The moon's monthly cycle synchronizes reproduction in countless marine organisms. The mass-spawning bristle worm Platynereis dumerilii uses an endogenous monthly oscillator set by full moon to phase ...reproduction to specific days. But how do organisms recognize specific moon phases? We uncover that the light receptor L-Cryptochrome (L-Cry) discriminates between different moonlight durations, as well as between sun- and moonlight. A biochemical characterization of purified L-Cry protein, exposed to naturalistic sun- or moonlight, reveals the formation of distinct sun- and moonlight states characterized by different photoreduction- and recovery kinetics of L-Cry's co-factor Flavin Adenine Dinucleotide. In Platynereis, L-Cry's sun- versus moonlight states correlate with distinct subcellular localizations, indicating different signaling. In contrast, r-Opsin1, the most abundant ocular opsin, is not required for monthly oscillator entrainment. Our work reveals a photo-ecological concept for natural light interpretation involving a "valence interpreter" that provides entraining photoreceptor(s) with light source and moon phase information.
Abstract
Cryptochromes (CRYs) are a structurally conserved but functionally diverse family of proteins that can confer unique sensory properties to organisms. In the marine bristle worm Platynereis ...dumerilii, its light receptive cryptochrome L-CRY (
Pd
LCry) allows the animal to discriminate between sunlight and moonlight, an important requirement for synchronizing its lunar cycle-dependent mass spawning. Using cryo-electron microscopy, we show that in the dark,
Pd
LCry adopts a dimer arrangement observed neither in plant nor insect CRYs. Intense illumination disassembles the dimer into monomers. Structural and functional data suggest a mechanistic coupling between the light-sensing flavin adenine dinucleotide chromophore, the dimer interface, and the C-terminal tail helix, with a likely involvement of the phosphate binding loop. Taken together, our work establishes
Pd
LCry as a CRY protein with inverse photo-oligomerization with respect to plant CRYs, and provides molecular insights into how this protein might help discriminating the different light intensities associated with sunlight and moonlight.
A major obstacle in diabetes is the metabolic or hyperglycemic memory, which lacks specific therapies. Here we show that glucose-mediated changes in gene expression largely persist in diabetic kidney ...disease (DKD) despite reversing hyperglycemia. The senescence-associated cyclin-dependent kinase inhibitor p21 (Cdkn1a) was the top hit among genes persistently induced by hyperglycemia and was associated with induction of the p53-p21 pathway. Persistent p21 induction was confirmed in various animal models, human samples and in vitro models. Tubular and urinary p21-levels were associated with DKD severity and remained elevated despite improved blood glucose levels in humans. Mechanistically, sustained tubular p21 expression in DKD is linked to demethylation of its promoter and reduced DNMT1 expression. Two disease resolving agents, protease activated protein C (3K3A-aPC) and parmodulin-2, reversed sustained tubular p21 expression, tubular senescence, and DKD. Thus, p21-dependent tubular senescence is a pathway contributing to the hyperglycemic memory, which can be therapeutically targeted.
Diabetes mellitus is a metabolic disease largely due to lifestyle and nutritional imbalance, resulting in insulin resistance, hyperglycemia and vascular complications. Diabetic kidney disease (DKD) ...is a major cause of end-stage renal failure contributing to morbidity and mortality worldwide. Therapeutic options to prevent or reverse DKD progression are limited. Endothelial and glomerular filtration barrier (GFB) dysfunction and sterile inflammation are associated with DKD. Neutrophil extracellular traps (NETs), originally identified as an innate immune mechanism to combat infection, have been implicated in sterile inflammatory responses in non-communicable diseases. However, the contribution of NETs in DKD remains unknown. Here, we show that biomarkers of NETs are increased in diabetic mice and diabetic patients and that these changes correlate with DKD severity. Mechanistically, NETs promote NLRP3 inflammasome activation and glomerular endothelial dysfunction under high glucose stress in vitro and in vivo. Inhibition of NETs (PAD4 inhibitor) ameliorate endothelial dysfunction and renal injury in DKD. Taken together, NET-induced sterile inflammation promotes diabetes-associated endothelial dysfunction, identifying a new pathomechanism contributing to DKD. Inhibition of NETs may be a promising therapeutic strategy in DKD.
Significance The moon provides highly reliable time information to organisms. Whereas sunlight is known to set daily animal timing systems, mechanistic insight into the impact of moonlight on such ...systems remains scarce. We establish that the marine bristleworm
times the precise hours of mass spawning by integrating lunar light information into a plastic daily timing system able to run with circadian (∼24 h) or circalunidian (∼24.8 h) periodicity. The correct interpretation of moonlight is mediated by the interplay of two light sensors: a cryptochrome and a melanopsin ortholog provide information on light valence and moonrise time, respectively. Besides its ecological relevance, our work provides a plausible explanation for long-standing observations of light intensity-dependent differences in circadian clock periods.
