Structural mechanisms of DIAP1 auto-inhibition and DIAP1-mediated inhibition of drICE

Li, Xiaochun; Wang, Jiawei; Shi, Yigong

doi:10.1038/ncomms1418

Cited by 27 publications

(34 citation statements)

References 41 publications

(81 reference statements)

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“…In fruit flies, cleavage of the inhibitor of apoptosis protein DIAP1 by activated caspases constitutes an important regulatory mechanism for cell death (34). Because Bir1p contains two baculovirus IAP repeat (BIR) domains and might be an IAP homolog, we examined whether Bir1p could be a substrate of the Yca1 metacaspase.…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure of the Yeast Metacaspase Yca1

Wong

Yan

Shi

2012

Journal of Biological Chemistry

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Background: Yca1 is a metacaspase and plays an important role in cell death of the yeast Saccharomyces cerevisiae. Results: Crystal structure of Yca1 reveals a monomeric architecture that differs significantly from other canonical caspases. Conclusion: Both catalytic mechanism and function of Yca1 may be distinct from canonical caspases. Significance: This structure offers insights into metacaspase function.

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Section: Resultsmentioning

confidence: 99%

Crystal Structure of the Yeast Metacaspase Yca1

Wong

Yan

Shi

2012

Journal of Biological Chemistry

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“…If the loop 2/loop 2′ interaction is lost, loops 3 and 4 become disordered and the enzyme is unable to bind substrate ( Figure 5c). Based on examination of the DrICE structure (3SIP), 51 residues G213 and G219 are both contained within loop 2 of DrICE. Neither of these positions can accommodate any residue larger than a glycine (Figure 5b) and the G213D and G219E mutations are predicted to inhibit critical interactions between loops 2 and 2'.…”

Section: Resultsmentioning

confidence: 99%

“…67,68 The substrate binds in the same region as the inhibitory region of the DIAP1 present in the DrICE (3SIP) structure. 51 (b) Based on examination of the DrICE structure (3SIP), residues G213 and G219 are both contained within loop 2 of DrICE. G213 forms an exceptionally tight contact with the backbone of F256 on loop 3, the loop that forms the base of the substrate-binding groove.…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, the N terminus of DIAP1 is an intramolecular inhibitor of DIAP1, keeping DIAP1 in an auto-inhibited conformation, unable to bind and inhibit DrICE. 51,[57][58][59] After caspase cleavage at D20 (likely by DrICE), the inhibitory N terminus is removed and now activated DIAP1 can bind to DrICE and inhibit it. Because DIAP1 is a substrate of DrICE before it becomes an inhibitor, the wt/class C heterotetramer would produce less-active DIAP1 and thus would be less-efficiently inhibited.…”

Section: Discussionmentioning

confidence: 99%

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Genetic characterization of two gain-of-function alleles of the effector caspase DrICE in Drosophila

Lindblad

Garnett

et al. 2015

Cell Death Differ

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Caspases are the executioners of apoptosis. Although much is known about their physiological roles and structures, detailed analyses of missense mutations of caspases are lacking. As mutations within caspases are identified in various human diseases, the study of caspase mutants will help to elucidate how caspases interact with other components of the apoptosis pathway and how they may contribute to disease. DrICE is the major effector caspase in Drosophila required for developmental and stressinduced cell death. Here, we report the isolation and characterization of six de novo drICE mutants, all of which carry point mutations affecting amino acids conserved among caspases in various species. These six mutants behave as recessive loss-offunction mutants in a homozygous condition. Surprisingly, however, two of the newly isolated drICE alleles are gain-of-function mutants in a heterozygous condition, although they are loss-of-function mutants homozygously. Interestingly, they only behave as gain-of-function mutants in the presence of an apoptotic signal. These two alleles carry missense mutations affecting conserved amino acids in close proximity to the catalytic cysteine residue. This is the first time that viable gain-of-function alleles of caspases are described in any intact organism and provides a significant exception to the expectation that mutations of conserved amino acids always abolish the pro-apoptotic activity of caspases. We discuss models about how these mutations cause the gain-offunction character of these alleles. Cell Death and Differentiation (2016) 23, 723-732; doi:10.1038/cdd.2015.144; published online 6 November 2015Apoptosis is a major form of programmed cell death. 1 The core apoptotic machinery is evolutionary conserved with caspases as the fundamental components. [1][2][3] Caspases are specific cysteine proteases that are produced as inactive zymogens composed of an N-terminal pro-domain, a large subunit region with the catalytic cysteine residue, and a small subunit region at the carboxyl end. 2,4 Depending on their structures and functions, caspases are grouped into initiator and effector caspases. 2,3 Initiator caspases possess long pro-domains, which facilitate the recruitment of initiator caspases into cell death signaling complexes for activation. 2,3,5 Effector caspases are activated by initiator caspase complexes through proteolytic processing, cleaving off the pro-domain and separating the large and small subunits. The active effector caspase is a tetramer composed of two large and two small subunits and contains two catalytic sites. 2,3 Activated effector caspases cleave many protein targets to trigger the physiological and morphological changes characteristic of apoptosis. In mammals, apoptotic initiator caspases are Caspase-8, -9, -2 and -10, and effector caspases involved in apoptosis are 3 Of the seven Drosophila caspases, only the initiator caspase Dronc (Caspase-9-like) and the effector caspases DrICE and Dcp-1 (Caspase-3-like) have been implicated in apoptosis in imagina...

