Proteasome- and p38-dependent Regulation of ERK3 Expression

Abstract

Proteasome inhibition leads to accumulation of transcription factors, heat shock proteins, cyclins, and other proteasome substrate proteins by blocking their proteolytic degradation. An increase in gene transcription upon proteasome inhibition was found for a group of proteins, including p21 WAF1/CIP1 , ubiquitin, and transcription factors. In this study, we have demonstrated selective up-regulation of extracellular signal-regulated kinase 3 (ERK3) mRNA and protein expression upon treatment with peptide-based proteasome inhibitors or lactacystin. ERK3 is a family member of the mitogenactivated protein kinases (also called ERK) that are key mediators of signal transduction from the cell surface to the nucleus. ERK3 up-regulation is independent of the p53, Bcl2, and caspase 3 status of cells. p38 pathway kinase inhibitors prevent proteasome-dependent ERK3 induction and enhance the antiproliferative effect of proteasome inhibitors. MCF-7 cells expressing ERK3 ectopically show increased resistance toward proteasome inhibition. The results indicate that ERK3 expression is a consequence of p38 pathway activation and most probably represents an intracellular defense or rescue mechanism against cell stress and damage induced by proteasome inhibition.Proteasome inhibition leads to an increase in the expression of a large number of proteins by both posttranslational and transcriptional mechanisms. Various proteins crucial for cell cycle regulation and stress response, such as cyclins and transcription factors, are substrates of the ubiquitin-proteasome proteolytic pathway and directly accumulate in a polyubiquitinylated state after proteasome inhibitor treatment. On the other hand, proteasome inhibition has been reported to increase transcription and translation of a group of genes, including p21 WAF1/CIP1 (1), and a number of proteins involved in heat shock response (2) and transcriptional regulation, such as Gadd153, ATF3, and MAD1 (3).As reported previously, we have used a quantitative fluorescent cDNA hybridization approach to identify genes regulated transcriptionally in response to proteasome inhibitor treatment. Changes in mRNA expression of 7900 genes from the UniGene collection were compared upon exposure of cells to the proteasome inhibitors lactacystin, lactacystin-␤-lactone, or MG132 by means of microarray-based cDNA hybridization (3). All these inhibitors block the proteolytic activity of the 26 S proteasome without influencing its ATPase or isopeptidase activities. The three gene expression profiles were very similar, revealing 52 genes that are induced more than 5-fold and 34 genes that are repressed more than 5-fold by at least one of the inhibitors.A gene raising interest and found to be up-regulated on all three cDNA array chips was ERK3, a MAP 1 kinase of the extracellular signal-regulated kinase (ERK) subfamily. MAP kinases are serine/threonine kinases that are phosphorylated and thereby activated in response to a wide array of stimuli and are part of sequentially acting complex protein kinase cascades...

Cardiac Transcriptome Analysis in Obesity-Related Hypertension

“…51 ERK3, also called p97, is activated by protein kinase C 52 and is responsive to different growth factors, implying a mechanism for specificity in cellular signaling 53 in response to activation of the p38 pathway. 54 As expected in a situation of tissue growth, we observed upregulation of RNA levels encoding ribosomal proteins and elongation factor-1␥, a protein involved in mRNA translation. Taken together, these changes in gene expression are in accordance with a situation of cell proliferation in response to extracellular stimuli associated with an HFD.…”

Kinetic analysis of cardiac transcriptome regulation during chronic high-fat diet in dogs

“…In this same group of genes, we also found downregulation of mRNA levels for ERK3, a mitogen-activated protein kinase present in the nucleus (9). ERK3, also called p97 or MAPK6, is responsive to different growth factors during activation of the p38 pathway (57). Downregulation of ERK3 may be a feedback control mechanism of cellular proliferation which attempts to slow down cellular proliferation during the process of ventricular hypertrophy.…”

Rapid Turnover of Extracellular Signal-Regulated Kinase 3 by the Ubiquitin-Proteasome Pathway Defines a Novel Paradigm of Mitogen-Activated Protein Kinase Regulation during Cellular Differentiation

“…A role for the proteasome in the regulation of ERK3 expression was recently reported by Zimmermann et al, who showed, by using a microarray-based differential cDNA hybridization technology, that ERK3 mRNA is upregulated by various proteasome inhibitors (58). Proteasome inhibition also resulted in the accumulation of ERK3 protein.…”