Diabetes mellitus is hallmarked by accelerated atherosclerosis, a major cause of mortality among patients with diabetes. Efficient therapies for diabetes-associated atherosclerosis are absent. ...Accelerated atherosclerosis in diabetic patients is associated with reduced endothelial thrombomodulin (TM) expression and impaired activated protein C (aPC) generation. Here, we directly compared the effects of high glucose and oxidized LDL, revealing that high glucose induced more pronounced responses in regard to maladaptive unfolded protein response (UPR), senescence, and vascular endothelial cell barrier disruption. Ex vivo, diabetic ApoE−/− mice displayed increased levels of senescence and UPR markers within atherosclerotic lesions compared with nondiabetic ApoE−/− mice. Activated protein C pretreatment maintained barrier permeability and prevented glucose-induced expression of senescence and UPR markers in vitro. These data suggest that high glucose-induced maladaptive UPR and associated senescence promote vascular endothelial cell dysfunction, which—however—can be reversed by aPC. Taken together, current data suggest that reversal of glucose-induced vascular endothelial cell dysfunction is feasible.
Bone-derived osteocalcin has been suggested to be a metabolic regulator. To scrutinize the relation between osteocalcin and peripheral insulin sensitivity, we analyzed changes in serum osteocalcin ...relative to changes in insulin sensitivity, low-grade inflammation, and bone mineral density following lifestyle-induced weight loss in individuals with metabolic syndrome (MetS). Participants with MetS were randomized to a weight loss program or to a control group. Before and after the 6-month intervention period, clinical and laboratory parameters and serum osteocalcin levels were determined. Changes in body composition were analyzed by dual-energy X-ray absorptiometry (DXA). In participants of the intervention group, weight loss resulted in improved insulin sensitivity and amelioration of inflammation. Increased serum levels of osteocalcin correlated inversely with BMI (r = −0.63; p< 0.001), total fat mass (r = −0.58, p < 0.001), total lean mass (r = −0.45, p < 0.001), C-reactive protein (CRP) (r = −0.37; p < 0.01), insulin (r = −0.4; p < 0.001), leptin (r = −0.53; p < 0.001), triglycerides (r = −0.42; p < 0.001), and alanine aminotransferase (ALAT) (r = −0.52; p < 0.001). Regression analysis revealed that osteocalcin was independently associated with changes in CRP but not with changes in insulin concentration, fat mass, or bone mineral density, suggesting that weight loss-induced higher serum osteocalcin is primarily associated with reduced inflammation.
The process of embryonic development involves remarkable cellular plasticity, which governs the coordination between cells necessary to build an organism. One role of this plasticity is to ensure ...that when aberrant cells are eliminated, growth adjustment occurs so that the size of the tissue is maintained. An important regulator of cellular plasticity that ensures cellular cooperation is a fitness-sensing mechanism termed cell competition. During cell competition, cells with defects that lower fitness but do not affect viability, such as those that cause impaired signal transduction, slower cellular growth, mitochondrial dysregulation or impaired protein homeostasis, are killed when surrounded by fitter cells. This is accompanied by the compensatory proliferation of the surviving cells. The underlying factors and mechanisms that demarcate certain cells as less fit than their neighbouring cells and losers of cell competition are still relatively unknown. Recent evidence has pointed to mitochondrial defects and proteotoxic stress as important hallmarks of these loser cells. Here, we review recent advances in this area, focussing on the role of mitochondrial activity and protein homeostasis as major mechanisms determining competitive cell fitness during development and the importance of cell proteostasis in determining cell fitness.
Dysfunction of mesangial cells plays a major role in the pathogenesis of diabetic kidney disease (DKD), the leading cause of kidney failure. However, the underlying molecular mechanisms are ...incompletely understood. By unbiased gene expression analysis of glucose-exposed mesangial cells, we identified the transmembrane receptor CD248 as the most upregulated gene, and the maladaptive unfolded protein response (UPR) as one of the most stimulated pathways. Upregulation of CD248 was further confirmed in glucose-stressed mesangial cells in vitro, in kidney glomeruli isolated from diabetic mice (streptozotocin; STZ and db/db models, representing type 1 and type 2 diabetes mellitus, respectively) in vivo, and in glomerular kidney sections from patients with DKD. Time course analysis revealed that glomerular CD248 induction precedes the onset of albuminuria, mesangial matrix expansion and maladaptive UPR activation (hallmarked by transcription factor C/EBP homologous protein (CHOP) induction) but is paralleled by loss of the adaptive UPR regulator spliced X box binding protein (XBP1). Mechanistically, CD248 promoted maladaptive UPR signaling via inhibition of the inositol requiring enzyme 1α (IRE1α)-mediated transcription factor XBP1 splicing in vivo and in vitro. CD248 induced a multiprotein complex comprising heat shock protein 90, BH3 interacting domain death agonist (BID) and IRE1α, in which BID impedes IRE1α-mediated XBP1 splicing and induced CHOP mediated maladaptive UPR signaling. While CD248 knockout ameliorated DKD-associated glomerular dysfunction and reverses maladaptive unfolded protein response signaling, concomitant XBP1 deficiency abolished the protective effect in diabetic CD248 knockout mice, supporting a functional interaction of CD248 and XBP1 in vivo. Hence, CD248 is a novel mesangial cell receptor inducing maladaptive UPR signaling in DKD.
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