Project description:Human mutations in the death receptor Fas or its ligand FasL cause autoimmune lymphoproliferative syndrome (ALPS), whereas mutations in caspase-8 or its adaptor FADD â which mediate cell death downstream of Fas/FasL â cause severe immunodeficiency in addition to ALPS. Mouse models have corroborated a role for FADD-caspase-8 in promoting inflammatory responses, but the mechanisms underlying immunodeficiency remain undefined. Here, we identify NEDD4-binding protein 1 (N4BP1) as a suppressor of cytokine production that is cleaved and inactivated by caspase-8. N4BP1 deletion in mice significantly increased production of select cytokines upon Toll-like receptor (TLR) 1/2, TLR7, or TLR9 stimulation, but not upon TLR3 or TLR4 engagement. N4BP1 did not suppress TLR3 or TLR4 responses in wild-type macrophages owing to TRIF- and caspase-8-dependent cleavage of N4BP1. Notably, impaired TLR3 and TLR4 cytokine responses of caspase-8-deficient macrophages were largely rescued by co-deletion of N4BP1. Thus, persistence of intact N4BP1 in caspase-8-deficient macrophages impairs their ability to mount robust cytokine responses. Tumor necrosis factor (TNF), like TLR3 or TLR4 agonists, also induced caspase-8-dependent cleavage of N4BP1, thereby licensing TRIF-independent TLRs to produce higher levels of inflammatory cytokines. Illustrating the importance of this function of TNF in vivo, TNF blockade increased the mortality of mice infected with Streptococcus Pneumoniae, but did not do so when infected mice lacked N4BP1. Collectively, our results identify N4BP1 as a potent suppressor of cytokine responses; reveal N4BP1 cleavage by Caspase-8 as a point of signal integration during inflammation; and offer an explanation for immunodeficiency caused by FADD-caspase-8 mutations.
Project description:Human mutations in the death receptor Fas or its ligand FasL cause autoimmune lymphoproliferative syndrome (ALPS), whereas mutations in caspase-8 or its adaptor FADD â which mediate cell death downstream of Fas/FasL â cause severe immunodeficiency in addition to ALPS. Mouse models have corroborated a role for FADD-caspase-8 in promoting inflammatory responses, but the mechanisms underlying immunodeficiency remain undefined. Here, we identify NEDD4-binding protein 1 (N4BP1) as a suppressor of cytokine production that is cleaved and inactivated by caspase-8. N4BP1 deletion in mice significantly increased production of select cytokines upon Toll-like receptor (TLR) 1/2, TLR7, or TLR9 stimulation, but not upon TLR3 or TLR4 engagement. N4BP1 did not suppress TLR3 or TLR4 responses in wild-type macrophages owing to TRIF- and caspase-8-dependent cleavage of N4BP1. Notably, impaired TLR3 and TLR4 cytokine responses of caspase-8-deficient macrophages were largely rescued by co-deletion of N4BP1. Thus, persistence of intact N4BP1 in caspase-8-deficient macrophages impairs their ability to mount robust cytokine responses. Tumor necrosis factor (TNF), like TLR3 or TLR4 agonists, also induced caspase-8-dependent cleavage of N4BP1, thereby licensing TRIF-independent TLRs to produce higher levels of inflammatory cytokines. Illustrating the importance of this function of TNF in vivo, TNF blockade increased the mortality of mice infected with Streptococcus Pneumoniae, but did not do so when infected mice lacked N4BP1. Collectively, our results identify N4BP1 as a potent suppressor of cytokine responses; reveal N4BP1 cleavage by Caspase-8 as a point of signal integration during inflammation; and offer an explanation for immunodeficiency caused by FADD-caspase-8 mutations.
Project description:Here, we show that HuR cleavage is dependent on active caspase-3 in oral cancer cells treated with ionizing radiation and the chemotherapeutic drug paclitaxel. We determined that oral cancer cells overexpressing cyclooxygenase-2 (COX-2) limited the cleavage of both caspase-3 and HuR, which in turn, reduced the rate of apoptosis in paclitaxel treated cells. Specific inhibition of COX-2 by celecoxib promoted apoptosis through activation of caspase-3 and cleavage of HuR in paclitaxel-resistant oral cancer cells. In addition, oral cancer cells overexpressing cellular HuR increased the half-life of COX-2 mRNA and promoted COX-2 expression, exhibiting enhanced tumor growth in vivo in comparison with the cleavable form of HuR. Finally, our RNP IP and RNA transcriptome analysis of HuR under IR revealed that the HuR cleavage product-1 (HuR-CP1) associates and promotes the expression of mRNAs encoding proteins involved in apoptosis.
Project description:Excessive responses to pattern-recognition receptors are prevented by regulatory mechanisms that affect the amounts, conformation, and associative properties of their signaling proteins. We report that signaling by the ribonucleic acid sensor RIG-I is restricted, in addition, by caspase-mediated cleavage that results in conversion of a signaling enhancer to a signaling inhibitor. RIP1 and caspase-8, two proteins known to mediate effects of receptors of the TNF/NGF family, are recruited to the RIG-I complex following viral infection, and serve in a coordinated manner antagonistic regulatory roles: conjugation of a ubiquitin chain to Lys-377 in RIP1 facilitates assembly of the RIG-I complex, but it also renders RIP1 susceptible to caspase-8-mediated cleavage, yielding an inhibitory RIP1 fragment. The dependence of RIP1 cleavage on the same molecular change as the one that facilitates RIG-I signaling allows for RIG-I signaling to be restricted in its duration without compromising its initial activation. Transcriptional profiling of human SV80 cells comparing cells infected with control lenti virus to cells infected with caspase-8 siRNA expressing lenti virus. Goal was to determine the effects of caspase-8 knock down on global gene expression. Two-condition experiment, Control lenti Vs caspase-8 siRNA expressing lenti. Biological replicates: 4 control, 4 caspase-8 siRNA infected
Project description:This data identifies the cleavage fragment of an in vitro reaction between recombinant, active caspase 7 and recombinant SATB2. The data confirms that this fragment is indeed a part of SATB2 and this information was used to further our investigation into the role SATB2 in mammalian skeletal muscle satellite cells.
Project description:A comparison of the embryonic transcriptome of wild type embryos (sggisoD-DS-SFS ) with embryos harbouring mutated DEVD caspase recognition sites ( sggisoD-cI-DS-SFS ) in a major shaggy isoforms class to examine the role of caspase cleavage in sgg function. The unique N-terminal exon undegoing caspase cleavage is tagged with DsRED at its N-terminus and StrepII-Flag-StrepII upstream of caspase cleavage sites for the wild type and caspase insensitive variant versions.