S100B increases proliferation in PC12 neuronal cells and reduces their responsiveness to nerve growth factor via Akt activation.
S100B is a Ca2+-modulated protein of the EF-hand type expressed in high abundance in a restricted set of cell types including certain neuronal populations. S100B has been suggested to participate in cell cycle progression, and S100B levels are high in tumor cells, compared with normal parental cells. We expressed S100B in the neuronal cell line PC12, which normally does not express the protein, by the Tet-Off technique, and found the following: (i) proliferation was higher in S100B+ PC12 cells than in S100B- PC12 cells; (ii) nerve growth factor (NGF), which decreased the proliferation of S100B- PC12 cells, was less effective in the case of S100B+ PC12 cells; (iii) expression of S100B made PC12 cells resistant to the differentiating effect of NGF; and (iv) interruption of S100B expression did not result in an immediate restoration of PC12 cell sensitivity to the differentiating effect of NGF. Expression of S100B in PC12 cells resulted in activation of Akt; increased levels of p21WAF1, an inhibitor of cyclin-dependent kinase (cdk) 2 and a positive regulator of cdk4; increased p21WAF1-cyclin D1 complex formation; and increased phosphorylation of the retinoblastoma suppressor protein, Rb. These S100B-induced effects, as well as the reduced ability of S100B+ PC12 cells to respond to NGF, were dependent on Akt activation because they were remarkably reduced or abrogated in the presence of LY294002, an inhibitor of the Akt upstream kinase phosphatidylinositol 3-kinase. Thus, S100B might promote cell proliferation and interfere with NGF-induced PC12 cell differentiation by stimulating a p21WAF1/cyclin D1/cdk4/Rb/E2F pathway in an Akt-mediated manner.
Arcuri
Cataldo
C
Section of Anatomy, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, 06122 Perugia, Italy.
Bianchi
Roberta
R
Brozzi
Flora
F
Donato
Rosario
R
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D002469:Cell Separation; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D019938:Cyclin D1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004318:Doxycycline / Q000494:pharmacology; D004789:Enzyme Activation; D005434:Flow Cytometry; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009025:Morpholines / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D018797:Cell Cycle Proteins; D002867:Chromones; D019938:Cyclin D1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004318:Doxycycline; D008156:Luciferases; D009025:Morpholines; D020932:Nerve Growth Factor; D009414:Nerve Growth Factors; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D016159:Tumor Suppressor Protein p53; C493958:Cdkn1a protein, rat; C579158:S100b protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494920:Akt1 protein, rat