A peptide binding protein having a role in antigen presentation is a member of the HSP70 heat shock family.
The T cell recognition of globular protein antigens requires the processing and presentation of the antigen by Ia-expressing APCs. Processing is believed to involve the uptake of antigen into an acidic compartment where proteolysis occurs. The resulting peptides containing the T cell antigenic determinant are associated with Ia and presented at the cell surface to the specific T cells. The mechanisms by which antigenic peptides become associated with Ia is not known. We previously described a peptide binding protein of 72/74 x 10(3) Mr (PBP72/74) that plays a role in antigen presentation as shown by the ability of an antiserum raised in rabbits to affinity-purified PBP72/74 to block presentation of cytochrome c to a cytochrome c-specific T cell hybrid. Here we show that PBP72/74 is recognized by mAbs specific for members of the HSP70 family of proteins. In Western blots PBP72/74 is bound by mAb 7.10, specific for an evolutionarily conserved epitope of HSP proteins and by mAb N27, specific for both the constitutively expressed and inducible 72/73 x 10(3) Mr HSP70 proteins. In addition, PBP72/74 shares a second common feature of the HSP proteins, that of binding to ATP. Indeed, ATP causes the release of PBP72/74 from binding to a peptide fragment of cytochrome c (Pc 81-104) and PBP72/74 can be eluted from ATP columns by Pc 81-104. Finally, a portion of PBP72/74 is shown to be present on B cell surfaces by immunofluorescence staining. Thus, it appears that characteristics of the heat shock proteins are shared by a protein playing a role in antigen presentation, suggesting some commonality in function.
Vanbuskirk
A
A
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208.
Crump
B L
BL
Margoliash
E
E
Pierce
S K
SK
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology*; D002352:Carrier Proteins / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D006649:Histocompatibility Antigens / Q000502:physiology; D051379:Mice; D008808:Mice, Inbred CBA; D011817:Rabbits
D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D006649:Histocompatibility Antigens; D000255:Adenosine Triphosphate