Poster Presentation 50th Lorne Proteins Conference 2025

Novel peptide-based inhibitors of protein kinase Cε interactions for the treatment of type 2 diabetes mellitus (#136)

Abisola A Siedoks 1 , Kathryn J Fincham 1 , Dorothy CC Wai 1 , Lewin Small 2 , Carsten Schmitz-Peiffer 2 , Ray S Norton 1 3
  1. Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
  2. School of Life and Environment Sciences, University of Sydney, Sydney, New South Wales, Australia
  3. ARC Centre for Fragment-Based Design, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia

Type 2 Diabetes Mellitus (T2DM) is a multifactorial metabolic disorder characterised by defective insulin secretion, insulin resistance and chronic inflammation. The involvement of the lipid-activated novel protein kinase C, PKCε, in the progression of T2DM, has been demonstrated through gene targeting techniques.1 Chronic activation of PKCε has been implicated as a driver in these processes; a consequence of its phosphorylation of key proteins involved in insulin secretion and activity.1 The spatial specificity of PKCε activity has been linked to interaction with RACK2, the Receptor for Activated C Kinase 2 (aka COPB2) involved in the retrograde Golgi-ER transport of proteins.2 Consequently, blockade of the PKCε-RACK2 interaction has been viewed as a strategy to modulate the deleterious effects of PKCε. Using a proximity-based chemiluminescent assay to monitor the binding of lipid-activated PKCε to RACK2, we have discovered inhibitory peptides derived from the PKCε sequence. In particular, a pentapeptide derived from the N-terminal C2-like domain of PKCε potently inhibits this interaction. By contrast, a previously-described PKCε inhibitor peptide, εV1-2, also derived from this region, exhibited no significant inhibition of the PKCe-RACK2 interaction in this assay. The pentapeptide exhibited good cell penetrating ability, when compared to TAT in the Split Luciferase Endosomal Escape Quantification assay.3 These findings highlight the potential of PKCε modulation via trafficking motif mimicry and afford an opportunity for the rational design of a novel generation of peptides for T2DM prevention and/or treatment.

  1. Schmitz-Peiffer C. Deconstructing the Role of PKC Epsilon in Glucose Homeostasis. Trends Endocrinol Metab. 2020, 31(5): 344-356.
  2. Jackson LP, Lewis M, Kent HM, Edeling MA, Evans PR, Duden R, Owen DJ. Molecular basis for recognition of dilysine trafficking motifs by COPI. Dev Cell. 2012, 23(6): 1255-1262.
  3. Teo SLY, Rennick JJ, Yuen D, Al-Wassiti H, Johnston APR, Pouton CW. Unravelling cytosolic delivery of cell penetrating peptides with a quantitative endosomal escape assay. Nat Commun. 2021, 12(1): 3721.