Spirocyclic dimer SpiD7 activates the unfolded protein response to selectively inhibit growth and induce apoptosis of cancer cells.

The unfolded protein response (UPR) is an adaptation mechanism activated to resolve transient accumulation of unfolded/misfolded proteins in the endoplasmic reticulum. Failure to resolve the transient accumulation of such proteins results in UPR-mediated programmed cell death. Loss of tumor suppressor gene or oncogene addiction in cancer cells can result in sustained higher basal UPR levels; however, it is not clear if these higher basal UPR levels in cancer cells can be exploited as a therapeutic strategy. We hypothesized that covalent modification of surface-exposed cysteine (SEC) residues could simulate unfolded/misfolded proteins to activate the UPR, and that higher basal UPR levels in cancer cells would provide the necessary therapeutic window. To test this hypothesis, here we synthesized analogs that can covalently modify multiple SEC residues and evaluated them as UPR activators. We identified a spirocyclic dimer, SpiD7, and evaluated its effects on UPR activation signals, that is, XBP1 splicing, phosphorylation of eIF2α, and a decrease in ATF 6 levels, in normal and cancer cells, which were further confirmed by RNA-Seq analyses. We found that SpiD7 selectively induced caspase-mediated apoptosis in cancer cells, whereas normal cells exhibited robust XBP1 splicing, indicating adaptation to stress. Furthermore, SpiD7 inhibited the growth of high-grade serous carcinoma cell lines ~3-15-fold more potently than immortalized fallopian tube epithelial (paired normal control) cells and reduced clonogenic growth of high-grade serous carcinoma cell lines. Our results suggest that induction of the UPR by covalent modification of SEC residues represents a cancer cell vulnerability and can be exploited to discover novel therapeutics.

Malondialdehyde-Acetaldehyde Extracellular Matrix Protein Adducts Attenuate Unfolded Protein Response During Alcohol and Smoking-Induced Pancreatitis.

BACKGROUND & AIMS: Epidemiological studies have established alcohol and smoking as independent risk factors for recurrent acute pancreatitis and chronic pancreatitis. However, the molecular players responsible for the progressive loss of pancreatic parenchyma and fibroinflammatory response are poorly characterized. METHODS: Tandem mass tag-based proteomic and bioinformatics analyses were performed on the pancreata of mice exposed to alcohol, cigarette smoke, or a combination of alcohol and cigarette smoke. Biochemical, immunohistochemistry, and transcriptome analyses were performed on the pancreatic tissues and primary acinar cells treated with cerulein in combination with ethanol (50 mmol/L) and cigarette smoke extract (40 µg/mL) for the mechanistic studies. RESULTS: A unique alteration in the pancreatic proteome was observed in mice exposed chronically to the combination of alcohol and cigarette smoke (56.5%) compared with cigarette smoke (21%) or alcohol (17%) alone. The formation of toxic metabolites (P < .001) and attenuated unfolded protein response (P < .04) were the significantly altered pathways on combined exposure. The extracellular matrix (ECM) proteins showed stable malondialdehyde-acetaldehyde (MAA) adducts in the pancreata of the combination group and chronic pancreatitis patients with a history of smoking and alcohol consumption. Interestingly, MAA-ECM adducts significantly suppressed expression of X-box-binding protein-1, leading to acinar cell death in the presence of alcohol and smoking. The stable MAA-ECM adducts persist even after alcohol and smoking cessation, and significantly delay pancreatic regeneration by abrogating the expression of cyclin-dependent kinases (CDK7 and CDK5) and regeneration markers. CONCLUSIONS: The combined alcohol and smoking generate stable MAA-ECM adducts that increase endoplasmic reticulum stress and acinar cell death due to attenuated unfolded protein response and suppress expression of cell cycle regulators. Targeting aldehyde adducts might provide a novel therapeutic strategy for the management of recurrent acute pancreatitis and chronic pancreatitis.

UBR5 HECT domain mutations identified in mantle cell lymphoma control maturation of B cells.

