Synthesis and evaluation of iodinated analogues of diacylglycerols as potential probes for protein kinase C.
Analogues of diacylglycerol containing a 3-(3-amino-2,4,6-triiodophenyl)-2-ethylpropanoyl or 3-(3-amino-2,4,6-triiodophenyl)propanoyl group in the 2-position (1a and 1b, respectively) were synthesized and shown to compete with [3H]phorbol dibutyrate [( 3H]PDBu) for binding in a crude rat brain preparation. Phorbol diesters have been shown to bind specifically to protein kinase C and the PDBu receptor has been copurified with protein kinase C activity. The four diastereomers of 1a (1c-f) were synthesized from chiral starting material and studied in the same assay. The affinities for the [3H]PDBu binding site of 1a, 1b, and two isomers of 1a with naturally occurring L configuration were comparable to that of 1-oleoyl-2-acetyl-rac-glycerol (OAG), but the D isomers of 1a were essentially inactive. The chirality of the side chain did not influence the binding affinity. Activation of protein kinase C by 1a, 1c, and 1e demonstrated the same stereochemical requirements, but none were as active as OAG. For the 1,3-isomers 2, 2a, and 2b, the competitive binding studies gave different results. The racemic mixture and the D isomer, 2b, were able to compete for binding, but the L isomer, 2a, did not compete. These studies demonstrate that diacylglycerol binding to and activation of protein kinase C is stereospecific for the glycerol backbone, but not the side chain. Furthermore, the D-1,3-isomer must exist in a conformation such that the acyl and hydroxyl oxygens assume a spatial relationship similar to that in the L-1,2-isomers.
Strawn
L M
LM
Department of Medicinal Chemistry, University of Michigan, Ann Arbor 48109.
Martell
R E
RE
Simpson
R U
RU
Leach
K L
KL
Counsell
R E
RE
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D055598:Chemical Phenomena; D002621:Chemistry; D004075:Diglycerides / Q000138:chemical synthesis* / Q000378:metabolism; D004789:Enzyme Activation; D005989:Glycerides / Q000138:chemical synthesis*; D066298:In Vitro Techniques; D007480:Iopanoic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D004075:Diglycerides; D005989:Glycerides; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D011493:Protein Kinase C; D007480:Iopanoic Acid