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“…The resulting data sets were used to calculate the percentage of lysine residues at conserved positions within BIR1 and BIR2 after ClustalW alignment using the MEGA6.06 program (52). As determined by an NCBI blastp search of the RCSB Protein Data Bank, SfIAP's BIR1 (residues 97 to 167) is most closely related (44% identity, 63% similarity) to BIR1 (residues 41 to 112) of Drosophila DIAP1 (PDB 3SIP) from DIAP1 (53). Using PyMol (54), DIAP1 BIR1 residues 41 to 112 were modeled such that R43 and D53 were replaced with the corresponding SfIAP residues K99 and K109, respectively.…”

Section: Cells and Infectionsmentioning

confidence: 99%

Baculovirus Inhibitor-of-Apoptosis Op-IAP3 Blocks Apoptosis by Interaction with and Stabilization of a Host Insect Cellular IAP

Byers

Vandergaast

Friesen

2016

J Virol

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Baculovirus-encoded inhibitor of apoptosis (IAP) proteins likely evolved from their host cell IAP homologs, which function as critical regulators of cell death. Despite their striking relatedness to cellular IAPs, including the conservation of two baculovirus IAP repeat (BIR) domains and a C-terminal RING, viral IAPs use an unresolved mechanism to suppress apoptosis in insects. To define this mechanism, we investigated Op-IAP3, the prototypical IAP from baculovirus OpMNPV. We found that Op-IAP3 forms a stable complex with SfIAP, the native, short-lived IAP of host insect Spodoptera frugiperda. Long-lived Op-IAP3 prevented virus-induced SfIAP degradation, which normally causes caspase activation and apoptosis. In uninfected cells, Op-IAP3 also increased SfIAP steady-state levels and extended SfIAP's half-life. Conversely, SfIAP stabilization was lost or reversed in the presence of mutated Op-IAP3 that was engineered for reduced stability. Thus, Op-IAP3 stabilizes SfIAP and preserves its antiapoptotic function. In contrast to SfIAP, Op-IAP3 failed to bind or inhibit native Spodoptera caspases. Furthermore, BIR mutations that abrogate binding of well-conserved IAP antagonists did not affect Op-IAP3's capacity to prevent virus-induced apoptosis. Remarkably, Op-IAP3 also failed to prevent apoptosis when endogenous SfIAP was ablated by RNA silencing. Thus, Op-IAP3 requires SfIAP as a cofactor. Our findings suggest a new model wherein Op-IAP3 interacts directly with SfIAP to maintain its intracellular level, thereby suppressing virus-induced apoptosis indirectly. Consistent with this model, Op-IAP3 has evolved an intrinsic stability that may serve to repress signal-induced turnover and autoubiquitination when bound to its targeted cellular IAP. IMPORTANCEThe IAPs were first discovered in baculoviruses because of their potency for preventing apoptosis. However, the antiapoptotic mechanism of viral IAPs in host insects has been elusive. We show here that the prototypical viral IAP, Op-IAP3, blocks apoptosis indirectly by associating with unstable, autoubiquitinating host IAP in such a way that cellular IAP levels and antiapoptotic activities are maintained. This mechanism explains Op-IAP3's requirement for native cellular IAP as a cofactor and the dispensability of caspase inhibition. Viral IAP-mediated preservation of the host IAP homolog capitalizes on normal IAP-IAP interactions and is likely the result of viral IAP evolution in which degron-mediated destabilization and ubiquitination potential have been reduced. This mechanism illustrates another novel means by which DNA viruses incorporate host death regulators that are modified for resistance to host regulatory controls for the purpose of suppressing host cell apoptosis and acquiring replication advantages.A poptosis is an important defense against virus infection. This highly conserved self-destruct process is regulated by the inhibitor of apoptosis (IAP) proteins, a family of critical survival factors that are also involved in development, mitosis, inflam...

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Structural mechanisms of DIAP1 auto-inhibition and DIAP1-mediated inhibition of drICE

Cited by 27 publications

References 41 publications

Crystal Structure of the Yeast Metacaspase Yca1

Crystal Structure of the Yeast Metacaspase Yca1

Genetic characterization of two gain-of-function alleles of the effector caspase DrICE in Drosophila

Baculovirus Inhibitor-of-Apoptosis Op-IAP3 Blocks Apoptosis by Interaction with and Stabilization of a Host Insect Cellular IAP

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