Utilization Of Lipid Droplets Research Articles

MoJMJD6, a Nuclear Protein, Regulates Conidial Germination and Appressorium Formation at the Early Stage of Pathogenesis in Magnaporthe oryzae.

In plant-pathogen interactions, Magnaporthe oryzae causes blast disease on more than 50 species of 14 monocot plants, including important crops such as rice, millet, and most 15 recently wheat. M. oryzae is a model fungus for studying plant-microbe interaction, and the main source for fungal pathogenesis in the field. Here we report that MoJMJD6 is required for conidium germination and appressorium formation in M. oryzae. We obtained MoJMJD6 mutants (ΔMojmjd6) using a target gene replacement strategy. The MoJMD6 deletion mutants were delayed for conidium germination, glycogen, and lipid droplets utilization and consequently had decreased virulence. In the ΔMojmjd6 null mutants, global histone methyltransferase modifications (H3K4me3, H3K9me3, H3K27me3, and H3K36me2/3) of the genome were unaffected. Taken together, our results indicated that MoJMJD6 function as a nuclear protein which plays an important role in conidium germination and appressorium formation in the M. oryzae. Our work provides insights into MoJMJD6-mediated regulation in the early stage of pathogenesis in plant fungi.

Intestinal Immune Deficiency and Juvenile Hormone Signaling Mediate a Metabolic Trade-off in Adult Drosophila Females

A trade-off hypothesis pertains to the biased allocation of limited resources between two of the most important fitness traits, reproduction and survival to infection. This quid pro quo manifests itself within animals prioritizing their energetic needs according to genetic circuits balancing metabolism, germline activity and immune response. Key evidence supporting this hypothesis includes dipteran fecundity being compromised by systemic immunity, and female systemic immunity being compromised by mating. Here, we reveal a local trade-off taking place in the female Drosophila midgut upon immune challenge. Genetic manipulation of intestinal motility, permeability, regeneration and three key midgut immune pathways provides evidence of an antagonism between specific aspects of intestinal defense and fecundity. That is, juvenile hormone (JH)-controlled egg laying, lipid droplet utilization and insulin receptor expression are specifically compromised by the immune deficiency (Imd) and the dual oxidase (Duox) signaling in the midgut epithelium. Moreover, antimicrobial peptide (AMP) expression under the control of the Imd pathway is inhibited upon mating and JH signaling in the midgut. Local JH signaling is further implicated in midgut dysplasia, inducing stem cell-like clusters and gut permeability. Thus, midgut JH signaling compromises host defense to infection by reducing Imd-controlled AMP expression and by inducing dysplasia, while midgut signaling through the Imd and Duox pathways compromises JH-guided metabolism and fecundity.

Glioblastoma Cells Counteract PARP Inhibition through Pro-Survival Induction of Lipid Droplets Synthesis and Utilization.

Simple SummaryGlioblastoma multiforme (GBM) is the most common and deadly primary brain tumor in adults and one of the most aggressive cancers. The use of Poly ADP-Ribose Polymerase (PARP) inhibitors is being expanded as therapeutic alternative in multiple types of cancer beyond BRCA1/2 mutant breast and ovarian cancer. Here we have analyzed glioma cells’ traits that limit the efficacy of PARPi as anti-glioma agents and we found that PARPi triggered the synthesis of lipid droplets (LDs) that fueled glioma cells by inducing pro-survival lipid consumption. Notably, blocking Fatty Acids utilization by inhibition of β-oxidation with etomoxir, increased PARPi-induced glioma cell death while treatment with oleic acid (OA) prevented the anti-glioma effect of PARPi. We uncover a novel mechanism by which glioblastoma escapes to anti-tumor agents through metabolic reprogramming, inducing the synthesis and utilization of LDs as a pro-survival strategy in response to PARP inhibition.Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults. Poly (ADP-ribose) polymerase inhibitors (PARPi) represent a new class of anti-neoplastic drugs. In the current study, we have characterized the mechanism by which glioblastoma cells evade the effect of PARPi as anti-tumor agents. We have found that suppression of PARP activity exerts an anti-stemness effect and has a dual impact on autophagy, inducing its activation in the first 24 h (together with down-regulation of the pro-survival mTOR pathway) and preventing autophagosomes fusion to lysosomes at later time-points, in primary glioma cells. In parallel, PARPi triggered the synthesis of lipid droplets (LDs) through ACC-dependent activation of de novo fatty acids (FA) synthesis. Notably, inhibiting β-oxidation and blocking FA utilization, increased PARPi-induced glioma cell death while treatment with oleic acid (OA) prevented the anti-glioma effect of PARPi. Moreover, LDs fuel glioma cells by inducing pro-survival lipid consumption as confirmed by quantitation of oxygen consumption rates using Seahorse respirometry in presence or absence of OA. In summary, we uncover a novel mechanism by which glioblastoma escapes to anti-tumor agents through metabolic reprogramming, inducing the synthesis and utilization of LDs as a pro-survival strategy in response to PARP inhibition.

