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Clathrin light chain b is capable of affecting potently a major protein phosphatase from microtubules (MT-PP1)

Akira Hiraga1, Nick Morrice, Eiko Honda

  • 1Department of Biochemistry, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan. hiraga@idac.tohoku.ac.jp

FEBS Letters
|February 8, 2006
PubMed

Insights

Clathrin light chain b (CLb) potently inhibits protein phosphatase 1 (PP1) activity. This suggests CLb may be a key regulator of PP1 in the brain.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Neuroscience

Background:

  • Protein phosphatases (PPs) are crucial enzymes involved in cellular regulation.
  • Clathrin light chain b (CLb) is a component of the clathrin coat involved in protein trafficking.

Purpose of the Study:

  • To investigate the interaction between CLb and protein phosphatases.
  • To determine if CLb affects the catalytic activity of major protein phosphatases.

Main Methods:

  • Purification of CLb from bovine brain post-microtubule supernatant.
  • Mass spectrometry for CLb identification.
  • Enzyme assays to measure protein phosphatase activity in the presence of CLb.

Main Results:

  • Purified CLb potently inhibited a major protein phosphatase (PP) recognized by anti-PP1 antibodies, which was copurified with microtubules.
  • CLb affected both the catalytic subunit and holoenzyme of PP1 but had little effect on PP2A.
  • CLb from clathrin-coated vesicles was significantly less potent than purified CLb, but CLb in the post-microtubule supernatant was highly active.

Conclusions:

  • CLb is a potent inhibitor of protein phosphatase 1.
  • CLb present in the post-microtubule supernatant, whether soluble or sedimentable, exhibits significant PP1 inhibitory activity.
  • CLb may function as a critical regulator of PP1 activity in vivo.

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