title: Pref-1 interacts with fibronectin to inhibit adipocyte differentiation.
abstract: Pref-1/Dlk1 is made as an epidermal growth factor (EGF) repeat-containing transmembrane protein but is cleaved by tumor necrosis factor alpha converting enzyme (TACE) to generate a biologically active soluble form. Soluble Pref-1 inhibits adipocyte differentiation through the activation of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) and the subsequent upregulation of Sox9 expression. However, others have implicated Notch in Pref-1 signaling and function. Here, we show that Pref-1 does not interact with, or require, Notch for its function. Instead, we show a direct interaction of Pref-1 and fibronectin via the Pref-1 juxtamembrane domain and fibronectin C-terminal domain. We also show that fibronectin is required for the Pref-1-mediated inhibition of adipocyte differentiation, the activation of ERK/MAPK, and the upregulation of Sox9. Furthermore, disrupting fibronectin binding to integrin by the addition of RGD peptides or by the knockdown of alpha 5 integrin prevents the Pref-1 inhibition of adipocyte differentiation. Pref-1 activates the integrin downstream signaling molecules, FAK and Rac, and ERK activation by Pref-1 is blunted by the knockdown of Rac or by the forced expression of dominant-negative Rac. We conclude that, by interacting with fibronectin, Pref-1 activates integrin downstream signaling to activate MEK/ERK and to inhibit adipocyte differentiation.
authors.affiliation: Department of Nutritional Science and Toxicology, University of California, Berkeley, CA 94720, USA.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Wang
authors.forename: Ling
authors.initials: L
authors.lastname: Zhao
authors.forename: Cynthia
authors.initials: C
authors.lastname: Smas
authors.forename: Hei Sook
authors.initials: HS
authors.lastname: Sul
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D066298:In Vitro Techniques; D039482:Integrin alpha5 / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics; D051880:Receptors, Notch / Q000378:metabolism; D055758:SOX9 Transcription Factor / Q000235:genetics; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D002135:Calcium-Binding Proteins; C512925:Dlk1 protein, mouse; D005353:Fibronectins; D039482:Integrin alpha5; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D051880:Receptors, Notch; D055758:SOX9 Transcription Factor; C527933:Sox9 protein, mouse
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