Sulfated glycoprotein-2 (SGP-2) is the major secreted product of Sertoli cells and probably plays a critical role in
spermatogenesis. Murphy et al. (1988) described a novel serum protein, SP-40,40, using a series of monoclonal
antibodies directed to the immune deposit-containing glomerular basement membranes of a patient with membranous
glomerulonephritis. The protein was shown to be a normal constituent of human blood. It consists of two 40-kD chains,
alpha and beta, covalently joined by disulfide bonds. They established that SP-40,40 is a member of the human
complement system by directly demonstrating its presence within the S-protein-containing soluble variant of the C5b-9
complex, SC5b-9. Sp-40,40 is also called complement lysis inhibitor. It acts as a control mechanism of the complement
cascade; specifically, it prevents the binding of a C5b-C7 complex to the membrane of the target cell and in this way
inhibits complement-mediated cytolysis. Kirszbaum et al. (1989) document a
link between the immune and reproductive systems. Cloning and sequencing of cDNA corresponding to the SP-40,40
protein from a human liver library showed strong sequence homology with a rat Sertoli cell product, sulfated
glycoprotein-2, also known as clusterin. SP-40,40 was also demonstrated in human seminal plasma; for this reason the
term clusterin is used for the protein in both human serum and seminal fluid.
NCBI Summary:
The protein encoded by this gene is a secreted chaperone that can under some stress conditions also be found in the cell cytosol. It has been suggested to be involved in several basic biological events such as cell death, tumor progression, and neurodegenerative disorders. Alternate splicing results in both coding and non-coding variants.[provided by RefSeq, May 2011]
General function
Cell death/survival, Anti-apoptotic, Apoptosis
Comment
Cellular localization
Secreted, Cytoplasmic
Comment
Ovarian function
Follicle atresia, Luteolysis
Comment
A Role for H2O2 and TRPM2 in the Induction of Cell Death: Studies in KGN Cells. Hack CT et al. (2019) Recent studies showed that KGN cells, derived from a human granulosa cell tumor (GCT), express NADPH oxidase 4 (NOX4), an important source of H2O2. Transient receptor potential melastatin 2 (TRPM2) channel is a Ca2+ permeable cation channel that can be activated by H2O2 and plays an important role in cellular functions. It is also able to promote susceptibility to cell death. We studied expression and functionality of TRPM2 in KGN cells and examined GCT tissue microarrays (TMAs) to explore in vivo relevance. We employed live cell, calcium and mitochondrial imaging, viability assays, fluorescence activated cell sorting (FACS) analysis, Western blotting and immunohistochemistry. We confirmed that KGN cells produce H2O2 and found that they express functional TRPM2. H2O2 increased intracellular Ca2+ levels and N-(p-Amylcinnamoyl)anthranilic acid (ACA), a TRPM2 inhibitor, blocked this action. H2O2 caused mitochondrial fragmentation and apoptotic cell death, which could be attenuated by a scavenger (Trolox). Immunohistochemistry showed parallel expression of NOX4 and TRPM2 in all 73 tumor samples examined. The results suggest that GCTs can be endowed with a system that may convey susceptibility to cell death. If so, induction of oxidative stress may be beneficial in GCT therapy. Our results also imply a therapeutic potential for TRPM2 as a drug target in GCTs.