Coordination of a number of molecular mechanisms including transcription, alternative splicing, and class switch recombination are required to facilitate development, activation, and survival of B cells. Disruption of these pathways can result in malignant transformation. Recently, next-generation sequencing has identified a number of novel mutations in mantle cell lymphoma (MCL) patients including mutations in the ubiquitin E3 ligase UBR5. Approximately 18% of MCL patients were found to have mutations in UBR5, with the majority of mutations within the HECT domain of the protein that can accept and transfer ubiquitin molecules to the substrate. Determining if UBR5 controls the maturation of B cells is important to fully understand malignant transformation to MCL. To elucidate the role of UBR5 in B-cell maturation and activation, we generated a conditional mutant disrupting UBR5's C-terminal HECT domain. Loss of the UBR5 HECT domain leads to a block in maturation of B cells in the spleen and upregulation of proteins associated with messenger RNA splicing via the spliceosome. Our studies reveal a novel role of UBR5 in B-cell maturation by stabilization of spliceosome components during B-cell development and suggests UBR5 mutations play a role in MCL transformation.

Lipid droplet membrane proteome remodeling parallels ethanol-induced hepatic steatosis and its resolution.

Lipid droplets (LDs) are composed of neutral lipids enclosed in a phospholipid monolayer, which harbors membrane-associated proteins that regulate LD functions. Despite the crucial role of LDs in lipid metabolism, remodeling of LD protein composition in disease contexts, such as steatosis, remains poorly understood. We hypothesized that chronic ethanol consumption, subsequent abstinence from ethanol, or fasting differentially affects the LD membrane proteome content and that these changes influence how LDs interact with other intracellular organelles. Here, male Wistar rats were pair-fed liquid control or ethanol diets for 6 weeks, and then, randomly chosen animals from both groups were either refed a control diet for 7 days or fasted for 48 h before euthanizing. From all groups, LD membrane proteins from purified liver LDs were analyzed immunochemically and by MS proteomics. Liver LD numbers and sizes were greater in ethanol-fed rats than in pair-fed control, 7-day refed, or fasted rats. Compared with control rats, ethanol feeding markedly altered the LD membrane proteome, enriching LD structural perilipins and proteins involved in lipid biosynthesis, while lowering LD lipase levels. Ethanol feeding also lowered LD-associated mitochondrial and lysosomal proteins. In 7-day refed (i.e., ethanol-abstained) or fasted-ethanol-fed rats, we detected distinct remodeling of the LD proteome, as judged by lower levels of lipid biosynthetic proteins, and enhanced LD interaction with mitochondria and lysosomes. Our study reveals evidence of significant remodeling of the LD membrane proteome that regulates ethanol-induced steatosis, its resolution after withdrawal and abstinence, and changes in LD interactions with other intracellular organelles.

Aminopyrazole based CDK9 PROTAC sensitizes pancreatic cancer cells to venetoclax.

Cyclin-dependent kinase 9 (CDK9) is a member of the cyclin-dependent kinase (CDK) family which is involved in transcriptional regulation of several genes, including the oncogene Myc, and is a validated target for pancreatic cancer. Here we report the development of an aminopyrazole based proteolysis targeting chimera (PROTAC 2) that selectively degrades CDK9 (DC50 = 158 ± 6 nM). Mass spectrometry-based kinome profiling shows PROTAC 2 selectively degrades CDK9 in MiaPaCa2 cells and sensitizes them to Venetoclax mediated growth inhibition.

Preferential Targeting of Lateral Entorhinal Inputs onto Newly Integrated Granule Cells.

Mature dentate granule cells in the hippocampus receive input from the entorhinal cortex via the perforant path in precisely arranged lamina, with medial entorhinal axons innervating the middle molecular layer and lateral entorhinal cortex axons innervating the outer molecular layer. Although vastly outnumbered by mature granule cells, adult-generated newborn granule cells play a unique role in hippocampal function, which has largely been attributed to their enhanced excitability and plasticity (Schmidt-Hieber et al., 2004; Ge et al., 2007). Inputs from the medial and lateral entorhinal cortex carry different informational content. Thus, the distribution of inputs onto newly integrated granule cells will affect their function in the circuit. Using retroviral labeling in combination with selective optogenetic activation of medial or lateral entorhinal inputs, we examined the functional innervation and synaptic maturation of newly generated dentate granule cells in the mouse hippocampus. Our results indicate that lateral entorhinal inputs provide the majority of functional innervation of newly integrated granule cells at 21 d postmitosis. Despite preferential functional targeting, the dendritic spine density of immature granule cells was similar in the outer and middle molecular layers, which we speculate could reflect an unequal distribution of shaft synapses. However, chronic blockade of neurotransmitter release of medial entorhinal axons with tetanus toxin disrupted normal synapse development of both medial and lateral entorhinal inputs. Our results support a role for preferential lateral perforant path input onto newly generated neurons in mediating pattern separation, but also indicate that medial perforant path input is necessary for normal synaptic development.SIGNIFICANCE STATEMENT The formation of episodic memories involves the integration of contextual and spatial information. Newly integrated neurons in the dentate gyrus of the hippocampus play a critical role in this process, despite constituting only a minor fraction of the total number of granule cells. Here we demonstrate that these neurons preferentially receive information thought to convey the context of an experience. Each newly integrated granule cell plays this unique role for ∼1 month before reaching maturity.

