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Trends in Endocrinology and Metabolism:... Mar 2017Emerging findings disclose unexpected components of G protein-coupled receptor (GPCR) signaling and cell biology. Select GPCRs exhibit classical signaling, that is... (Review)
Review
Emerging findings disclose unexpected components of G protein-coupled receptor (GPCR) signaling and cell biology. Select GPCRs exhibit classical signaling, that is restricted to cell membranes, as well as newly described persistent signaling that depends on internalization of the GPCR bound to β-arrestins. Termination of non-canonical endosomal signaling requires intraluminal acidification and sophisticated protein trafficking machineries. Recent studies reveal the structural determinants of the trafficking chaperones. This review summarizes advances in GPCR signaling and trafficking with a focus on the parathyroid hormone receptor (PTHR) as a prototype, and on the actin-sorting nexin 27 (SNX27)-retromer tubule (ASRT) complex, an endosomal sorting hub responsible for recycling and preservation of cell surface receptors. The findings are integrated into a model of PTHR trafficking with implications for signal transduction, bone growth, and mineral ion metabolism.
Topics: Animals; Endosomes; Humans; Protein Transport; Receptor, Parathyroid Hormone, Type 1; Receptors, G-Protein-Coupled; Signal Transduction; Sorting Nexins
PubMed: 27889227
DOI: 10.1016/j.tem.2016.10.007 -
Nature Nov 2022G-protein-coupled receptors (GPCRs), the largest family of signalling receptors, as well as important drug targets, are known to activate extracellular-signal-regulated...
G-protein-coupled receptors (GPCRs), the largest family of signalling receptors, as well as important drug targets, are known to activate extracellular-signal-regulated kinase (ERK)-a master regulator of cell proliferation and survival. However, the precise mechanisms that underlie GPCR-mediated ERK activation are not clearly understood. Here we investigated how spatially organized β-adrenergic receptor (βAR) signalling controls ERK. Using subcellularly targeted ERK activity biosensors, we show that βAR signalling induces ERK activity at endosomes, but not at the plasma membrane. This pool of ERK activity depends on active, endosome-localized Gα and requires ligand-stimulated βAR endocytosis. We further identify an endosomally localized non-canonical signalling axis comprising Gα, RAF and mitogen-activated protein kinase kinase, resulting in endosomal ERK activity that propagates into the nucleus. Selective inhibition of endosomal βAR and Gα signalling blunted nuclear ERK activity, MYC gene expression and cell proliferation. These results reveal a non-canonical mechanism for the spatial regulation of ERK through GPCR signalling and identify a functionally important endosomal signalling axis.
Topics: Adrenergic Agents; Cell Proliferation; Endosomes; Extracellular Signal-Regulated MAP Kinases; Genes, myc; GTP-Binding Protein alpha Subunits, Gs; Mitogen-Activated Protein Kinase Kinases; Phosphorylation; Receptors, Adrenergic, beta-2; Signal Transduction
PubMed: 36289326
DOI: 10.1038/s41586-022-05343-3 -
Nature Communications Sep 2019RNA-based therapeutics hold great promise for treating diseases and lipid nanoparticles (LNPs) represent the most advanced platform for RNA delivery. However, the fate...
RNA-based therapeutics hold great promise for treating diseases and lipid nanoparticles (LNPs) represent the most advanced platform for RNA delivery. However, the fate of the LNP-mRNA after endosome-engulfing and escape from the autophagy-lysosomal pathway remains unclear. To investigate this, mRNA (encoding human erythropoietin) was delivered to cells using LNPs, which shows, for the first time, a link between LNP-mRNA endocytosis and its packaging into extracellular vesicles (endo-EVs: secreted after the endocytosis of LNP-mRNA). Endosomal escape of LNP-mRNA is dependent on the molar ratio between ionizable lipids and mRNA nucleotides. Our results show that fractions of ionizable lipids and mRNA (1:1 molar ratio of hEPO mRNA nucleotides:ionizable lipids) of endocytosed LNPs were detected in endo-EVs. Importantly, these EVs can protect the exogenous mRNA during in vivo delivery to produce human protein in mice, detected in plasma and organs. Compared to LNPs, endo-EVs cause lower expression of inflammatory cytokines.
