Dkk-1, Recombinant, Rat (Dickkopf 1, Dickkopf 1-like, Dickkopf Homolog 1, Dickkopf-related Protein 1

Dickkopf related protein 1 (Dkk-1) is the founding member of the Dickkopf family of proteins that includes Dkk-1, -2, -3, -4, and a related protein, Soggy. 1, 2 Dkk proteins are secreted proteins that contain two conserved cysteine-rich domains separated by a linker region. Each domain contains ten cysteine residues. 1-3 Mature rat Dkk-1 is a 40 kD glycosylated protein that shows 96%, 86% and 82% aa sequence identity with mouse, human and cow Dkk-1, respectively. It also shows 41% and 34% aa identity with rat Dkk-2 and Dkk-4, respectively. Dkk-1 and Dkk-4 are well documented antagonists of the canonical Wnt signaling pathway. 1, 2 This pathway is activated by Wnt engagement of a receptor complex composed of the Frizzled proteins and one of two low-density lipoprotein receptor-related proteins, LRP5 or LRP6. 4 Dkk-1 antagonizes Wnt by forming ternary complexes of LRP5/6 with Kremen1 or Kremen2. 4, 5 Dkk-1/LRP6/Krm2 complex internalization has been shown to downregulate Wnt signaling. 4, 5 Dkk-1 is expressed throughout development and antagonizes Wnt-7a during limb development. 6, 7 Other sites of expression include developing neurons, hair follicles and the retina of the eye. 8, 9 The balance between Wnt signaling and Dkk-1 inhibition is critical for bone formation and homeostasis. Insufficient or excess Dkk-1 activity in bone results in increased or decreased bone density, respectively. 8, 10 In adults, Dkk-1 is expressed in osteoblasts and osteocytes, and neurons. Neuronal expression appears to be required for ischemic neuronal death. 11, Description: Fusion protein composed of Rat Dkk-1 (Ser23-His270) (Accession Number XP_219804, NP_001099820) and 6His expressed in mouse myeloma cell line, NSO. Molecular Mass: Monomeric recombinant rat Dkk-1 has a calculated MW of 27.6kD. As a result of glycosylation, the protein migrates at ~38-42kD in SDS-PAGE under reducing conditions. Activity: Able to inhibit Wnt-3A's ability to induce alkaline phosphatase synthesis in the presence of BMP-2 by MC3T3E1, mouse pre-osteoblastic cells. The ND 50 is typically 0.4-1.6ug/ml in the presence of 10ng/ml of rmWnt-3A. Storage and Stability: Lyophilized powder may be stored at -20°C. Stable for 12 months at -20°C. Reconstitute with sterile PBS, 0.1% HSA or BSA. Aliquot to avoid repeated freezing and thawing. Store at -20°C/-70°C. Reconstituted product is stable for 6 months at -20°C/-70°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.