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JNK mediates UVB-induced apoptosis upstream lysosomal membrane permeabilization and Bcl-2 family proteins

Cecilia Bivik1, Karin Ollinger

  • 1Division of Dermatology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, 581 85 Linköping, Sweden. cecbi@ibk.liu.se

Apoptosis : an International Journal on Programmed Cell Death
|July 25, 2008
PubMed

Insights

UVB radiation triggers apoptosis in human melanocytes via JNK signaling. Suppressing JNK protected cells by preventing lysosomal damage and regulating key proteins, highlighting JNK

Area of Science:

  • Cell Biology
  • Dermatology
  • Molecular Biology

Background:

  • UVB irradiation is a known inducer of cellular damage in human melanocytes.
  • Apoptosis, or programmed cell death, is a critical cellular process.
  • JNK (c-Jun N-terminal kinase) is a key signaling pathway involved in stress responses.

Purpose of the Study:

  • To investigate the role of JNK signaling in UVB-induced apoptosis in human melanocytes.
  • To elucidate the molecular mechanisms by which JNK mediates apoptosis following UVB exposure.

Main Methods:

  • siRNA-mediated depletion of JNK1 and JNK2 expression.
  • Assessment of apoptosis markers: nuclear fragmentation and caspase-3 activity.
  • Mitochondrial translocation of Bax protein.
  • Analysis of lysosomal membrane permeabilization (release of cathepsin B and D).
  • Co-immunoprecipitation to study protein interactions (Mcl-1 and Bim).
  • Western blotting to detect protein levels and phosphorylation.

Main Results:

  • UVB irradiation induced JNK phosphorylation and subsequent apoptosis in human melanocytes.
  • Depletion of JNK1/JNK2 protected against apoptosis, reducing nuclear fragmentation and caspase-3 activity.
  • JNK suppression inhibited Bax translocation to mitochondria and lysosomal membrane permeabilization.
  • UVB reduced the interaction between pro-survival Mcl-1 and pro-apoptotic Bim, with Bim phosphorylation occurring in a JNK-dependent manner.
  • Proteasome inhibition prevented the UVB-induced decrease in Mcl-1 protein levels.

Conclusions:

  • JNK signaling plays a critical pro-apoptotic role in human melanocytes following UVB irradiation.
  • JNK acts upstream of lysosomal membrane permeabilization and regulates Bim phosphorylation and Mcl-1 degradation.
  • Targeting JNK signaling may offer a therapeutic strategy to protect melanocytes from UVB-induced damage.

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