RESUMEN
Taurine is used to bolster immunity, but its effects on antitumor immunity are unclear. Here, we report that cancer-related taurine consumption causes T cell exhaustion and tumor progression. The taurine transporter SLC6A6 is correlated with aggressiveness and poor outcomes in multiple cancers. SLC6A6-mediated taurine uptake promotes the malignant behaviors of tumor cells but also increases the survival and effector function of CD8+ T cells. Tumor cells outcompete CD8+ T cells for taurine by overexpressing SLC6A6, which induces T cell death and malfunction, thereby fueling tumor progression. Mechanistically, taurine deficiency in CD8+ T cells increases ER stress, promoting ATF4 transcription in a PERK-JAK1-STAT3 signaling-dependent manner. Increased ATF4 transactivates multiple immune checkpoint genes and induces T cell exhaustion. In gastric cancer, we identify a chemotherapy-induced SP1-SLC6A6 regulatory axis. Our findings suggest that tumoral-SLC6A6-mediated taurine deficiency promotes immune evasion and that taurine supplementation reinvigorates exhausted CD8+ T cells and increases the efficacy of cancer therapies.
Asunto(s)
Linfocitos T CD8-positivos , Glicoproteínas de Membrana , Taurina , Taurina/metabolismo , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Animales , Humanos , Ratones , Línea Celular Tumoral , Ratones Endogámicos C57BL , Estrés del Retículo Endoplásmico , Factor de Transcripción Activador 4/metabolismo , Transducción de Señal , Femenino , Proteínas de Transporte de Membrana/metabolismo , Proteínas de Transporte de Membrana/genética , Factor de Transcripción STAT3/metabolismoRESUMEN
Selective clearance of organelles, including endoplasmic reticulum (ER) and mitochondria, by autophagy plays an important role in cell health. Here, we describe a developmentally programmed selective ER clearance by autophagy. We show that Parkinson's disease-associated PINK1, as well as Atl, Rtnl1, and Trp1 receptors, regulate ER clearance by autophagy. The E3 ubiquitin ligase Parkin functions downstream of PINK1 and is required for mitochondrial clearance while having the opposite function in ER clearance. By contrast, Keap1 and the E3 ubiquitin ligase Cullin3 function downstream of PINK1 to regulate ER clearance by influencing Rtnl1 and Atl. PINK1 regulates a change in Keap1 localization and Keap1-dependent ubiquitylation of the ER-phagy receptor Rtnl1 to facilitate ER clearance. Thus, PINK1 regulates the selective clearance of ER and mitochondria by influencing the balance of Keap1- and Parkin-dependent ubiquitylation of substrates that determine which organelle is removed by autophagy.
Asunto(s)
Retículo Endoplásmico , Factor 2 Relacionado con NF-E2 , Retículo Endoplásmico/metabolismo , Proteína 1 Asociada A ECH Tipo Kelch , Proteínas Quinasas , Ubiquitina-Proteína Ligasas , Drosophila melanogaster , AnimalesRESUMEN
The mechanism that initiates autophagosome formation on the ER in multicellular organisms is elusive. Here, we showed that autophagy stimuli trigger Ca2+ transients on the outer surface of the ER membrane, whose amplitude, frequency, and duration are controlled by the metazoan-specific ER transmembrane autophagy protein EPG-4/EI24. Persistent Ca2+ transients/oscillations on the cytosolic ER surface in EI24-depleted cells cause accumulation of FIP200 autophagosome initiation complexes on the ER. This defect is suppressed by attenuating ER Ca2+ transients. Multi-modal SIM analysis revealed that Ca2+ transients on the ER trigger the formation of dynamic and fusion-prone liquid-like FIP200 puncta. Starvation-induced Ca2+ transients on lysosomes also induce FIP200 puncta that further move to the ER. Multiple FIP200 puncta on the ER, whose association depends on the ER proteins VAPA/B and ATL2/3, assemble into autophagosome formation sites. Thus, Ca2+ transients are crucial for triggering phase separation of FIP200 to specify autophagosome initiation sites in metazoans.
