CD44, a receptor for hyaluronate, is an integral cell membrane glycoprotein with a postulated role in matrix adhesion lymphocyte activation and lymph node homing. Aruffo et al. (1990) demonstrated that CD44 is the main cell surface receptor for hyaluronate. Upstream of Hippo signaling. CD44 promotes cell to cell contact inhibition by inactivating merlin.//////CD44 acts through RhoA to regulate YAP signaling. Zhang Y 2014 et al.
The Hippo pathway plays an important role in both physical and pathogenesis processes. As crucial downstream effectors of Hippo pathway, YAP is inhibited by Lats1/2 through phosphorylation. However, upstream signals that regulate the Hippo pathway have been still poorly understood. Here, we found that knockdown of CD44 reduced YAP expression and nuclear localization, but nearly had no effect on its upstream effectors, Mst1 and Lats1. Downregulated CD44 expression also significantly decreased the expression of YAP downstream effectors CTGF, Cyr61 and EDN1 at mRNA level. Our next study showed that knockdown of CD44 inhibited RhoA expression, which was consistent with RhoA knockdown mediated YAP downregulation. Furthermore, we demonstrated that over expression of the constitutively active RhoA (RhoA-V14) could block the YAP expression decrease mediated by CD44 knockdown. Moreover, downregulation of CD44 significantly promoted cell apoptosis and inhibited cell proliferation, cell cycle progression and migration, which were consistent with the effects of RNAi-mediated YAP knockdown in both A549 and HepG2 cells. Overall, data are presented showing that CD44 could act through RhoA signaling to regulate YAP expression and this study also provide new insights into the regulatory mechanisms of the Hippo-YAP pathway.
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Adhesion glycoprotein CD44 functions as an upstream regulator of a network connecting ERK, AKT and Hippo-YAP pathways in cancer progression. Yu S et al. (2015) Targeted therapies are considered to be the future of cancer treatment. However, the mechanism through which intracellular signaling pathways coordinate to modulate oncogenesis remains to be elucidated. In this study, we describe a novel crosstalk among ERK, AKT and Hippo-YAP pathways, with CD44 as an upstream regulator. High cell density leads to activation of ERK and AKT but inactivation of YAP in cancer cells. CD44 modulates cell proliferation and cell cycle but not apoptosis. The expression and activity of cell cycle genes were cooperatively regulated by ERK, AKT and Hippo-YAP signaling pathways through CD44-mediated mechanisms. In addition, CD44 depletion abrogates cancer stem cell properties of tumor initiating cells. Taken together, we described a paradigm where CD44 functions as an upstream regulator sensing the extracellular environment to modulate ERK, AKT and Hippo-YAP pathways which cooperatively control downstream gene expression to modulate cell contact inhibition of proliferation, cell cycle progression and maintenance of tumor initiating cells. Our current study provides valuable information to design targeted therapeutic strategies in cancers.//////////////////upstream of Hippo signaling
NCBI Summary:
The protein encoded by this gene is a cell-surface glycoprotein involved in cell-cell interactions, cell adhesion and migration. It is a receptor for hyaluronic acid (HA) and can also interact with other ligands, such as osteopontin, collagens, and matrix metalloproteinases (MMPs). This protein participates in a wide variety of cellular functions including lymphocyte activation, recirculation and homing, hematopoiesis, and tumor metastasis. Transcripts for this gene undergo complex alternative splicing that results in many functionally distinct isoforms, however, the full length nature of some of these variants has not been determined. Alternative splicing is the basis for the structural and functional diversity of this protein, and may be related to tumor metastasis. [provided by RefSeq, Jul 2008]
Induction of Oocyte Maturation by Hyaluronan-CD44 Interaction in Pigs. Yokoo M et al. In most mammals, the oocyte is surrounded with compact multilayers of cumulus cells; these form cumulus-oocyte complexes (COCs). During oocyte maturation, the COCs dramatically expand and this is termed 'cumulus expansion'. We have previously demonstrated that cumulus expansion is the result of hyaluronan synthesis and accumulation in the extracellular space between cumulus cells in the COCs and that hyaluronan accumulation within the COCs affects oocyte maturation. We have also demonstrated that CD44, the principal hyaluronan receptor, is expressed in the COCs during cumulus expansion and that the interaction between hyaluronan and CD44 appears to be closely related to gap junctional communication of the COCs during the process of meiotic resumption. Based on our previous studies, we review herein that the physiological significance and the molecular mechanism of cumulus expansion for porcine oocyte maturation.
