title: A novel cell penetrating aspartic protease inhibitor blocks processing and presentation of tetanus toxoid more efficiently than pepstatin A.
abstract: Selective inhibition of enzymes involved in antigen processing such as cathepsin E and cathepsin D is a valuable tool for investigating the roles of these enzymes in the processing pathway. However, the aspartic protease inhibitors, including the highly potent pepstatin A (PepA), are inefficiently transported across the cell membrane and thus have limited access to antigen processing compartments. Previously described mannose-pepstatin conjugates were efficiently taken up by the cells via receptor mediated uptake. However, cells without mannose receptors are unable to take up these conjugates efficiently. The aim of the present study was to synthesize new cell-permeable aspartic protease inhibitors by conjugating pepstatin A with well-known cell penetrating peptides (CPPs). To achieve this, the most commonly used CPPs namely pAntp(43-58) (penetratin), Tat(49-60), and 9-mer of l-arginine (R9), were synthesized and coupled to pepstatin. The enzyme inhibitory properties of these bioconjugates and their cellular uptake into MCF7 (human breast cancer cell line), Boleths (EBV-transformed B-cell line) and dendritic cells (DC) were the focus of our study. We found that the bioconjugate PepA-penetratin (PepA-P) was the most efficient cell-permeable aspartic protease inhibitor tested, and was more efficient than unconjugated PepA. Additionally, we found that PepA-P efficiently inhibited the tetanus toxoid C-fragment processing in peripheral blood mononuclear cells (PBMC), primary DC and in primary B cells. Therefore, PepA-P can be used in studying the role of intracellular aspartic proteases in the MHC class II antigen processing pathway. Moreover, inhibition of tetanus toxoid C-fragment processing by PepA-P clearly implicates the role of aspartic proteinases in antigen processing.
authors.affiliation: Medical and Natural Sciences Research Centre, University of Tübingen, Ob dem Himmelreich 7, 72074 Tübingen, Germany.
authors.forename: Nousheen
authors.initials: N
authors.lastname: Zaidi
authors.forename: Timo
authors.initials: T
authors.lastname: Burster
authors.forename: Vinod
authors.initials: V
authors.lastname: Sommandas
authors.forename: Timo
authors.initials: T
authors.lastname: Herrmann
authors.forename: Bernhard O
authors.initials: BO
authors.lastname: Boehm
authors.forename: Christoph
authors.initials: C
authors.lastname: Driessen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Voelter
authors.forename: Hubert
authors.initials: H
authors.lastname: Kalbacher
mesh_terms: D017951:Antigen Presentation / Q000187:drug effects; D001120:Arginine / Q000737:chemistry / Q000494:pharmacology*; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D002352:Carrier Proteins / Q000737:chemistry / Q000494:pharmacology*; D002463:Cell Membrane Permeability; D057846:Cell-Penetrating Peptides; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology; D015696:Gene Products, tat / Q000737:chemistry*; D006801:Humans; D010436:Pepstatins / Q000737:chemistry / Q000494:pharmacology*; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013745:Tetanus Toxoid / Q000276:immunology*
chemical_list: D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D015696:Gene Products, tat; D010436:Pepstatins; D010446:Peptide Fragments; D013745:Tetanus Toxoid; D001120:Arginine; C414409:penetratin; D016282:Aspartic Acid Endopeptidases; C031375:pepstatin