minutes, and in a receptor activation-dependent manner. In human epidermoid carcinoma A431 cells, receptor activation and Shc translocation persisted over the 20-minute time course of the experiments. However, at the subcellular level the positive correlation of receptor activation and Shc translocation observed at 5-8 minutes dissipated, indicating a time-dependent decoupling of the two events and variation in the kinetics of signal transduction for different subcellular locations.
Brock
R
R
Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany. roland.brock@uni-tuebingen.de
Jovin
T M
TM
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D046508:Culture Techniques; D066246:ErbB Receptors / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D007091:Image Processing, Computer-Assisted; D019751:Intramolecular Transferases / Q000378:metabolism*; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008863:Microspheres; D015398:Signal Transduction; D013347:Subcellular Fractions; D013997:Time Factors; D014407:Tumor Cells, Cultured
D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D066246:ErbB Receptors; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase