Klotho (KL) Recombinant Murine

Klotho, also called Klotho-a, is the founding member of the Klotho family within the glycosidase-1 superfamily. Klotho is expressed in areas concerned with calcium regulation, predominantly in the kidney distal convoluted tubules, but also in the brain choroid plexus (which produces cerebrospinal fluid) and the parathyroid. The 1014 amino acid (aa) type I transmembrane protein contains a 34 aa signal sequence, a 948 aa extracellular domain (ECD) containing two extracellular glycosidase-like domains, a 21 aa transmembrane domain and an 11 aa intracellular domain. Within the ECD, mouse Klotho shares 95%, 87% and 87% aa identity with rat, human and equine Klotho, respectively. Although a truncated 554 aa isoform predicts a soluble 70kD form, the soluble form found in plasma and cerebrospinal fluid is a 130kD form produced by proteolytic cleavage of the glycosylated 135kD full-length Klotho. A prominent intracellular 120kD form of Klotho is localized to endoplasmic reticulum and Golgi membranes. Klotho is named for the Greek goddess who spins the thread of life. The phenotype of Klotho-deficient mice resembles premature aging, including arteriosclerosis, osteoporosis, skin atrophy, infertility, emphysema and premature death. Conversely, excess Klotho extends lifespan. Klotho acts as a cofactor for interaction of FGF23 with FGF R1.6 This interaction negatively regulates 1a-hydroxylase, the rate-limiting enzyme in the synthesis of 1,25(OH)2D3 (vitamin D). Klotho-deficient mice show severe hyperphosphatemia and ectopic calcification of soft tissues due to excess vitamin D. Both Klotho and Klotho-b are cofactors for FGF19 binding. Klotho also shows glucuronidase activity which activates the renal ion channel TRPV5 to reabsorb urinary calcium. Klotho has been reported to downregulate insulin or IGF-1 signaling in adipocytes, to bind and antagonize Wnt molecules, and to facilitate release of parathyroid hormone. Source: A DNA sequence encoding the extracellular domain of mouse Klotho (Ala 35-Lys 982, Accession # AA138260, Variant Arg 948 Lys) was fused to a 6-His tag at the C-terminus. The protein was expressed in a Chinese hamster ovary cell line. Molecular Mass: Recombinant mouse Klotho has a predicted molecular mass of ~109.5kD. As a result of glycosylation, the protein migrates at ~125-130kD in SDS-PAGE under reducing conditions. Biological Activity: Measured by its ability to induce proliferation of human FGF RIIIC transfected BaF3 mouse pro-B cells. The ED50 for this effect is typically 0.04-0.4ug/ml in the presence of 1ug/ml of rhFGF-23 and 10ug/ml of heparin., Also measured by its ability to induce proliferation of NIH 3T3 mouse embryonic cells. The ED50 for this effect is typically 0.04-0.4ug/ml in the presence of 1ug/ml of rhFGF-23 and 10ug/ml of heparin. Endotoxin:<1EU/ug (LAL) , Storage and Stability:, May be stored at 4°C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Aliquots are stable for at least 6 months at -20°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.