Kaneko T, et al 2000 reported that hyaluronic acid (HA) inhibits apoptosis in granulosa cells via CD44.
Mural and cumulus granulosa cells were obtained from in vitro
fertilization patients. The cells were cultured with various concentrations of
HA or HA pills various concentrations of anti-CD44 antibody without serum
supplement. After 24 hr of culture, the cells were fixed and stained with
Hoechst 33258. One thousand granulosa cells of each conditions were observed
by fluorescence microscopy.
HA inhibited apoptosis in both kinds of granulosa cells, and
anti-CD44 antibody prevented this effect of HA.
Expression and Glycosylation with Polylactosamine of CD44 Antigen on Macrophages During Follicular Atresia in Pig Ovaries Miyake Y, et al .
Macrophages are essential in cleaning up apoptotic debris during follicular atresia. However, the key factors of this process are still unclear. In the present study, we evaluated CD44 mRNA, CD44 protein, and CD44 antigen glycosylation on macrophages during follicular atresia in the pig. Atresia was classified into five stages; stage I, healthy follicles; stage II, early atretic follicles having apoptotic granulosa cells with an unclear basement membrane; stage III, progressing atretic follicles having apoptotic granulosa cells completely diffused from the basement membrane; stage IV, late atretic follicles with increasing lysosomal activity; stage V, disintegrated atretic follicles having collapsed theca cells and strong lysosomal activity. Immunohistological analysis showed that macrophages expressing CD44 invaded the inside of stage III follicles accompanied by a collapse of basement membrane. Semi-quantitative RT-PCR showed that only mRNA of the CD44 standard isoform (CD44s) was present in inner cells of follicles, but not any CD44 variant isoform (CD44v) mRNAs. The amount of CD44s mRNA was increased at stage III. Western blot and lectin blot analyses showed that CD44 was markedly expressed at stage III and glycosylated with polylactosamine at the same time. After macrophages invaded atretic follicles at stages III-V, the CD44 expressed on macrophages was glycosylated with polylactosamine. The lysosomal activity began to increase at stage IV, and reached the highest level at stage V. Increased CD44s protein and posttranslational modification of CD44 with polylactosamine on macrophages from stage III could be involved in the cleaning up apoptotic granulosa cells.
Identification of Potential Markers of Oocyte Competence Expressed in Bovine Cumulus Cells Matured with Follicle-Stimulating Hormone and/or Phorbol Myristate Acetate In Vitro. Assidi M et al. Oocyte competence is the ability of the oocyte to complete maturation, undergo successful fertilization and reach the blastocyst stage. Cumulus cells are indispensable for this process. Their removal significantly affects the blastocyst rates. Moreover, the properties and functions of cumulus cells are regulated by the oocyte. They also reflect the oocyte's degree of maturation. Our study was aimed at identifying markers of oocyte competence that are expressed in bovine cumulus cells. In a previous study in our laboratory, the blastocyst yield following FSH or phorbol myristate acetate (PMA) treatment was 45%. Therefore, we tested four sets of conditions during the first 6 hrs of in vitro maturation (IVM): FSH (0.1 microg/ml), PMA (0.1 microM), FSH+PMA and negative control. Extracts from each IVM treatment were hybridized against the same negative control on a microarray containing partial library of differentially expressed transcripts in the cumulus of competent oocytes collected at 6 hrs post-LH in vivo. Common positive clones between diffentially-treated cells were selected and 15 candidates were validated by real time PCR. Based on this, the main candidates expressed in cumulus cells and that could be valuable and indirect markers of oocyte competence are hyaluronan synthase 2 (HAS2), inhibin betaA (INHBA), epidermal growth factor receptor (EGFR), gremlin 1 (GREM1), betacellulin (BTC), CD44, tumor necrosis factor-induced protein 6 (TNFAIP6) and prostaglandin-endoperoxide synthase 2 (PTGS2). These biomarkers could be potential candidates to predict oocyte competence and to select higher quality embryos for transfer. Additionally, these indirect predictors of oocyte competence and follicular health could improve our knowledge of gene expression patterns in the cumulus and yield insights into the molecular pathways controlling oocyte competence.