Identification of Potential Cerebrospinal Fluid Biomarkers To Discriminate between Infection and Sterile Inflammation in a Rat Model of Staphylococcus epidermidis Catheter Infection.

Staphylococcus epidermidis cerebrospinal fluid (CSF) shunt infection is a common complication of hydrocephalus treatment, creating grave neurological consequences for patients, especially when diagnosis is delayed. The current method of diagnosis relies on microbiological culture; however, awaiting culture results may cause treatment delays, or culture may fail to identify infection altogether, so newer methods are needed. To investigate potential CSF biomarkers of S. epidermidis shunt infection, we developed a rat model allowing for serial CSF sampling. We found elevated levels of interleukin-10 (IL-10), IL-1ß, chemokine ligand 2 (CCL2), and CCL3 in the CSF of animals implanted with S. epidermidis-infected catheters compared to sterile controls at day 1 postinfection. Along with increased chemokine and cytokine expression early in infection, neutrophil influx was significantly increased in the CSF of animals with infected catheters, suggesting that coupling leukocyte counts with inflammatory mediators may differentiate infection from sterile inflammation. Mass spectrometry analysis revealed that the CSF proteome in sterile animals was similar to that in infected animals at day 1; however, by day 5 postinfection, there was an increase in the number of differently expressed proteins in the CSF of infected compared to sterile groups. The expansion of the proteome at day 5 postinfection was interesting, as bacterial burdens began to decline by this point, yet the CSF proteome data indicated that the host response remained active, especially with regard to the complement cascade. Collectively, these results provide potential biomarkers to distinguish S. epidermidis infection from sterile postoperative inflammation.

Proximity Labeling To Map Host-Pathogen Interactions at the Membrane of a Bacterium-Containing Vacuole in Chlamydia trachomatis-Infected Human Cells.

Many intracellular bacteria, including the obligate intracellular pathogen Chlamydia trachomatis, grow within a membrane-bound bacterium-containing vacuole (BCV). Secreted cytosolic effectors modulate host activity, but an understanding of the host-pathogen interactions that occur at the BCV membrane is limited by the difficulty in purifying membrane fractions from infected host cells. We used the ascorbate peroxidase (APEX2) proximity labeling system, which labels proximal proteins with biotin in vivo, to study the protein-protein interactions that occur at the chlamydial vacuolar, or inclusion, membrane. An in vivo understanding of the secreted chlamydial inclusion membrane protein (Inc) interactions (e.g., Inc-Inc and Inc-eukaryotic protein) and how these contribute to overall host-chlamydia interactions at this unique membrane is lacking. We hypothesize some Incs organize the inclusion membrane, whereas other Incs bind eukaryotic proteins to promote chlamydia-host interactions. To study this, Incs fused to APEX2 were expressed in C. trachomatis L2. Affinity purification-mass spectrometry (AP-MS) identified biotinylated proteins, which were analyzed for statistical significance using significance analysis of the interactome (SAINT). Broadly supporting both Inc-Inc and Inc-host interactions, our Inc-APEX2 constructs labeled Incs as well as known and previously unreported eukaryotic proteins localizing to the inclusion. We demonstrate, using bacterial two-hybrid and coimmunoprecipitation assays, that endogenous LRRFIP1 (LRRF1) is recruited to the inclusion by the Inc CT226. We further demonstrate interactions between CT226 and the Incs used in our study to reveal a model for inclusion membrane organization. Combined, our data highlight the utility of APEX2 to capture the complex in vivo protein-protein interactions at the chlamydial inclusion.

