TrkA mediates the nerve growth factor-induced intracellular calcium accumulation.
Regulation of the cytosolic free Ca2+ concentration by nerve growth factor was investigated in C6-2B glioma cells newly expressing the high affinity nerve growth factor receptor trkA, using Fura-2 fluorescence ratio imaging. In these cells, nerve growth factor (50 ng/ml) evoked a novel approximately 3-fold increase in cytosolic free Ca2+ concentration, while no measurable Ca2+ response was observed in wild type or mock-transfected cells lacking a functional trkA receptor. K-252a, a tyrosine kinase inhibitor which prevents nerve growth factor-mediated responses in C6-2B cells expressing trkA, also blocked the rise in cytosolic free Ca2+ concentration by nerve growth factor. Moreover, basic fibroblast growth factor, which in these cells elicits biochemical changes similar to nerve growth factor, failed to affect cytosolic free Ca2+ concentration, further supporting the specificity of nerve growth factor/trkA receptor in mediating a Ca2+ response. While insensitive to chelation of extracellular Ca2+, the response was abolished following depletion of Ca2+ stores or blockade of intracellular Ca2+ release, providing strong evidence that intracellular Ca2+ is the main source for nerve growth factor-evoked cytosolic free Ca2+ concentration increase. Nerve growth factor increased the cytosolic free Ca2+ concentration also in NIH3T3 cells overexpressing trkA but devoid of p75 nerve growth factor receptor. Our data suggest that trkA but not p75 is required for nerve growth factor-evoked Ca2+ signaling.
De Bernardi
M A
MA
Department of Biochemistry and Molecular Biology, Georgetown University, School of Medicine, Washington, DC 20007, USA.
Rabins
S J
SJ
Colangelo
A M
AM
Brooker
G
G
Mocchetti
I
I
D016475:3T3 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D003600:Cytosol; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D026121:Indole Alkaloids; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
D002227:Carbazoles; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D009414:Nerve Growth Factors; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D017475:Receptors, Nerve Growth Factor; D016222:Fibroblast Growth Factor 2; C049985:staurosporine aglycone; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D002118:Calcium