Synthesis and Evaluation of Dimeric Derivatives of Diacylglycerol–Lactones as Protein Kinase C Ligands

Abstract

Protein kinase C (PKC) mediates a central cellular signal transduction pathway involved in disorders such as cancer and Alzheimer's disease. PKC is regulated by binding of the second messenger sn-1,2-diacylglycerol (DAG) to its tandem C1 domains, designated C1a and C1b, leading both to PKC activation and to its translocation to the plasma membrane and to internal organelles. Depending on the isoform, there may be differences in the ligand selectivity of the C1a and C1b domains, and there is different spacing between the C1 domains of the conventional and novel PKCs. Bivalent ligands have the potential to exploit these differences between isoforms, yielding isoform selectivity. In the present study, we describe the synthesis of a series of dimeric derivatives of conformationally constrained diacylglycerol (DAG) analogs (DAG-lactones). We characterize the derivatives in vitro for their binding affinities, both to a single C1 domain (the C1b domain of PKCδ) as well as to the conventional PKCα isoform and the novel PKCδ isoform, and we measure their abilities to cause translocation of PKCδ and PKCε in intact cells. The dimeric compound with the 10-carbon linker was modestly more effective for the isolated PKCδ C1b domain than was the monomeric compound. For the intact PKCα and PKCδ, the shortest DAG-lactone dimer had similar affinity to the monomer and affinity decreased progressively up to the 16-carbon linker. The dimeric derivatives did not cause the Golgi accumulation of PKCδ. The present results provide important insights into the development of new chemical tools for biological studies on PKC.

Characterization of AJH-836, a diacylglycerol-lactone with selectivity for novel PKC isozymes

“…This is quite remarkable because, as demonstrated in early studies, DAG generated physiologically upon activation of receptors displays similar in vitro affinities for cPKCs and nPKCs, a pattern also observed for prototypical phorbol esters. Unlike AJH-836, other DAG-lactones have been reported to have similar activities for cPKCs and nPKCs in vitro and better translocate PKC␣ to the plasma membrane (22,46). Other natural compounds with C1 domain-binding capabilities such as 12-deoxyphorbol esters, mezerein, and thymeleatoxin have higher affinities for cPKCs relative to nPKCs (25).…”

Scaffold hopping from (5-hydroxymethyl) isophthalates to multisubstituted pyrimidines diminishes binding affinity to the C1 domain of protein kinase C

“…To improve the affinity and selectivity of C1 domain ligands Ohashi and coworkers recently presented a novel set of dimeric DAG-lactone derivatives [ 17 ]. These dimeric lactones showed no enhanced binding affinity to the full-length PKC α or - δ compared to their monomeric constructs, and they indicated higher lipophilicity (clog P values: 10.7–16.7).…”

“…When binding to the C1 domains, phorbol esters contribute to the formation of a continuous hydrophobic surface, which allows the protein-ligand complex to anchor to membranes and stabilize the activated protein-ligand-membrane complex. From two studies on DAG lactones, it appears that the amphipathic properties and the log P of a C1 domain–targeted ligand substantially affect the affinity for the protein [ 16 , 17 ].…”

The function of Golgi apparatus in LRRK2-associated Parkinson’s disease

“…Golgi-associated protein kinase C (PKC) is composed of calcium- and phospholipid-dependent Ser/Thr protein kinases that mediate central cell signaling pathways and cause several neurological disorders such as PD ( Rosse et al, 2010 ; Ohashi et al, 2017 ). The GA function is regulated by PKC and oxidative stress ( Lenkavska et al, 2020 ).…”