Functional Impacts of the BRCA1-mTORC2 Interaction in Breast Cancer.

Deleterious mutations in Breast Cancer 1 (BRCA1) are associated with an increased risk of breast and ovarian cancer. Mutations in the tandem BRCA1 C-terminal (tBRCT) protein domain disrupt critical protein interactions required for the faithful repair of DNA through homologous recombination, which contributes to oncogenesis. Our studies have identified RICTOR, PRR5, and SIN1 subunits of the mammalian target of rapamycin complex 2 (mTORC2) as interacting partners with the tBRCT domain of BRCA1 leading to the disruption of the mTORC2 complex. However, the interplay between mTORC2 signaling and BRCA1 function in the DNA damage response (DDR) remains to be determined. In this study, we used protein interaction assays to determine the binary interactions between the tBRCT domain and mTORC2 subunits, evaluated the impact of mTOR inhibition on the transcriptional function of the tBRCT, evaluated the impact of mTOR signaling on BRCA1 recruitment to DNA damage-induced foci and determined the breast cancer cell line response to mTOR inhibition dependent upon BRCA1 expression and mutation. This study determined that PRR5, RICTOR, and SIN1 could each independently interact with the BRCA1 tBRCT. Inhibition of mTORC1, but not mTORC1/2, increases BRCA1 transcriptional activation activity. Treatment with pan-mTOR inhibitor PP242 diminishes DNA damage-induced γH2AX and BRCA1 foci formation. Breast cancer cells lacking expression of functional BRCA1 are more sensitive to mTOR inhibitors. These data suggest that mTOR signaling is required for BRCA1 response to DNA damage and breast cancer cells lacking BRCA1 are more sensitive to pan-mTOR inhibition. This work suggests chemotherapeutic strategies using mTOR inhibitors could be tailored for patients that lack functional BRCA1.

Germline missense pathogenic variants in the BRCA1 BRCT domain, p.Gly1706Glu and p.Ala1708Glu, increase cellular sensitivity to PARP inhibitor olaparib by a dominant negative effect.

BRCA1-deficient cells show defects in DNA repair and rely on other members of the DNA repair machinery, which makes them sensitive to PARP inhibitors (PARPi). Although carrying a germline pathogenic variant in BRCA1/2 is the best determinant of response to PARPi, a significant percentage of the patients do not show sensitivity and/or display increased toxicity to the agent. Considering previously suggested mutation-specific BRCA1 haploinsufficiency, we aimed to investigate whether there are any differences in cellular response to PARPi olaparib depending on the BRCA1 mutation type. Lymphoblastoid cell lines derived from carriers of missense pathogenic variants in the BRCA1 BRCT domain (c.5117G > A, p.Gly1706Glu and c.5123C > A, p.Ala1708Glu) showed higher sensitivity to olaparib than cells with truncating variants or wild types (WT). Response to olaparib depended on a basal PARP enzymatic activity, but did not correlate with PARP1 expression. Interestingly, cellular sensitivity to the agent was associated with the level of BRCA1 recruitment into γH2AX foci, being the lowest in cells with missense variants. Since these variants lead to partially stable protein mutants, we propose a model in which the mutant protein acts in a dominant negative manner on the WT BRCA1, impairing the recruitment of BRCA1 into DNA damage sites and, consequently, increasing cellular sensitivity to PARPi. Taken together, our results indicate that carriers of different BRCA1 mutations could benefit from olaparib in a distinct way and show different toxicities to the agent, which could be especially relevant for a potential future use of PARPi as prophylactic agents in BRCA1 mutation carriers.

Long-term seizure suppression and optogenetic analyses of synaptic connectivity in epileptic mice with hippocampal grafts of GABAergic interneurons.

