Import of TAT-Conjugated Propionyl Coenzyme A Carboxylase Using Models of Propionic Acidemia

Propionic acidemia is caused by a deficiency of the enzyme propionyl
coenzyme A carboxylase (PCC) located in the mitochondrial matrix. Cell-penetrating
peptides, including transactivator of transcription (TAT), offer a potential to deliver a
cargo into the mitochondrion. Here, we investigated the delivery of an 66 PCC enzyme
into mitochondria using the HIV TAT peptide at several levels: into isolated
mitochondria, in patient fibroblast cells, and in a mouse model. Results from Western
blots and enzyme activity assays confirmed the import of TAT-PCC into mitochondria,
as well as into patient fibroblasts, where the colocalization of imported
TAT-PCC and mitochondria was also confirmed by confocal fluorescence microscopy.
Furthermore, a single-dose intraperitoneal injection into PCC-deficient mice decreased
the propionylcarnitine/acetylcarnitine (C3/C2) ratio toward the normal level.
These results show that a cell-penetrating peptide can deliver active multimeric enzyme
into mitochondria in vitro, in situ, and in vivo and push the size limit of intracellular
delivery achieved so far. Our results are promising for other mitochondrionspecific
deficiencies.