Role of prodomain in importin-mediated nuclear localization and activation of caspase-2.
Caspase-2 is unique among mammalian caspases because it localizes to the nucleus in a prodomain-dependent manner. The caspase-2 prodomain also regulates caspase-2 activity via a caspase recruitment domain that mediates oligomerization of procaspase-2 molecules and their subsequent autoactivation. In this study we sought to map specific functional regions in the caspase-2 prodomain that regulate its nuclear transport and also its activation. Our data indicate that caspase-2 contains a classical nuclear localization signal (NLS) at the C terminus of the prodomain which is recognized by the importin alpha/beta heterodimer. The mutation of a conserved Lys residue in the NLS abolishes nuclear localization of caspase-2 and binding to the importin alpha/beta heterodimer. Although caspase-2 is imported into the nucleus, mutants lacking the NLS were still capable of inducing apoptosis upon overexpression in transfected cells. We define a region in the prodomain that regulates the ability of caspase-2 to form dot- and filament-like structures when ectopically expressed, which in turn promotes cell killing. Our data provides a mechanism for caspase-2 nuclear import and demonstrate that association of procaspase-2 into higher order structures, rather than its nuclear localization, is required for caspase-2 activation and its ability to induce apoptosis.
Baliga
Belinda C
BC
Hanson Institute, Frome Road, Adelaide 5000, Australia.
Colussi
Paul A
PA
Read
Stuart H
SH
Dias
Manisha M
MM
Jans
David A
DA
Kumar
Sharad
S
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D053143:Caspase 2; D020169:Caspases / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D004789:Enzyme Activation; D028884:Karyopherins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism
D028884:Karyopherins; D011498:Protein Precursors; D011994:Recombinant Proteins; D053143:Caspase 2; D020169:Caspases