Three mutations repurpose a plant karrikin receptor to a strigolactone receptor.

Uncovering the basis of small-molecule hormone receptors' evolution is paramount to a complete understanding of how protein structure drives function. In plants, hormone receptors for strigolactones are well suited to evolutionary inquiries because closely related homologs have different ligand preferences. More importantly, because of facile plant transgenic systems, receptors can be swapped and quickly assessed functionally in vivo. Here, we show that only three mutations are required to turn the nonstrigolactone receptor, KAI2, into a receptor that recognizes the plant hormone strigolactone. This modified receptor still retains its native function to perceive KAI2 ligands. Our directed evolution studies indicate that only a few keystone mutations are required to increase receptor promiscuity of KAI2, which may have implications for strigolactone receptor evolution in parasitic plants.

A novel strigolactone receptor antagonist provides insights into the structural inhibition, conditioning, and germination of the crop parasite Striga.

Crop parasites of the Striga genera are a major biological deterrent to food security in Africa and are one of the largest obstacles to poverty alleviation on the continent. Striga seeds germinate by sensing small-molecule hormones, strigolactones (SLs), that emanate from host roots. Although SL receptors (Striga hermonthica HYPOSENSITIVE TO LIGHT [ShHTL]) have been identified, discerning their function has been difficult because these parasites cannot be easily grown under laboratory conditions. Moreover, many Striga species are obligate outcrossers that are not transformable, hence not amenable to genetic analysis. By combining phenotypic screening with ShHTL structural information and hybrid drug discovery methods, we discovered a potent SL perception inhibitor for Striga, dormirazine (DOZ). Structural analysis of this piperazine-based antagonist reveals a novel binding mechanism, distinct from that of known SLs, blocking access of the hormone to its receptor. Furthermore, DOZ reduces the flexibility of protein-protein interaction domains important for receptor signaling to downstream partners. In planta, we show, via temporal additions of DOZ, that SL receptors are required at a specific time during seed conditioning. This conditioning is essential to prime seed germination at the right time; thus, this SL-sensitive stage appears to be critical for adequate receptor signaling. Aside from uncovering a function for ShHTL during seed conditioning, these results suggest that future Ag-Biotech Solutions to Striga infestations will need to carefully time the application of antagonists to exploit receptor availability and outcompete natural SLs, critical elements for successful parasitic plant invasions.

Factors associated with drug survival on first biologic therapy in patients with rheumatoid arthritis: a population-based cohort study.

Lack of sufficient head-to-head trials comparing biologic disease-modifying antirheumatic drugs (bDMARDs) in rheumatoid arthritis (RA), makes the choice of the first bDMARD a matter of rheumatologist's preference. Longer drug survival on the first bDMARD usually correlates with early remission. We aimed to identify factors associated with longer drug survival. We conducted a population-based retrospective longitudinal cohort study. We identified RA patients using the relevant International Classification of Disease 9th codes. "True" RA patients were defined as patients fulfilling, additionally, at least one of the following: receiving conventional DMARDs (cDMARDs), being positive for rheumatoid factor or anti-cyclic citrullinated peptide, or being diagnosed by a rheumatologist. We compared drug survival times and identified factors associated with longer drug survival. We identified 4268 true RA patients between the years of 2000-2017. 820 patients (19.2%) received at least one bDMARD. The most commonly prescribed bDMARDs were etanercept (352, 42.9%), adalimumab (143, 17.4%), infliximab (142, 17.3%) and tocilizumab (58, 7.1%). Infliximab was associated with the longest drug survival (47.1 months ± 46.3) while golimumab was associated with the shortest drug survival (14.9 months ± 15.1). Male gender [hazard ratio (HR) = 0.76, 95% confidence interval (CI), 0.63-0.86, p = 0.001], concurrent conventional DMARDs use (HR = 0.79, 95% CI 0.68 - 0.98, p = .031) and initiating bDMARD therapy in earlier calendric years (HR = 1.12, 95% CI 1.10 -1.18, p = 0.0001) were associated with longer drug survival. Male gender, concomitant cDMARDs and initiating biologic therapy at earlier calendric years are associated with longer drug survival.

Structural analysis of a hormone-bound Striga strigolactone receptor.

Strigolactones (SLs) regulate many aspects of plant development, but ambiguities remain about how this hormone is perceived because SL-complexed receptor structures do not exist. We find that when SL binds the Striga receptor, ShHTL5, a series of conformational changes relative to the unbound state occur, but these events are not sufficient for signalling. Ligand-complexed receptors, however, form internal tunnels that posit an explanation for how SL exits its receptor after hydrolysis.

Cognitive Impairment in Anti-Phospholipid Syndrome and Anti-Phospholipid Antibody Carriers.

Cognitive impairment is frequently reported among anti-phospholipid syndrome (APS) patients as well as anti-phospholipid antibody (aPL) carriers, but it is less studied than other manifestations of this condition. Moreover, the exact prevalence of cognitive impairment in these patients has not been accurately determined, mainly due to inconsistency in the tools used to identify impairment, small sample sizes, and variability in the anti-phospholipid antibodies measured and positivity cutoffs. The notion of a direct pathogenic effect is supported by the observation that the higher the number of aPLs present and the higher the load of the specific antibody, the greater the risk of cognitive impairment. There is some evidence to suggest that besides the thrombotic process, inflammation-related pathways play a role in the pathogenesis of cognitive impairment in APS. The cornerstone treatments of APS are anti-coagulant and anti-thrombotic medications. These treatments have shown some favorable effects in reversing cognitive impairment, but solid evidence for the efficacy and safety of these treatments in the context of cognitive impairment is still lacking. In this article, we review the current knowledge regarding the epidemiology, pathophysiology, clinical associations, and treatment of cognitive impairment associated with APS and aPL positivity.

Lung uptake in a young patient with hypercalcemia who was found to have systemic lupus erythematosus.

We report the case of 19-year-old woman with severe hypercalcemia who was evaluated with a bone scan to exclude bone metastases. Increased uptake in both lungs was detected on the bone scan. The patient's final diagnosis was systemic lupus erythematous (SLE). There is no reported pattern of bone scanning in SLE, and diffuse lung uptake has not been reported in these patients.