The immediate responses to inhibition of phosphatidylcholine (PC) biosynthesis in yeast are altered phospholipid levels, slow growth, and defects in the morphology and localization of ER and mitochondria. With chronic lipid imbalance, yeast adapt. Lipid droplet (LD) biogenesis and conversion of phospholipids to triacylglycerol are required for restoring some phospholipids to near wild-type levels. We confirmed that the Unfolded Protein Response is activated by this lipid stress and find that Hsp104p is recruited to ER aggregates. We also find that LDs form at ER aggregates, contain polyubiquitinated proteins and an ER chaperone, and are degraded in the vacuole by a process resembling microautophagy. This process, microlipophagy, is required for restoration of organelle morphology and cell growth during adaptation to lipid stress. Microlipophagy does not require ATG7 but does requires ESCRT components and a newly identified class E VPS protein that localizes to ER and is up-regulated by lipid imbalance.

SUMMARY During its life cycle, Plasmodium falciparum undergoes rapid proliferation fueled by de novo synthesis and acquisition of host cell lipids. Consistent with this essential role, Plasmodium lipid synthesis enzymes are emerging as potential drug targets. To explore their broader potential for therapeutic interventions, we assayed the global lipid landscape during P. falciparum asexual blood stage (ABS) and sexual development. Using liquid chromatography–mass spectrometry, we analyzed 304 lipids constituting 24 classes in ABS parasites, infected red blood cell (RBC)-derived microvesicles, gametocytes, and uninfected RBCs. Ten lipid classes were previously uncharacterized in P. falciparum and 70–75% of the lipid classes exhibited changes in abundance during ABS and gametocyte development. Utilizing compounds that target lipid metabolism, we affirmed the essentiality of major classes, including triacylglycerols. These studies highlight the interplay between host and parasite lipid metabolism and provide a comprehensive analysis of P. falciparum lipids with candidate pathways for drug discovery efforts.

Gasdermin D (GSDMD) is an effector molecule for pyroptosis downstream of canonical and noncanonical inflammasome signaling pathways. Cleavage of GSDMD by inflammatory caspases triggers the oligomerization and lipid binding by its N-terminal domain, which assembles membrane pores, whereas its C-terminal domain binds the N-terminal domain to inhibit pyroptosis. Despite recent progress in our understanding of the structure and function of the murine gasdermin A3 (mGSDMA3), the molecular mechanisms of GSDMD activation and regulation remain poorly characterized. Here, we report the crystal structures of the full-length murine and human GSDMDs, which reveal the architecture of the GSDMD N-terminal domains and demonstrate distinct and common features of autoinhibition among gasdermin family members utilizing their b1-b2 loops. Disruption of the intramolecular domain interface enhanced pyroptosis, whereas mutations at the predicted lipid-binding or oligomerization surface reduced cytolysis. Our study provides a framework for understanding the autoinhibition, lipid binding, and oligomerization of GSDMD by using overlapping interfaces.

m6A is the most common form of mRNA modification. However, little is known about its role in clear cell renal cell carcinoma (ccRCC). This study aims to identify gene signatures and prognostic values of m6A regulators in ccRCC. In this study, a total of 528 ccRCC patients from TCGA database with sequencing and CNV data were included. Survival analysis was performed using log-rank tests and Cox regression model. The association between alteration of m6A regulators and clinicopathological characteristics was examined using chi-square test. The results showed that alteration of m6A regulators was associated with pathologic stage. Patients with any CNVs of the regulatory genes had worse OS and DFS than those with diploid genes. Moreover, deletion of m6A “writer” genes was an independent risk factor for OS, and copy number gain of “eraser” genes could magnify the effect in a synergistic way. Additionally, low expression of the writer gene METTL3 was related to activations of adipogenesis and mTOR pathways. Thus, we for the first time determined genetic alterations of m6A regulators in ccRCC and found a significant relationship between the alterations and worse clinical characteristics. The findings provide us clues to understand epigenetic modification of RNA in ccRCC.

Chronic stress is a major risk factor for several human disorders that affect modern societies. The brain is a key target of chronic stress. In fact, there is growing evidence indicating that exposure to stress affects learning and memory, decision making and emotional responses, and may even predispose for pathological processes, such as Alzheimer’s disease (AD) and depression. Lipids are a major constituent of the brain, and specifically signaling lipids have been shown to regulate brain function. Here, we used a mass spectrometry-based lipidomic approach to evaluate the impact of a chronic unpredictable stress paradigm on the rat brain in a region-specific manner. We found that the prefrontal cortex (PFC) was the area with the highest degree of changes induced by chronic stress. Although the hippocampus presented relevant lipidomic changes, the amygdala and to a more extent, the cerebellum, presented few lipid changes upon chronic stress exposure. The sphingolipid and phospholipid metabolism were profoundly affected, showing an increase in ceramide and a decrease in sphingomyelin and dihydrosphingomyelin levels, and decreased phosphatidylethanolamine and ether phosphatidylcholine and increased lysophosphatidylethanolamine levels, respectively. Furthermore, the fatty acyl profile of phospholipids and diacylglycerol revealed that chronic stressed rats had higher 38 carbon(38C)-lipid levels in the hippocampus and a decrease in 36C-lipid levels in the PFC. Finally, lysophosphatidylcholine levels in the PFC were found to be correlated with blood corticosterone levels. In summary, lipidomic profiling of the effect of chronic stress allowed for the identification of dysregulated lipid pathways, revealing putative targets for pharmacological intervention that may potentially be used to modulate stress-induced deficits.

Highlights d Determined crystal structure of human caspase-1 bound to the full-length murine GSDMD d The active site of caspase-1 engages the GSDMD linker cleavage sequence d The exosite at the caspase-1 L2 and L2 0 loops bind the GSDMD C-terminal domain d Both interfaces contribute to enzyme-substrate engagement and pyroptosis

Highlights d Inflammasome activation in the absence of gasdermin D activates gasdermin E d Gasdermin E permits IL-1b release independent of cell death in a sublytic phase d Lysis depends on substantial gasdermin E oligomerization and pore formation

Accumulating evidence from genetic and biochemical studies implicates dysfunction of the autophagic-lysosomal pathway as a key feature in the pathogenesis of Parkinson's disease (PD). Most studies have focused on accumulation of neurotoxic ␣-synuclein secondary to defects in autophagy as the cause of neurodegeneration, but abnormalities of the autophagic-lysosomal system likely mediate toxicity through multiple mechanisms. To further explore how endolysosomal dysfunction causes PD-related neurodegeneration, we generated a murine model of Kufor-Rakeb syndrome (KRS), characterized by early-onset Parkinsonism with additional neurological features. KRS is caused by recessive loss-of-function mutations in the ATP13A2 gene encoding the endolysosomal ATPase ATP13A2. We show that loss of ATP13A2 causes a specific protein trafficking defect, and that Atp13a2 null mice develop age-related motor dysfunction that is preceded by neuropathological changes, including gliosis, accumulation of ubiquitinated protein aggregates, lipofuscinosis, and endolysosomal abnormalities. Contrary to predictions from in vitro data, in vivo mouse genetic studies demonstrate that these phenotypes are ␣-synuclein independent. Our findings indicate that endolysosomal dysfunction and abnormalities of ␣-synuclein homeostasis are not synonymous, even in the context of an endolysosomal genetic defect linked to Parkinsonism, and highlight the presence of ␣-synucleinindependent neurotoxicity consequent to endolysosomal dysfunction.