Studies in rodent epilepsy models suggest that GABAergic interneuron progenitor grafts can reduce hyperexcitability and seizures in temporal lobe epilepsy (TLE). Although integration of the transplanted cells has been proposed as the underlying mechanism for these disease-modifying effects, prior studies have not explicitly examined cell types and synaptic mechanisms for long-term seizure suppression. To address this gap, we transplanted medial ganglionic eminence (MGE) cells from embryonic day 13.5 VGAT-Venus or VGAT-ChR2-EYFP transgenic embryos into the dentate gyrus (DG) of adult mice 2 weeks after induction of TLE with pilocarpine. Beginning 3-4 weeks after status epilepticus, we conducted continuous video-electroencephalographic recording until 90-100 d. TLE mice with bilateral MGE cell grafts in the DG had significantly fewer and milder electrographic seizures, compared with TLE controls. Immunohistochemical studies showed that the transplants contained multiple neuropeptide or calcium-binding protein-expressing interneuron types and these cells established dense terminal arborizations onto the somas, apical dendrites, and axon initial segments of dentate granule cells (GCs). A majority of the synaptic terminals formed by the transplanted cells were apposed to large postsynaptic clusters of gephyrin, indicative of mature inhibitory synaptic complexes. Functionality of these new inhibitory synapses was demonstrated by optogenetically activating VGAT-ChR2-EYFP-expressing transplanted neurons, which generated robust hyperpolarizations in GCs. These findings suggest that fetal GABAergic interneuron grafts may suppress pharmacoresistant seizures by enhancing synaptic inhibition in DG neural circuits.

Incorporating computational resources in a cancer research program.

Recent technological advances have transformed cancer genetics research. These advances have served as the basis for the generation of a number of richly annotated datasets relevant to the cancer geneticist. In addition, many of these technologies are now within reach of smaller laboratories to answer specific biological questions. Thus, one of the most pressing issues facing an experimental cancer biology research program in genetics is incorporating data from multiple sources to annotate, visualize, and analyze the system under study. Fortunately, there are several computational resources to aid in this process. However, a significant effort is required to adapt a molecular biology-based research program to take advantage of these datasets. Here, we discuss the lessons learned in our laboratory and share several recommendations to make this transition effective. This article is not meant to be a comprehensive evaluation of all the available resources, but rather highlight those that we have incorporated into our laboratory and how to choose the most appropriate ones for your research program.

Interleukin polymorphisms associated with overall survival, disease-free survival, and recurrence in non-small cell lung cancer patients.

Biomarkers based on germline DNA variations could have translational implications by identifying prognostic factors and sub-classifying patients to tailored, patient-specific treatment. To investigate the association between germline variations in interleukin (IL) genes and lung cancer outcomes, we genotyped 251 single nucleotide polymorphisms (SNPs) from 33 different IL genes in 651 non-small cell lung cancer (NSCLC) patients. Analyses were performed to investigate overall survival, disease-free survival, and recurrence. Our analyses revealed 24 different IL SNPs significantly associated with one or more of the lung cancer outcomes of interest. The GG genotype of IL16:rs7170924 was significantly associated with disease-free survival (HR = 0.65; 95% CI 0.50-0.83) and was the only SNP that produced a false discovery rate (FDR) of modest confidence that the association is unlikely to represent a false-positive result (FDR = 0.142). Classification and regression tree (CART) analyses were used to identify potential higher-order interactions. We restricted the CART analyses to the five SNPs that were significantly associated with multiple endpoints (IL1A:rs1800587, IL1B:rs1143634, IL8:s12506479, IL12A:rs662959, and IL13:rs1881457) and IL16:rs7170924 which had the lowest FDR. CART analyses did not yield a tree structure for overall survival; separate CART tree structures were identified for recurrence, based on three SNPs (IL13:rs1881457, IL1B:rs1143634, and IL12A:rs662959), and for disease-free survival, based on two SNPs (IL12A:rs662959 and IL16:rs7170924), which may suggest that these candidate IL SNPs have a specific impact on lung cancer progression and recurrence. These data suggest that germline variations in IL genes are associated with clinical outcomes in NSCLC patients.

Localization of BRCA1 protein in breast cancer tissue and cell lines with mutations.

