Effects of Cellular, Chemical, and Pharmacological Chaperones on the Rescue of a Trafficking-defective Mutant of the ATP-binding Cassette Transporter Proteins ABCB1/ABCB4

Abstract

Background: Mutations of ABCB4, a transporter highly homologous to ABCB1, cause severe liver disease. Results: The I541F mutation induces misfolding and intracellular retention that is rescued by the ABCB1-competitive substrate cyclosporin A but not by modulating the chaperones calnexin or Hsp/Hsc70. Conclusion: Pharmacological chaperones are potential therapeutic tools for ABCB4 misfolded mutants. Significance: This opens perspectives to treat ABCB4-linked genetic diseases.

Mutations in Intracellular Loops 1 and 3 Lead to Misfolding of Human P-glycoprotein (ABCB1) That Can Be Rescued by Cyclosporine A, Which Reduces Its Association with Chaperone Hsp70

“…Pharmacological chaperones (CsA, FK506, and small molecule CFTR correctors) rescue the misfolded double mutant P-gp via an immunophilinindependent pathway by decreasing its association with the Hsp70 chaperone and thus allow the protein to be trafficked to the Golgi for maturation and then localize to the cell surface. Our results strongly suggest that a similar mechanism may be operative in the rescue of misfolded mutant CFTR (ABCC7), ABCG2 (25), and other ABC transporters (19,40) associated with disease conditions, which should be further investigated.…”

“…The beads were incubated at 37°C for an additional 30 min after diluting with running buffer. Cell lysates were subjected to Endo H and PNGase F digestion (19) for 60 min at 37°C according to the manufacturer's protocol. Samples were denatured in sample buffer for 30 min at 37°C.…”

The Role of Canalicular ABC Transporters in Cholestasis

“…Although UDCA treatment can be helpful in the presence of a partial ABCB4 defect, hepatic transplantation will remain the only definitive therapy before gene therapy becomes available in most patients (Deleuze et al, 1996;De Vree et al, 1998). Patients with misfolding of the transporter, such as the reported PFIC3 heterozygous mutation I541F, may benefit from chaperone treatment to correct these folding defects in the future (Delaunay et al, 2009;Gautherot et al, 2012). Cyclosporine A was indeed able to restore a correct maturation of the endoplasmic reticulum sequestered I541F mutant in vitro (Gautherot et al, 2012).…”

“…Patients with misfolding of the transporter, such as the reported PFIC3 heterozygous mutation I541F, may benefit from chaperone treatment to correct these folding defects in the future (Delaunay et al, 2009;Gautherot et al, 2012). Cyclosporine A was indeed able to restore a correct maturation of the endoplasmic reticulum sequestered I541F mutant in vitro (Gautherot et al, 2012). Less severe ABCB4 mutations can lead to the low phospholipid associated cholelithiasis syndrome (LPAC) and intrahepatic cholestasis of pregnancy (ICP).…”

Clinical utility gene card for: Progressive familial intrahepatic cholestasis type 3

“…Recently, treatment with ciclosporin A was shown to partially correct, in vitro, the aberrant folding caused by one missense mutation. 14 In the future, cell, gene or targeted mutation-specific pharmacological therapies might be useful tools for the management of patients with all types of PFIC. 15 A beneficial effect of UDCA is usually observed in patients who harbour at least one missense variation (unlike in children with biallelic mutations that both lead to the synthesis of a truncated protein).…”