PTPN2 copper-sensing rapidly relays copper level fluctuations into EGFR/CREB activation and associatedCTR1transcriptional repression

Abstract

AbstractFluxes in human intra- and extracellular copper levels recently garnered attention for roles in cellular signaling, including affecting levels of the signaling molecule cyclic adenosine monophosphate (cAMP). We herein applied an unbiased temporal evaluation of the whole-genome transcriptional activities modulated by fluctuations in copper levels to identify the copper sensor proteins responsible for driving these activities. We found that fluctuations in physiologically-relevant copper levels rapidly modulate EGFR/MAPK/ERK signal transduction and activation of the transcription factor cAMP response element-binding protein (CREB). Both intracellular and extracellular assays support Cu1+inhibition of the EGFR-phosphatase PTPN2 (and potentially the homologous PTPN1)–via direct ligation to the PTPN2 active site cysteine side chain–as the underlying mechanism of copper-stimulated EGFR signal transduction activation. Depletion of copper represses this signaling pathway. We additionally showi) copper supplementation drives transcriptional repression of the copper importerCTR1andii) CREB activity is inversely correlated withCTR1expression. In summary, our study reveals PTPN2 as a physiological copper sensor and defines a regulatory mechanism linking feedback control of copper-stimulated MAPK/ERK/CREB-signaling andCTR1expression, thereby uncovering a previously unrecognized link between copper levels and cellular signal transduction.