Molecular characterization of a mouse short chain dehydrogenase/reductase active with all-trans-retinol in intact cells, mRDH1.

Min Zhang,Joseph L Napoli,Susan M Smith,Weiguo Chen

doi:10.1074/jbc.m105748200

Abstract

Metabolic activation of retinol (vitamin A) via sequential actions of retinol and retinal dehydrogenases produces the active metabolite all-trans-retinoic acid. This work reports cDNA cloning, enzymatic characterization, function in a reconstituted path of all-trans-retinoic acid biosynthesis in cell culture, and mRNA expression patterns in adult tissues and embryos of a mouse retinol dehydrogenase, RDH1. RDH1 represents a new member of the short chain dehydrogenase/reductase superfamily that differs from other mouse RDH in relative activity with all-trans and cis-retinols. RDH1 has a multifunctional catalytic nature, as do other short chain dehydrogenase/reductases. In addition to retinol dehydrogenase activity, RDH1 has strong 3alpha-hydroxy and weak 17beta-hydroxy steroid dehydrogenase activities. RDH1 has widespread and intense mRNA expression in tissues of embryonic and adult mice. The mouse embryo expresses RDH1 as early as 7.0 days post-coitus, and expression is especially intense within the neural tube, gut, and neural crest at embryo day 10.5. Cells cotransfected with RDH1 and any one of three retinal dehydrogenase isozymes synthesize all-trans-retinoic acid from retinol, demonstrating that RDH1contributes to a path of all-trans-retinoic acid biosynthesis in intact cells. These characteristics are consistent with RDH1 functioning in a path of all-trans-retinoic acid biosynthesis starting early during embryogenesis.

Highlights

Occurring retinoids function beyond their well known contributions to vision, conception, growth, and epithelial differentiation
CDNA Cloning—To obtain mouse Retinol Dehydrogenase Type 1 (RDH1), degenerate reverse transcription-PCR was done with mRNA from e17 mice
Concluding Summary—This report identifies the first alltrans-retinol RDH/SDR candidate in the mouse and suggests that mouse and rat may differ in the initial step of RA biosynthesis from retinol

Summary

Introduction

Occurring retinoids (vitamin A and its metabolites) function beyond their well known contributions to vision, conception, growth, and epithelial differentiation. The medium chain dehydrogenases, ADH classes I and IV, convert retinol into retinal in vitro These enzymes belong to a family that largely detoxifies xenobiotics and have kinetic characteristics more consistent with xenobiotic clearance than for producing endocrine factors [13]. ADHIV is expressed episodically during mouse embryogenesis; it is notably absent at various loci and times of atRA need These considerations indicate that ADH1 and ADHIV do not function universally to generate endocrine levels of atRA. Pursuit of universal RDH candidates has identified several previously unknown members of the SDR superfamily [11] This phylogenetically diverse enzyme family consists of numerous mammalian members that regulate the concentrations of estrogens, androgens, glucocorticoids, and prostaglandins [16]. As for retinoid-specific receptors and binding proteins, an RDH physiologically significant in atRA biosynthesis should be

Methods

Results

Conclusion