Stemcell, 100-1729, Human Recombinant R-Spondin-1 (E. coli-expressed), ACF

R-Spondin-1 (RSPO1) is the prototype member of the R-Spondin (RSPO) protein subfamily of a superfamily of thrombospondin type 1 repeat (TSR-1)-containing proteins (Chen et al. Mol Biol Rep, 2002; Kazanskaya et al. Dev Cell, 2004; Kim et al. Cell Cycle, 2006). Although unable to initialize signaling, RSPO family members are potent enhancers of WNT signaling (Cruciat & Niehrs. Cold Spring Harb Perspect Biol, 2013; de Lau et al. Genome Biol, 2012; Kazanskaya et al. Dev Cell, 2004). They are characterized by a TSR-1 domain, a carboxy-terminal region with positively charged amino acids, and two N-terminal furin-like cysteine-rich repeats (Glinka et al. EMBO Rep, 2012; Kazanskaya et al. Dev Cell, 2004). RSPO1 activates β-catenin signaling via the WNT signaling cascade and by indirectly increasing low-density lipoprotein receptor-related protein 6 (LRP6) on the cell surface. It does this by binding leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), and competing with WNT antagonist DKK-1 for binding to the WNT coreceptors Kremen and LRP6, which reduces DKK-1-mediated internalization of LRP6 (Binnerts et al. Proc Natl Acad Sci USA, 2007). RSPO1 is involved in a wide range of pleiotropic roles during embryogenesis, it is required for the specification of hematopoietic stem cells, and it has been shown to be important in the growth, survival, and migration of ovarian cancer cells (Cruciat & Niehrs. Cold Spring Harb Perspect Biol, 2013; de Lau et al. Genome Biol, 2012; Genthe & Clements. Development, 2017; Liu et al. Gene, 2019).