Cell membrane lipid rafts mediate caveolar endocytosis of HIV-1 Tat fusion proteins.
The transactivator protein of human immunodeficiency virus type 1 Tat has the unique property of mediating the delivery of large protein cargoes into the cells when present in the extracellular milieu. Here we show that Tat fusion proteins are internalized by the cells through a temperature-dependent endocytic pathway that originates from cell membrane lipid rafts and follows caveolar endocytosis. These conclusions are supported by the study of the slow kinetics of the internalization of Tat endosomes, by their resistance to nonionic detergents, the colocalization of internalized Tat with markers of caveolar endocytosis, and the impairment of the internalization process by drugs that disrupt lipid rafts or disturb caveolar trafficking. These results are of interest for all those who exploit Tat as a vehicle for transcellular protein delivery.
Fittipaldi
Antonio
A
Scuola Normale Superiore and NEST-Istituto Nazionale per la Fisica della Materia, and Istituto di Fisiologia Clinica, Consiglio Nazionale delle Ricerche, 56100 Pisa, Italy.
Ferrari
Aldo
A
Zoppé
Monica
M
Arcangeli
Caterina
C
Pellegrini
Vittorio
V
Beltram
Fabio
F
Giacca
Mauro
M
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D005434:Flow Cytometry; D015696:Gene Products, tat / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D017830:Octoxynol / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D013696:Temperature; D013997:Time Factors; D015533:Transcriptional Activation; D014168:Transferrin / Q000378:metabolism
D003902:Detergents; D015696:Gene Products, tat; D008164:Luminescent Proteins; D014168:Transferrin; D049452:Green Fluorescent Proteins; D017830:Octoxynol; D005982:Glutathione Transferase