//////////////////Transient receptor potential melastatin 2 ion channel activity in ovarian hyperstimulation syndrome physiopathology. Şanli C et al. (2020) Ovarian hyperstimulation syndrome (OHSS) is a complication of ovarian stimulation with increased vascular endothelial growth factor (VEGF) and vascular permeability in ovarian tissue. Transient receptor potential melastatin 2 (TRPM2) is known to be associated with angiogenesis and vascular permeability. In this experimental study, we aimed to investigate the activity of TRPM2 in the development of OHSS. Fourteen immature female rats were divided into two groups. Group 1 was the control group, and Group 2 was the OHSS group which was exposed to 10 IU of subcutaneous application of FSH for four days and 30 IU of human chorionic gonadotropin (hCG) on 5th day. At the end of the experiment, the ovaries were removed. The right ovarian tissues were stored in 10% formol for histopathological and immunohistochemical examination. The left ovarian tissues were stored at ?80°C for biochemical examinations. VEGF, tumor necrosis factor-alpha (TNF??) and malondialdehyde (MDA) levels were measured in the ovarian tissue. Congestion, edema, apoptosis and TRPM2 immunoreactivity were evaluated. There was a significant increase in ovarian weight in the OHSS group compared to the control group. There was a significant increase in congestion, edema, apoptosis and TRPM2 immunoreactivity in the OHSS group. A significant increase in tissue levels of VEGF, TNF?? and MDA was also found in the OHSS group compared to the control group. As a result of our experiment, Increased TRPM2 immunoreactivity on hyperstimulated rat ovary may be the reason or result of edema and congestion. Further studies are needed to discuss our results.//////////////////
Zwain I, et al 2000 reported that clusterin protects granulosa cells from apoptotic cell death
during follicular atresia.
Clusterin expression in the healthy and
atretic follicles was examined by immunohistochemical and Western blot
analyses, and gene expression was examined by Northen blot analysis. Clusterin
protein and its mRNA are only expressed in granulosa cells of atretic follicles obtained from PMSG-treated rats on day 5 of the treatment. Healthy
follicles from PMSG-treated rats on day 2 of the treatment do not express
clusterin. Theca and stroma cells of both healthy and atretic follicles showed
no signs of apoptosis and did not express clusterin. Withdrawal of trophic
support from granulosa cells in cultures to induce apoptosis resulted in a
dramatic increase in the levels of clusterin and its mRNA compared to cells
cultured in serum-supplemented medium.
Treatment of granulosa cells with the antisense oligonucleotide resulted in an
increase in the apoptotic cell death compared to the control. These findings
indicate that depletion of clusterin can lead to the programmed cell death in
ovary, suggesting a functional role for this protein in follicular atresia.
Hurwitz A et al reported the atresia-associated increase in the
ovarian expression of the putative apoptotic marker sulfated glycoprotein-2.
Expression regulated by
FSH, LH
Comment
Kaynard AH, et al reported that ovarian 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and sulfated
glycoprotein-2 gene expression are differentially regulated by the
induction of ovulation, pseudopregnancy, and luteolysis in the
immature rat.
PMSG treatment alone
(48 h), and in combination with hCG, dramatically reduced SGP-2 mRNA to
12-27% of controls . SGP-2 levels were not elevated until 7
days after hCG; levels then remained constant through day 14 of pseudopregnancy.
Since luteal progesterone secretion begins to diminish 5-7 days after hCG, the
increased expression of SGP-2 on day 7 may be related to the initiation of the
regression/degeneration of luteal cells which occurs during luteolysis. Thus, alterations in SGP-2 expression by the ovary may precede
or occur simultaneously with cellular events initiating luteolysis and suggests a
role for this glycoprotein as an early marker for luteolysis and implicates it in yet
another instance of programmed cell death.
