The fibronectin receptor, a member of the integrin family of heterodimeric glycopeptides, mediates the binding of cells
to fibronectin substrata. Argraves et al. (1986) isolated cDNA clones coding for
the alpha subunit from a placental cDNA library. The cDNAs code for 229 amino acids from the C-terminus of the
alpha subunit. The deduced sequence had a hydrophobic region with properties characteristic of a membrane-spanning
domain.
NCBI Summary:
ITGA5 encodes the integrin alpha 5 chain. Integrins are heterodimeric integral membrane proteins composed of an alpha chain and a beta chain. Alpha chain 5 undergoes post-translational cleavage in the extracellular domain to yield disulfide-linked light and heavy chains that join with beta 1 to form a fibronectin receptor ('FNR') that is known variously: in lymphocytes as very late (activation) antigen 5 ('VLA-5'); in platelets as glycoprotein Ic-IIa; and in fibroblasts as extracellular matrix receptor 6 ('ECM VI'). In addition to adhesion, integrins are known to participate in cell-surface mediated signalling.
General function
Receptor
Comment
Cellular localization
Extracellular Matrix, Plasma membrane
Comment
Ovarian function
Luteinization, Early embryo development
Comment
Expression of integrin fraction and adhesion molecules on human granulosa cells and its relation with oocyte maturity and follicular steroidogenesis.
Clavero A, et al .
PURPOSE: To study the correlation between the expression of integrin fractions and adhesion molecules on granulosa cells (GC) and follicular development. METHODS: GC and follicular fluid (FF) were obtained at oocyte retrieval for ICSI. Expression of adhesion molecules on GC was studied by flow cytometry. Statistics were evaluated using the Student t test and simple linear regression analysis. RESULTS: alpha5 integrin fraction was significantly (p < 0.01) higher, while alpha6 fraction and CD9 were significantly (p < 0.01 and p < 0.001, respectively) lower in GC from FF with metaphase II oocytes. A direct significant correlation was observed between FF progesterone and the alpha5 expression on GC (r = 0.54). In contrast, an inverse significant correlation was observed between FF progesterone level and the expression of alpha6 and CD9 (r = -0.40 and -0.41, respectively). CONCLUSIONS: The expression pattern for integrin fractions and adhesion molecules may be of predictive value in assessing the state of differentiation of the human follicle.
Expression regulated by
LH
Comment
Ovarian localization
Granulosa, Luteal cells
Comment
Honda T, et al reported that integrin alpha5 is expressed on human luteinizing granulosa cells during corpus luteum formation, and its expression is enhanced by human chorionic gonadotrophin in vitro.
The expression of integrin alpha5 and fibronectin (FN) was examined by immunohistochemistry. Integrin alpha5 was undetectable on human GC in preovulatory follicles, but it was intensely expressed on luteinizing GC of CL in the early luteal phase, and it was weakly expressed on large luteal cells (LL) in the midluteal phase. GC obtained from preovulatory follicles were cultured for 3 days without (control) or with HCG (1 IU/ml), and expression of integrin alpha5 was examined by flow cytometry. Although the positivity rate did not differ, the mean relative fluorescence intensity was 3.4-fold higher in the HCG-treated group (n = 8, P < 0.01). These findings indicate that integrin alpha5 is rapidly expressed on GC during luteinization, probably under LH stimulation, and suggest that integrin alpha5 is involved in CL formation via interaction with its ligand FN.