BACKGROUND: The breast and ovarian cancer susceptibility gene (BRCA1) encodes a tumor suppressor. The BRCA1 protein is found primarily in cell nuclei and plays an important role in the DNA damage response and transcriptional regulation. Deficiencies in DNA repair capabilities have been associated with higher histopathological grade and worse prognosis in breast cancer. METHODS: In order to investigate the subcellular distribution of BRCA1 in tumor tissue we randomly selected 22 breast carcinomas and tested BRCA1 protein localization in frozen and contiguous formalin-fixed, paraffin embedded (FFPE) tissue, using pressure cooker antigen-retrieval and the MS110 antibody staining. To assess the impact of BRCA1 germline mutations on protein localization, we retrospectively tested 16 of the tumor specimens to determine whether they contained the common Ashkenazi Jewish founder mutations in BRCA1 (185delAG, 5382insC), and BRCA2 (6174delT). We also compared co-localization of BRCA1 and nucleolin in MCF7 cells (wild type) and a mutant BRCA1 cell line, HCC1937 (5382insC). RESULTS: In FFPE tissue, with MS110 antibody staining, we frequently found reduced BRCA1 nuclear staining in breast tumor tissue compared to normal tissue, and less BRCA1 staining with higher histological grade in the tumors. However, in the frozen sections, BRCA1 antibody staining showed punctate, intra-nuclear granules in varying numbers of tumor, lactating, and normal cells. Two mutation carriers were identified and were confirmed by gene sequencing. We have also compared co-localization of BRCA1 and nucleolin in MCF7 cells (wild type) and a mutant BRCA1 cell line, HCC1937 (5382insC) and found altered sub-nuclear and nucleolar localization patterns consistent with a functional impact of the mutation on protein localization. CONCLUSIONS: The data presented here support a role for BRCA1 in the pathogenesis of sporadic and inherited breast cancers. The use of well-characterized reagents may lead to further insights into the function of BRCA1 and possibly the further development of targeted therapeutics.

Yeast two-hybrid junk sequences contain selected linear motifs.

Yeast two-hybrid (Y2H) screenings result in identification of many out-of-frame (OOF) clones that code for short (2-100 amino acids) peptides with no sequence homology to known proteins. We hypothesize that these peptides can reveal common short linear motifs (SLiMs) responsible for their selection. We present a new protocol to address this issue, using an existing SLIM detector (TEIRESIAS) as a base method, and applying filters derived from a mathematical model of SLiM selection in OOF clones. The model allows for initial analysis of likely presence of SLiM(s) in a collection of OOF sequences, assisting investigators with the decision of whether to invest resources in further analysis. If SLiM presence is detected, it estimates the length and number of amino acid residues involved in binding specificity and the amount of noise in the Y2H screen. We demonstrate that our model can double the prediction sensitivity of TEIRESIAS and improve its specificity from 0 to 1.0 on simulated data and apply the model to seven sets of experimentally derived OOF clones. Finally, we experimentally validate one SLiM found by our method, demonstrating its utility.

Interactome Profiling of DNA Damage Response (DDR) Mediators with Immunoprecipitation-Mass Spectrometry.

Immunoprecipitation-mass spectrometry (IP-MS) is a versatile tool to probe for global protein-protein interactions (PPIs) in biological samples. Such interactions coordinate complex biological processes, such as the DNA damage response (DDR). Induction of DNA damage activates signaling networks where posttranslational modifications cause PPI that facilitate DNA repair and cell cycle coordination. Protein interactome profiling of DDR sensors, transducers, and effectors has the potential to identify novel DDR mechanisms that could advance our understanding and treatment of diseases associated with DDR defects, such as cancer. The protocol described here is a routine PPI analysis procedure that can be performed on samples stimulated with DNA damage. All processes and reagents are optimized for maximum sensitivity on the interactome and minimal contamination for the mass spectrometer.

Luteal Lipid Droplets: A Novel Platform for Steroid Synthesis.