Asunto(s)
Autofagosomas , Calcio , Animales , Autofagosomas/metabolismo , Calcio/metabolismo , Retículo Endoplásmico/metabolismo , Proteínas Relacionadas con la Autofagia/metabolismo , Autofagia , Proteínas de Ciclo Celular/metabolismoRESUMEN
The polytopic, endoplasmic reticulum (ER) membrane protein 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase produces mevalonate, the key intermediate in the synthesis of cholesterol and many nonsterol isoprenoids including geranylgeranyl pyrophosphate (GGpp). Transcriptional, translational, and posttranslational feedback mechanisms converge on this reductase to ensure cells maintain a sufficient supply of essential nonsterol isoprenoids but avoid overaccumulation of cholesterol and other sterols. The focus of this review is mechanisms for the posttranslational regulation of HMG CoA reductase, which include sterol-accelerated ubiquitination and ER-associated degradation (ERAD) that is augmented by GGpp. We discuss how GGpp-induced ER-to-Golgi trafficking of the vitamin K2 synthetic enzyme UbiA prenyltransferase domain-containing protein-1 (UBIAD1) modulates HMG CoA reductase ERAD to balance the synthesis of sterol and nonsterol isoprenoids. We also summarize the characterization of genetically manipulated mice, which established that sterol-accelerated, UBIAD1-modulated ERAD plays a major role in regulation of HMG CoA reductase and cholesterol metabolism in vivo.
Asunto(s)
Colesterol/biosíntesis , Degradación Asociada con el Retículo Endoplásmico/fisiología , Hidroximetilglutaril-CoA Reductasas/metabolismo , Animales , Dimetilaliltranstransferasa/metabolismo , Degradación Asociada con el Retículo Endoplásmico/efectos de los fármacos , Humanos , Hidroximetilglutaril-CoA Reductasas/química , Hidroximetilglutaril-CoA Reductasas/genética , Ratones , Fosfatos de Poliisoprenilo/metabolismo , Procesamiento Proteico-Postraduccional , Esteroles/metabolismo , Terpenos/metabolismo , Terpenos/farmacología , UbiquitinaciónRESUMEN
The functions of coat protein complex II (COPII) coats in cargo packaging and the creation of vesicles at the endoplasmic reticulum are conserved in eukaryotic protein secretion. Standard COPII vesicles, however, cannot handle the secretion of metazoan-specific cargoes such as procollagens, apolipoproteins, and mucins. Metazoans have thus evolved modules centered on proteins like TANGO1 (transport and Golgi organization 1) to engage COPII coats and early secretory pathway membranes to engineer a novel mode of cargo export at the endoplasmic reticulum.
Asunto(s)
Translocador Nuclear del Receptor de Aril Hidrocarburo/metabolismo , Retículo Endoplásmico/metabolismo , Proteínas/metabolismo , Animales , Apolipoproteínas/metabolismo , Translocador Nuclear del Receptor de Aril Hidrocarburo/química , Translocador Nuclear del Receptor de Aril Hidrocarburo/genética , Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Colágeno/metabolismo , Evolución Molecular , Humanos , Mucinas/metabolismo , Familia de Multigenes , Transporte de Proteínas , Proteínas/químicaRESUMEN
Collagen is the most abundant protein in mammals. A unique feature of collagen is its triple-helical structure formed by the Gly-Xaa-Yaa repeats. Three single chains of procollagen make a trimer, and the triple-helical structure is then folded in the endoplasmic reticulum (ER). This unique structure is essential for collagen's functions in vivo, including imparting bone strength, allowing signal transduction, and forming basement membranes. The triple-helical structure of procollagen is stabilized by posttranslational modifications and intermolecular interactions, but collagen is labile even at normal body temperature. Heat shock protein 47 (Hsp47) is a collagen-specific molecular chaperone residing in the ER that plays a pivotal role in collagen biosynthesis and quality control of procollagen in the ER. Mutations that affect the triple-helical structure or result in loss of Hsp47 activity cause the destabilization of procollagen, which is then degraded by autophagy. In this review, we present the current state of the field regarding quality control of procollagen.
