An optimized protein kinase C activating diacylglycerol combining high binding affinity (Ki) with reduced lipophilicity (log P).
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 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-Calpha, 3B was able to translocate the full length protein to the membrane with an optimal dose of 100 microM 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-Cdelta 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-Cdelta) or Tyr252 (PK-Calpha). 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.
Nacro
K
K
Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA.
Sigano
D M
DM
Yan
S
S
Nicklaus
M C
MC
Pearce
L L
LL
Lewin
N E
NE
Garfield
S H
SH
Blumberg
P M
PM
Marquez
V E
VE
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D019992:Databases as Topic; D004075:Diglycerides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D004789:Enzyme Activation; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D015240:Phorbol 12,13-Dibutyrate / Q000493:pharmacokinetics; D011487:Protein Conformation; D011493:Protein Kinase C / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection; D014364:Tryptophan; D014443:Tyrosine; D016335:Zinc Fingers
D004075:Diglycerides; D011993:Recombinant Fusion Proteins; D015240:Phorbol 12,13-Dibutyrate; D014443:Tyrosine; D014364:Tryptophan; D011493:Protein Kinase C