LRG ELISA/人人亮氨酸丰富α2-糖蛋白ELISA检测

LRG (leucine-rich alpha-2-glycoprotein) is a glycoprotein with a molecular mass of 38.2 kDa. It is encoded by the human gene LRG-1 which is mapped on chromosome 19 at the cytogenetic band 19p13.3. The protein LRG (or also named LRG1) runs at approximately 50 kDa under reducing conditions, as it contains a carbohydrate content of 23% (Haupt et al., 1977). LRG is present in serum, plasma and urine (Kharbanda et al., 2012; Kentsis et al., 2012). LRG is the founding member of the family of leucine-rich repeat proteins (Takahashi et al., 1985). The mature protein consists of 312 amino acids, from Val36 to Gln347, with a leucine content of 66 amino acids. It is folded to eight leucine-rich repeat (LRR) domains of 22 amino acid length, and a C-terminal LRRCT domain with 49 amino acid length (O’Donnell et al., 2002). Human LRG1 shows 62,5% sequence identity with mouse LRG1, and 60,7% with rat LRG1. LRG binds to the TGFβ accessory receptor endoglin, and in the presence of TGFβ1 this leads to the induction of the TβRII-ALK1-Smad1/5/8 signaling pathway (Wang et al., 2013). TGFβ1 therefore promotes binding of LRG to the proangiogenic ALK1 but inhibits the interaction with angiostatic ALK5. Induced signaling leads to endothelial cell proliferation and blood vessel outgrowth (Wang et al., 2013). Like many other family members of the LRG family, LRG is described to have multiple binding partners. LRG is described to directly interact with the mitochondrial electron transfer protein cytochrome c (Cummings et al., 2006), whereas the physiological relevance of this interaction in not known yet. LRG further binds to TGFβ1, the most frequently expressed TGFβ isoform.