Asunto(s)
Colágeno/química , Fibrosis/metabolismo , Proteínas del Choque Térmico HSP47/metabolismo , Procolágeno/química , Procolágeno/metabolismo , Animales , Colágeno/metabolismo , Retículo Endoplásmico/metabolismo , Fibrosis/genética , Proteínas del Choque Térmico HSP47/química , Proteínas del Choque Térmico HSP47/genética , Humanos , Hidroxilación , Chaperonas Moleculares/metabolismo , Prolina/química , Prolina/metabolismo , Conformación Proteica , Pliegue de Proteína , Procesamiento Proteico-PostraduccionalRESUMEN
Estrogen receptor α (ERα) is a hormone receptor and key driver for over 70% of breast cancers that has been studied for decades as a transcription factor. Unexpectedly, we discover that ERα is a potent non-canonical RNA-binding protein. We show that ERα RNA binding function is uncoupled from its activity to bind DNA and critical for breast cancer progression. Employing genome-wide cross-linking immunoprecipitation (CLIP) sequencing and a functional CRISPRi screen, we find that ERα-associated mRNAs sustain cancer cell fitness and elicit cellular responses to stress. Mechanistically, ERα controls different steps of RNA metabolism. In particular, we demonstrate that ERα RNA binding mediates alternative splicing of XBP1 and translation of the eIF4G2 and MCL1 mRNAs, which facilitates survival upon stress conditions and sustains tamoxifen resistance of cancer cells. ERα is therefore a multifaceted RNA-binding protein, and this activity transforms our knowledge of post-transcriptional regulation underlying cancer development and drug response.
Asunto(s)
Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Resistencia a Antineoplásicos , Receptor alfa de Estrógeno/metabolismo , Proteínas de Unión al ARN/metabolismo , Animales , Secuencia de Bases , Neoplasias de la Mama/genética , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Progresión de la Enfermedad , Resistencia a Antineoplásicos/efectos de los fármacos , Resistencia a Antineoplásicos/genética , Receptor alfa de Estrógeno/química , Factor 4G Eucariótico de Iniciación/genética , Factor 4G Eucariótico de Iniciación/metabolismo , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Genómica , Humanos , Ratones Endogámicos NOD , Proteína 1 de la Secuencia de Leucemia de Células Mieloides/genética , Proteína 1 de la Secuencia de Leucemia de Células Mieloides/metabolismo , Oncogenes , Unión Proteica/efectos de los fármacos , Dominios Proteicos , Empalme del ARN/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Tamoxifeno/farmacología , Proteína 1 de Unión a la X-Box/metabolismoRESUMEN
Selective autophagy of organelles is critical for cellular differentiation, homeostasis, and organismal health. Autophagy of the ER (ER-phagy) is implicated in human neuropathy but is poorly understood beyond a few autophagosomal receptors and remodelers. By using an ER-phagy reporter and genome-wide CRISPRi screening, we identified 200 high-confidence human ER-phagy factors. Two pathways were unexpectedly required for ER-phagy. First, reduced mitochondrial metabolism represses ER-phagy, which is opposite of general autophagy and is independent of AMPK. Second, ER-localized UFMylation is required for ER-phagy to repress the unfolded protein response via IRE1α. The UFL1 ligase is brought to the ER surface by DDRGK1 to UFMylate RPN1 and RPL26 and preferentially targets ER sheets for degradation, analogous to PINK1-Parkin regulation during mitophagy. Our data provide insight into the cellular logic of ER-phagy, reveal parallels between organelle autophagies, and provide an entry point to the relatively unexplored process of degrading the ER network.
Asunto(s)
Autofagia/fisiología , Retículo Endoplásmico/genética , Retículo Endoplásmico/metabolismo , Autofagia/genética , Estrés del Retículo Endoplásmico/fisiología , Endorribonucleasas/metabolismo , Estudio de Asociación del Genoma Completo/métodos , Células HCT116 , Células HEK293 , Células HeLa , Homeostasis , Humanos , Proteínas de la Membrana/metabolismo , Mitocondrias/genética , Mitocondrias/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas/metabolismo , Proteínas Ribosómicas/metabolismo , Respuesta de Proteína Desplegada/fisiologíaRESUMEN
Many cytosolic proteins lacking a signal peptide, called leaderless cargoes, are secreted through unconventional secretion. Vesicle trafficking is a major pathway involved. It is unclear how leaderless cargoes enter into the vesicle. Here, we find a translocation pathway regulating vesicle entry and secretion of leaderless cargoes. We identify TMED10 as a protein channel for the vesicle entry and secretion of many leaderless cargoes. The interaction of TMED10 C-terminal region with a motif in the cargo accounts for the selective release of the cargoes. In an in vitro reconstitution assay, TMED10 directly mediates the membrane translocation of leaderless cargoes into the liposome, which is dependent on protein unfolding and enhanced by HSP90s. In the cell, TMED10 localizes on the endoplasmic reticulum (ER)-Golgi intermediate compartment and directs the entry of cargoes into this compartment. Furthermore, cargo induces the formation of TMED10 homo-oligomers which may act as a protein channel for cargo translocation.
