The Bulk of Autotaxin Activity Is Dispensable for Adult Mouse Life.

Autotaxin (ATX, Enpp2) is a secreted lysophospholipase D catalysing the production of lysophosphatidic acid, a pleiotropic growth factor-like lysophospholipid. Increased ATX expression has been detected in a number of chronic inflammatory diseases and different types of cancer, while genetic interventions have proven a role for ATX in disease pathogenesis. Therefore, ATX has emerged as a potential drug target and a large number of ATX inhibitors have been developed exhibiting promising therapeutic potential. However, the embryonic lethality of ATX null mice and the ubiquitous expression of ATX and LPA receptors in adult life question the suitability of ATX as a drug target. Here we show that inducible, ubiquitous genetic deletion of ATX in adult mice, as well as long-term potent pharmacologic inhibition, are well tolerated, alleviating potential toxicity concerns of ATX therapeutic targeting

No effect of Tmx-induced genetic inactivation of ATX in mouse survival rate.

<p>Kaplan–Meier survival curves of R26Cre-ER^T2/<i>Enpp2</i>^n/n and control mice administered with different Tmx concentrations (50, 100 and 180 mg/kg) using two different routes of delivery (IP, PO), as indicated and as described in the text. Presented results are cumulative from 1 (A), 3 (B) and 4 (C and D) experiments. No statistical significant differences were observed, as assessed with the Logrank test. Overlapping curves are indicated by consecutive symbols.</p

Tmx-induced (180 mg/kg PO) R26Cre-ER^T2-mediated genetic ablation of ATX results in diminished ATX levels in tissues and plasma.

<p>(A) Real-Time RT-PCR analysis of relative ATX mRNA expression levels in different tissues normalized to the expression levels of B2M. (n = 5–10; exp = 2; with the exception of BAT/WAT n = 4, exp = 1). (B) Real-Time RT-PCR analysis of ATX mRNA expression levels, normalized to the expression levels of B2M, in different tissues following Tmx-induced genetic ablation of the <i>Enpp2</i> gene. (n = 5–10; exp = 2; with the exception of BAT/WAT n = 4, exp = 1). (C) Section from a western blot for ATX (4F1 Ab) in the plasma of the indicated mice. The full images, together with a coomassie brilliant blue staining of the same samples as loading control, and an alternate blot with a commercial antibody can be found at <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143083#pone.0143083.s007" target="_blank">S7 Fig</a> (D) Plasma ATX activity in the plasma of the indicated mice as determined with the TOOS assay on natural LPC substrates (n = 13–27; exp = 3). (E) Plasma LPA levels of the indicated mice as determined by HPLC-MS/MS (n = 9–13; exp = 2). (D) Plasma lysophospholipid (LPLs) levels remain unchanged as measured with HPLC-MS/ MS (n = 9–13; exp = 2). All values in every panel are means (± SEM) and are presented (except A) normalised (%) to control values.</p

Autotaxin expression from synovial fibroblasts is essential for the pathogenesis of modeled arthritis

Rheumatoid arthritis is a destructive arthropathy characterized by chronic synovial inflammation that imposes a substantial socioeconomic burden. Under the influence of the proinflammatory milieu, synovial fibroblasts (SFs), the main effector cells in disease pathogenesis, become activated and hyperplastic, releasing proinflammatory factors and tissue-remodeling enzymes. This study shows that activated arthritic SFs from human patients and animal models express significant quantities of autotaxin (ATX; ENPP2), a lysophospholipase D that catalyzes the conversion of lysophosphatidylcholine to lysophosphatidic acid (LPA). ATX expression from SFs was induced by TNF, and LPA induced SF activation and effector functions in synergy with TNF. Conditional genetic ablation of ATX in mesenchymal cells, including SFs, resulted in disease attenuation in animal models of arthritis, establishing the ATX/LPA axis as a novel player in chronic inflammation and the pathogenesis of arthritis and a promising therapeutic target

Living without Fur: the subtlety and complexity of iron-responsive gene reulgation in the symbiotic bacterium Rhizobium and other a-proteobacteria

The alpha-proteobacteria include several important genera, including the symbiotic N2-fixing “rhizobia” the plant pathogen Agrobacterium, the mammalian pathogens Brucella, Bartonella as well as many others that are of environmental or other interest—including Rhodobacter, Caulobacter and the hugely abundant marine genus Pelagibacter. Only a few species—mainly different members of the rhizobia—have been analyzed directly for their ability to use and to respond to iron. These studies, however, have shown that at least some of the “alphas” differ fundamentally in the ways in which they regulate their genes in response to Fe availability. In this paper, we build on our own work on Rhizobium leguminosarum (the symbiont of peas, beans and clovers) and on Bradyrhizobium japonicum, which nodulates soybeans and which has been studied in Buffalo and Zürich. In the former species, the predominant Fe-responsive regulator is not Fur, but RirA, a member of the Rrf2 protein family and which likely has an FeS cluster cofactor. In addition, there are several R. leguminosarum genes that are expressed at higher levels in Fe-replete conditions and at least some of these are regulated by Irr, a member of the Fur superfamily and which has the unusual property of being degraded by the presence of heme. In silico analyses of the genome sequences of other bacteria indicate that Irr occurs in all members of the Rhizobiales and the Rhodobacterales and that RirA is found in all but one branch of these two lineages, the exception being the clade that includes B. japonicum. Nearly all the Rhizobiales and the Rhodobacterales contain a gene whose product resembles bona fide Fur. However, direct genetic studies show that in most of the Rhizobiales and in the Rhodobacterales it is a “Mur” (a manganese responsive repressor of a small number of genes involved in Mn uptake) or, in Bradyrhizobium, it recognizes the operator sequences of only a few genes that are involved in Fe metabolism. We propose that the Rhizobiales and the Rhodobacterales have relegated Fur to a far more minor role than in (say) E. coli and that they employ Irr and, in the Rhizobiales, RirA as their global Fe-responsive transcriptional regulators. In contrast to the direct interaction between Fe2+ and conventional Fur, we suggest that these bacteria sense Fe more indirectly as functions of the intracellular concentrations of FeS clusters and of heme. Thus, their “iron-omes” may be more accurately linked to the real-time needs for the metal and not just to its absolute concentration in the environment