Classically, canonical autophagy has been considered a survival mechanism initiated in response to nutrient insufficiency. We now understand that autophagy functions in multiple scenarios where it is ...necessary to maintain homeostasis. Recent evidence has established that a variety of non-canonical functions for autophagy proteins are mechanistically and functionally distinct from autophagy. LC3-associated phagocytosis (LAP) is one such novel function for autophagy proteins and is a contributor to immune regulation and inflammatory responses across various cell and tissue types. Characterized by the conjugation of LC3 family proteins to phagosome membranes, LAP uses a portion of the canonical autophagy machinery, following ligation of surface receptors that recognize a variety of cargos including pathogens, dying cells, soluble ligands and protein aggregates. However, instead of affecting canonical autophagy, manipulation of the LAP pathway
alters immune activation and inflammatory responses. In this Cell Science at a Glance article and the accompanying poster, we detail the divergence of this distinctive mechanism from that of canonical autophagy by comparing and contrasting shared and unique components of each pathway.
The clearance of dead cells by efferocytosis Boada-Romero, Emilio; Martinez, Jennifer; Heckmann, Bradlee L ...
Nature reviews. Molecular cell biology,
07/2020, Letnik:
21, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Multiple modes of cell death have been identified, each with a unique function and each induced in a setting-dependent manner. As billions of cells die during mammalian embryogenesis and daily in ...adult organisms, clearing dead cells and associated cellular debris is important in physiology. In this Review, we present an overview of the phagocytosis of dead and dying cells, a process known as efferocytosis. Efferocytosis is performed by macrophages and to a lesser extent by other 'professional' phagocytes (such as monocytes and dendritic cells) and 'non-professional' phagocytes, such as epithelial cells. Recent discoveries have shed light on this process and how it functions to maintain tissue homeostasis, tissue repair and organismal health. Here, we outline the mechanisms of efferocytosis, from the recognition of dying cells through to phagocytic engulfment and homeostatic resolution, and highlight the pathophysiological consequences that can arise when this process is abrogated.
LC3-Associated Phagocytosis and Inflammation Heckmann, Bradlee L.; Boada-Romero, Emilio; Cunha, Larissa D. ...
Journal of molecular biology,
11/2017, Letnik:
429, Številka:
23
Journal Article
Recenzirano
Odprti dostop
LC3-associated phagocytosis (LAP) is a novel form of non-canonical autophagy where LC3 (microtubule-associated protein 1A/1B–light chain 3) is conjugated to phagosome membranes using a portion of the ...canonical autophagy machinery. The impact of LAP to immune regulation is best characterized in professional phagocytes, in particular macrophages, where LAP has instrumental roles in the clearance of extracellular particles including apoptotic cells and pathogens. Binding of dead cells via receptors present on the macrophage surface results in the translocation of the autophagy machinery to the phagosome and ultimately LC3 conjugation. These events promote a rapid form of phagocytosis that produces an “immunologically silent” clearance of the apoptotic cells. Consequences of LAP deficiency include a decreased capacity to clear dying cells and the establishment of a lupus-like autoimmune disease in mice. The ability of LAP to attenuate autoimmunity likely occurs through the dampening of pro-inflammatory signals upon engulfment of dying cells and prevention of autoantigen presentation to other immune cells. However, it remains unclear how LAP shapes both the activation and outcome of the immune response at the molecular level. Herein, we provide a detailed review of LAP and its known roles in the immune response and provide further speculation on the putative mechanisms by which LAP may regulate immune function, perhaps through the metabolic reprogramming and polarization of macrophages.
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•Comprehensive overview of LC3-associated phagocytosis (LAP).•LAP bridges the phagocytic and autophagic pathways.•Signaling to LAP and regulation of LAP activation by the canonical autophagy machinery.•LAP quenches inflammation and shapes the immune response towards anti-inflammation.•LAP promotes the immunosilent clearance of dying cells and prevents autoimmunity.
The G0/G1 switch gene 2 (G0S2) was originally identified in blood mononuclear cells following induced cell cycle progression. Translation of G0S2 results in a small basic protein of 103 amino acids ...in size. It was initially believed that G0S2 mediates re-entry of cells from the G0 to G1 phase of the cell cycle. Recent studies have begun to reveal the functional aspects of G0S2 and its protein product in various cellular settings. To date the best-known function of G0S2 is its direct inhibitory capacity on the rate-limiting lipolytic enzyme adipose triglyceride lipase (ATGL). Other studies have illustrated key features of G0S2 including sub-cellular localization, expression profiles and regulation, and possible functions in cellular proliferation and differentiation. In this review we present the current knowledge base regarding all facets of G0S2, and pose a variety of questions and hypotheses pertaining to future research directions.
► In this review we describe the G0/G1 switch gene 2 (G0S2) and its functions. ► We illustrate the key features of G0S2's localization, expression, and regulation. ► We present the currently known functions of G0S2 in lipid metabolism and beyond. ► We pose further questions and hypotheses for future research directions of G0S2.
