The IkappaB function of NF-kappaB2 p100 controls stimulated osteoclastogenesis.

The prototranscription factor p100 represents an intersection of the NF-kappaB and IkappaB families, potentially serving as both the precursor for the active NF-kappaB subunit p52 and as an IkappaB capable of retaining NF-kappaB in the cytoplasm. NF-kappaB-inducing kinase (NIK) controls processing of p100 to generate p52, and thus NIK-deficient mice can be used to examine the biological effects of a failure in such processing. We demonstrate that treatment of wild-type osteoclast precursors with the osteoclastogenic cytokine receptor activator of NF-kappaB ligand (RANKL) increases both expression of p100 and its conversion to p52, resulting in unchanged net levels of p100. In the absence of NIK, p100 expression is increased by RANKL, but its conversion to p52 is blocked, leading to cytosolic accumulation of p100, which, acting as an IkappaB protein, binds NF-kappaB complexes and prevents their nuclear translocation. High levels of unprocessed p100 in osteoclast precursors from NIK-/- mice or a nonprocessable form of the protein in wild-type cells impair RANKL-mediated osteoclastogenesis. Conversely, p100-deficient osteoclast precursors show enhanced sensitivity to RANKL. These data demonstrate a novel, biologically relevant means of regulating NF-kappaB signaling, with upstream control and kinetics distinct from the classical IkappaBalpha pathway.

Posttranscriptional downregulation of c-IAP2 by the ubiquitin protein ligase c-IAP1 in vivo.

Inhibitor of apoptosis proteins (IAPs) c-IAP1 and c-IAP2 were identified as part of the tumor necrosis factor receptor 2 (TNFR2) signaling complex and have been implicated as intermediaries in tumor necrosis factor alpha signaling. Like all RING domain-containing IAPs, c-IAP1 and c-IAP2 have ubiquitin protein ligase (E3) activity. To explore the function of c-IAP1 in a physiologic setting, c-IAP1-deficient mice were generated by homologous gene recombination. These animals are viable and have no obvious sensitization to proapoptotic stimuli. Cells from c-IAP1(-/-) mice do, however, express markedly elevated levels of c-IAP2 protein in the absence of increased c-IAP2 mRNA. In contrast to reports implicating c-IAPs in the activation of NF-kappaB, resting and cytokine-induced NF-kappaB activation was not impaired in c-IAP1-deficient cells. Transient transfection studies with wild-type and E3-defective c-IAP1 revealed that c-IAP2 is a direct target for c-IAP1-mediated ubiquitination and subsequent degradation, which are potentiated by the adaptor function of TRAF2. Thus, the c-IAPs represent a pair of TNFR-associated ubiquitin protein ligases in which one regulates the expression of the other by a posttranscriptional and E3-dependent mechanism.

Effective asymmetric epoxidation of styrenes by chiral dioxirane.

High enantioselectivity (80-92% enantiomeric excess (ee)) has been obtained for the epoxidation of various styrenes using an easily prepared ketone (4) catalyst.

NF-kappa B-inducing kinase regulates selected gene expression in the Nod2 signaling pathway.

The innate immune system surveys the extra- and intracellular environment for the presence of microbes. Among the intracellular sensors is a protein known as Nod2, a cytosolic protein containing a leucine-rich repeat domain. Nod2 is believed to play a role in determining host responses to invasive bacteria. A key element in upregulating host defense involves activation of the NF-kappaB pathway. It has been suggested through indirect studies that NF-kappaB-inducing kinase, or NIK, may be involved in Nod2 signaling. Here we have used macrophages derived from primary explants of bone marrow from wild-type mice and mice that either bear a mutation in NIK, rendering it inactive, or are derived from NIK-/- mice, in which the NIK gene has been deleted. We show that NIK binds to Nod2 and mediates induction of specific changes induced by the specific Nod2 activator, muramyl dipeptide, and that the role of NIK occurs in settings where both the Nod2 and TLR4 pathways are activated by their respective agonists. Specifically, we have linked NIK to the induction of the B-cell chemoattractant known as BLC and suggest that this chemokine may play a role in processes initiated by Nod2 activation that lead to improved host defense.

TNF-R1 signaling: a beautiful pathway.

Tumor necrosis factor (TNF) is a major mediator of apoptosis as well as inflammation and immunity, and it has been implicated in the pathogenesis of a wide spectrum of human diseases, including sepsis, diabetes, cancer, osteoporosis, multiple sclerosis, rheumatoid arthritis, and inflammatory bowel diseases. The interaction of TNF with TNF receptor-1 (TNF-R1) activates several signal transduction pathways. A common feature of each pathway is the TNF-induced formation of a multiprotein signaling complex at the cell membrane. Over the past decade, many of the components and mechanisms of these signaling pathways have been elucidated. We provide an overview of current knowledge of TNF signaling and introduce an STKE Connections Map that depicts a canonical view of this process.

Highly enantioselective epoxidation of styrenes: implication of an electronic effect on the competition between spiro and planar transition states.

Asymmetric epoxidation of various styrenes using carbocyclic oxazolidinone-containing ketone 3 has been investigated. High enantioselectivity (89-93% enantiomeric excess) has been attained for this challenging class of alkenes. Mechanistic studies show that substituents on the ketone catalyst can have electronic influences on secondary orbital interactions, which affects the competition between spiro and planar transition states and, ultimately, enantioselectivity. The results described herein not only reveal the potential of chiral dioxirane catalyzed asymmetric epoxidation as a viable entry into this important class of olefins but also further enhance the understanding of the mechanistic aspects of chiral ketone-catalyzed asymmetric epoxidation.

TNF-induced recruitment and activation of the IKK complex require Cdc37 and Hsp90.

The IKK complex, containing two catalytic subunits IKKalpha and IKKbeta and a regulatory subunit NEMO, plays central roles in signal-dependent activation of NF-kappaB. We identify Cdc37 and Hsp90 as two additional components of the IKK complex. IKKalpha/IKKbeta/NEMO and Cdc37/Hsp90 form an approximately 900 kDa heterocomplex, which is assembled via direct interactions of Cdc37 with Hsp90 and with the kinase domain of IKKalpha/IKKbeta. Geldanamycin (GA), an antitumor agent that disrupts the formation of this heterocomplex, prevents TNF-induced activation of IKK and NF-kappaB. GA treatment reduces the size of the IKK complex and abolishes TNF-dependent recruitment of the IKK complex to TNF receptor 1 (TNF-R1). Therefore, heterocomplex formation with Cdc37/Hsp90 is a prerequisite for TNF-induced activation and trafficking of IKK from the cytoplasm to the membrane.

An improved synthesis of a ketone catalyst for asymmetric epoxidation of olefins.

An efficient synthesis of a ketone catalyst for asymmetric epoxidation of olefins from D-glucose in six steps is described.