KRAS Controls Pancreatic Cancer Cell Lipid Metabolism and Invasive Potential through the Lipase HSL

Oncogene-induced metabolic reprogramming is a hallmark of pancreatic cancer (PDAC), yet the metabolic drivers of metastasis are unclear. In PDAC, obesity and excess fatty acids accelerate tumor growth and increase metastasis. Here, we report that excess lipids, stored in organelles called lipid droplets (LD), are a key resource to fuel the energy-intensive process of metastasis. The oncogene KRAS controlled the storage and utilization of LD through regulation of hormone-sensitive lipase (HSL), which was downregulated in human PDAC. Disruption of the KRAS-HSL axis reduced lipid storage, reprogrammed tumor cell metabolism, and inhibited invasive migration in vitro and metastasis in vivo. Finally, microscopy-based metabolic analysis revealed that migratory cells selectively utilize oxidative metabolism during the process of migration to metabolize stored lipids and fuel invasive migration. Taken together, these results reveal a mechanism that can be targeted to attenuate PDAC metastasis. SIGNIFICANCE: KRAS-dependent regulation of HSL biases cells towards lipid storage for subsequent utilization during invasion of pancreatic cancer cells, representing a potential target for therapeutic intervention.See related commentary by Man et al., p. 4886.

Lipid droplet utilization by the mouse embryo

High numbers of lipid droplets (LDs) in mammalian eggs are stored and maintained throughout embryo development without marked signs of their utilization. It was previously demonstrated in large domestic mammals that removing lipids from the zygote does not influence post-implantation development in terms of the rate of delivered offspring. Previously studied pig and cow eggs contain considerable amounts of LDs, while mice have a very low level of ooplasmic lipids, which allows to more precisely analyze any effect of lipid removal on developmental dynamics in vitro. We wanted to know if lipid fraction removal would influence the dynamics of preimplantation development of mouse embryos. To do this, mouse zygotes were mechanically delipidated and their progression to the blastocyst stage was evaluated in vitro. Part of blastocysts were transferred to pseudopregnant females for development to term, and then offspring health parameters were evaluated. Our experiments showed no effects of lipid removal on the rate and timing of mouse embryo development. Furthermore, there were no differences in post-natal characteristics of offspring developed from delipidated and non-delipidated embryos. In conclusion, normal developmental progression of dilapidated embryos indicates that LDs are largely unutilized during preimplantation stages. The apparent dispensability of the LDs fraction throughout preimplantation development prompts questions about their so far uncovered role in mammalian embryo. Based on our preliminary observation of the ultrastructure of diapaused blastocysts from mouse and sheep, we speculate that LDs are utilized by the embryo during delayed implantation, i.e., while waiting for the maternal receptivity signal before implantation.

Abstract PR09: KRas modulates pancreatic cancer cell metabolism and invasive potential through the lipase HSL

Abstract Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of only 9%, due in part to its robust metastatic capability. Metastatic invasion is a particularly energy-intensive cellular process; thus, novel therapeutic strategies could include targeting the energy source for tumor cell invasion and migration. Excess lipids, present due to increased fatty acid synthesis or obesity, could provide a fuel source for cancer progression and metastasis. Neutral lipids are stored in organelles called lipid droplets (LDs). How LDs contribute to PDAC tumor cell invasion and metastasis remains unknown. We hypothesize that PDAC cells can store excess lipid to drive metastatic invasion. Indeed, introduction of excess exogenous fatty acids augments LD production and accumulation in PDAC cells and leads to enhanced PDAC cell motility and invasion in vitro. LDs are metabolized by the concerted action of lipases. Importantly, we have found that treatment of tumor cells with lipase inhibitors blocks tumor cell invasion, indicating that utilization of stored lipids via lipase-mediated LD breakdown is required for invasive migration. Hormone sensitive lipase (HSL) is a lipolytic enzyme, best characterized in adipose tissue, that is critical to the breakdown and utilization of LDs in vitro and in vivo. We have made the surprising observation that oncogenic KRas downregulates expression of HSL in pancreatic cancer cells, which shifts the cells towards lipid storage. In PDAC, mutational activation of the oncogene KRas occurs in 95% of tumors and contributes to metabolic rewiring of tumor cells. Our data suggest that the metabolic shift induced by mutant KRas is comprised of decreased LD utilization via downregulation of HSL. Indeed, re-expression of HSL shifts tumor cell metabolism towards elevated oxidative phosphorylation. Importantly, KRas-mutant cells still require the catalytic activity of HSL for tumor cell invasion, even though HSL expression is downregulated. Using redox ratio imaging, we have found that migratory cells selectively utilize oxidative phosphorylation during the process of migration to metabolize stored lipid droplets and fuel invasive migration. Finally, depletion of LD stores via overexpression of HSL blocks tumor cell invasion in vitro and metastasis in mice, even in the context of oncogenic KRas. These data indicate that regulation of HSL is important for both lipid storage and maintaining cancer cell invasiveness. Therefore, we propose a novel mechanism by which oncogenic KRas mediates HSL activity in a tunable manner, thereby altering the metabolism of PDAC cells and leading to increased metastatic ability. This abstract is also being presented as Poster B47. Citation Format: Cody Rozeveld, Ryan Schulze, Lizhi Zhang, Gina L Razidlo. KRas modulates pancreatic cancer cell metabolism and invasive potential through the lipase HSL [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr PR09.

