IIAEK Targets Intestinal Alkaline Phosphatase (IAP) to Improve Cholesterol Metabolism with a Specific Activation of IAP and Down-Regulation of ABCA1

Asahi Takeuchi; Kentaro Hisamatsu; Natsuki Okumura; Yuki Sugimitsu; Emiko Yanase; Yoshihito Ueno; Satoshi Nagaoka

doi:10.20944/preprints202008.0055.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 1 August 2020 / Approved: 3 August 2020 / Online: 3 August 2020 (00:14:52 CEST)

IIAEK (Ile-Ile-Ala-Glu-Lys, lactostatin) is a novel pentapeptide from bovine milk β-lactoglobulin which lowers cholesterol levels. However, the molecular mechanisms underlying the suppression of intestinal cholesterol absorption by IIAEK are unknown. Therefore, we evaluated the effects of IIAEK on intestinal cholesterol metabolism in Caco-2 cells in a human intestinal model. We found that IIAEK significantly reduced the expression of intestinal cholesterol metabolism-associated genes, particularly that of the ATP-binding cassette transporter A1 (ABCA1) protein. Subsequently, we chemically synthesized a novel molecular probe, IIXEK, which can visualize a complex of target proteins interacting with photoaffinity-labeled IIAEK by fluorescent substances. Photoaffinity labeling and MS analysis with IIXEK for the rat small intestinal mucosa and intestinal lipid raft fractions of Caco-2 cells, we identified intestinal alkaline phosphatase (IAP) as a specific molecule interacting with IIAEK and discovered IIAEK common binding amino acid sequence, GFYLFVEGGR. Transfection of IAP siRNA counteracted the decrease in ABCA1 mRNA levels in Caco-2 cells. IIAEK significantly increased IAP mRNA and protein levels, and significantly decreased ABCA1 mRNA and protein levels in Caco-2 cells. In conclusion, we found that IIAEK targets IAP to improve cholesterol metabolism via a novel signaling pathway with a specific activation of IAP and down-regulation of intestinal ABCA1.

IIAEK; IAP; photoaffinity labeling; click reaction; Caco-2 cells; cholesterol; ABCA1

LIFE SCIENCES, Biochemistry

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IIAEK Targets Intestinal Alkaline Phosphatase (IAP) to Improve Cholesterol Metabolism with a Specific Activation of IAP and Down-Regulation of ABCA1

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