Project description:To identify downstream phosphorylation substrates of Erk, we treated the iErk1; Erk KO cell line with and without doxycycline (DOX) for 48 hours. In the untreated group, intracellular Erk was found to be deficient. Mass spectrometry-based quantitative analysis was subsequently used to identify phosphorylated substrates regulated by Erk
Project description:Studies were undertaken to determine whether oscillatory behavior in the extracellular signal regulated kinase (ERK) pathway results in unique gene regulation patterns. Microarray analysis was performed on three subcloned populations of human keratinocytes with distinct ERK signaling/oscillation phenotypes. Microarray analysis identified 45 genes that overlapped between 2 subclones with oscillation phenotypes but not in the subclone which is non-oscillatory. Transcription factor networks revealed a role for MED1 in mediating ERK oscillation-dependent gene expression, which was confirmed with Western blot analysis. Further experimentation confirmed a role for p38 in the mediation of MED1 phosphorylation and ERK oscillatory behavior. hTERT-immortalized normal human keratinocytes (provided by Dr. Jerry Shay, The University of Texas Southwestern Medical Center) were stably transfected with ERK1-green fluorescent protein chimera and stable subclones were isolated with distinct ERK activation/oscillation patterns: Clone #1 exhibits transient ERK activation with ligand activation but does not oscillate; Clone #2 exhibits persistent ERK oscillations that are dependent on ligand activation; and Clone #3 exhibits spontaneous ERK oscillations in the absence of ligand activation.
Project description:Epidermal keratinocytes respond to extracellular influences by activating cytoplasmic signal transduction pathways that change the transcriptional profiles of affected cells. To define responses to two such pathways, p38 and ERK, we used SB203580 and PD98059 as specific inhibitors, and identified the regulated genes after 1, 4, 24 and 48 hrs, using Affymetrix’ Hu133Av2 microarrays. Additionally, we compared genes specifically regulated by p38 and ERKs with those regulated by JNK and by all three pathways simultaneously. We find that the p38 pathway induces the expression of extracellular matrix and proliferation-associated genes, while suppressing microtubule-associated genes; the ERK pathway induces the expression of nuclear envelope and mRNA splicing proteins, while suppressing steroid synthesis and mitochondrial energy production enzymes. Both pathways promote epidermal differentiation and induce feedback inactivation of MAPK signaling. c-FOS, SRY and N-Myc appear to be the principal targets of the p38 pathway, Elk-1 SAP1 and HLH2 of ERK, while FREAC-4, ARNT and USF are common to both. The results for the first time comprehensively define the genes regulated by the p38 and ERK pathways in epidermal keratinocytes and suggest a list of targets potentially useful in therapeutic interventions. Human epidermal keratinocytes are grown in Keratinocyte Serum-Free Medium (Gibco) supplemented with 0.05 mg/ml bovine pituitary extract, 2.5 ng/ml epidermal growth factor, 0.09 mM CalCl2 and 1% penicillin/streptomycin (KGM). They are switched to Keratinocyte Serum Free-Media (Gibco) supplemented only with 1% penicillin/streptomycin (KBM) 24 h prior to commencing experiments. A set is left as controls, others treated with 5 uM JNK inhibitor SP600125, 15 uM p38 inhibitor SB203580, or 50 um ERK inhibitor PD98059. Timecourse of treated and parellel control samples over a 48 hr period was performed.