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Description

Cholesterol 25-hydroxylase (UniProt: O95992, also known as EC:1.14.99.38, Cholesterol 25-monooxygenase, h25OH) is encoded by the CH25H gene (Gene ID: 9023) in human. CH25H is a multi-pass membrane glycoprotein with three transmembrane domains (aa 38-58, 84-104, and 121-141) that catalyzes the formation of 25-hydroxycholesterol from cholesterol, which in turn leads to repression of cholesterol biosynthesis. It is also reported to play a role in regulating lipid metabolism by synthesizing a corepressor that blocks sterol regulatory element binding protein (SREBP) processing. CH25H is an interferon inducible enzyme that has broad-spectrum antiviral functions. Stimulation of macrophage Toll-like receptors (TLR) is also reported to increase its expression and synthesis of 25-hydroxycholesterol. Treatment of naïve B cells with nanomolar concentrations of 25-hydroxycholesterol is shown to suppress IL-2-mediated stimulation of B cell proliferation, repress activation induced cytidine deaminase expression, and reduce IgA production. Deletion of CH25H gene in mouse is shown to increase in serum IgA. In testis tissue, production of 25-hydroxycholesterol by macrophages may play a role in Leydig cell differentiation. (Ref.: Bauman, DR., et al. (2009). Proc. Natl. Acad. Sci. USA. 106(39), 16764-16769).