Binding of tumor antigen mucin (MUC1) derived peptides to the heat shock protein DnaK.
The human epithelial mucin encoded by the gene MUC1 is a tumor-associated antigen expressed on breast, pancreatic, colon and ovarian cancer cells recognized by cytotoxic T-cells and antibodies. Underglycosylated as well as glycosylated mucin-peptide epitopes are promising targets for vaccination against cancer. Heat shock proteins of 70 kDa (HSP70), also highly expressed in tumor cells, can function as chaperones for peptides and proteins and are involved in antigen processing. The involvement of HSP70 molecules in mucin antigen binding, processing and presentation has not yet been examined. Here we present first results concerning the relative binding affinities of various mucin-derived peptides to the bacterial 70 kDa heat shock protein DnaK. Interestingly, longer mucin peptides reveal a higher affinity to DnaK than short peptides. The non-glycosylated mucin-derived peptides of 5-8 amino acids length were able to compete with a high affinity (unrelated) reference peptide at millimolar concentrations. Glycosylation of the investigated short peptides lowers their binding affinity to DnaK, depending on the position of the carbohydrate. The binding affinity is not influenced by free charges at unprotected ends. The peptide (MUC1)5 consisting of five repeating units has an affinity enhanced by a factor of three as compared to the peptide with only one repeating unit. Mucin-peptide-HSP-complexes could be the basis of developing new kinds of tumor vaccines.
Schreiber
J
J
Max-Delbrück-Center for Molecular Medicine (MDC), Berlin-Buch, Germany.
Stahn
R
R
Schenk
J A
JA
Karsten
U
U
Pecher
G
G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006031:Glycosylation; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; C116055:MUC1 tandem repeat peptide; D018832:Molecular Chaperones; D018396:Mucin-1; D010446:Peptide Fragments; C063842:dnaK protein, E coli