IkappaBbeta is an essential co-activator for LPS-induced IL-1beta transcription in vivo.

Inhibitor of κB (IκB) ß (IκBß) represents one of the major primary regulators of NF-κB in mammals. In contrast to the defined regulatory interplay between NF-κB and IκBα, much less is known about the biological function of IκBß. To elucidate the physiological role of IκBß in NF-κB signaling in vivo, we generated IκBß-deficient mice. These animals proved to be highly refractory to LPS-induced lethality, accompanied by a strong reduction in sepsis-associated cytokine production. In response to LPS, IκBß is recruited to the IL-1ß promoter forming a complex with the NF-κB subunits RelA/c-Rel required for IL-1ß transcription. Further transcriptome analysis of LPS-stimulated wild-type and IκBß-deficient BM-derived macrophages revealed several other genes with known regulatory functions in innate immunity arguing that a subset of NF-κB target genes is under control of IκBß. Collectively, these findings provide an essential proinflammatory role for IκBß in vivo, and establish a critical function for IκBß as a transcriptional coactivator under inflammatory conditions.

Interleukin 1 beta gene promoter SNPs are associated with risk of pancreatic cancer.

Epidemiological and experimental data demonstrate, that inflammation contributes significantly to pancreatic carcinogenesis. IL1beta, a pleiotropic cytokine produced by inflammatory cells and tumor cells, promotes cancer progression. Single nucleotide polymorphisms (SNPs) of the IL1beta promoter were found to be associated with an increased risk for certain cancers. In this case-control study we determined IL1beta promoter SNPs in 73 patients with pancreatic cancer and 235 controls. We found that the IL1beta -511CT/-31TC genotype was significantly associated with an increased risk for pancreatic cancer (OR 1.42, p=0.0456). Among pancreatic cancer cases, patients with the -511CT/-31TC genotype had less frequently resectable disease than patients with other IL1beta -511/-31 genotypes (p=0.0323). Furthermore, the IL1beta -511CT/-31TC genotype was more frequent observed in UICC stage IV (p=0.039) and undifferentiated tumors (G3) (p=0.019). In addition, we found that the proinflammatory IL1beta -511CT/-31TC alleles define an IL1beta secretory phenotype in pancreatic cancer cell lines in vitro. These findings provide a first evidence for an association of the IL1beta gene promoter SNPs with risk for pancreatic cancer.

Translational repression of MCL-1 couples stress-induced eIF2 alpha phosphorylation to mitochondrial apoptosis initiation.

The integrated stress response (ISR) integrates a broad range of environmental and endogenous stress signals to the phosphorylation of the alpha-subunit of eukaryotic translation initiation factor 2 (eIF2 alpha). Although intense or prolonged activation of this pathway is known to induce apoptosis, the molecular mechanisms coupling stress-induced eIF2 alpha phosphorylation to the cell death machinery have remained incompletely understood. In this study, we characterized apoptosis initiation in response to classical activators of the ISR (tunicamycin, UVC, elevated osmotic pressure, arsenite). We found that all applied stress stimuli activated a mitochondrial pathway of apoptosis initiation. Rapid and selective down-regulation of the anti-apoptotic BCL-2 family protein MCL-1 preceded the activation of BAX, BAK, and caspases. Stabilization of MCL-1 blocked apoptosis initiation, while cells with reduced MCL-1 protein content were strongly sensitized to stress-induced apoptosis. Stress-induced elimination of MCL-1 occurred with unchanged protein turnover and independently of MCL-1 mRNA levels. In contrast, stress-induced phosphorylation of eIF2 alpha at Ser(51) was both essential and sufficient for the down-regulation of MCL-1 protein in stressed cells. These findings indicate that stress-induced phosphorylation of eIF2 alpha is directly coupled to mitochondrial apoptosis regulation via translational repression of MCL-1. Down-regulation of MCL-1 enables but not enforces apoptosis initiation in stressed cells.