Caspases mediate nucleoporin cleavage, but not early redistribution of nuclear transport factors and modulation of nuclear permeability in apoptosis.
In eukaryotic cells, both soluble transport factors and components of the nuclear pore complex mediate protein and RNA trafficking between the nucleus and the cytoplasm. Here, we investigated whether caspases, the major execution system in apoptosis, target the nuclear pore or components of the nuclear transport machinery. Four nucleoporins, Nup153, RanBP2, Nup214 and Tpr are cleaved by caspases during apoptosis. In contrast, the nuclear transport factors, Ran, importin alpha and importin beta are not proteolytically processed, but redistribute across the nuclear envelope independently and prior to caspase activation. Also, mRNA accumulates into the nucleus before caspases become active. Microinjection experiments further revealed that early in apoptosis, the nucleus becomes permeable to dextran molecules of 70 kD molecular weight. Redistribution of import factors and mRNA, as well as nuclear permeabilisation, occur prior to caspase-mediated nucleoporin cleavage. Our findings suggest that the apoptotic programme includes modifications in the machinery responsible for nucleocytoplasmic transport, which are independent from caspase-mediated degradation of nuclear proteins.
Ferrando-May
E
E
Chair of Molecular Toxicology, Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
Cordes
V
V
Biller-Ckovric
I
I
Mirkovic
J
J
Görlich
D
D
Nicotera
P
P
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D028884:Karyopherins; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism*; D022022:Nuclear Pore / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019311:Staurosporine / Q000494:pharmacology; D020931:ran GTP-Binding Protein / Q000378:metabolism
D061945:Caspase Inhibitors; D004268:DNA-Binding Proteins; D028884:Karyopherins; D018832:Molecular Chaperones; C079377:NUP153 protein, human; C085914:NUP214 protein, human; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C073597:TPR protein, human; C094493:ran-binding protein 2; D003609:Dactinomycin; D020169:Caspases; D020931:ran GTP-Binding Protein; D019311:Staurosporine