FKBP12 Rabbit Recombinant mAb detects endogenous levels of total Mutant FKBP12.

FKBP12, the 12-kDa FK506-binding protein, is a ubiquitous abundant protein that acts as a receptor for the immunosuppressant drug FK506, binds tightly to intracellular calcium release channels and to the transforming growth factor β (TGF-β) type I receptor. FKBP12 occurs in all tissues, with particularly high densities in the brain, and appears to have diverse functions. It is a subunit of two intracellular calcium release channels, the inositol 1,4,5-trisphosphate receptor and the ryanodine receptor, and is also a subunit of the TGF-β type I receptor. FKBP12 inhibits basal signaling of these three receptors and also regulates the P-glycoprotein multidrug transporter. Binding of FKBP12 to FK506 and calcineurin forms a ternary complex to inhibit the serine/threonine phosphatase activity of calcineurin, which is important for several cellular processes such as T-cell activation. In addition, FKBP12 exhibits many other functions which involve binding to different cellular receptors or targets. For example, in the absence of FK506, FKBP12 binds to the ryanodine receptor, which is one of the major calcium-release channels in the sarcoplasmic and endoplasmic reticula. Interaction between FKBP12 and ryanodine receptor stabilizes the ryanodine receptor channel and modulates channel gating, leading to increased channel conductance levels and mean open-time. FKBP12 has also been shown to interact with transforming growth factor-β type I receptor to inhibit receptor-mediated signal transduction. Furthermore, FKBP12 has an inhibitory effect on the cellular activity of epidermal growth factor receptor by modulating the receptor's phosphorylation status.