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Science 3 June 2005:
Vol. 308. no. 5727, pp. 1472 - 1477
DOI: 10.1126/science.1107627

Reports

Mechanism of Divergent Growth Factor Effects in Mesenchymal Stem Cell Differentiation

Irina Kratchmarova,1* Blagoy Blagoev,1* Mandana Haack-Sorensen,2 Moustapha Kassem,2 Matthias Mann1{dagger}

Closely related signals often lead to very different cellular outcomes. We found that the differentiation of human mesenchymal stem cells into bone-forming cells is stimulated by epidermal growth factor (EGF) but not platelet-derived growth factor (PDGF). We used mass spectrometry–based proteomics to comprehensively compare proteins that were tyrosine phosphorylated in response to EGF and PDGF and their associated partners. More than 90% of these signaling proteins were used by both ligands, whereas the phosphatidylinositol 3-kinase (PI3K) pathway was exclusively activated by PDGF, implicating it as a possible control point. Indeed, chemical inhibition of PI3K in PDGF-stimulated cells removed the differential effect of the two growth factors, bestowing full differentiation effect onto PDGF. Thus, quantitative proteomics can directly compare entire signaling networks and discover critical differences capable of changing cell fate.

1 Center for Experimental BioInformatics (CEBI), Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
2 Department of Endocrinology, Odense University Hospital, DK-5000 Odense C, Denmark.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: mann{at}bmb.sdu.dk

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Science. ISSN 0036-8075 (print), 1095-9203 (online)