Mixed Lineage kinase-3 Stabilizes and Functionally Cooperates With TRIBBLES-3 to Compromise Mitochondrial Integrity in Cytokine-Induced Death of Pancreatic Beta Cells

J Biol Chem. 2010 Jul 16;285(29):22426-36. doi: 10.1074/jbc.M110.123786. Epub 2010 Apr 26.

Abstract

Mixed lineage kinases (MLKs) have been implicated in cytokine signaling as well as in cell death pathways. Our studies show that MLK3 is activated in leukocyte-infiltrated islets of non-obese diabetic mice and that MLK3 activation compromises mitochondrial integrity and induces apoptosis of beta cells. Using an ex vivo model of islet-splenocyte co-culture, we show that MLK3 mediates its effects via the pseudokinase TRB3, a mammalian homolog of Drosophila Tribbles. TRB3 expression strongly coincided with conformational change and mitochondrial translocation of BAX. Mechanistically, MLK3 directly interacted with and stabilized TRB3, resulting in inhibition of Akt, a strong suppressor of BAX translocation and mitochondrial membrane permeabilization. Accordingly, attenuation of MLK3 or TRB3 expression each prevented cytokine-induced BAX conformational change and attenuated the progression to apoptosis. We conclude that MLKs compromise mitochondrial integrity and suppress cellular survival mechanisms via TRB3-dependent inhibition of Akt.

Publication types

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

MeSH terms

  • Adult
  • Animals
  • Cell Cycle Proteins / metabolism*
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Coculture Techniques
  • Cytokines / pharmacology*
  • Enzyme Activation / drug effects
  • Gene Knockdown Techniques
  • Humans
  • Insulin-Secreting Cells / drug effects
  • Insulin-Secreting Cells / enzymology*
  • Insulin-Secreting Cells / pathology*
  • MAP Kinase Kinase Kinases / metabolism*
  • Mice
  • Mitochondria / drug effects*
  • Mitochondria / metabolism*
  • Protein Binding / drug effects
  • Protein Conformation
  • Protein Stability / drug effects
  • Protein Transport / drug effects
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Repressor Proteins / metabolism*
  • bcl-2-Associated X Protein / chemistry
  • bcl-2-Associated X Protein / metabolism

Substances

  • Cell Cycle Proteins
  • Cytokines
  • Repressor Proteins
  • TRB3 protein, mouse
  • bcl-2-Associated X Protein
  • Proto-Oncogene Proteins c-akt
  • MAP Kinase Kinase Kinases
  • mitogen-activated protein kinase kinase kinase 11