Asunto(s)
Sistemas de Translocación de Proteínas/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Animales , Transporte Biológico , Línea Celular , Línea Celular Tumoral , Membrana Celular/metabolismo , Citosol/metabolismo , Retículo Endoplásmico/metabolismo , Aparato de Golgi/metabolismo , Humanos , Ratones , Ratones Endogámicos C57BL , Señales de Clasificación de Proteína , Sistemas de Translocación de Proteínas/fisiología , Transporte de Proteínas/fisiología , Proteínas/metabolismo , Vías Secretoras , Proteínas de Transporte Vesicular/fisiologíaRESUMEN
Estrogen receptor-positive (ER+) breast cancers frequently remain dependent on ER signaling even after acquiring resistance to endocrine agents, prompting the development of optimized ER antagonists. Fulvestrant is unique among approved ER therapeutics due to its capacity for full ER antagonism, thought to be achieved through ER degradation. The clinical potential of fulvestrant is limited by poor physicochemical features, spurring attempts to generate ER degraders with improved drug-like properties. We show that optimization of ER degradation does not guarantee full ER antagonism in breast cancer cells; ER "degraders" exhibit a spectrum of transcriptional activities and anti-proliferative potential. Mechanistically, we find that fulvestrant-like antagonists suppress ER transcriptional activity not by ER elimination, but by markedly slowing the intra-nuclear mobility of ER. Increased ER turnover occurs as a consequence of ER immobilization. These findings provide proof-of-concept that small molecule perturbation of transcription factor mobility may enable therapeutic targeting of this challenging target class.
Asunto(s)
Neoplasias de la Mama/metabolismo , Antagonistas del Receptor de Estrógeno/farmacología , Fulvestrant/farmacología , Receptores de Estrógenos/antagonistas & inhibidores , Receptores de Estrógenos/metabolismo , Animales , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/patología , Proliferación Celular/efectos de los fármacos , Cinamatos/farmacología , Resistencia a Antineoplásicos , Antagonistas del Receptor de Estrógeno/uso terapéutico , Femenino , Fulvestrant/uso terapéutico , Células HEK293 , Xenoinjertos , Humanos , Indazoles/farmacología , Ligandos , Células MCF-7 , Ratones , Ratones Endogámicos NOD , Ratones Desnudos , Ratones SCID , Polimorfismo de Nucleótido Simple , Proteolisis/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Transcripción Genética/efectos de los fármacosRESUMEN
Maintaining the optimal performance of cell processes and organelles is the task of auto-regulatory systems. Here we describe an auto-regulatory device that helps to maintain homeostasis of the endoplasmic reticulum (ER) by adjusting the secretory flux to the cargo load. The cargo-recruiting subunit of the coatomer protein II (COPII) coat, Sec24, doubles as a sensor of folded cargo and, upon cargo binding, acts as a guanine nucleotide exchange factor to activate the signaling protein Gα12 at the ER exit sites (ERESs). This step, in turn, activates a complex signaling network that activates and coordinates the ER export machinery and attenuates proteins synthesis, thus preventing large fluctuations of folded and potentially active cargo that could be harmful to the cell or the organism. We call this mechanism AREX (autoregulation of ER export) and expect that its identification will aid our understanding of human physiology and diseases that develop from secretory dysfunction.
Asunto(s)
Retículo Endoplásmico/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Transporte Biológico , Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Vesículas Cubiertas por Proteínas de Revestimiento/fisiología , Línea Celular , Proteína Coatómero/metabolismo , Retículo Endoplásmico/fisiología , Estrés del Retículo Endoplásmico/fisiología , Femenino , Subunidades alfa de la Proteína de Unión al GTP G12-G13/metabolismo , Aparato de Golgi/metabolismo , Factores de Intercambio de Guanina Nucleótido/fisiología , Células HeLa , Humanos , Masculino , Pliegue de Proteína , Transporte de Proteínas , Proteostasis/fisiología , Transducción de SeñalRESUMEN
Necrosis of infected macrophages constitutes a critical pathogenetic event in tuberculosis by releasing mycobacteria into the growth-permissive extracellular environment. In zebrafish infected with Mycobacterium marinum or Mycobacterium tuberculosis, excess tumor necrosis factor triggers programmed necrosis of infected macrophages through the production of mitochondrial reactive oxygen species (ROS) and the participation of cyclophilin D, a component of the mitochondrial permeability transition pore. Here, we show that this necrosis pathway is not mitochondrion-intrinsic but results from an inter-organellar circuit initiating and culminating in the mitochondrion. Mitochondrial ROS induce production of lysosomal ceramide that ultimately activates the cytosolic protein BAX. BAX promotes calcium flow from the endoplasmic reticulum into the mitochondrion through ryanodine receptors, and the resultant mitochondrial calcium overload triggers cyclophilin-D-mediated necrosis. We identify ryanodine receptors and plasma membrane L-type calcium channels as druggable targets to intercept mitochondrial calcium overload and necrosis of mycobacterium-infected zebrafish and human macrophages.
