An Optimized Protein Kinase C Activating Diacylglycerol Combining High Binding Affinity (Ki) with Reduced Lipophilicity (log P)

Publisher Website
Google Scholar
Abstract
A small, focused combinatorial library encompassing all possible permutations of acyl branched alkyl chainssmall and large, saturated and unsaturatedwas generated from the active diacylglycerol enantiomer (S-DAG) to help identify the analogue with the highest binding affinity (lowest Ki) for protein kinase C (PK-C) combined with the minimum lipophilicity (log P). The selected ligand (3B) activated PK-C more effectively than sn-1,2-dioctanoylglycerol (diC8) despite being 1.4 log units more hydrophilic. Compound 3B indeed represents the most potent, hydrophilic DAG ligand to date. With the help of a green fluorescent protein (GFP)-tagged PK-Cα, 3B was able to translocate the full length protein to the membrane with an optimal dose of 100 μM in CHO-K1 cells, while diC8 failed to achieve translocation even at doses 3-fold higher. Molecular modeling of 3B into an empty C1b domain of PK-Cδ clearly showed the existence of a preferred binding orientation. In addition, molecular dynamic simulations suggest that binding discrimination could result from a favorable van der Waals (VDW) interaction between the large, branched sn-1 acyl group of 3B and the aromatic rings of Trp252 (PK-Cδ) or Tyr252 (PK-Cα). The DAG analogue of 3B in which the acyl groups are reversed (2C) showed a decrease in binding affinity reflecting the capacity of PK-C to effectively discriminate between alternative orientations of the acyl chains.