Expression regulated by
LH
Comment
Ovarian localization
Oocyte, Cumulus, Granulosa, macrophage
Comment
CD44, a polymorphic and polyfunctional transmembrane glycoprotein widely expressed in many types of cells, was found to be expressed in human membrana granulosa (Ohta et al., 1999). Using confocal laser scanning microscopy with the mouse monoclonal antibody to human CD44, cells immunoreactive for CD44 were observed in both cumulus and mural granulosa cell masses.Furnus CC, et al reported that hyaluronic acid receptor (CD44) is expressed in bovine oocytes and early stage embryos.
Hyaluronic acid (HA) is a high molecular weight polysaccharide found in the extracellular matrix of most animal tissues, that exerts a profound influence on cell behavior. HA is one of the most abundant glycosaminoglycans (GAGs) in the uterine, oviductal and follicular fluids in mouse, pig, human and cattle. CD44, the principal cell membrane receptor for HA, is expressed from the 1- to 8-cell stage in human embryos, during post-implantation mouse embryogenesis and on the surface of differentiated embryonic stem cells. In the present study, we have analyzed by immunofluorescence, whether CD44 is present in bovine oocytes, fertilized oocytes and early stage embryos. Bovine cumulus-oocyte complexes (COCs) were aspirated from follicles (2-5mm) and were selected for IVM and incubated for 24h. Oocytes showing an expanded cumulus (generally 90-95%) were used for IVF. Fertilized oocytes were separated for immunofluorescence assay after 16h of sperm incubation in order to fix the eggs at the pronuclear stage. The embryos were cultured for 8 days and the different stages of development for immunofluorescence assay were separated every 24h of culture. The CD44 receptor was detected at every observation time examined. Fluorescence-tagged HA for the internalization assay was prepared by mixing fluorescein amine, Isomer I and 1mg of HA from umbilical cord. Fluorescence-tagged HA was internalized in 2-, 4-, 8- and 16-cell-stage embryos, morulae and blastocysts. CD44 is expressed on the surface and in the cytoplasm of bovine oocytes and embryos in different stages of development.
////////////Transcriptome Landscape of Human Folliculogenesis Reveals Oocyte and Granulosa Cell Interactions. Zhang Y et al. (2018) The dynamic transcriptional regulation and interactions of human germlines and surrounding somatic cells during folliculogenesis remain unknown. Using RNA sequencing (RNA-seq) analysis of human oocytes and corresponding granulosa cells (GCs) spanning five follicular stages, we revealed unique features in transcriptional machinery, transcription factor networks, and reciprocal interactions in human oocytes and GCs that displayed developmental-stage-specific expression patterns. Notably, we identified specific gene signatures of two cell types in particular developmental stage that may reflect developmental competency and ovarian reserve. Additionally, we uncovered key pathways that may concert germline-somatic interactions and drive the transition of primordial-to-primary follicle, which represents follicle activation. Thus, our work provides key insights into the crucial features of the transcriptional regulation in the stepwise folliculogenesis and offers important clues for improving follicle recruitment in vivo and restoring fully competent oocytes in vitro. most variable genes that contributed to PC1 in GCs were ZEB2, CD44, HSPG2, KDSR, and SRRM3, with ZEB2 and CD44 as the two top variable genes (Figure 1F)./////////////////
Follicle stages
Preovulatory
Comment
Naoko Kimura et al 2002 reported the expression of Hyaluronan Synthases and CD44
Messenger RNAs in Porcine Cumulus-Oocyte
Complexes During In Vitro Maturation.
