The cells were treated with PEP-1-FK506BP (5 μM) proteins for 2 h and observed by confocal microscopy (C).
Transduction of PEP-1-FK506BP into WT9-7 cells. Purified PEP-1-FK506BP and control FK506BP were analyzed by 15% SDS-PAGE (A) and subjected to Western blot analysis with an anti-histidine antibody (B). Purification and transduction of PEP-1-FK506BP into WT9-7 cells. Our results showed that PEP-1-FK506BP markedly inhibited cell proliferation and cyst formation in PKD cells. Therefore, we investigated the effect of PEP-1-FK506BP on cell proliferation and cyst formation in PKD. Although FK506BP is known to perform multiple functions in cellular processes, the effects of FK506BP in PKD remains unclear. In a previous study, we have shown that PEP-1-FK506BP inhibited atopic dermatitis (AD) and eye diseases ( 35, 36). This fusion protein was able to cross membranes such as the blood-brain barrier (BBB) without any toxic effects ( 33, 34). Therefore, we fused FK506BP and a PEP-1 peptide (one of the various protein transduction domains ). The complex of FK506BP and rapamycin plays a role as inhibitor of mTORC1 activation which, in turn, leads to suppression of cell growth via regulation of cell signaling in various cells, including cancer cells ( 30– 32).Īlthough FK506BP has multiple potent therapeutic functions, it is limited for therapeutic application since it is very low delivery efficiency. In addition, other studies have shown that FK506BP has protective effects in neurodegenerative processes and apoptotic neuronal cell death in diseases, including Parkinson’s diseases, suggesting that FKBP plays important roles in cell survival and may provide a new therapeutic target for neurodegenerative diseases ( 23– 29). FK506BP performs multiple functions in cells e.g., protein folding, regulation of calcium-dependent phosphatase calcineurin (CaN) and transforming growth factor-β (TGF-β) ( 21, 22). In addition, other studies have shown that phosphorylation of PI3K, Akt, mTOR, and mitogen-activated protein kinase (MAPK) pathways markedly inhibited cancer cell proliferation and growth, suggesting that understanding of these mechanisms may contribute to the development of drugs for the inhibition of cell proliferation and growth ( 17– 20).įK506 binding protein 12 (FK506BP), one of the FKBP family of proteins, is a major immunophilin protein and demonstrates peptidylprolyl cis/trans isomerase (PPIase) activity ( 21). Therefore, the regulation of mTOR activation is important in the development of therapeutic strategies for PKD treatment ( 13– 16). The collective evidence suggests that the common feature of PKD is mTOR activation.
It has been shown that mammalian target of rapamycin (mTOR) and Akt signaling play important roles in the pathophysiology of PKD via increased mTOR activation in both human PKD and animal models. Although the exact mechanisms of cyst formation in PKD are not clear yet, recent studies have demonstrated that various factors, including cytokines, growth factors, extracellular matrix (ECM) components and matrix metalloproteinases (MMPs) contribute significantly to cell proliferation and cyst formation in human patients and animal models of PKD ( 4, 7– 12). ARPKD is caused by a PKHD1 gene mutation and affects one in 20,000 children ( 4– 6). ADPKD is the most highly prevalent inherited disorder caused by either PKD1 or PKD2 gene mutations and affects one in 1000 adults. Two major PKD subtypes have been identified i.e, autosomal dominant PKD (ADPKD) and autosomal recessive PKD (ARPKD). Polycystic kidney disease (PKD), one of the most common genetic kidney disorders, is characterized by progressive cyst formation and development of fluid-filled cysts in the kidney, ultimately leading to end-stage kidney disease ( 1– 3).