The WNT signaling cascade is involved in regulation of cytoskeletal rearrangements, apoptosis, and
proliferation. WNT-mediated simulation of 'frizzled' receptors (e.g., FZD2; OMIM 600667) can activate the beta-catenin
(CTNNB1; OMIM 116806) pathway, mitogen-activated protein kinase (MAPK) cascades, and G protein-dependent pathways. The
signaling function of the WNT/frizzled pathway is antagonized by secreted frizzled-related proteins ,
which bind to either WNTs or frizzled receptors. Frizzled-related proteins contain a
cysteine-rich domain of approximately 110 residues that is 30 to 40% identical to the putative ligand-binding domain
of FZ proteins, but lacks the 7-transmembrane motif that anchors FZ proteins to the plasma membrane.
Secreted frizzled-related protein 1 (SFRP1) is a member of the SFRP family that contains a cysteine-rich domain homologous to the putative Wnt-binding site of Frizzled proteins. SFRPs act as soluble modulators of Wnt signaling. SFRP1 and SFRP5 may be involved in determining the polarity of photoreceptor cells in the retina. SFRP1 is expressed in several human tissues, with the highest levels in heart.
Extracellular binding protein
Expression regulated by
Theca, Stromal cells
Jabara S, et al 2003 reported stromal cells of the human postmenopausal ovary display a
distinctive biochemical and molecular phenotype.
The stroma of the human postmenopausal ovary is postulated to produce androgens,
but evidence for and against this idea exits in the literature. The purpose of this study
was to determine whether key steroidogenic enzymes involved in androgen synthesis
are expressed in the postmenopausal ovarian stroma. Stromal cells were isolated
from postmenopausal ovaries and expression for genes involved in steroidogenesis
[steroidogenic acute regulatory protein (StAR), P450scc, 3beta-hydroxysteroid
dehydrogenase (3beta-HSD) P450c17, and P450c27] as well as for several growth
factor binding proteins [gremlin, IGF binding protein-4, follistatin, and secreted
frizzled-related protein (sFRP)-1 and -4], were compared with cultured human theca
cells and dermal fibroblasts. Follistatin, gremlin, IGF
binding protein-4, and sFRP-1 and -4 transcripts were detected in the stromal cells in
relative amounts significantly higher than theca cells, but not significantly different
from fibroblasts, except for sFRP-1, which was significantly higher in stromal cells.
The observations demonstrate that stromal cells of the postmenopausal ovary have a
signature biochemical and molecular phenotype that can be distinguished from