title: Inositol 1,4,5-trisphosphate receptor type 1 is a substrate for caspase-3 and is cleaved during apoptosis in a caspase-3-dependent manner.
abstract: The inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R), an IP(3)-gated Ca(2+) channel located on intracellular Ca(2+) stores, modulates intracellular Ca(2+) signaling. During apoptosis of the human T-cell line, Jurkat cells, as induced by staurosporine or Fas ligation, IP(3)R type 1 (IP(3)R1) was found to be cleaved. IP(3)R1 degradation during apoptosis was inhibited by pretreatment of Jurkat cells with the caspase-3 (-like protease) inhibitor, Ac-DEVD-CHO, and the caspases inhibitor, z-VAD-CH(2)DCB but not by the caspase-1 (-like protease) inhibitor, Ac-YVAD-CHO, suggesting that IP(3)R1 was cleaved by a caspase-3 (-like) protease. The recombinant caspase-3 cleaved IP(3)R1 in vitro to produce a fragmentation pattern consistent with that seen in Jurkat cells undergoing apoptosis. N-terminal amino acid sequencing revealed that the major cleavage site is (1888)DEVD*(1892)R (mouse IP(3)R1), which involves consensus sequence for caspase-3 cleavage (DEVD). To determine whether IP(3)R1 is cleaved by caspase-3 or is proteolyzed in its absence by other caspases, we examined the cleavage of IP(3)R1 during apoptosis in the MCF-7 breast carcinoma cell line, which has genetically lost caspase-3. Tumor necrosis factor-alpha- or staurosporine-induced apoptosis in caspase-3-deficient MCF-7 cells failed to demonstrate cleavage of IP(3)R1. In contrast, MCF-7/Casp-3 cells stably expressing caspase-3 showed IP(3)R1 degradation upon apoptotic stimuli. Therefore IP(3)R1 is a newly identified caspase-3 substrate, and caspase-3 is essential for the cleavage of IP(3)R1 during apoptosis. This cleavage resulted in a decrease in the channel activity as IP(3)R1 was digested, indicating that caspase-3 inactivates IP(3)R1 channel functions.
authors.affiliation: Mikoshiba Calciosignal Net Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, 2-28-8 Honkomagome, Bunkyo-ku, Tokyo 113-0021, Japan. jhirota@ims.u-tokyo.ac.jp
authors.forename: J
authors.initials: J
authors.lastname: Hirota
authors.forename: T
authors.initials: T
authors.lastname: Furuichi
authors.forename: K
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019169:Jurkat Cells; D051379:Mice; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D015544:Inositol 1,4,5-Trisphosphate; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D002118:Calcium