An Optimized Protein Kinase C Activating Diacylglycerol Combining High Binding Affinity (<i>K</i><sub>i</sub>) with Reduced Lipophilicity (log P)
作者:Kassoum Nacro、Dina M. Sigano、Shunqi Yan、Marc C. Nicklaus、Larry L. Pearce、Nancy E. Lewin、Susan H. Garfield、Peter M. Blumberg、Victor E. Marquez
DOI:10.1021/jm010052e
日期:2001.6.1
A small, focused combinatorial library encompassing all possible permutations of acyl branched alkyl chains-small and large, saturated and unsaturated-was generated from the active diacylglycerol enantiomer (S-DAG) to help identify the analogue with the highest binding affinity (lowest K-i) 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-C alpha, 3B was able to translocate the full length protein to the membrane with an optimal dose of 100 muM 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-C delta 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-C delta) or Tyr252 (PK-C alpha). 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.