Cell surface heparan sulfate proteoglycans are composed of a membrane-associated protein core substituted with a
variable number of heparan sulfate chains.
Perlecan, a ubiquitous heparan sulfate proteoglycan, possesses angiogenic and growth-promoting attributes primarily by
acting as a coreceptor for basic fibroblast growth factor, FGF2.
NCBI Summary:
This gene encodes the perlecan protein, which consists of a core protein to which three long chains of glycosaminoglycans (heparan sulfate or chondroitin sulfate) are attached. The perlecan protein is a large multidomain proteoglycan that binds to and cross-links many extracellular matrix components and cell-surface molecules. It has been shown that this protein interacts with laminin, prolargin, collagen type IV, FGFBP1, FBLN2, FGF7 and transthyretin, etc., and it plays essential roles in multiple biological activities. Perlecan is a key component of the vascular extracellular matrix, where it helps to maintain the endothelial barrier function. It is a potent inhibitor of smooth muscle cell proliferation and is thus thought to help maintain vascular homeostasis. It can also promote growth factor (e.g., FGF2) activity and thus stimulate endothelial growth and re-generation. It is a major component of basement membranes, where it is involved in the stabilization of other molecules as well as being involved with glomerular permeability to macromolecules and cell adhesion. Mutations in this gene cause Schwartz-Jampel syndrome type 1, Silverman-Handmaker type of dyssegmental dysplasia, and tardive dyskinesia. Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, May 2014]
What maintains the high intra-follicular estradiol concentration in pre-ovulatory follicles? Bentov Y et al. (2015) The purpose of the study was to establish the mechanism by which the estrogen concentration difference between the follicular fluid and the serum is maintained. We used dialysis membrane with a pore size of <3 KD to characterize the estrogen-binding capacity of the follicular fluid. We performed PCR, western blot, and ELISA on luteinized granulosa cells to determine if sex hormone-binding globulin (SHBG) is produced by granulosa cells, and finally we used affinity columns and mass spectrometry to identify the estrogen-binding protein in the follicular fluid. We found that a significant estrogen concentration difference is maintained in a cell-free system and is lost with proteolysis of the follicular fluid proteins. Luteinized granulosa cells are likely not a source of SHBG, as we were not able to detect expression of SHBG in these cells. Perlecan was the most highly enriched follicular fluid protein in the affinity columns. We were able to identify perlecan as the most likely candidate for the major estrogen-binding protein in the follicular fluid.//////////////////
Princivalle M, et al 2001 reported anticoagulant heparan sulfate proteoglycans expression in the rat ovary peaks in preovulatory granulosa cells.
Ovarian granulosa cells synthesize anticoagulant heparan sulfate proteoglycans (aHSPGs), which bind and activate antithrombin III. To determine if aHSPGs
could contribute to the control of proteolytic activities involved in
follicular development and ovulation, the authors studied the pattern of expression of these proteoglycans during the ovarian cycle. aHSPGs were localized on cells
and tissues by I-125-labeled antithrombin III binding followed by microscopic
autoradiography. Localization of aHSPCs has shown that cultured granulosa
cells, hormonally stimulated by gonadotropins to differentiate in vitro,
up-regulate their synthesis and release of aHSPGs. In vivo, during
gonadotropin-stimulated cycle, aHSPGs are present on granulosa cells of antral
follicles and are strongly labeled in preovulatory follicles. These data
demonstrate that aHSPG expression in the ovarian follicle is hormonally
induced to culminate in preovulatory follicles. Moreover, five heparan sulfate core proteins mRNA (perlecan; syndecan-1, -2, and -4; and
glypican-1) are synthesized by granulosa cells, providing attachment for
anticoagulant heparan sulfate chains on the cell surface and in the
extracellular matrix. These core proteins are constantly expressed during the
cycle, indicating that modulations of aHSPG levels observed in the ovary are
likely controlled at the level of the biosynthesis of anticoagulant heparan
sulfate glycosaminoglycan chains. This expression pattern enables aHSPGs to
focus serine protease inhibitors in the developing follicle to control
proteolysis and fibrin formation at ovulation.(Kokia et al. (1993) studied the cellular accumulation and secretion of heparan sulfate (HS) as well as dermatan sulfate (DS) and hyaluronic acid (HA) in response to IL-1beta. The secretion of all 3 substances were increase by IL-1beta, an effect which was significantly enhanced by granulosa-theca cell-cell interaction. The intracellular accumulation however was noted only for DS and HA but not for HS.
Human follicular fluid heparan sulfate contains abundant 3-O-sufated chains with anticoagulant activity. de Agostini AI et al. Anticoagulant heparan sulfate proteoglycans bind and activate antithrombin by virtue of their specific 3-O-sulfated pentasaccharide binding site. They have been detected in the vascular wall but also in extravascular tissues such as the ovary and their function in these compartments remains unknown. The rupture of the ovarian follicle at ovulation is one of the most striking examples of tissue remodelling in adult mammals. It involves tightly controlled inflammation, proteolysis and fibrin deposition. We hypothesized that ovarian heparan sulfates could contribute to modulate these processes through interactions with effector proteins. Previous work has shown that anticoagulant heparan sulfates are synthesized by rodent ovarian granulosa cells and we have set out to characterize heparan sulfates from human follicular fluid. We report the first anticoagulant heparan sulfate from a natural human extravascular source, the purification of human follicular fluid heparan sulfate chains of a modal Mr of 30,000 Da. These chains were fractionated according to their affinity for antithrombin and their structure analyzed by 1H-NMR and MS/MS. The results show that human follicular fluid is a rich source of anticoagulant heparan sulfate. It contains about 6% 3-O-sulfated glucosamines and 50.4% of these chains bind antithrombin and have anticoagulant activity of 2.5 IU/ml of human follicular fluid with a specific anti-Factor Xa activity of this purified compound of 167 IU/mg. The high content in 3-O-sulfated glucosamine residues in those heparan sulfate chains that do not bind antithrombin suggests that they may exhibit biological activities through interactions with other proteins.
