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

J Biol Chem. 2018 Jun 1;293(22):8330-8341. doi: 10.1074/jbc.RA117.000235. Epub 2018 Apr 10.


Diacylglycerol (DAG) is a key lipid second messenger downstream of cellular receptors that binds to the C1 domain in many regulatory proteins. Protein kinase C (PKC) isoforms constitute the most prominent family of signaling proteins with DAG-responsive C1 domains, but six other families of proteins, including the chimaerins, Ras-guanyl nucleotide-releasing proteins (RasGRPs), and Munc13 isoforms, also play important roles. Their significant involvement in cancer, immunology, and neurobiology has driven intense interest in the C1 domain as a therapeutic target. As with other classes of targets, however, a key issue is the establishment of selectivity. Here, using [3H]phorbol 12,13-dibutyrate ([3H]PDBu) competition binding assays, we found that a synthetic DAG-lactone, AJH-836, preferentially binds to the novel PKC isoforms PKCδ and PKCϵ relative to classical PKCα and PKCβII. Assessment of intracellular translocation, a hallmark for PKC activation, revealed that AJH-836 treatment stimulated a striking preferential redistribution of PKCϵ to the plasma membrane relative to PKCα. Moreover, unlike with the prototypical phorbol ester phorbol 12-myristate 13-acetate (PMA), prolonged exposure of cells to AJH-836 selectively down-regulated PKCδ and PKCϵ without affecting PKCα expression levels. Biologically, AJH-836 induced major changes in cytoskeletal reorganization in lung cancer cells, as determined by the formation of membrane ruffles, via activation of novel PKCs. We conclude that AJH-836 represents a C1 domain ligand with PKC-activating properties distinct from those of natural DAGs and phorbol esters. Our study supports the feasibility of generating selective C1 domain ligands that promote novel biological response patterns.

Keywords: C1 domain; cPKC; cell signaling; cytoskeleton; diacylglycerol; diacylglycerol lactone; ligand-binding protein; lipid signaling; nPKC; phorbol ester; protein kinase C (PKC); protein kinase activation; second messenger.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Binding, Competitive
  • Diglycerides / chemistry*
  • HeLa Cells
  • Humans
  • Lactones / metabolism*
  • Ligands
  • Protein Binding
  • Protein Kinase C-alpha / metabolism*
  • Protein Kinase C-delta / metabolism*
  • Protein Kinase C-epsilon / metabolism*
  • Protein Transport
  • Substrate Specificity


  • 1,2-diacylglycerol
  • Diglycerides
  • Lactones
  • Ligands
  • PRKCA protein, human
  • PRKCD protein, human
  • PRKCE protein, human
  • Protein Kinase C-alpha
  • Protein Kinase C-delta
  • Protein Kinase C-epsilon