Defining the pathway for Tat-mediated delivery of β-glucuronidase in cultured cells and MPS VII mice

Koji O. Orii, Jeffrey H. Grubb, Carole Vogler, Beth Levy, Yun Tan, Kamelia Markova, Beverly L. Davidson, Q. Mao, Tadao Orii, Naomi Kondo, William S. Sly*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


We used recombinant forms of human β-glucuronidase (GUS) purified from secretions from stably transfected CHO cells to compare the native enzyme to a GUS-Tat C-terminal fusion protein containing the 11-amino-acid HIV Tat protein transduction domain for: (1) susceptibility to endocytosis by cultured cells, (2) rate of clearance following intravenous infusion, and (3) tissue distribution and effectiveness in clearing lysosomal storage following infusion in the MPS VII mouse. We found: (1) Native GUS was more efficiently taken up by cultured human fibroblasts and its endocytosis was exclusively mediated by the M6P receptor. The GUS-Tat fusion protein showed only 30-50% as much M6P-receptor-mediated uptake, but also was taken up by adsorptive endocytosis through binding of the positively charged Tat peptide to cell surface proteoglycans. (2) GUS-Tat was less rapidly cleared from the circulation in the rat (t1/2 = 13 min vs 7 min). (3) Delivery to most tissues of the MPS VII mouse was similar, but GUS-Tat was more efficiently delivered to kidney. Histology showed that GUS-Tat more efficiently reduced storage in renal tubules, retina, and bone. These studies demonstrate that Tat modification can extend the range of tissues corrected by infused enzyme.

Original languageEnglish (US)
Pages (from-to)345-352
Number of pages8
JournalMolecular Therapy
Issue number2
StatePublished - Aug 2005


  • Adsorptive endocytosis
  • Enzyme replacement therapy
  • Lysosomal storage disease
  • MPS VII mouse
  • Mannose 6-phosphate
  • Receptor-mediated endocytosis
  • Sly syndrome
  • Tat peptide
  • β-glucuronidase

ASJC Scopus subject areas

  • Drug Discovery
  • Genetics
  • Molecular Medicine
  • Molecular Biology
  • Pharmacology


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