Asunto(s)
Macrófagos/microbiología , Macrófagos/patología , Mitocondrias/metabolismo , Infecciones por Mycobacterium no Tuberculosas/metabolismo , Tuberculosis/inmunología , Tuberculosis/patología , Factor de Necrosis Tumoral alfa/metabolismo , Animales , Apoptosis , Calcio/metabolismo , Retículo Endoplásmico/microbiología , Humanos , Lisosomas/microbiología , Potencial de la Membrana Mitocondrial , Infecciones por Mycobacterium no Tuberculosas/patología , Mycobacterium marinum , Mycobacterium tuberculosis , Necrosis , Especies Reactivas de Oxígeno/metabolismo , Células THP-1 , Pez CebraRESUMEN
Intracellular accumulation of misfolded proteins causes toxic proteinopathies, diseases without targeted therapies. Mucin 1 kidney disease (MKD) results from a frameshift mutation in the MUC1 gene (MUC1-fs). Here, we show that MKD is a toxic proteinopathy. Intracellular MUC1-fs accumulation activated the ATF6 unfolded protein response (UPR) branch. We identified BRD4780, a small molecule that clears MUC1-fs from patient cells, from kidneys of knockin mice and from patient kidney organoids. MUC1-fs is trapped in TMED9 cargo receptor-containing vesicles of the early secretory pathway. BRD4780 binds TMED9, releases MUC1-fs, and re-routes it for lysosomal degradation, an effect phenocopied by TMED9 deletion. Our findings reveal BRD4780 as a promising lead for the treatment of MKD and other toxic proteinopathies. Generally, we elucidate a novel mechanism for the entrapment of misfolded proteins by cargo receptors and a strategy for their release and anterograde trafficking to the lysosome.
Asunto(s)
Benzamidas/metabolismo , Compuestos Bicíclicos con Puentes/farmacología , Heptanos/farmacología , Lisosomas/efectos de los fármacos , Proteínas de Transporte Vesicular/metabolismo , Factor de Transcripción Activador 6/metabolismo , Animales , Benzamidas/química , Benzamidas/farmacología , Compuestos Bicíclicos con Puentes/uso terapéutico , Células Epiteliales/citología , Células Epiteliales/metabolismo , Femenino , Mutación del Sistema de Lectura , Heptanos/uso terapéutico , Humanos , Receptores de Imidazolina/antagonistas & inhibidores , Receptores de Imidazolina/genética , Receptores de Imidazolina/metabolismo , Células Madre Pluripotentes Inducidas/citología , Células Madre Pluripotentes Inducidas/metabolismo , Riñón/citología , Riñón/metabolismo , Riñón/patología , Enfermedades Renales/metabolismo , Enfermedades Renales/patología , Lisosomas/metabolismo , Masculino , Ratones , Ratones Transgénicos , Mucina-1/química , Mucina-1/genética , Mucina-1/metabolismo , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Respuesta de Proteína Desplegada/efectos de los fármacos , Proteínas de Transporte Vesicular/químicaRESUMEN
Scap is a polytopic membrane protein that functions as a molecular machine to control the cholesterol content of membranes in mammalian cells. In the 21 years since our laboratory discovered Scap, we have learned how it binds sterol regulatory element-binding proteins (SREBPs) and transports them from the endoplasmic reticulum (ER) to the Golgi for proteolytic processing. Proteolysis releases the SREBP transcription factor domains, which enter the nucleus to promote cholesterol synthesis and uptake. When cholesterol in ER membranes exceeds a threshold, the sterol binds to Scap, triggering several conformational changes that prevent the Scap-SREBP complex from leaving the ER. As a result, SREBPs are no longer processed, cholesterol synthesis and uptake are repressed, and cholesterol homeostasis is restored. This review focuses on the four domains of Scap that undergo concerted conformational changes in response to cholesterol binding. The data provide a molecular mechanism for the control of lipids in cell membranes.