Expression regulated by
FSH, LH, Growth Factors/ cytokines, IL-1beta
Comment
Ovarian localization
Granulosa, Theca
Comment
Heparan Sulfate Proteoglycans Regulate Responses to Oocyte Paracrine Signals in Ovarian Follicle Morphogenesis. Watson LN et al. In the ovarian follicle, oocyte-secreted factors induce cumulus-specific genes and repress mural granulosa cell specific genes to establish these functionally distinct cell lineages. The mechanism establishing this precise morphogenic pattern of oocyte signaling within the follicle is unknown. The present study investigated a role for heparan sulphate proteoglycans (HSPG) as coreceptors mediating oocyte secreted factor signaling. In vitro maturation of cumulus oocyte complexes in the presence of exogenous heparin, which antagonizes HSPG signaling, prevented cumulus expansion and blocked the induction of cumulus-specific matrix genes, Has2 and Tnfaip6, whereas conversely, the mural granulosa-specific genes, Lhcgr and Cyp11a1, were strongly up-regulated. Heparin also blocked phosphorylation of SMAD2. Exogenous growth differentiation factor (GDF)-9 reversed these heparin effects; furthermore, GDF9 strongly bound to heparin sepharose. These observations indicate that heparin binds endogenous GDF9 and disrupts interaction with heparan sulphate proteoglycan coreceptor(s), important for GDF9 signaling. The expression of candidate HSPG coreceptors, Syndecan 1-4, Glypican 1-6, and Betaglycan, was examined. An ovulatory dose of human chorionic gonadotropin down-regulated Betaglycan in cumulus cells, and this regulation required GDF9 activity; conversely, Betaglycan was significantly increased in luteinizing mural granulosa cells. Human chorionic gonadotropin caused very strong induction of Syndecan 1 and Syndecan 4 in mural granulosa as well as cumulus cells. Glypican 1 was selectively induced in cumulus cells, and this expression appeared dependent on GDF9 action. These data suggest that HSPG play an essential role in GDF9 signaling and are involved in the patterning of oocyte signaling and cumulus cell function in the periovulatory follicle.
Extracellular matrices of the avian ovarian follicle: Molecular characterization of chicken perlecan Hummel S, et al 2004 .
In egg-laying species, such as the chicken, the mode of transport of lipoprotein particles from the capillary plasma to endocytic receptors on the oocyte surface is largely unknown. Here the authors show by molecular characterization that the large prominent heparan sulfate proteoglycan of extracellular matrices, termed perlecan or HSPG2 (the product of the hspg2 gene), is a component of ovarian follicles that may participate in this process. However, while normally a major HSPG of basement membranes or basal laminae, in chicken follicles perlecan is absent from the membraneous structure between the theca interna and granulosa cell layers, which to date has been considered a bona-fide basement membrane. Rather, the protein is localized in the extracellular matrix of theca externa cells, which produce this HSPG. Furthermore, in chicken testes, perlecan is localized in the peritubular spaces, but in less organized fashion than the classical basement membrane components, agrin and laminin. All five domains and structural hallmarks of chicken perlecan (4071 residues) have been conserved in its mammalian counterparts. We have produced the recombinant domain II (containing LDL-receptor-like binding repeats) of chicken perlecan and demonstrate its capacity to bind LDL and VLDL, apolipoprotein B-containing lipoproteins ultimately destined for uptake into oocytes via members of the low density lipoprotein receptor family. Binding to perlecan heparan sulfate side chains may facilitate the interaction of lipoproteins with domain II. Based on the current results and on domain-domain interactions revealed by recent ultrastructural investigations of the LDL receptor, nidogen, and laminin (Rudenko, G., Henry, L., Henderson, K., Ichtchenko, K., Brown, M. S., Goldstein, J. L. and Deisenhofer, J. (2002) Science 298, 2353-2358; and Takagi, J., Yang, Y., Liu, J. H., Wang, J. H., and Springer, T. A. (2003) Nature 424, 969-974), we propose a novel role of perlecan in mediating plasma-to-oocyte surface transport of VLDL particles.
Follicle stages
Antral, Preovulatory
Comment
Princivalle M, et al. (Glycobiology. 2001) aHSPGs were localized on cells and tissues by (125)I-labeled antithrombin III binding followed by microscopic autoradiography. Localization of aHSPGs has shown that cultured granulosa cells, hormonally stimulated by gonadotropins to differentiate in vitro, up-regulate their synthesis and release of aHSPGS: In vivo, during gonadotropin-stimulated cycle, aHSPGs are present on granulosa cells of antral follicles and are strongly labeled in preovulatory follicles. These data demonstrate that aHSPG expression in the ovarian follicle is hormonally induced to culminate in preovulatory follicles. Moreover, we have shown that five heparan sulfate core proteins mRNA (perlecan; syndecan-1, -2, and -4; and glypican-1) are synthesized by granulosa cells, providing attachment for anticoagulant heparan sulfate chains on the cell surface and in the extracellular matrix. These core proteins are constantly expressed during the cycle, indicating that modulations of aHSPG levels observed in the ovary are likely controlled at the level of the biosynthesis of anticoagulant heparan sulfate glycosaminoglycan chains. This expression pattern enables aHSPGs to focus serine protease inhibitors in the developing follicle to control proteolysis and fibrin formation at ovulation.