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Hid, Rpr and Grim negatively regulate DIAP1 levels through distinct mechanisms

Soon Ji Yoo1, Jun R Huh, Israel Muro

  • 1Division of Biology, MC156-29, California Institute of Technology, Pasadena, CA 91125, USA.

Nature Cell Biology
|May 22, 2002
PubMed

Insights

Head involution defective (Hid), Reaper (Rpr), and Grim proteins regulate apoptosis by controlling levels of Inhibitor of Apoptosis (IAP) proteins. These proteins reduce DIAP1 levels through distinct ubiquitination and protein translation mechanisms, promoting cell death.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Inhibitor of Apoptosis (IAP) proteins are crucial regulators that suppress programmed cell death (apoptosis) by inhibiting caspases.
  • Many IAPs possess ubiquitin-protein ligase activity, yet the regulators of their auto-ubiquitination and protein levels remain largely unknown.

Purpose of the Study:

  • To identify regulators of Inhibitor of Apoptosis protein levels.
  • To elucidate the mechanisms by which Head involution defective (Hid), Reaper (Rpr), and Grim proteins influence the levels of Drosophila melanogaster IAP1 (DIAP1).

Main Methods:

  • Investigated the effects of Hid, Rpr, and Grim on DIAP1 protein levels in Drosophila melanogaster.
  • Analyzed DIAP1 polyubiquitination and degradation pathways.
  • Examined the impact of these proteins on global protein translation.

Main Results:

  • Hid, Rpr, and Grim were identified as factors that downregulate DIAP1 protein levels.
  • Hid directly stimulates DIAP1 polyubiquitination and subsequent degradation.
  • Rpr and Grim reduce DIAP1 levels via mechanisms independent of DIAP1's ligase activity, potentially involving suppression of protein translation.

Conclusions:

  • Two distinct mechanisms control DIAP1 ubiquitination and subsequent cell death: direct degradation via ubiquitination and differential loss of short-lived proteins due to suppressed translation.
  • These regulatory pathways highlight novel ways DIAP1 levels are controlled, ultimately promoting apoptosis through caspase activation.

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