Membrane‐Surface Anchoring of Charged Diacylglycerol‐Lactones Correlates with Biological Activities

Abstract

Synthetic diacylglycerol lactones (DAG-lactones) are effective modulators of critical cellular signaling pathways, downstream of the lipophilic second messenger diacylglycerol, that activate a host of protein kinase C (PKC) isozymes and other non-kinase proteins that share with PKC similar C1 membrane-targeting domains. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study examines the biological properties of charged DAG-lactones exhibiting different alkyl groups attached to the heterocyclic nitrogen of an α–pyridylalkylidene chain, and particularly the relationship between membrane interactions of the substituted DAG-lactones and their respective biological activities. Our results suggest that bilayer interface localization of the N-alkyl chain in the R2 position of the DAG-lactones inhibits translocation of PKC isoenzymes onto the cellular membrane. However, the orientation of a branched alkyl chain at the bilayer surface facilitates PKC binding and translocation. This investigation emphasizes that bilayer localization of the aromatic side residues of positively-charged DAG lactone derivatives play a central role in determining biological activity and that this factor contributes to the diversity of biological actions of these synthetic biomimetic ligands.

Molecular Basis for Failure of “Atypical” C1 Domain of Vav1 to Bind Diacylglycerol/Phorbol Ester

“…The presence and extent of branching in the alkyl groups on either the sn-1 or the sn-2 side chains also affect their binding affinities. We have shown previously that subtle differences in the chemical structure of the side chains on the DAG-lactone template can produce widely varying biological responses (63), due in part to differences in the degree of penetration of charged DAG-lactones into the membrane (40). These results suggest that the 3-pyridyl and guanidyl series of compounds could be explored further to optimize their alkyl substituents and examine their biological effects against charged C1 domains in vivo.…”

“…Nominal mass spectra were obtained at a resolution of 1200, and matrix-derived ions were background-subtracted during data system processing. Full experimental details and characterization have been reported previously for 6a, 6c, and 8b-e (40). Full characterization of novel DAG-lactones designated as compounds 6b, 8a, and 8f is described below.…”