Ovarian localization
Granulosa, Luteal cells, Follicular Fluid
Comment
Proteome mining of human follicular fluid reveals a crutial role of complement cascade and key biological pathways in women undergoing in vitro fertilisation. Jarkovska K et al. In vitro fertilisation (IVF) is fraught with problems and currently proteomics approaches are being tried out to examine the microenvironment of the follicle in order to assess biological and immunological parameters that may affect its development. Additionaly, better understanding of reproductive process may help increase IVF birth rate per embryo transfer and at the same time avoid spontaneous miscarriages or life threatening conditions such as ovarian hyperstimulation syndrom. The primary aim of this study was to search for specific differences in protein composition of human follicular fluid (HFF) and plasma in order to identify proteins that accumulate or are absent in HFF. Depletion of abundant proteins combined with multi-dimensional protein fractionation allowed the study of middle and lower abundant proteins. Paired comparison study examining HFF with plasma/serum from women undergoing successful IVF revealed important differences in the protein composition which may improve our knowledge of the follicular microenvironment and its biological role. This study showed involvement of innate immune function of complement cascade in HFF. Complement inhibition and the presence of C-terminal fragment of perlecan suggested possible links to angiogenesis which is a vital process in folliculogenesis and placental development. Differences in proteins associated with blood coagulation were also found in the follicular milieu. Several specific proteins were observed, many of which have not yet been associated with follicle/oocyte maturation. These proteins together with their regulatory pathways may play a vital role in the reproductive process. Clusterin levels in FF is 2.7 fold higher than plasma.
Mahon MG, et al reported the multiple involvement of clusterin in chicken ovarian follicle
development and its binding to two oocyte-specific members of the low density lipoprotein receptor gene family.
In contrast to
mammalian clusterin, the chicken protein appears not to be cleaved intracellularly
into a disulfide-linked heterodimer; possibly as a consequence thereof, it is not
secreted constitutively and is absent from the circulation, where most of clusterin
is found in mammals. In the ovary, clusterin is a major product of the somatic
granulosa cells, in a pattern correlating with the developmental phases of
individual follicles. In that, transcript levels are high not only at onset of vitellogenesis, but also in atretic follicles and in the postovulatory follicle sac,
i.e. in situations characterized by apoptotic events. Yolk of growing oocytes
contains a 43-kDa truncated form of clusterin that does not appear to be
synthesized within the oocyte. 70-kDa
clusterin interacts not only with megalin, but also with two chicken
oocyte-specific members of the low density lipoprotein receptor (LDLR) gene
family. These receptors, termed LDLR-related protein with eight ligand binding
repeats (LR8) and LDLR-related protein (380 kDa), likely internalize granulosa
cell-derived 70-kDa clusterin, which may subsequently be processed to the
43-kDa product. Thus, chicken clusterin could serve as a marker for follicular
atresia and resorption, and, may serve as carrier for the receptor-mediated endocytosis into oocytes of
components important for embryonic development.
Changes in mouse granulosa cell gene expression during early luteinization. McRae RS et al. Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.
Follicle stages
Antral, Corpus luteum
Comment
Analysis of gene expression in non-regressed and regressed bovine corpus luteum tissue using a customized ovarian cDNA array Casey OM, et al .
The lifespan of the bovine corpus luteum (CL) is an important factor in the control of normal ovarian cyclicity and the establishment and maintenance of pregnancy. There is increasing evidence that CL lifespan is regulated by alternative expression of genes that promote or inhibit luteolysis. To gain further insights into these events a 434 character ovarian cDNA array comprising genes attributed to key aspects of CL function including more than 100 anonymous expressed sequence tags (ESTs) was constructed and screened with alpha(33)P dATP labeled RNA isolated from non-regressed (n=6) and regressed (n=6) CL tissue. Significance analysis of microarrays (SAM) identified 15 genes that changed expression 1.7-fold or more with a false discovery rate of <5%. The differentially expressed genes encoded enzymes involved in steroid biosynthesis and oxygen radical metabolism and proteins involved in extracellular matrix remodeling, apoptosis and cell structure. Results for five of the differentially expressed genes including matrix gla protein and collagen alpha1(I) (extracellular matrix), glutathione-S-transferase alphaI (oxygen metabolism), clusterin (apoptosis) and scavenger receptor BI (steroid biosynthesis) were confirmed by Northern blot analysis and found to be significantly different (P<0.01) between non-regressed and regressed CL tissue. Collectively this study identified genes with recognized roles in CL regression, genes with potential roles in this process and genes whose function have yet to be defined in this event.