Abstracts (complete list) - Wissenschaft Online

Nousheen Zaidi, Timo Burster, Vinod Sommandas, Timo Herrmann, Bernhard O.
Boehm, Wolfgang Voelter, Hubert Kalbacher
Synthesis of novel cell penetrating aspartic proteases
inhibitors as the targeted inhibitors of antigen processing
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 thus
have a limited access to antigen processing compartments. Previously described
mannose-pepstatin conjugates were efficiently taken up by the cells via receptor
mediated uptake. But the cells that do not carry mannose receptors are not able 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 frequently used CPPs namely, Tat
(49-60), pAntp(43-58) (Penetratin) and 9-mer of L-arginine (R9), were synthesized on
a trityl resin followed by coupling pepstatin A to the peptides as a complete molecule to
the N-terminal amino group. The enzyme inhibition properties of these bioconjugates
and their cellular uptake into dendritic cells, Boleths (EBV-transformed B cell line) and
MCF7 (human breast cancer cell line) was studied. We found that the bioconjugate PepA-
Penetratin (PepA-P) was the most efficient cell-permeable aspartic protease inhibitor in
comparison to PepA. Moreover, we found that PepA-P efficiently inhibited the antigen
processing in PMBCs (peripheral mononuclear blood cells), primary DCs (dendritic cells)
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.