Asunto(s)
Colesterol/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas de la Membrana/metabolismo , Animales , Homeostasis , Humanos , Péptidos y Proteínas de Señalización Intracelular/química , Péptidos y Proteínas de Señalización Intracelular/genética , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Modelos Biológicos , Modelos Moleculares , Conformación Proteica , Transporte de Proteínas , Proteolisis , Receptores de LDL/metabolismo , Proteínas de Unión a los Elementos Reguladores de Esteroles/metabolismoRESUMEN
Immunosuppressive macrophages restrict anti-cancer immunity in glioblastoma (GBM). Here, we studied the contribution of microglia (MGs) and monocyte-derived macrophages (MDMs) to immunosuppression and mechanisms underlying their regulatory function. MDMs outnumbered MGs at late tumor stages and suppressed T cell activity. Molecular and functional analysis identified a population of glycolytic MDM expressing GLUT1 with potent immunosuppressive activity. GBM-derived factors promoted high glycolysis, lactate, and interleukin-10 (IL-10) production in MDMs. Inhibition of glycolysis or lactate production in MDMs impaired IL-10 expression and T cell suppression. Mechanistically, intracellular lactate-driven histone lactylation promoted IL-10 expression, which was required to suppress T cell activity. GLUT1 expression on MDMs was induced downstream of tumor-derived factors that activated the PERK-ATF4 axis. PERK deletion in MDM abrogated histone lactylation, led to the accumulation of intratumoral T cells and tumor growth delay, and, in combination with immunotherapy, blocked GBM progression. Thus, PERK-driven glucose metabolism promotes MDM immunosuppressive activity via histone lactylation.
Asunto(s)
Glioblastoma , Glucosa , Histonas , Macrófagos , Glioblastoma/inmunología , Glioblastoma/metabolismo , Glioblastoma/patología , Animales , Histonas/metabolismo , Ratones , Macrófagos/inmunología , Macrófagos/metabolismo , Glucosa/metabolismo , Humanos , Línea Celular Tumoral , Neoplasias Encefálicas/inmunología , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patología , Transportador de Glucosa de Tipo 1/metabolismo , Transportador de Glucosa de Tipo 1/genética , Interleucina-10/metabolismo , Glucólisis , Microglía/metabolismo , Microglía/inmunología , Ratones Endogámicos C57BL , Linfocitos T/inmunología , Linfocitos T/metabolismo , Tolerancia InmunológicaRESUMEN
Macroautophagy is an intracellular degradation system that delivers diverse cytoplasmic materials to lysosomes via autophagosomes. Recent advances have enabled identification of several selective autophagy substrates and receptors, greatly expanding our understanding of the cellular functions of autophagy. In this review, we describe the diverse cellular functions of macroautophagy, including its essential contribution to metabolic adaptation and cellular homeostasis. We also discuss emerging findings on the mechanisms and functions of various types of selective autophagy.
Asunto(s)
Autofagosomas/metabolismo , Autofagia/genética , Retículo Endoplásmico/metabolismo , Lisosomas/metabolismo , Mitocondrias/metabolismo , Animales , Autofagosomas/enzimología , Autofagosomas/microbiología , Autofagia/fisiología , Retículo Endoplásmico/fisiología , Homeostasis/genética , Homeostasis/fisiología , Humanos , Lisosomas/patología , Mitocondrias/patología , Nutrientes/deficiencia , Nutrientes/metabolismo , Peroxisomas/metabolismo , Peroxisomas/fisiologíaRESUMEN
Constitutive cell-autonomous immunity in metazoans predates interferon-inducible immunity and comprises primordial innate defense. Phagocytes mobilize interferon-inducible responses upon engagement of well-characterized signaling pathways by pathogen-associated molecular patterns (PAMPs). The signals controlling deployment of constitutive cell-autonomous responses during infection have remained elusive. Vita-PAMPs denote microbial viability, signaling the danger of cellular exploitation by intracellular pathogens. We show that cyclic-di-adenosine monophosphate in live Gram-positive bacteria is a vita-PAMP, engaging the innate sensor stimulator of interferon genes (STING) to mediate endoplasmic reticulum (ER) stress. Subsequent inactivation of the mechanistic target of rapamycin mobilizes autophagy, which sequesters stressed ER membranes, resolves ER stress, and curtails phagocyte death. This vita-PAMP-induced ER-phagy additionally orchestrates an interferon response by localizing ER-resident STING to autophagosomes. Our findings identify stress-mediated ER-phagy as a cell-autonomous response mobilized by STING-dependent sensing of a specific vita-PAMP and elucidate how innate receptors engage multilayered homeostatic mechanisms to promote immunity and survival after infection.
