Angiotensin II (Ang II) is a peptide hormone that, like many cytokines, acts as a proinflammatory agent and growth factor. After injury to the liver, the hormone assists in tissue repair by stimulating hepatocytes and hepatic stellate cells to synthesize extracellular matrix proteins and secrete secondary cytokines and by stimulating myofibroblasts to proliferate. However, under conditions of chronic liver injury, all of these effects conspire to promote pathologic liver fibrosis. Much of this effect of Ang II results from activation of the proinflammatory NF-B transcription factor in response to stimulation of the type 1 Ang II receptor, a G protein-coupled receptor. Here, we characterize a previously undescribed signaling pathway mediating Ang II-dependent activation of NF-B, which is composed of three principal proteins, CARMA3, Bcl10, and MALT1. Blocking the function of any of these proteins, through the use of either dominant-negative mutants, RNAi, or gene targeting, effectively abolishes Ang II-dependent NF-B activation in hepatocytes. In addition, Bcl10 ؊/؊ mice show defective hepatic cytokine production after Ang II treatment. Evidence also is presented that this pathway activates NF-B through ubiquitination of IKK␥, the regulatory subunit of the I B kinase complex. These results elucidate a concrete series of molecular events that link ligand activation of the type 1 Ang II receptor to stimulation of the NF-B transcription factor. These findings also uncover a function of the CARMA, Bcl10, and MALT1 proteins in cells outside the immune system. G protein-coupled receptor ͉ hepatocyte ͉ IkB kinase ͉ inflammation ͉ ubiquitination

Mucosa-associated lymphoid tissue (MALT) lymphoma is the most common extranodal lymphoid neoplasm. Chromosomal translocation t(11;18)(q21,q21) is found in 30% of gastric MALT lymphomas and is associated with a failure to respond to standard treatment and a tendency to disseminate. This translocation generates a chimeric protein composed of N-terminal sequences of Inhibitor of Apoptosis 2 (API2, also known as BIRC3 and cIAP2) fused to C-terminal sequences of MALT1. API2-MALT1 promotes cell survival and proliferation via activation of nuclear factor-jB (NF-jB). Here, we investigate the mechanism by which the API2 moiety contributes to NF-jB stimulation. We find that the API2 moiety mediates oligomerization of API2-MALT1 as well as interaction with tumor necrosis factor receptor-associated factor 2 (TRAF2). Surprisingly, oligomerization does not occur via homotypic interaction; rather, the API2 moiety of one monomer interacts with the MALT1 moiety of another monomer. Further, the specific region of the API2 moiety responsible for mediating oligomerization is distinct from that mediating TRAF2 binding. Although deletion or mutation of the TRAF2 binding site does not inhibit oligomerization, it does lead to dramatically decreased NF-jB activation. Deletion of both TRAF2 binding and oligomerization regions results in nearcomplete loss of NF-jB activation. Thus, API2 moietymediated heterotypic oligomerization and TRAF2 binding both contribute to maximal API2-MALT1-dependent NF-jB stimulation.

Effective methods for monitoring eukaryotic gene expression and regulation based on bioluminescence - the emission of light by living organisms - are well established. Typically, the expression of a gene of interest is reported on with high sensitivity and over a wide dynamic range by the emission of light from a variety of engineered luciferase genes from beetles and marine organisms. The luciferase reporter genes are expressed downstream of the target gene or promoter and detected after exogenous addition of luciferin substrates. We describe a novel bioluminescence reporter method for the simultaneous monitoring of two genes expressing engineered firefly luciferase variants that emit readily distinguishable green and red light signals. The key feature is the selectivity of the enzymes for two luciferin substrates that determine each emission color. To validate our method, we performed a complex promoter transactivation experiment side-by-side with the Dual-Luciferase Reporter protocol and obtained essentially identical results. Additional comparative experiments demonstrated that our assay system provided improvements in background, cell normalization, and detectability compared to representative available methods. With access to a luminometer equipped with two optical filters, this method is an excellent choice for genetic reporter assays that can be performed with a single reagent solution.