Recent biochemical and cell-based studies identified G0/G1 switch gene 2 (G0S2) as an inhibitor of adipose triglyceride lipase (ATGL), a key mediator of intracellular triacylglycerol (TG) ...mobilization. Here, we show that upon fasting, G0S2 protein expression exhibits an increase in liver and a decrease in adipose tissue. Global knockout of G0S2 in mice enhanced adipose lipolysis and attenuated gain of body weight and adiposity. More strikingly, G0S2 knockout mice displayed a drastic decrease in hepatic TG content and were resistant to high-fat diet (HFD)-induced liver steatosis, both of which were reproduced by liver-specific G0S2 knockdown. Mice with hepatic G0S2 knockdown also showed increased ketogenesis, accelerated gluconeogenesis, and decelerated glycogenolysis. Conversely, overexpression of G0S2 inhibited fatty acid oxidation in mouse primary hepatocytes and caused sustained steatosis in liver accompanied by deficient TG clearance during the fasting-refeeding transition. In response to HFD, there was a profound increase in hepatic G0S2 expression in the fed state. Global and hepatic ablation of G0S2 both led to improved insulin sensitivity in HFD-fed mice. Our findings implicate a physiological role for G0S2 in the control of adaptive energy response to fasting and as a contributor to obesity-associated liver steatosis.
Intracellular triglyceride (TG) hydrolysis or lipolysis is catalyzed by the key intracellular triglyceride hydrolase, adipose triglyceride lipase (ATGL). The G0/G1 Switch Gene 2 (G0S2) was recently ...identified as the major selective inhibitor of ATGL and its hydrolase function. Since G0S2 levels are dynamically linked and rapidly responsive to nutrient status or metabolic requirements, the identification of its regulation at the protein level is of significant value. Earlier evidence from our laboratory demonstrated that G0S2 is a short-lived protein degraded through the proteasomal pathway. However, little is currently known regarding the underlying mechanisms. In the current study we find that 1) protein degradation is initiated by K48-linked polyubiquitination of the lysine- 25 in G0S2; and 2) G0S2 protein is stabilized in response to ATGL expression and TG accumulation. Mutation of lysine-25 of G0S2 abolished ubiquitination and increased protein stability. More importantly, G0S2 was stabilized via different mechanisms in the presence of ATGL vs. in response to fatty acid (FA)-induced TG accumulation. Furthermore, G0S2 protein but not mRNA levels were reduced in the adipose tissue of ATGL-deficient mice, corroborating the involvement of ATGL in the stabilization of G0S2. Taken together our data illustrate for the first time a crucial multifaceted mechanism for the stabilization of G0S2 at the protein level.
BACKGROUND AND PURPOSE The class III PI3K inhibitor, 3‐methyladenine (3‐MA), is commonly used to selectively block autophagy. Recent findings suggest a strong relationship between autophagy and lipid ...turnover. Here, we explore the effect of 3‐MA on adipocyte lipolysis.
EXPERIMENTAL APPROACH Assays were performed in 3T3‐L1 cells. Cells were treated with 3‐MA and wortmannin, a pan PI3K and autophagy inhibitor. Pharmacological and genetic manipulation of endogenous autophagic and lipolytic pathways was used to ascertain the contribution of 3‐MA to the observed effects on lipolysis.
KEY RESULTS 3T3‐L1 cells that were exposed to 3‐MA showed a consistent increase in lipolysis, approximately 50% over basal levels. The effect of 3‐MA was not secondary to autophagic inhibition as treatment of 3T3‐L1 cells with wortmannin yielded no such changes. Dosing and time course experiments showed that 3‐MA's ability to activate lipolysis was more sensitive than its inhibitory effect on autophagy. Knockdown of adipose triglyceride lipase (ATGL) negated the stimulatory effect of 3‐MA by >90%, indicating that 3‐MA enhanced ATGL‐dependent hydrolysis of triacylglycerols. Additionally, the lipolytic effect of 3‐MA was dependent on the activation of PKA and 3‐MA induced a rapid and potent elevation of intracellular cAMP levels in adipocytes.
CONCLUSIONS AND IMPLICATIONS Cumulatively, we show that 3‐MA potently modulated a cellular mechanism and its underlying signalling pathways not associated with autophagy. Furthermore, we describe a novel stimulatory effect on a major signalling pathway. Our findings provide valuable information to studies employing 3‐MA as a specific inhibitor for PI3K and autophagy.
•BSF-based biorefinery could valorize organic wastes into biobased products.•BSF biomass could substitute a substantial amount protein and fat in animal diets.•BSF biomass is rich in bioactive ...compounds and enhances the nutritive value as feed.•Automation and process scale up are needed for exploitation of BSF technology.