Lipid Droplets: A Significant but Understudied Contributor of Host⁻Bacterial Interactions.

Lipid droplets (LDs) are cytosolic lipid storage organelles that are important for cellular lipid metabolism, energy homeostasis, cell signaling, and inflammation. Several bacterial, viral and protozoal pathogens exploit host LDs to promote infection, thus emphasizing the importance of LDs at the host–pathogen interface. In this review, we discuss the thus far reported relation between host LDs and bacterial pathogens including obligate and facultative intracellular bacteria, and extracellular bacteria. Although there is less evidence for a LD–extracellular bacterial interaction compared to interactions with intracellular bacteria, in this review, we attempt to compare the bacterial mechanisms that target LDs, the host signaling pathways involved and the utilization of LDs by these bacteria. Many intracellular bacteria employ unique mechanisms to target host LDs and potentially obtain nutrients and lipids for vacuolar biogenesis and/or immune evasion. However, extracellular bacteria utilize LDs to either promote host tissue damage or induce host death. We also identify several areas that require further investigation. Along with identifying LD interactions with bacteria besides the ones reported, the precise mechanisms of LD targeting and how LDs benefit pathogens should be explored for the bacteria discussed in the review. Elucidating LD–bacterial interactions promises critical insight into a novel host–pathogen interaction.

Lipid droplet consumption is functionally coupled to vacuole homeostasis independent of lipophagy.

Lipid droplets (LDs) store neutral lipids and are integrated into a cellular metabolic network that relies on functional coupling with various organelles. Factors mediating efficient coupling and mechanisms regulating them remain unknown. Here, we conducted a global screen in S. cerevisiae to identify genes required for the functional coupling of LDs and other organelles during LD consumption. We show that LD utilization during growth resumption is coupled to vacuole homeostasis. ESCRT-, V-ATPase- and vacuole protein sorting-mutants negatively affect LD consumption, independent of lipophagy. Loss of ESCRT function leads to the accumulation of LD-derived diacylglycerol (DAG), preventing its conversion into phosphatidic acid (PA) and membrane lipids. In addition, channeling of DAG from LD-proximal sites to the vacuole is blocked. We demonstrate that utilization of LDs requires intact vacuolar signaling via TORC1 and its downstream effector Sit4p. These data suggest that vacuolar status is coupled to LD catabolism via TORC1-mediated regulation of DAG-PA interconversion and explain how cells coordinate organelle dynamics throughout cell growth.

Novel cellular evidence of lipophagy within the Sertoli cells during spermatogenesis in the turtle.

Spermatogenesis is a complex process producing haploid spermatozoa, and the formation of lipid droplets (LDs) within Sertoli cells is critical to maintaining normal spermatogenesis. However, the utilization of LDs within Sertoli cells is still largely unknown. In the present study, proliferation of spermatogonial cells had begun in May, whereas the meiotic cells occurred predominately in July and majority of spermiogenic cells were observed in the seminiferous tubules in October. However, TEM and Oil Red O staining demonstrated that a larger number of LDs had accumulated within the Sertoli cells in May compared to that in October. There were several LDs attached to the isolation membrane/phagophore, suggesting that the LDs may be a source of endogenous energy for the biogenesis of autophagosomes. The LDs were enclosed within the autophagosomes in May, whereas, autophagosomes and mitochondria were directly attached with large LDs within the Sertoli cells in October. Furthermore, immunohistochemistry results demonstrated the stronger localization of LC3 on the Sertoli cells in May than in October. This study is the first to provide clear evidence of the two different modes of lipophagy for lipid consumption within Sertoli cells, which is a key aspect of Sertoli germ cell communication during spermatogenesis.

You are what you eat: multifaceted functions of autophagy during C. elegans development.

Autophagy involves the sequestration of a portion of the cytosolic contents in an enclosed double-membrane autophagosomal structure and its subsequent delivery to lysosomes for degradation. Autophagy activity functions in multiple biological processes during Caenorhabditis elegans development. The basal level of autophagy in embryos removes aggregate-prone proteins, paternal mitochondria and spermatid-specific membranous organelles (MOs). Autophagy also contributes to the efficient removal of embryonic apoptotic cell corpses by promoting phagosome maturation. During larval development, autophagy modulates miRNA-mediated gene silencing by selectively degrading AIN-1, a component of miRNA-induced silencing complex, and thus participates in the specification of multiple cell fates controlled by miRNAs. During development of the hermaphrodite germline, autophagy acts coordinately with the core apoptotic machinery to execute genotoxic stress-induced germline cell death and also cell death when caspase activity is partially compromised. Autophagy is also involved in the utilization of lipid droplets in the aging process in adult animals. Studies in C. elegans provide valuable insights into the physiological functions of autophagy in the development of multicellular organisms.