Physico-chemical requirements for cellular uptake of pAntp peptide. Role of lipid-binding affinity.
The pAntp peptide, corresponding to the third helix of the Antennapedia homeodomain, is internalized by a receptor-independent process into eucaryotic cells. The precise mechanism of entry remains unclear but the interaction between the phospholipids of plasma membrane and pAntp is probably involved in the translocation process. In order to define the role of peptide-lipid interaction in this mechanism and the physico-chemical properties that are necessary for an efficient cellular uptake, we have carried out an Ala-Scan mapping. The peptides were labeled with a fluorescent group (7-nitrobenz-2-oxo-1,3-diazol-4-yl-; NBD) and their cell association was measured by flow cytometry. Furthermore, we determined the fraction of internalized peptide by using a dithionite treatment. Comparison between cell association and cell uptake suggests that the affinity of pAntp for the plasma membrane is required for the import process. To further investigate which are the physico-chemical requirements for phospholipid-binding of pAntp, we have determined the surface partition coefficient of peptides by titrating them with phospholipid vesicles having different compositions. In addition, we estimated by circular dichroism the conformation adopted by these peptides in a membrane-mimetic environment. We show that the phospholipid binding of pAntp depends on its helical amphipathicity, especially when the negative surface charge density of phospholipid vesicles is low. The cell uptake of pAntp, related to lipid-binding affinity, requires a minimal hydrophobicity and net charge. As pAntp does not seem to translocate through an artificial phospholipid bilayer, this might indicate that it could interact with other cell surface components or enters into cells by a nonelucidated biological mechanism.
Synt:em, Parc Scientifique Georges Besse, Nimes, France.
G
G
Drin
M
M
Mazel
P
P
Clair
D
D
Mathieu
M
M
Kaczorek
J
J
Temsamani
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D051943:Antennapedia Homeodomain Protein; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism; D004227:Dithionite / Q000378:metabolism; D004705:Endocytosis; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008823:Micelles; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012967:Sodium Dodecyl Sulfate / Q000378:metabolism; D055672:Static Electricity; D013329:Structure-Activity Relationship; D014157:Transcription Factors
D051943:Antennapedia Homeodomain Protein; D005456:Fluorescent Dyes; D018398:Homeodomain Proteins; D008051:Lipid Bilayers; D008081:Liposomes; D008823:Micelles; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010743:Phospholipids; D014157:Transcription Factors; D004227:Dithionite; D012967:Sodium Dodecyl Sulfate; D000409:Alanine