Adipsin, a Biomarker of Gastrointestinal Toxicity Mediated by a Functional γ-Secretase Inhibitor

• Published in: The Journal of biological chemistry Vol. 278; no. 46; pp. 46107 - 46116
• Main Authors: Searfoss, George H., Jordan, William H., Calligaro, David O., Galbreath, Elizabeth J., Schirtzinger, Linda M., Berridge, Brian R., Gao, Hong, Higgins, Marnie A., May, Patrick C., Ryan, Timothy P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14.11.2003
• Subjects: 3T3-L1 Cells; Amyloid beta-Peptides - chemistry; Amyloid beta-Peptides - metabolism; Amyloid Precursor Protein Secretases; Animals; Aspartic Acid Endopeptidases; Base Sequence; Binding Sites; Cell Differentiation; Complement Factor D; Digestive System - metabolism; Down-Regulation; Endopeptidases - chemistry; Endopeptidases - metabolism; Enzyme Inhibitors - pharmacology; Ileum - metabolism; Immunohistochemistry; Membrane Proteins - metabolism; Mice; Models, Chemical; Molecular Sequence Data; Oligonucleotide Array Sequence Analysis; Promoter Regions, Genetic; Rats; Receptors, Notch; Reverse Transcriptase Polymerase Chain Reaction; Serine Endopeptidases - chemistry; Signal Transduction; Time Factors; Transcription, Genetic; Up-Regulation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M307757200

Functional γ-secretase inhibitors (FGSIs) can block the cleavage of several transmembrane proteins including amyloid precursor protein (APP), and the cell fate regulator Notch-1. FGSIs, by inhibiting APP processing, block the generation of amyloid β (Aβ) peptides and may slow the development of Alzheimer's disease. FGSIs used to inhibit APP processing may disrupt Notch processing, thus interfering with cell fate determination. Described herein is a FGSI-mediated gastrointestinal toxicity characterized by cell population changes in the ileum of rats, which are indicative of Notch signaling disruption. Microarray analysis of ileum from FGSI-treated rats revealed differential expression responses in a number of genes indicative of Notch signaling perturbation, including the serine protease adipsin. We were able to show that FGSI-treated rats had elevated levels of adipsin protein in gastrointestinal contents and feces, and by immunohistochemistry demonstrated that adipsin containing ileum crypt cells were increased in FGSI-treated rats. The mouse Adipsin proximal promoter contains a putative binding site for the Notch-induced transcriptional regulator Hes-1, which we demonstrate is able to bind Hes-1. Additional studies in 3T3-L1 preadipocytes demonstrate that this FGSI inhibits Hes-1 expression while up-regulating adipsin expression. Overexpression of Hes-1 was able to down-regulate adipsin expression and block pre-adipocyte differentiation. We propose that adipsin is a Hes-1-regulated gene that is de-repressed during FGSI-mediated disruption of Notch/Hes-1 signaling. Additionally, the aberrant expression of adipsin, and its presence in feces may serve as a noninvasive biomarker of gastrointestinal toxicity associated with perturbed Notch signaling.