Year: 2022
Type: article
Abstract: We have previously shown that the serine/threonine kinase PKCα triggers MAPK/ERK kinase (MEK)-dependent G 1 →S cell cycle arrest in intestinal epithelial cells, characterized by downregulation of cyclin D1 and inhibitor of DNA-binding protein 1 (Id1) and upregulation of the cyclin-dependent kinase inhibitor p21 Cip1 . Here, we use pharmacological inhibitors, genetic approaches, siRNA-mediated knockdown, and immunoprecipitation to further characterize antiproliferative ERK signaling in intestinal cells. We show that PKCα signaling intersects the Ras-Raf-MEK-ERK kinase cascade at the level of Ras small GTPases and that antiproliferative effects of PKCα require active Ras, Raf, MEK, and ERK, core ERK pathway components that are also essential for pro-proliferative ERK signaling induced by epidermal growth factor (EGF). However, PKCα-induced antiproliferative signaling differs from EGF signaling in that it is independent of the Ras guanine nucleotide exchange factors (Ras-GEFs), SOS1/2, and involves prolonged rather than transient ERK activation. PKCα forms complexes with A-Raf, B-Raf, and C-Raf that dissociate upon pathway activation, and all three Raf isoforms can mediate PKCα-induced antiproliferative effects. At least two PKCα–ERK pathways that collaborate to promote growth arrest were identified: one pathway requiring the Ras-GEF, RasGRP3, and H-Ras, leads to p21 Cip1 upregulation, while additional pathway(s) mediate PKCα-induced cyclin D1 and Id1 downregulation. PKCα also induces ERK-dependent SOS1 phosphorylation, indicating possible negative crosstalk between antiproliferative and growth-promoting ERK signaling. Importantly, the spatiotemporal activation of PKCα and ERK in the intestinal epithelium in vivo supports the physiological relevance of these pathways and highlights the importance of antiproliferative ERK signaling to tissue homeostasis in the intestine.
Source: Journal of Biological Chemistry
Institution: University of Nebraska Medical Center
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,500
Funders: U.S. Department of Defense, Norges Idrettshøgskole, National Institutes of Health, Central States Center for Agricultural Safety and Health, University of Nebraska Medical Center, National Cancer Institute, National Institute of General Medical Sciences, National Institute of Diabetes and Digestive and Kidney Diseases
Awards: Regulation of cyclin D1 expression in the intestine, G4119534169, Evaluating the PKC Enzyme System in Human Colon Cancer, G5850682332, SPORE in Pancreatic Cancer, DISSECTING THE DRUGGABLE PP2A INTERACTOME FOR COLON CANCER TREATMENT, Cell Survival Determinants of Metastasis in IGF1R-Dependent CRC, Regulation of cyclin D1 expression in the intestine, G842032118, G9000066975, G9000108264, G9000168717, Nebraska Center for Molecular Target Discovery and Development, Buffett Cancer Center Support Grant
OpenAlex ID: W4281997333