Progesterone is an essential steroid hormone that is required to initiate and maintain pregnancy in mammals and serves as a metabolic intermediate in the synthesis of endogenously produced steroids, including sex hormones and corticosteroids. Steroidogenic luteal cells of the corpus luteum have the tremendous capacity to synthesize progesterone. These specialized cells are highly enriched with lipid droplets that store lipid substrate, which can be used for the synthesis of steroids. We recently reported that hormone-stimulated progesterone synthesis by luteal cells requires protein kinase A-dependent mobilization of cholesterol substrate from lipid droplets to mitochondria. We hypothesize that luteal lipid droplets are enriched with steroidogenic enzymes and facilitate the synthesis of steroids in the corpus luteum. In the present study, we analyzed the lipid droplet proteome, conducted the first proteomic analysis of lipid droplets under acute cyclic adenosine monophosphate (cAMP)-stimulated conditions, and determined how specific lipid droplet proteins affect steroidogenesis. Steroidogenic enzymes, cytochrome P450 family 11 subfamily A member 1 and 3 beta-hydroxysteroid dehydrogenase (HSD3B), were highly abundant on lipid droplets of the bovine corpus luteum. High-resolution confocal microscopy confirmed the presence of active HSD3B on the surface of luteal lipid droplets. We report that luteal lipid droplets have the capacity to synthesize progesterone from pregnenolone. Lastly, we analyzed the lipid droplet proteome following acute stimulation with cAMP analog, 8-Br-cAMP, and report increased association of HSD3B with luteal lipid droplets following stimulation. These findings provide novel insights into the role of luteal lipid droplets in steroid synthesis.

FBXO21 mediated degradation of p85α regulates proliferation and survival of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by clonal expansion of myeloid blasts in the bone marrow (BM). Despite advances in therapy, the prognosis for AML patients remains poor, and there is a need to identify novel molecular pathways regulating tumor cell survival and proliferation. F-box ubiquitin E3 ligase, FBXO21, has low expression in AML, but expression correlates with survival in AML patients and patients with higher expression have poorer outcomes. Silencing FBXO21 in human-derived AML cell lines and primary patient samples leads to differentiation, inhibition of tumor progression, and sensitization to chemotherapy agents. Additionally, knockdown of FBXO21 leads to up-regulation of cytokine signaling pathways. Through a mass spectrometry-based proteomic analysis of FBXO21 in AML, we identified that FBXO21 ubiquitylates p85α, a regulatory subunit of the phosphoinositide 3-kinase (PI3K) pathway, for degradation resulting in decreased PI3K signaling, dimerization of free p85α and ERK activation. These findings reveal the ubiquitin E3 ligase, FBXO21, plays a critical role in regulating AML pathogenesis, specifically through alterations in PI3K via regulation of p85α protein stability.

Neural dynamics underlying associative learning in the dorsal and ventral hippocampus.

Animals associate cues with outcomes and update these associations as new information is presented. This requires the hippocampus, yet how hippocampal neurons track changes in cue-outcome associations remains unclear. Using two-photon calcium imaging, we tracked the same dCA1 and vCA1 neurons across days to determine how responses evolve across phases of odor-outcome learning. Initially, odors elicited robust responses in dCA1, whereas, in vCA1, odor responses primarily emerged after learning and embedded information about the paired outcome. Population activity in both regions rapidly reorganized with learning and then stabilized, storing learned odor representations for days, even after extinction or pairing with a different outcome. Additionally, we found stable, robust signals across CA1 when mice anticipated outcomes under behavioral control but not when mice anticipated an inescapable aversive outcome. These results show how the hippocampus encodes, stores and updates learned associations and illuminates the unique contributions of dorsal and ventral hippocampus.

USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma.

In this study, we identify USP1 as a transcriptional target of EWS::FLI1 and demonstrate the requisite function of USP1 in Ewing sarcoma (EWS) cell survival in response to endogenous replication stress. EWS::FLI1 oncogenic transcription factor drives most EWS, a pediatric bone cancer. EWS cells display elevated levels of R-loops and replication stress. The mechanism by which EWS cells override activation of apoptosis or cellular senescence in response to increased replication stress is not known. We show that USP1 is overexpressed in EWS and EWS::FLI1 regulates USP1 transcript levels. USP1 knockdown or inhibition arrests EWS cell growth and induces cell death by apoptosis. Mechanistically, USP1 regulates Survivin (BIRC5/API4) protein stability and the activation of caspase-9 and caspase-3/7 in response to endogenous replication stress. Notably, USP1 inhibition sensitizes cells to doxorubicin and etoposide treatment. Together, our study demonstrates that USP1 is regulated by EWS::FLI1, the USP1-Survivin axis promotes EWS cell survival, and USP1 inhibition sensitizes cells to standard of care chemotherapy. IMPLICATIONS: High USP1 and replication stress levels driven by EWS::FLI1 transcription factor in EWS are vulnerabilities that can be exploited to improve existing treatment avenues and overcome drug resistance.