Ceramide disables 3-phosphoinositide binding to the pleckstrin homology domain of protein kinase B (PKB)/Akt by a PKCzeta-dependent mechanism.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory mechanistic study (bench research with no human data)
PubMed 14560023 · doi:10.1128/MCB.23.21.7794-7808.2003
What was done
Investigated the molecular mechanisms by which ceramide inhibits insulin-stimulated protein kinase B (PKB/Akt) activation in cell culture models, including L6 cells. Researchers examined the physical interaction between PKB and atypical PKCzeta, measured phosphorylation of the PKB pleckstrin homology (PH) domain at Thr(34), assessed phosphatidylinositol 3,4,5-trisphosphate (PIP3) binding to PKB, and tested the effects of a PKB T34A mutation, PKCzeta inhibitors, and kinase-dead PKCzeta.
What was found
The abstract reports directional biochemical mechanisms without quantitative numerical data. PKCzeta physically interacted with PKB in unstimulated cells; insulin promoted complex dissociation and activated PKB, but ceramide prevented dissociation and activated PKCzeta. Ceramide-activated PKCzeta phosphorylated the PKB-PH domain at Thr(34), blocking PIP3 binding and suppressing insulin-induced PKB activation. Expressing a PKB T34A mutant restored PIP3 binding and conferred resistance to ceramide inhibition in L6 cells, while PKCzeta inhibitors and kinase-dead PKCzeta antagonized ceramide-induced PKB suppression.
Why it matters
This study defines a specific biochemical mechanism linking ceramide accumulation to impaired insulin signaling and cell death via PKCzeta-mediated phosphorylation of PKB. It clarifies how lipid intermediates can directly disrupt downstream insulin transduction pathways.
Limits
The study is restricted to in vitro biochemical assays and cell culture models (L6 cells) without in vivo animal or human metabolic validation. The abstract provides no quantitative metrics, effect sizes, or statistical confidence intervals.
Cited by
- supports Ceramides directly block insulin signaling by inhibiting Akt phosphorylation.