Asunto(s)
Bacterias Grampositivas/fisiología , Infecciones por Bacterias Grampositivas/inmunología , Proteínas de la Membrana/metabolismo , Fagocitos/inmunología , Animales , Autofagia , Retículo Endoplásmico/metabolismo , Estrés del Retículo Endoplásmico , Femenino , Masculino , Ratones , Moléculas de Patrón Molecular Asociado a Patógenos/metabolismo , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
Newly synthesized proteins engage molecular chaperones that assist folding. Their progress is monitored by quality control systems that target folding errors for degradation. Paradoxically, chaperones that promote folding also direct unfolded polypeptides for degradation. Hence, a mechanism was previously hypothesized that prevents the degradation of actively folding polypeptides. In this study, we show that a conserved endoplasmic reticulum (ER) membrane protein complex, consisting of Slp1 and Emp65 proteins, performs this function in the ER lumen. The complex binds unfolded proteins and protects them from degradation during folding. In its absence, approximately 20%-30% of newly synthesized proteins that could otherwise fold are degraded. Although the Slp1-Emp65 complex hosts a broad range of clients, it is specific for soluble proteins. Taken together, these studies demonstrate the vulnerability of newly translated, actively folding polypeptides and the discovery of a new proteostasis functional class we term "guardian" that protects them from degradation.
Asunto(s)
Retículo Endoplásmico/metabolismo , Pliegue de Proteína , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Animales , Degradación Asociada con el Retículo Endoplásmico , Glicosilación , Ratones , Chaperonas Moleculares/metabolismo , Proteolisis , Saccharomyces cerevisiae/citología , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Transporte Vesicular/químicaRESUMEN
Malignant cells utilize diverse strategies that enable them to thrive under adverse conditions while simultaneously inhibiting the development of anti-tumor immune responses. Hostile microenvironmental conditions within tumor masses, such as nutrient deprivation, oxygen limitation, high metabolic demand, and oxidative stress, disturb the protein-folding capacity of the endoplasmic reticulum (ER), thereby provoking a cellular state of "ER stress." Sustained activation of ER stress sensors endows malignant cells with greater tumorigenic, metastatic, and drug-resistant capacity. Additionally, recent studies have uncovered that ER stress responses further impede the development of protective anti-cancer immunity by manipulating the function of myeloid cells in the tumor microenvironment. Here, we discuss the tumorigenic and immunoregulatory effects of ER stress in cancer, and we explore the concept of targeting ER stress responses to enhance the efficacy of standard chemotherapies and evolving cancer immunotherapies in the clinic.
Asunto(s)
Estrés del Retículo Endoplásmico , Neoplasias/inmunología , Neoplasias/patología , Animales , Metástasis de la Neoplasia/inmunología , Metástasis de la Neoplasia/patología , Neoplasias/tratamiento farmacológico , Neovascularización Patológica , Escape del Tumor , Microambiente Tumoral , Respuesta de Proteína DesplegadaRESUMEN
Mammalian membrane proteins perform essential physiologic functions that rely on their accurate insertion and folding at the endoplasmic reticulum (ER). Using forward and arrayed genetic screens, we systematically studied the biogenesis of a panel of membrane proteins, including several G-protein-coupled receptors (GPCRs). We observed a central role for the insertase, the ER membrane protein complex (EMC), and developed a dual-guide approach to identify genetic modifiers of the EMC. We found that the back of Sec61 (BOS) complex, a component of the multipass translocon, was a physical and genetic interactor of the EMC. Functional and structural analysis of the EMCâ BOS holocomplex showed that characteristics of a GPCR's soluble domain determine its biogenesis pathway. In contrast to prevailing models, no single insertase handles all substrates. We instead propose a unifying model for coordination between the EMC, the multipass translocon, and Sec61 for the biogenesis of diverse membrane proteins in human cells.