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The mitochondrial phosphatase PGAM5 functions at the convergence point of multiple necrotic death pathways

Zhigao Wang1, Hui Jiang, She Chen

  • 1Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.

Cell
|January 24, 2012
PubMed

Insights

Programmed necrosis involves RIP1 and RIP3 kinases. Mitochondrial phosphatase PGAM5 acts as a convergence point, regulating necrosis via Drp1-mediated mitochondrial fragmentation.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Programmed necrosis, a form of cell death, is regulated by specific kinases like RIP1 and RIP3.
  • TNF-α is a key inducer of programmed necrosis, involving interactions with MLKL.
  • Understanding the upstream regulators of necrosis is crucial for cell death research.

Purpose of the Study:

  • To identify protein complexes involved in TNF-α-induced necrosis.
  • To elucidate the role of mitochondrial phosphatase PGAM5 in programmed necrosis.
  • To define PGAM5 as a convergent point for multiple necrosis pathways.

Main Methods:

  • Proteomic analysis to identify RIP1 and RIP3 complexes.
  • siRNA knockdown of PGAM5 variants (PGAM5L, PGAM5S), RIP3, and MLKL.
  • Assessment of necrosis induction by TNF-α, ROS, and calcium ionophore.
  • Analysis of Drp1 recruitment, GTPase activity, and dephosphorylation at serine 637.
  • Mitochondrial fragmentation assays.

Main Results:

  • Identified RIP1- and RIP3-containing complexes forming upon necrosis induction.
  • PGAM5 (long and short forms) is a component of these complexes.
  • Knockdown of PGAM5 attenuated necrosis induced by various stimuli, while RIP3/MLKL knockdown only affected TNF-α-induced necrosis.
  • PGAM5S recruited and activated Drp1 by dephosphorylating serine 637, leading to mitochondrial fragmentation.
  • Mitochondrial fragmentation was identified as an early step in necrosis execution.

Conclusions:

  • PGAM5 functions as a crucial mitochondrial regulator in programmed necrosis.
  • PGAM5 acts as a convergent point for multiple necrosis-inducing pathways.
  • PGAM5-mediated Drp1 activation and subsequent mitochondrial fragmentation are essential for necrosis.

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