Population growth and unprecedented economic growth and urbanization, especially in low- and middle-income countries, coupled with extreme weather patterns, the high-environmental footprint of agricultural practices, and disposal-oriented waste management practices, require significant changes in the ways we produce food, feed and fuel, and manage enormous amounts of organic wastes. Farming insects such as the black soldier fly (BSF) (Hermetia illucens) on diverse organic wastes provides an opportunity for producing nutrient-rich animal feed, fuel, organic fertilizer, and biobased products with concurrent valorization of wastes. Inclusion of BSF larvae/pupae in the diets of poultry, fish, and swine has shown promise as a potential substitute of conventional feed ingredients such as soybean meal and fish meal. Moreover, the bioactive compounds such as antimicrobial peptides, medium chain fatty acids, and chitin and its derivatives present in BSF larvae/pupae, could also add values to the animal diets. However, to realize the full potential of BSF-based biorefining, more research and development efforts are necessary for scaling up the production and processing of BSF biomass using more mechanized and automated systems. More studies are also needed to ensure the safety of the BSF biomass grown on various organic wastes for animal feed (also food) and legalizing the feed application of BSF biomass to wider categories of animals. This critical review presents the current status of the BSF technology, identifies the research gaps, highlights the challenges towards industrial scale production, and provides future perspectives.
Neuroinflammation and neurodegeneration are key components in the establishment and progression of neurodegenerative diseases including Alzheimer's Disease (AD). Over the past decade increasing ...evidence is emerging for the use of components of the canonical autophagy machinery in pathways that are characterized by LC3 lipidation yet are distinct from traditional macro-autophagy. One such pathway that utilizes components of the autophagy machinery to target LC3 to endosomes, a process termed LC3-associated endocytosis (LANDO), has recently been identified and regulates neuroinflammation. Abrogation of LANDO in microglia cells results in a propensity for elevated neuroinflammatory cytokine production. Using the well-established 5xFAD model of AD to interrogate neuroinflammatory regulation, impairment of LANDO through deletion of a key upstream regulator Rubicon or other downstream autophagy components, exacerbated disease onset and severity, while deletion of microglial autophagy alone had no measurable effect. Mice presented with robust deposition of the neurotoxic AD protein β-amyloid (Aβ), microglial activation and inflammatory cytokine production, tau phosphorylation, and aggressive neurodegeneration culminating in severe memory impairment. LANDO-deficiency impaired recycling of receptors that recognize Aβ, including TLR4 and TREM2. LANDO-deficiency alone through deletion of the WD-domain of the autophagy protein ATG16L, revealed a role for LANDO in the spontaneous establishment of age-associated AD. LANDO-deficient mice aged to 2 years presented with advanced AD-like disease and pathology correlative to that observed in human AD patients. Together, these studies illustrate an important role for microglial LANDO in regulating CNS immune activation and protection against neurodegeneration. New evidence is emerging that demonstrates a putative linkage between pathways such as LANDO and cell death regulation via apoptosis and possibly necroptosis. Herein, we provide a review of the use of the autophagy machinery in non-canonical mechanisms that alter immune regulation and could have significant impact in furthering our understanding of not only CNS diseases like AD, but likely beyond.
Increased amino acid availability stimulates muscle protein synthesis (MPS), which is critical for maintaining or increasing muscle mass when combined with training. Previous research suggests that ...whey protein is superior to soy protein in regard to stimulating MPS and muscle mass. Nevertheless, with respect to a future lack of dietary protein and an increasing need for using eco-friendly protein sources it is of great interest to investigate the quality of alternative protein sources, like insect protein.
Our aim was to compare the postprandial amino acid (AA) availability and AA profile in the blood after ingestion of protein isolate from the lesser mealworm, whey isolate, and soy isolate.
Six healthy young men participated in a randomized cross-over study and received three different protein supplementations (25 g of crude protein from whey, soy, insect or placebo (water)) on four separate days. Blood samples were collected at pre, 0 min, 20 min, 40 min, 60 min, 90 min, and 120 min. Physical activity and dietary intake were standardized before each trial, and participants were instructed to be fasting from the night before. AA concentrations in blood samples were determined using ¹H NMR spectroscopy.
A significant rise in blood concentration of essential amino acids (EAA), branched-chain amino acids (BCAA) and leucine was detected over the 120 min period for all protein supplements. Nevertheless, the change in AA profile was significantly greater after ingestion of whey than soy and insect protein (
< 0.05). Area under the curve (AUC) analysis and AA profile revealed comparable AA concentrations for soy and insect protein, whereas whey promoted a ~97% and ~140% greater AUC value than soy and insect protein, respectively. A tendency towards higher AA concentrations beyond the 120 min period was observed for insect protein.
We report that ingestion of whey, soy, and insect protein isolate increases blood concentrations of EAA, BCAA, and leucine over a 120 min period (whey > insect = soy). Insect protein induced blood AA concentrations similar to soy protein. However, a tendency towards higher blood AA concentrations at the end of the 120 min period post ingestion was observed for insect protein, which indicates that it can be considered a "slow" digestible protein source.
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