Notch-1 Controls the Expression of Fatty Acid-activated Transcription Factors and Is Required for Adipogenesis

Abstract

Notch, a transmembrane receptor member of the homeotic epidermal growth factor-like family of proteins, participates in cell-to-cell signaling to control cell fate during development. Activated Notch-1 constructs lacking the extracellular region prevent differentiation of several mammalian cells in vitro. This effect, however, bypasses the normal mechanisms of cell-to-cell interactions in which Notch-1 participates. We investigated the role of Notch-1 in the hormone-induced adipocyte differentiation of 3T3-L1 fibroblasts, a paradigmatic model of adipogenesis that requires cell-to-cell contact. Unlike other differentiation models, Notch-1 expression and function were necessary conditions for adipogenesis. Impaired Notch-1 expression by antisense Notch-1 constructs prevented adipocyte differentiation. Strategies aimed at blocking putative Notch/ligand interactions also blocked adipogenesis, implicating Notch as a critical molecule in cell-to-cell signaling necessary for differentiation. Inhibition of Notch-1 expression or function decreased the expression of peroxisomal proliferatoractivated receptors ␦ and ␥, transcription factors that control adipocyte differentiation and that are up-regulated at cell confluence. These results implicate Notch in the commitment of 3T3-L1 cells to undergo adipogenesis by controlling the expression of the principal regulators of this process.

Notch signaling as a therapeutic target in cancer: a new approach to the development of cell fate modifying agents

“…Specific strategies that selectively target individual Notch receptors include antisense (Garces et al, 1997;Shelly et al, 1999;Yasutomo et al, 2000;Weijzen et al, 2002a;Weijzen et al, 2003), RNA interference (LM, unpublished) and monoclonal antibodies (Yasutomo et al, 2000), while pharmacological small-molecule inhibitors of individual Notch receptors have not been described yet. Nonselective strategies include soluble receptor decoys that act by sequestering Notch ligands (Garces et al, 1997;Nickoloff et al, 2002) and pharmacological inhibitors of gamma-secretase (Weijzen et al, 2002a), which prevent the second ligand-induced proteolytic cleavage of Notch receptors. These agents simultaneously target all Notch receptors (Mizutani et al, 2001).…”

“…Phosphorylation of intracellular Notch by GSK-3b (Foltz et al, 2002) and possibly by other, unspecified kinases (Ronchini and Capobianco, 2000;Shimizu et al, 2000;Ingles-Esteve et al, 2001) has been described and may contribute to regulating the half-life of Notch intracellular proteins. Notch target genes include among others helix-loop-helix inhibitory transcription factors of the hairy enhancer of split (HES) family (Enhancer of Split in Drosophila) (ArtavanisTsakonas et al, 1999) that modulate differentiation, cell cycle mediators such as p21 cip1/waf1 (Rangarajan et al, 2001b) and cyclin D1 (Ronchini and Capobianco, 2001), as well as NF-kB family (Cheng et al, 2001) and PPAR family (Garces et al, 1997;Nickoloff et al, 2002) transcription factors. Putative nontranscriptional effects of Notch signaling include direct activation of NF-kB by Notch ligands and inhibition of JNK activation Zecchini et al, 1999).…”

Tumor necrosis factor-α and endothelial cells modulate Notch signaling in the bone marrow microenvironment during inflammation

“…2D, lanes 2 and 3). To determine the specificity of this interaction, Notch-Jagged contact between CD34 + and BMEC cells was inhibited by blocking Notch receptors with an antibody directed to the extracellular domain of Notch1 (N1ab) [27,28], or with the soluble form of Notch ligand Delta4 (Dll4-Fc) [22]. Both reagents can bind to N1 and N2; antibodies directed to ligand binding region of Notch receptors and soluble ligand-fusion proteins have been used as antagonist to inhibit the full physiologic ligand-receptor binding and activation [dontu27, [37][38][39][40].…”

“…a) CD34 + and BMEC cocultures were grown for 5 days in the presence or absence of 2uM γ-secretase inhibitor GSI (GSI X, Calbiochem). b) Prior to seeding, CD34 + cells were blocked for 10 min on ice with human immunoglobulins (Sigma) and then incubated with saturating concentrations (25ug/ml) of soluble Dll4-Fc generated as described [22], the monoclonal antibody anti-N1 (Biomeda) [27,28] or Fc fragment control (Sigma) for 1 hour on ice. The CD34 + fraction adherent to BMEC was harvested (using 1 rinse of PBS and 1 rinse of PBS/EDTA) and used for further analysis after 24 hours (for western blot analysis) or 3 days (for colony assay).…”

Insulin-like Growth Factor-1/Insulin Bypasses Pref-1/FA1-mediated Inhibition of Adipocyte Differentiation

“…One of the best-characterized examples involving lateral protein-protein interaction of transmembrane proteins is provided by the Notch-Delta or Notch-Serrate/Jagged systems that play pivotal roles in cell fate determination during neurogenesis (24). Recently, Notch-1 was also shown to be implicated in adipocyte differentiation (25). The organization of the pref-1 gene and the structure of the individual EGF-like repeats strongly suggest that Pref-1 is most closely related to the Delta family (26).…”