The vitamin A derivative retinoic acid is known to be a potent agent for control of differentiation and proliferation of
epithelial cells and to exert profound effects on pattern formation during embryogenesis. Its action at the molecular level
appears to be mediated by two distinct classes of proteins: a family of nuclear receptors that regulates gene
transcription in a ligand-dependent fashion and a small cellular retinoic acid-binding protein (CRABP) for which a
precise function remains to be elucidated. Giguere, V et al described the identification (by molecular cloning of its cDNA) of an isoform of CRABP, referred to as CRABP-II, expressed at high levels during mouse embryogenesis and in
adult skin.
NCBI Summary:
A number of specific carrier proteins for members of the vitamin A family have been discovered. Cellular retinoic acid binding proteins (CRABP) are low molecular weight proteins whose precise function remains unknown. The inducibility of the CRABP2 gene suggests that this isoform is important in retinoic acid-mediated regulation of human skin growth and differentiation. It has been postulated that the CRABP2 gene is transcriptionally regulated by a newly synthesized regulatory protein. [provided by RefSeq]
General function
Receptor, Intracellular signaling cascade
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Cellular localization
Cytoplasmic
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Ovarian function
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Expression regulated by
FSH
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Zheng WL et al reported that induction of pseudopregnancy by the injection of eCG in rats results in the appearance of cellular
retinoic acid-binding protein type II (CRABP[II]) in the granulosa cells of the ovary. Granulosa cells from the ovary of the eCG-treated immature rat and luteal
cells from the ovary of the eCG/hCG-treated immature rat (both of which express CRABP[II])
synthesized markedly higher amounts of retinoic acid when cultured, compared to granulosa cells
cultured from the ovary of the prepubertal rat treated with control vehicle. These
data are consistent with the hypothesis that CRABP(II) expression is associated with retinoic acid
synthesis.
Ovarian localization
Oocyte, Cumulus, Granulosa, Luteal cells
Comment
Bucco RA, et al. reported inducible expression of cellular retinoic acid-binding protein II in rat ovary.
The pattern of rat CRABP(II) messenger RNA and protein
expression correlated with the appearance of corpora lutea and the rise in progesterone production as the
corpora lutea developed, and was similar to the induction of 3 beta-hydroxysteroid dehydrogenase.
Immunohistochemical localization revealed that CRABP(II) appeared in luteal cells and was
dramatically restricted to their cytoplasmic compartment, with no apparent presence in the nucleus. They
suggest that CRABP(II) may be expressed to restrict retinoic acid from occupying nuclear retinoic acid
receptors, implying that the differentiation and maintenance of the rat corpus luteum may involve in part a
release of certain pathways from retinoid suppression.