HIV Tat Domain Improves Cross-correction of Human Galactocerebrosidase in a Gene- and Flanking Sequence-dependent Manner.

[krabbe disease]

Krabbe disease is a devastating neurodegenerative lysosomal storage disorder caused by a deficiency of β-galactocerebrosidase (GALC ). Gene therapy is a promising therapeutic approach for Krabbe disease . As the human brain is large and it is difficult to achieve global gene transduction , the efficacy of cross-correction is a critical determinant of the outcome of gene therapy for this disease . We investigated whether HIV Tat protein transduction domain (PTD ) can improve the cross-correction of GALC . Tat-PTD significantly increased (~6 -fold ) cross-correction of GALC through enhanced secretion and uptake in a cell-culture model system . The effects of Tat-PTD were gene and flanking amino acids dependent . Tat-fusion increased the secretion of α-galactosidase A (α-gal A ), but this did not improve its cross-correction . Tat-fusion did not change either secretion or uptake of β-glucocerebrosidase (GC ). Tat-PTD increased GALC protein synthesis , abolished reactivity of GC to the 8 E 4 antibody , and likely reduced mannose phosphorylation in all these lysosomal enzymes . This study demonstrated that Tat-PTD can be useful for increasing cross-correction efficiency of lysosomal enzymes . However , Tat-PTD is not a mere adhesive motif but possesses a variety of biological functions . Therefore , the potential beneficial effect of Tat-PTD should be assessed individually on each lysosomal enzyme .M olecular Therapy-Nucleic Acids (2013 ) 2 , e 130 ; doi :10 .1038 /mtna .2013 .57 ; published online 22 October 2013 .