Topics: Animals; Biological Transport; Cell Line; Cytoplasm; Endosomes; Erythropoietin; Extracellular Vesicles; Female; Humans; Lipid Metabolism; Lipids; Mice; Mice, Inbred C57BL; Nanoparticles; RNA, Messenger
PubMed: 31551417
DOI: 10.1038/s41467-019-12275-6 -
Cells Feb 2023Autophagy-the lysosomal degradation of cytoplasm-plays a central role in cellular homeostasis and protects cells from potentially harmful agents that may accumulate in... (Review)
Review
Autophagy-the lysosomal degradation of cytoplasm-plays a central role in cellular homeostasis and protects cells from potentially harmful agents that may accumulate in the cytoplasm, including pathogens, protein aggregates, and dysfunctional organelles. This process is initiated by the formation of a phagophore membrane, which wraps around a portion of cytoplasm or cargo and closes to form a double-membrane autophagosome. Upon the fusion of the autophagosome with a lysosome, the sequestered material is degraded by lysosomal hydrolases in the resulting autolysosome. Several alternative membrane sources of autophagosomes have been proposed, including the plasma membrane, endosomes, mitochondria, endoplasmic reticulum, lipid droplets, hybrid organelles, and de novo synthesis. Here, we review recent progress in our understanding of how the autophagosome is formed and highlight the proposed role of vesicles that contain the lipid scramblase ATG9 as potential seeds for phagophore biogenesis. We also discuss how the phagophore is sealed by the action of the endosomal sorting complex required for transport (ESCRT) proteins.
Topics: Autophagosomes; Macroautophagy; Autophagy; Endosomes; Cell Membrane
PubMed: 36831335
DOI: 10.3390/cells12040668 -
Nature Immunology Jan 2023Inflammasome complexes are pivotal in the innate immune response. The NLR family pyrin domain containing protein 3 (NLRP3) inflammasome is activated in response to a...
Inflammasome complexes are pivotal in the innate immune response. The NLR family pyrin domain containing protein 3 (NLRP3) inflammasome is activated in response to a broad variety of cellular stressors. However, a primary and converging sensing mechanism by the NLRP3 receptor initiating inflammasome assembly remains ill defined. Here, we demonstrate that NLRP3 inflammasome activators primarily converge on disruption of endoplasmic reticulum-endosome membrane contact sites (EECS). This defect causes endosomal accumulation of phosphatidylinositol 4-phosphate (PI4P) and a consequent impairment of endosome-to-trans-Golgi network trafficking (ETT), necessary steps for endosomal recruitment of NLRP3 and subsequent inflammasome activation. Lowering endosomal PI4P levels prevents endosomal association of NLRP3 and inhibits inflammasome activation. Disruption of EECS or ETT is sufficient to enhance endosomal PI4P levels, to recruit NLRP3 to endosomes and to potentiate NLRP3 inflammasome activation. Mice with defects in ETT in the myeloid compartment are more susceptible to lipopolysaccharide-induced sepsis. Our study thus identifies a distinct cellular mechanism leading to endosomal NLRP3 recruitment and inflammasome activation.
Topics: Mice; Animals; Inflammasomes; NLR Family, Pyrin Domain-Containing 3 Protein; Immunity, Innate; Carrier Proteins; Endosomes
PubMed: 36443515
DOI: 10.1038/s41590-022-01355-3 -
Cell May 2023The Commander complex is required for endosomal recycling of diverse transmembrane cargos and is mutated in Ritscher-Schinzel syndrome. It comprises two sub-assemblies:...
The Commander complex is required for endosomal recycling of diverse transmembrane cargos and is mutated in Ritscher-Schinzel syndrome. It comprises two sub-assemblies: Retriever composed of VPS35L, VPS26C, and VPS29; and the CCC complex which contains twelve subunits: COMMD1-COMMD10 and the coiled-coil domain-containing (CCDC) proteins CCDC22 and CCDC93. Combining X-ray crystallography, electron cryomicroscopy, and in silico predictions, we have assembled a complete structural model of Commander. Retriever is distantly related to the endosomal Retromer complex but has unique features preventing the shared VPS29 subunit from interacting with Retromer-associated factors. The COMMD proteins form a distinctive hetero-decameric ring stabilized by extensive interactions with CCDC22 and CCDC93. These adopt a coiled-coil structure that connects the CCC and Retriever assemblies and recruits a 16th subunit, DENND10, to form the complete Commander complex. The structure allows mapping of disease-causing mutations and reveals the molecular features required for the function of this evolutionarily conserved trafficking machinery.
Topics: Humans; Abnormalities, Multiple; Craniofacial Abnormalities; Endosomes; Protein Transport; Proteins; Multiprotein Complexes
PubMed: 37172566
DOI: 10.1016/j.cell.2023.04.003 -
Small GTPases 2012Ras proteins are best known to function on the plasma membrane to mediate growth factor signaling. Controlling the length of time that Ras proteins stay on the plasma...
Ras proteins are best known to function on the plasma membrane to mediate growth factor signaling. Controlling the length of time that Ras proteins stay on the plasma membrane is an effective way to properly modulate the intensity and duration of growth factor signaling. It has been shown previously that H- and N-Ras proteins in the GTP-bound state can be ubiquitylated via a K-63 linkage, which leads to endosome internalization and results in a negative-feedback loop for efficient signal attenuation. In a more recent study, two new Ras effectors have been isolated, CHMP6 and VPS4A, which are components of the ESCRT-III complex, best known for mediating protein sorting in the endosomes. Surprisingly, these molecules are required for efficient Ras-induced transformation. They apparently do so by controlling recycling of components of the Ras pathway back to the plasma membrane, thus creating a positive-feedback loop to enhance growth factor signaling. These results suggest the fates of endosomal Ras proteins are complex and dynamic - they can be either stored and/or destroyed or recycled. Further work is needed to decipher how the fate of these endosomal Ras proteins is determined.
Topics: Animals; Cell Membrane; Cytoplasm; Endosomes; Humans; ras Proteins
PubMed: 22735486
DOI: 10.4161/sgtp.20460 -
Current Biology : CB Jul 2017Lucas and Hierro introduce the retromer and its role in endosomal protein sorting and trafficking.
Lucas and Hierro introduce the retromer and its role in endosomal protein sorting and trafficking.
Topics: Endosomes; Protein Transport; Vesicular Transport Proteins
PubMed: 28743009
DOI: 10.1016/j.cub.2017.05.072 -
Pharmaceutical Research Jun 2022Endosome escape is a key process for intracellular uptake of intact biomolecules and therapeutics, such as nucleic acids. Lysosome escape is a more common pathway during... (Review)
Review
Endosome escape is a key process for intracellular uptake of intact biomolecules and therapeutics, such as nucleic acids. Lysosome escape is a more common pathway during endocytosis, while some biomolecular, organic and inorganic materials are found to enhance the endosome escape, and several mechanisms have been proposed accordingly. Specifically, some inorganic nanomaterials show their unique mechanisms of action for enhanced endosome escape, including salt osmotic effect and gas blast effect. These inorganic nanomaterials are basically weakly alkaline and are naturally featured with the anti-acidification capacity, with limited solubility in neutral solutions. This review paper has briefly presented the strategies in the design of inorganic nanoparticle-based cellular delivery vehicles with endosome escapability and discussed a few typical inorganic nanomaterials that are currently widely examined for delivery purpose. A brief summary and prospect for this kind of inorganic nanomaterials are provided.
Topics: Endocytosis; Endosomes; Lysosomes; Nanoparticles; Nanostructures
PubMed: 35112228
DOI: 10.1007/s11095-022-03178-1 -
Journal of Cell Science Mar 2023The endosomal system orchestrates the transport of lipids, proteins and nutrients across the entire cell. Along their journey, endosomes mature, change shape via fusion... (Review)
Review
The endosomal system orchestrates the transport of lipids, proteins and nutrients across the entire cell. Along their journey, endosomes mature, change shape via fusion and fission, and communicate with other organelles. This intriguing endosomal choreography, which includes bidirectional and stop-and-go motions, is coordinated by the microtubule-based motor proteins dynein and kinesin. These motors bridge various endosomal subtypes to the microtubule tracks thanks to their cargo-binding domain interacting with endosome-associated proteins, and their motor domain interacting with microtubules and associated proteins. Together, these interactions determine the mobility of different endosomal structures. In this Review, we provide a comprehensive overview of the factors regulating the different interactions to tune the fascinating dance of endosomes along microtubules.
Topics: Dyneins; Kinesins; Endosomes; Microtubules; Microtubule-Associated Proteins
PubMed: 36382597
DOI: 10.1242/jcs.259689