Firefly luciferases, which emit visible light in a highly specific ATP-dependent process, have been adapted for a variety of applications including gene reporter assays, whole-cell biosensor measurements and in vivo imaging. We have previously reported the ~2-fold enhanced activity and 1.4-greater bioluminescence quantum yield properties of a chimeric enzyme that contains the N-domain of Photinus pyralis luciferase joined to the C-domain of Luciola italica luciferase. Subsequently, we identified 5 amino acid changes based on L. italica that are the main determinants of the improved bioluminescence properties. Further engineering to enhance thermal and pH stability produced a novel luciferase called PLG2. We present here a systematic comparison of the spectral and physical properties of the new protein with P. pyralis luciferase and demonstrate the potential of PLG2 for use in assays based on the detection of femtomol levels of ATP. Additionally, we compared the performance of a mammalian codon-optimized version of the cDNA for PLG2 with the luc2 gene in HEK293T cells. Using an optimized low-cost assay system, PLG2 activity can be monitored in mammalian cell lysates and in living cells offering an improved alternative to Promega’s luc2 for reporter and imaging applications.

Beetle luciferases have been adapted for live cell imaging where bioluminescence is dependent on the cellular availability of ATP, O 2 , and added luciferin. Previous Photinus pyralis red-emitting variants with high K m values for ATP have performed disappointingly in live cells despite having much higher relative specific activities than enzymes like Click Beetle Red (CBR). We engineered a luciferase variant PLR3 having a K m value similar to CBR and ~2.6-fold higher specific activity.The red-emitting PLR3 was ~2.5-fold brighter than CBR in living HEK293T and HeLa cells, an improvement consistent with the importance of the K m value in low ATP environments. KeywordsBioluminescence; firefly; luciferase; ATP; red-emitting; imaging Bioluminescent proteins, epitomized by the beetle luciferases (Lucs), are now proven reagents for noninvasive imaging studies. As reporters, bioluminescent enzymes can visualize genetic activity and many other cellular biochemical events; while in living animals, they can be used to track specific types of cells including tumors [1][2][3][4][5]. Major reasons for the current success of bioluminescence imaging (BLI) include: the great detectability (signal to noise) due to essentially nonexistent endogenous background; wide dynamic range; and the availability of reasonably priced commercial CCD-based detection devices [1][2][3]. Moreover, a particular advantage of the beetle Lucs, which produce light by oxidizing the luciferin substrate (LH 2 ) in reactions that also require Mg-ATP and molecular * To whom correspondence should be addressed: Tel.: + 1 860 439-2479, brbra@conncoll.edu. 1 Abbreviations used: BLI, bioluminescence imaging; CBR, Promega's click beetle red, recombinant Pyrophorus plagiophthalamus luciferase (GenBank: AY258591); LH 2 , D-firefly luciferin; Luc, luciferase; Luc2, Promega's Photinus pyralis-based luciferase (GenBank: AY738222); PLG2, recombinant P. pyralis luciferase variant (GenBank: KY486507); PLR3, recombinant P. pyralis luciferase variant (GenBank: KY486508); PpyRE9, recombinant P. pyralis luciferase variant (GenBank: GQ404466); and RLU, relative light units. All luciferases were expressed from the human codon optimized sequences indicated above. Competing interests statementThe authors declare no competing interests. Mainly for reasons of improved detectability that can be achieved by the more efficient transmission of light through animal tissues, light emission at wavelengths greater than 600 nm is highly advantageous [7,8] for good expression and stability at 37 °C, the specific activity was ~3.5-fold lower and the emission maxima was slightly blue-shifted (Table 1). Importantly, we succeeded in reducing both K m values: ~30-fold for Mg-ATP (3-fold greater than that for CBR) and ~7-fold for LH 2 (~2-fold lower than the CBR value). The mutations primarily responsible for the redshifted emission were Y255F and S284T, while the lowered K m values resulted from the G246A, F250H, and V351I amino acid changes that also contributed to the relative drop in...