Use of a holotoxin to reduce endoplasmic reticulum-associated degradation of misfolded proteins

Abstract

Provided is a use of a holotoxin to reduce endoplasmic reticulum-associated degradation (ERAD) of misfolded or abnormally folded proteins The holotoxin can thus be used in a method to treat diseases related to ERAD Examples of misfolded proteins that are degraded in the ER include the cystic fibrosis transmembrane conductance regulator (CFTR) delta F508 mutant protein, a misfolded mutant (G268V) of multi-drug resistance 1 (MDR1), and the glucocerebrosidase (GCC) enzyme in Gaucher's disease cells Examples of suitable holotoxins include ricin, shiga toxin, exotoxin A, plasmid-encoded toxin, cholera toxin, and verotoxin 1 (VT1) VT1 is also known as verotoxin A, shiga-like toxin 1, shiga-like toxin 1, or shiga toxin in type 1 A non-toxic inactive VT1 can also be used wherein crucial residues of the A subunit active site are mutated, for example, the mutations Y77S and E167Q

1 . The use of a holotoxin to block ERAD-mediated misfolded protein degradation. 
     
     
         2 . The use as defined in  claim 1  wherein the holotoxin comprises an inactivated A subunit. 
     
     
         3 . (canceled) 
     
     
         4 . (canceled) 
     
     
         5 . (canceled) 
     
     
         6 . The use as defined in  claim 1  wherein the holotoxin is selected from the group consisting of ricin, shiga toxin, cholera toxin, exotoxin A and plasmid-encoded toxin (Pet). 
     
     
         7 . The use as defined in  claim 1  wherein the holotoxin is a verotoxin. 
     
     
         8 . The use as defined in  claim 2  wherein the inactivated A subunit comprises a mutated amino acid sequence. 
     
     
         9 . The use as defined in  claim 2  wherein the holotoxin is a verotoxin comprising a mutated residue at at least one of positions 77 and 167. 
     
     
         10 . The use as defined in  claim 9  wherein the mutated residue is at least one of Y77S and E167Q. 
     
     
         11 . A method of treating an ERAD-related disease comprising the step of administering to a mammal a holotoxin. 
     
     
         12 . The method as defined in  claim 11  wherein the holotoxin comprises an inactivated A subunit. 
     
     
         13 . A method as defined in  claim 11  wherein the holotoxin is selected from the group consisting of ricin, shiga toxin, cholera toxin, exotoxin A and plasmid-encoded toxin (Pet). 
     
     
         14 . The method as defined of  claim 11  wherein the ERAD-related disease is a pathological condition that occurs as a result of the ERAD of misfolded functional proteins. 
     
     
         15 . The method as defined in  claim 13  wherein the ERAD-related disease is selected from the group consisting of arthritis, cystic fibrosis, glycosphingolipid lysosomal storage diseases, aspects of dislipidemia, hypertension, cholesterol biosynthesis, α1-antitripsin disease, Gaucher's disease and disease from HIV infection. 
     
     
         16 . The method as defined in  claim 11  wherein the holotoxin is modified to include a stop transfer sequence. 
     
     
         17 . The method as defined in  claim 11  wherein the holotoxin incorporates an endoplasmic reticulum inhibitor. 
     
     
         18 . The method as defined in  claim 17  wherein the inhibitor is a Sec61 inhibitor. 
     
     
         19 . The method as defined in  claim 18  wherein the inhibitor is CAM741 or Eeyarestatin I (EerI). 
     
     
         20 . The use as defined in  claim 1  to block degradation of one of an MDR1 mutant, a CFTR mutant or glucocerebrosidase. 
     
     
         21 . A composition comprising a holotoxin and a pharmaceutically acceptable adjuvant. 
     
     
         22 . The composition as defined in  claim 21  wherein the holotoxin comprises an inactivated A subunit. 
     
     
         23 . The composition as defined in  claim 21  wherein the holotoxin is modified to incorporate an entity which enhances inhibition of ERAD.