Kl
Developmental stage
Not expressed in the embryo. Expressed in the kidney of newborns.
Domain
Contains 2 glycosyl hydrolase 1 regions. However, the first region lacks the essential Glu active site residue at position 241, and the second one lacks the essential Glu active site residue at position 874.
Function
May have weak glycosidase activity towards glucuronylated steroids. However, it lacks essential active site Glu residues at positions 241 and 874, suggesting it may be inactive as a glycosidase in vivo. May be involved in the regulation of calcium and phosphorus homeostasis by inhibiting the synthesis of active vitamin D. Essential factor for the specific interaction between FGF23 and FGFR1.
The Klotho peptide generated by cleavage of the membrane-bound isoform may be an anti-aging circulating hormone which would extend life span by inhibiting insulin/IGF1 signaling.
Post-translational modifications
N-glycosylated.
Sequence Similarities
Belongs to the glycosyl hydrolase 1 family. Klotho subfamily.
Tissue Specificity
Membrane-bound protein is present in distal renal tubules, inner ear, ependymal cells of brain choroid plexus, elongating spermatids and mature oocytes (at protein level). Soluble peptide is present in serum (100 pM) and cerebrospinal fluid. Expressed strongly in kidney, moderately in brain choroid plexus, and at low levels in pituitary, placenta, skeletal muscle, urinary bladder, aorta, pancreas, testis, ovary, colon, thyroid gland and adipocytes.
Cellular localization
- Isoform 1
- Cell membrane
- Single-pass type I membrane protein
- Apical cell membrane
- Single-pass type I membrane protein
- Isoform 1 shedding leads to a soluble peptide.
- Isoform 2
- Secreted
- Klotho peptide
- Secreted
Alternative names
Klotho, Kl