The transient synthesis and accumulation of hyaluronan (HA), an extracellular matrix component of cumulus cells, brings
about expansion of cumulus-oocyte complexes (COCs) in preovulatory mammalian follicles. In this study, the authors investigated
the mRNA expressions of hyaluronan synthase 2 (has2), hyaluronan synthase 3 (has3), and CD44, as well as the
responsiveness to eCG and porcine follicular fluid (pFF) of these genes, in porcine COCs, oocytectomized complexes
(OXCs), and oocytes during in vitro maturation. Immunolocalization of CD44 was also analyzed in COCs. After 12 h of
culture, the area of cumulus expansion in medium 199 supplemented with both 10 IU/ml eCG and 10% (v/v) pFF was
significantly greater than that in the medium supplemented with eCG or pFF. Oocytectomy reduced the expansion area in the
group supplemented with eCG. In reverse transcription-polymerase chain reaction analysis, all transcripts were identified in
COCs, but has3 transcript was not found in OXCs. Only has3 mRNA was detectable in oocytes, indicating that cumulus cells
express has2 and CD44 mRNAs, and oocytes express has3 mRNA. The expression levels of has2 and CD44 mRNAs in
COCs and OXCs increased in the presence of eCG and pFF after 24 h of culture, suggesting that these genes have a positive
dependency on eCG and pFF. In contrast, the high level of has3 mRNA was detected in COCs cultured in the medium alone.
Oocytectomy slightly reduced the expression level of has2 mRNA. On immunostaining for CD44, CD44 was expressed
apparently in COCs cultured with eCG and pFF for 24 h. The positive staining was distributed on cytoplasm along the
perimembrane of cumulus cells and at the junctions between cumulus cells and oocytes. CD44 was also localized on
cytoplasm of some oocytes. These results indicate that 1) porcine oocytes promote eCG-dependent cumulus expansion and
the expression of has2 mRNA in cumulus cells, but these are not essential for expansion of cumulus cells and the expression
of has2 mRNA; 2) HAS2 is involved in HA synthesis during cumulus expansion, and eCG and pFF up-regulate its
expression; 3) the expression profile of the has3 mRNA that is transcribed in oocytes is different from those of has2 and
CD44 mRNA; and 4) CD44 may participate in the interaction between cumulus cells and oocytes.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: type: null mutation fertility: fertile Comment: CD44 regulates hematopoietic progenitor distribution, granuloma formation, and tumorigenicity. Schmits R et al. (1997) CD44 is expressed in various isoforms on numerous cell types and tissues during embryogenesis and in the mature organism. CD44 may also be involved in tumor growth. To study the multiple roles of CD44, we abolished expression of all known isoforms of CD44 in mice by targeting exons encoding the invariant N-terminus region of the molecule. Surprisingly, mice were born in Mendelian ratio without any obvious developmental or neurological deficits. Hematological impairment was evidenced by altered tissue distribution of myeloid progenitors with increased levels of colony-forming unit-granulocyte-macrophage (CFU-GM) in bone marrow and reduced numbers of CFU-GM in spleen. Fetal liver colony-forming unit-spleen and granulocyte colony-stimulating factor mobilization assays, together with reduced CFU-GM in peripheral blood, suggested that progenitor egress from bone marrow was defective. In what was either a compensatory response to CD44 deficiency or an immunoregulatory defect, mice also developed exaggerated granuloma responses to Cryotosporidium parvum infection. Finally, tumor studies showed that SV40-transformed CD44-deficient fibroblasts were highly tumorigenic in nude mice, whereas reintroduction of CD44s expression into these fibroblasts resulted in a dramatic inhibition of tumor growth.//////////////////