Calmodulin modulates mitogen-activated protein kinase activation in response to membrane depolarization in PC12 cells.
In the absence of neurotrophic factors, chronic depolarization of plasma membrane has been shown to maintain several populations of primary neurons in culture. We report that in the PC12 cell line, depolarization causes Ca2+ influx through voltage-gated Ca2+ channels, which is able to stimulate extracellular-regulated kinase (ERK) activity. We studied which mediators were responsible for ERK activation resulting from increased levels of Ca2+ in the cytoplasm and found that calmodulin was involved in this process. The addition of W13, a calmodulin inhibitor, to the culture medium, prevented ERK activation when PC12 cells were depolarized. In addition, we show that high K+ treatment did not induce Trk A phosphorylation, thus excluding the possibility of Ca2+ operating through this receptor to activate the ERK signal transduction pathway. Moreover, although high K+ treatment is able to phosphorylate the epidermal growth factor receptor (EGFR) and thus to activate the ERK signal transduction pathway, we demonstrate that W13 did not alter the state of EGFR phosphorylation in conditions that almost completely blocked ERK activation. These data suggest that calmodulin mediates ERK activation induced by increases in intracellular Ca2+ concentration in PC12 cells by a mechanism that seems to be independent of Trk A and EGFR activation.
Egea
J
J
Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina, Universitat de Lleida, Catalonia, Spain.
Espinet
C
C
Comella
J X
JX
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D004594:Electrophysiology; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D016716:PC12 Cells; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D015220:Calcium Channels; D002147:Calmodulin; D011518:Proto-Oncogene Proteins; D017475:Receptors, Nerve Growth Factor; D013449:Sulfonamides; D014443:Tyrosine; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium