Follistatin-related Gene (FLRG), also known as Follistatin-like 3 (FSTL3) and Follistatin-related protein (FSRP), is a 30-35kD secreted glycoprotein that exerts a broad range of activities by neutralizing Activin A and Myostatin function. Mature human FLRG consists of an Activin and Myostatin binding N-terminal domain, two Follistatin-like domains, and two Kazal-like domains. BMP-2, -6, and -7 do not compete for Activin A binding, and FLRG binds only weakly to Activin B. Unlike Follistatin, FLRG does not contain a heparin-binding domain and does not interact with heparan sulfate proteoglycans. A short form of FLRG, which lacks the signal sequence and is found in the nucleus, retains Activin-blocking capability. Nuclear FLRG binds to the transcription factor AF10, induces AF10 homo-oligomerization, and enhances AF10-dependent gene transcription. Mature human FLRG shares 84% aa sequence identity with mouse and rat FLRG. FLRG expression is induced by Activin A, providing negative feedback regulation of Activin A function. FLRG is expressed in the uterus, ovary, testis, placenta, trophoblast, and adrenal gland. It is upregulated in cardiac myocytes following myocardial injury and blocks the prosurvival and hypertrophic effects of Activin A on these cells. FLRG is also expressed by astroglial cells in areas of neuronal trauma. Its binding to ADAM12 as well as to Activin A inhibits osteoclastic differentiation from macrophages. The Activin-neutralizing function enables FLRG to regulate energy balance and metabolism, as shown in FLRG knockout mice which exhibit increased pancreatic islet number and size, improved glucose tolerance and insulin sensitivity, and a shift from visceral to subcutaneous fat. Obese ob/ob mice show FLRG downregulation in visceral fat and upregulation in subcutaneous fat relative to wild type mice. Circulating FLRG levels are decreased in women with gestational diabetes. FLRG is upregulated in breast cancer and promotes tumor cell proliferation. The FLRG, Human, BioAssay™ ELISA Kit is a 4.5h solid-phase ELISA designed to measure human FLRG in cell culture supernates, serum, plasma, urine, and human milk. It contains NS0-expressed recombinant human FLRG and has been shown to accurately quantitate the recombinant factor. Results obtained using natural human FLRG showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for naturally occurring human FLRG.
Sample Type:Cell culture supernates, serum, plasma, urine, and human milk.
Intended Use:For the quantitative determination of Follistatin-related Gene (FLRG) concentrations in cell culture supernates, serum, plasma, urine, and human milk.
Sensitivity:~3.68pg/ml
Range:2.01-8.55pg/ml
Specificity:Human FLRG
Test Principle:This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for FLRG has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any FLRG present is bound by the immobilized antibody. After washing away any unbound substances, an enzyme-linked monoclonal antibody specific for FLRG is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of FLRG bound in the initial step. The color development is stopped and the intensity of the color is measured.
Kit Components:FLRG Microplate: 96 well polystyrene microplate (12 strips x 8 wells) coated with a monoclonal antibody to FLRG
FLRG Conjugate: 1x21ml of monoclonal antibody to FLRG conjugated to HRP with preservatives
FLRG Standard: 40ng of recombinant human FLRG in a buffered protein base with preservatives; lyophilized
Assay Diluent RD1W: 1x11ml of of a buffered protein base with preservatives
Calibrator Diluent RD5-24: 1x21ml of a buffered protein base with preservatives
Wash Buffer Concentrate: 1x21ml of a 25-fold concentrated solution of buffered surfactant with preservativesColor Reagent A: 1x12ml of stabilized hydrogen peroxideColor Reagent B: 1x12ml of stabilized chromogen (tetramethylbenzidine)Stop Solution: 1x6ml of 2 N sulfuric acidPlate Sealers: 4 adhesive strips
Storage and Stability:See Kit Protocol for detailed storage instructions.
