Apoptotic cleavage of rabaptin-5-like proteins and a model for rabaptin-5 inactivation in apoptosis

Cell Cycle. 2006 Aug;5(16):1854-8. doi: 10.4161/cc.5.16.3092. Epub 2006 Aug 15.

Abstract

Intracellular membrane transport from the plasma membrane is one of the processes affected in apoptotic cells. Apoptotic inhibition of endosomal transport occurs due to cleavage of Rabaptin-5, an effector of small GTPase Rab5, which results in inhibition of early endosome fusion. Recently several novel Rabaptin-5-like proteins were identified. We investigated whether Rabaptin-5-like proteins, Rabaptin-5gamma and Rabaptin-5delta, are also cleaved in apoptosis and found that both proteins are cleaved in apoptotic cell extracts by caspase-3-related proteases. This suggests that functional inactivation of these proteins is necessary for apoptotic cell death. We also mapped a novel, N-terminal, putative Rab5 binding site in Rabaptin-5-like proteins, which becomes physically separated from the previously known C-terminal Rab5 binding site after apoptotic cleavage of these proteins. Presence of the second Rab5 binding site provides a new insight into Rabaptin-5 function in early endosome fusion and a mechanistic model for functional inactivation of Rabaptin-5 in apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis*
  • COS Cells
  • Caspase 3
  • Caspases / metabolism
  • Chlorocebus aethiops
  • Endosomes / physiology
  • Etoposide / pharmacology
  • Green Fluorescent Proteins / genetics
  • HL-60 Cells / drug effects
  • Humans
  • Membrane Fusion
  • Mutation
  • Protein Isoforms / genetics
  • Recombinant Fusion Proteins / metabolism
  • Transfection
  • Two-Hybrid System Techniques
  • Vesicular Transport Proteins / genetics*
  • rab5 GTP-Binding Proteins / genetics
  • rab5 GTP-Binding Proteins / metabolism

Substances

  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Vesicular Transport Proteins
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Etoposide
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • rab5 GTP-Binding Proteins