Calpain A modulates Toll responses by limited Cactus/IκB proteolysis

Mol Biol Cell. 2013 Sep;24(18):2966-80. doi: 10.1091/mbc.E13-02-0113. Epub 2013 Jul 17.

Abstract

Calcium-dependent cysteine proteases of the calpain family are modulatory proteases that cleave their substrates in a limited manner. Among their substrates, calpains target vertebrate and invertebrate IκB proteins. Because proteolysis by calpains potentially generates novel protein functions, it is important to understand how this affects NFκB activity. We investigate the action of Calpain A (CalpA) on the Drosophila melanogaster IκB homologue Cactus in vivo. CalpA alters the absolute amounts of Cactus protein. Our data indicate, however, that CalpA uses additional mechanisms to regulate NFκB function. We provide evidence that CalpA interacts physically with Cactus, recognizing a Cactus pool that is not bound to Dorsal, a fly NFκB/Rel homologue. We show that proteolytic cleavage by CalpA generates Cactus fragments lacking an N-terminal region required for Toll responsiveness. These fragments are generated in vivo and display properties distinct from those of full-length Cactus. We propose that CalpA targets free Cactus, which is incorporated into and modulates Toll-responsive complexes in the embryo and immune system.

Publication types

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

MeSH terms

  • Animals
  • Body Patterning
  • Calpain / metabolism*
  • Cell Line
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / immunology
  • Drosophila melanogaster / metabolism*
  • Embryo, Nonmammalian / cytology
  • Embryo, Nonmammalian / metabolism
  • Fat Body / cytology
  • Fat Body / metabolism
  • I-kappa B Proteins / metabolism*
  • Immune System / metabolism
  • Larva / cytology
  • Larva / metabolism
  • Models, Biological
  • Mutation / genetics
  • NF-KappaB Inhibitor alpha
  • Phosphoproteins / chemistry
  • Phosphoproteins / metabolism*
  • Protein Binding
  • Proteolysis*
  • Toll-Like Receptors / metabolism*

Substances

  • DNA-Binding Proteins
  • Drosophila Proteins
  • I-kappa B Proteins
  • Phosphoproteins
  • Tl protein, Drosophila
  • Toll-Like Receptors
  • NF-KappaB Inhibitor alpha
  • cact protein, Drosophila
  • Calpain
  • calpain A, Drosophila