In both physiological and cell culture systems, EGF-stimulated ERK activity occurs in discrete pulses within individual cells. Many feedback loops are present in the EGF receptor (EGFR)-ERK network, but the mechanisms driving pulsatile ERK kinetics are unknown. Here, we find that in cells that respond to EGF with frequency-modulated pulsatile ERK activity, stimulation through a heterologous TrkA receptor system results in non-pulsatile, amplitude-modulated activation of ERK. We further dissect the kinetics of pulse activity using a combination of FRET- and translocation-based reporters and find that EGFR activity is required to maintain ERK activity throughout the 10-20-minute lifetime of pulses. Together, these data indicate that feedbacks operating within the core Ras-Raf-MEK-ERK cascade are insufficient to drive discrete pulses of ERK activity and instead implicate mechanisms acting at the level of EGFR.
Keywords: EKAR; ERKTR; TRK1-transforming tyrosine kinase protein (Trk-A); epidermal growth factor receptor (EGFR); extracellular-signal-regulated kinase (ERK); fluorescence resonance energy transfer (FRET); mitogen-activated protein kinase (MAPK); nerve growth factor (NGF); signal transduction.
© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.