Calcium activation of ERK mediated by calmodulin kinase I.
Elevated intracellular Ca(2+) triggers numerous signaling pathways including protein kinases such as the calmodulin-dependent kinases (CaMKs) and the extracellular signal-regulated kinases (ERKs). In the present study we examined Ca(2+)-dependent "cross-talk" between these two protein kinase families. Using a combination of pharmacological inhibitors and dominant-negative kinases (dnKinase), we identified a requirement for CaMKK acting through CaMKI in the stimulation of ERKs upon depolarization of the neuroblastoma cell line, NG108. Depolarization stimulated prolonged ERK and JNK activation that was blocked by the CaMKK inhibitor, STO-609; this inhibition of ERK activation by STO-609 was rescued by expression of a STO-609-insensitive mutant of CaMKK. However, activation of ERK by epidermal growth factor or carbachol were not suppressed by inhibition of CaMKK, indicating specificity for this "cross-talk." To identify the downstream target of CaMKK that mediated ERK activation upon depolarization, dnKinases were expressed. The dnCaMKI completely suppressed ERK2 activation whereas dnAKT/PKB or nuclear-targeted dnCaMKIV, other substrates for CaMKK, were not inhibitory. ERK activation upon depolarization or transfection with constitutively active (ca) CaMKI was blocked by dnRas. Additionally, depolarization of NG108 cells promoted neurite outgrowth, and this effect was blocked by inhibition of either CaMKK (STO-609) or ERK (UO126). Co-transfection with caCaMKK plus caCaMKI also stimulated neurite outgrowth that was blocked by inhibition of ERK (UO126). These data are the first to suggest that ERK activation and neurite outgrowth in response to depolarization are mediated by CaMKK activation of CaMKI.
Schmitt
John M
JM
Vollum Institute, Oregon Health and Sciences University, Portland 97239, USA.
Wayman
Gary A
GA
Nozaki
Naohito
N
Soderling
Thomas R
TR
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D007150:Immunohistochemistry; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection
D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517699:Camkk1 protein, mouse; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium