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EMBO Reports Oct 2002The endoplasmic reticulum (ER) is a continuous membrane system but consists of various domains that perform different functions. Structurally distinct domains of this... (Review)
Review
The endoplasmic reticulum (ER) is a continuous membrane system but consists of various domains that perform different functions. Structurally distinct domains of this organelle include the nuclear envelope (NE), the rough and smooth ER, and the regions that contact other organelles. The establishment of these domains and the targeting of proteins to them are understood to varying degrees. Despite its complexity, the ER is a dynamic structure. In mitosis it must be divided between daughter cells and domains must be re-established, and even in interphase it is constantly rearranged as tubules extend along the cytoskeleton. Throughout these rearrangements the ER maintains its basic structure. How this is accomplished remains mysterious, but some insight has been gained from in vitro systems.
Topics: Animals; Cell Division; Cytoskeleton; Endoplasmic Reticulum; Green Fluorescent Proteins; Humans; Luminescent Proteins; Microscopy, Fluorescence; Mitosis; Models, Biological; Protein Biosynthesis
PubMed: 12370207
DOI: 10.1093/embo-reports/kvf202 -
Experimental Cell Research Jul 2012The endoplasmic reticulum (ER) consists of the nuclear envelope and a peripheral network of tubules and membrane sheets. The tubules are shaped by a specific class of... (Review)
Review
The endoplasmic reticulum (ER) consists of the nuclear envelope and a peripheral network of tubules and membrane sheets. The tubules are shaped by a specific class of curvature stabilizing proteins, the reticulons and DP1; however it is still unclear how the sheets are assembled. The ER is the cellular compartment responsible for secretory and membrane protein synthesis. The reducing conditions of ER lead to the intra/inter-chain formation of new disulphide bonds into polypeptides during protein folding assessed by enzymatic or spontaneous reactions. Moreover, ER represents the main intracellular calcium storage site and it plays an important role in calcium signaling that impacts many cellular processes. Accordingly, the maintenance of ER function represents an essential condition for the cell, and ER morphology constitutes an important prerogative of it. Furthermore, it is well known that ER undergoes prominent shape transitions during events such as cell division and differentiation. Thus, maintaining the correct ER structure is an essential feature for cellular physiology. Now, it is known that proper ER-associated proteins play a fundamental role in ER tubules formation. Among these ER-shaping proteins are the reticulons (RTN), which are acquiring a relevant position. In fact, beyond the structural role of reticulons, in very recent years new and deeper functional implications of these proteins are emerging in relation to their involvement in several cellular processes.
Topics: Animals; Calcium; Endoplasmic Reticulum; Humans; Membrane Proteins; Protein Folding
PubMed: 22425683
DOI: 10.1016/j.yexcr.2012.03.002 -
Endocrine Development 2012Endocrine and neuroendocrine cells differ from cells which rapidly release all their secreted proteins in that they store some secretory proteins in concentrated forms... (Review)
Review
Endocrine and neuroendocrine cells differ from cells which rapidly release all their secreted proteins in that they store some secretory proteins in concentrated forms in secretory granules to be rapidly released when cells are stimulated. Protein aggregation is considered as the first step in the secretory granule biosynthesis and, at least in the case of prolactin and growth hormone, greatly depends on zinc ions that facilitate this process. Hence, regulation of cellular zinc transport especially that within the regulated secretory pathway is of importance to understand. Various zinc transporters of Slc30a/ZnT and Slc39a/Zip families have been reported to fulfil this role and to participate in fine tuning of zinc transport in and out of the endoplasmic reticulum, Golgi complex and secretory granules, the main cellular compartments of the regulated secretory pathway. In this review, we will focus on the role of zinc in the formation of hormone-containing secretory granules with special emphasis on conditions required for growth hormone dimerization/aggregation. In addition, we highlight the role of zinc transporters that govern the process of zinc homeostasis in the regulated hormone secretion.
Topics: Animals; Endoplasmic Reticulum; Growth Hormone; Humans; Models, Biological; Protein Binding; Protein Multimerization; Protein Transport; Secretory Pathway; Secretory Vesicles; Zinc
PubMed: 23182824
DOI: 10.1159/000341763 -
Annual Review of Medicine 2012Perturbations in the normal functions of the endoplasmic reticulum (ER) trigger a signaling network that coordinates adaptive and apoptotic responses. There is... (Review)
Review
Perturbations in the normal functions of the endoplasmic reticulum (ER) trigger a signaling network that coordinates adaptive and apoptotic responses. There is accumulating evidence implicating prolonged ER stress in the development and progression of many diseases, including neurodegeneration, atherosclerosis, type 2 diabetes, liver disease, and cancer. With the improved understanding of the underlying molecular mechanisms, therapeutic interventions that target the ER stress response would be potential strategies to treat various diseases driven by prolonged ER stress.
Topics: Apoptosis; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Humans; Metabolic Diseases
PubMed: 22248326
DOI: 10.1146/annurev-med-043010-144749 -
Journal of Lipid Research Apr 2009This review presents an overview of mammalian phospholipid synthesis and the cellular locations of the biochemical activities that produce membrane lipid molecular... (Review)
Review
This review presents an overview of mammalian phospholipid synthesis and the cellular locations of the biochemical activities that produce membrane lipid molecular species. The generalized endoplasmic reticulum compartment is a central site for membrane lipid biogenesis, and examples of the emerging relationships between alterations in lipid composition, regulation of membrane lipid biogenesis, and cellular secretory function are discussed.
Topics: Animals; Endoplasmic Reticulum; Golgi Apparatus; Membrane Lipids; Phospholipids
PubMed: 18952570
DOI: 10.1194/jlr.R800049-JLR200 -
Current Opinion in Investigational... Oct 2008The endoplasmic reticulum (ER) has emerged as a key to understanding the development and consequences of hepatic fat accumulation in nonalcoholic fatty liver disease... (Review)
Review
The endoplasmic reticulum (ER) has emerged as a key to understanding the development and consequences of hepatic fat accumulation in nonalcoholic fatty liver disease (NAFLD). An essential function of this organelle is the proper assembly of proteins that are destined for intracellular organelles and the cell surface. Recent evidence suggests that chemical chaperones that enhance the functional capacity of the ER improve liver function in obesity and NAFLD. These chaperones may therefore provide a novel potential therapeutic strategy in NAFLD.
Topics: Animals; Diabetes Mellitus; Endoplasmic Reticulum; Fatty Liver; Humans; Molecular Chaperones; Obesity
PubMed: 18821470
DOI: No ID Found -
Protoplasma Sep 2019Plasmodesmata enable the trafficking of various signaling molecules, as well as viruses that exploit these channels for their intercellular movement. Viral movement...
Plasmodesmata enable the trafficking of various signaling molecules, as well as viruses that exploit these channels for their intercellular movement. Viral movement relies on the endoplasmic reticulum (ER), which serves as a stable platform for the assembly of viral replication complexes and their subsequent shuttling toward plasmodesmata. The role of the ER in the intercellular movement of endogenous proteins is less clear. In the root meristem, the mobile transcription factor SHORT-ROOT (SHR) traffics between cell layers to regulate root radial patterning and differentiation. Movement of SHR is a regulated process that requires several cellular factors including the endomembrane system, intact microtubules and an endosome-associated protein named SHR-interacting-embryonic-lethal (SIEL). Recently, we found that KINESIN G (KinG) interacts with both SIEL and microtubules to support the cell-to-cell movement of SHR. Here, we provide evidence that both SHR-associated endosomes and KinG localize to the endoplasmic reticulum (ER) and that movement of SHR-associated endosomes occurs on the ER. Moreover, we show that compromised ER structure leads to a reduction in the cell-to-cell movement of SHR. Collectively, these results support the hypothesis that the ER plays a role in SHR movement.
Topics: Cell Movement; Endoplasmic Reticulum; Plant Roots
PubMed: 31123903
DOI: 10.1007/s00709-019-01369-z -
Cold Spring Harbor Perspectives in... Jan 2013To cause infection, a virus enters a host cell, replicates, and assembles, with the resulting new viral progeny typically released into the extracellular environment to... (Review)
Review
To cause infection, a virus enters a host cell, replicates, and assembles, with the resulting new viral progeny typically released into the extracellular environment to initiate a new infection round. Virus entry, replication, and assembly are dynamic and coordinated processes that require precise interactions with host components, often within and surrounding a defined subcellular compartment. Accumulating evidence pinpoints the endoplasmic reticulum (ER) as a crucial organelle supporting viral entry, replication, and assembly. This review focuses on the molecular mechanism by which different viruses co-opt the ER to accomplish these crucial infection steps. Certain bacterial toxins also hijack the ER for entry. An interdisciplinary approach, using rigorous biochemical and cell biological assays coupled with advanced microscopy strategies, will push to the next level our understanding of the virus-ER interaction during infection.
Topics: Cholera Toxin; Endoplasmic Reticulum; Host-Pathogen Interactions; Immune Evasion; Models, Biological; Polyomavirus; Virus Assembly; Virus Internalization; Virus Replication
PubMed: 23284050
DOI: 10.1101/cshperspect.a013250 -
Proceedings of the National Academy of... Jan 2022Recent advances in super-resolution microscopy revealed the previously unknown nanoscopic level of organization of endoplasmic reticulum (ER), one of the most vital...
Recent advances in super-resolution microscopy revealed the previously unknown nanoscopic level of organization of endoplasmic reticulum (ER), one of the most vital intracellular organelles. Membrane nanostructures of 10- to 100-nm intrinsic length scales, which include ER tubular matrices, ER sheet nanoholes, internal membranes of ER exit sites (ERES), and ER transport intermediates, were discovered and imaged in considerable detail, but the physical factors determining their unique geometrical features remained unknown. Here, we proposed and computationally substantiated a common concept for mechanisms of all ER nanostructures based on the membrane intrinsic curvature as a primary factor shaping the membrane and ultra-low membrane tensions as modulators of the membrane configurations. We computationally revealed a common structural motif underlying most of the nanostructures. We predicted the existence of a discrete series of equilibrium configurations of ER tubular matrices and recovered the one corresponding to the observations and favored by ultra-low tensions. We modeled the nanohole formation as resulting from a spontaneous collapse of elements of the ER tubular network adjacent to the ER sheet edge and calculated the nanohole dimensions. We proposed the ERES membrane to have a shape of a super flexible membrane bead chain, which acquires random walk configurations unless an ultra-low tension converts it into a straight conformation of a transport intermediate. The adequacy of the proposed concept is supported by a close qualitative and quantitative similarity between the predicted and observed configurations of all four ER nanostructures.
Topics: Endoplasmic Reticulum; Nanostructures
PubMed: 34930828
DOI: 10.1073/pnas.2116142119 -
Current Opinion in Cell Biology Aug 1993Proteins fold and assemble in the endoplasmic reticulum in an environment that is very different from the cytosol. The presence of relatively high concentrations of... (Review)
Review
Proteins fold and assemble in the endoplasmic reticulum in an environment that is very different from the cytosol. The presence of relatively high concentrations of calcium, an oxidizing state, ATP and lumenal proteins are all important in mediating these events.
Topics: Animals; Chaperonins; Chemical Phenomena; Chemistry, Physical; Endoplasmic Reticulum; Humans; Membrane Proteins; Peptides; Protein Folding; Proteins
PubMed: 7903041
DOI: 10.1016/0955-0674(93)90127-c