Molecular determinants for cellular uptake of Tat protein of human immunodeficiency virus type 1 in brain cells.
We measured the cellular uptake of 125I-labeled full-length Tat (amino acids 1 to 86) (125I-Tat(1-86)) and 125I-Tat(1-72) (first exon) in human fetal astrocytes, neuroblastoma cells, and human fetal neurons and demonstrated that the uptake of 125I-Tat(1-72) without the second exon was much lower than that of 125I-Tat(1-86) (P < 0.01). This suggests an important role for the C-terminal region of Tat for its cellular uptake. 125I-Tat uptake could be inhibited by dextran sulfate and competitively inhibited by unlabeled Tat but not by overlapping 15-mer peptides, suggesting that Tat internalization is charge and conformationally dependent. Interestingly, one of 15-mer peptides, Tat(28-42), greatly enhanced 125I-Tat uptake. These findings are important for understanding the neuropathogenesis of human immunodeficiency virus type 1 infection and in the potential application of Tat for drug delivery to cells.
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Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
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D000595:Amino Acid Sequence; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D002460:Cell Line; D016264:Dextran Sulfate / Q000494:pharmacology; D015696:Gene Products, tat / Q000493:pharmacokinetics*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D016023:Integrins; D054322:tat Gene Products, Human Immunodeficiency Virus; D016264:Dextran Sulfate