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Location matters: the endoplasmic reticulum and protein trafficking in dendrites
Ramírez,Omar A; H?rtel,Steffen; Couve,Andrés;
Biological Research , 2011, DOI: 10.4067/S0716-97602011000100003
Abstract: neurons are highly polarized, but the trafficking mechanisms that operate in these cells and the topological organization of their secretory organelles are still poorly understood. particularly incipient is our knowledge of the role of the neuronal endoplasmic reticulum. here we review the current understanding of the endoplasmic reticulum in neurons, its structure, composition, dendritic distribution and dynamics. we also focus on the trafficking of proteins through the dendritic endoplasmic reticulum, emphasizing the relevance of transport, retention, assembly of multi-subunit protein complexes and export. we additionally discuss the roles of the dendritic endoplasmic reticulum in synaptic plasticity.
Location matters: the endoplasmic reticulum and protein trafficking in dendrites  [cached]
Omar A Ramírez,Steffen H?rtel,Andrés Couve
Biological Research , 2011,
Abstract: Neurons are highly polarized, but the trafficking mechanisms that operate in these cells and the topological organization of their secretory organelles are still poorly understood. Particularly incipient is our knowledge of the role of the neuronal endoplasmic reticulum. Here we review the current understanding of the endoplasmic reticulum in neurons, its structure, composition, dendritic distribution and dynamics. We also focus on the trafficking of proteins through the dendritic endoplasmic reticulum, emphasizing the relevance of transport, retention, assembly of multi-subunit protein complexes and export. We additionally discuss the roles of the dendritic endoplasmic reticulum in synaptic plasticity.
Endoplasmic reticulum stress and diabetic retinopathy  [cached]
Toshiyuki Oshitari,Natsuyo Hata,Shuichi Yamamoto
Vascular Health and Risk Management , 2008,
Abstract: Toshiyuki Oshitari1,2, Natsuyo Hata1, Shuichi Yamamoto11Department of Ophthalmology and Visual Science, Chiba University Graduate School of Medicine, Chiba City, Chiba, Japan; 2Department of Ophthalmology, Kimitsu Central Hospital, Kisarazu City, Chiba, JapanAbstract: Endoplasmic reticulum (ER) stress is involved in the pathogenesis of several diseases including Alzheimer disease and Parkinson disease. Many recent studies have shown that ER stress is related to the pathogenesis of diabetes mellitus, and with the death of pancreatic β-cells, insulin resistance, and the death of the vascular cells in the retina. Diabetic retinopathy is a major complication of diabetes and results in death of both neural and vascular cells. Because the death of the neurons directly affects visual function, the precise mechanism causing the death of neurons in early diabetic retinopathy must be determined. The ideal therapy for preventing the onset and the progression of diabetic retinopathy would be to treat the factors involved with both the vascular and neuronal abnormalities in diabetic retinopathy. In this review, we present evidence that ER stress is involved in the death of both retinal neurons and vascular cells in diabetic eyes, and thus reducing or blocking ER stress may be a potential therapy for preventing the onset and the progression of diabetic retinopathy.Keywords: endoplasmic reticulum stress, diabetic retinopathy, vascular cell death, neuronal cell death
Endoplasmic Reticulum Stress and Apoptosis Mechanisms  [cached]
G.Seyda Seydel,Kiymet Aksoy
Arsiv Kaynak Tarama Dergisi , 2012,
Abstract: Thhe endoplasmic reticulum (ER) is the principal site for the synthesis, folding and maturation of most secreted proteins in the cell and essential for most cellular activities. Conditions that impair the folding capacity of the ER cause ER stress and induce a set of signaling pathways termed the unfolded protein response (UPR). If the protective mechanism activated by the UPR is not sufficient to restore normal ER function, cells die by apoptosis mechanism. Recent research suggests that ER stress and UPR play important roles in the metabolic disorders such as diabetes and obesity, cancer, immune response and in some neurodegenerative diseases such as Alzheimer, Parkinson, Huntington. Further studies on ER stress and UPR are necessary to clarify the exact role of this physiological mechanism and provide novel avenues to potential therapies. This review will provide an overview of ER stress, the UPR signaling pathways and ER stress induced apoptosis mechanism. [Archives Medical Review Journal 2012; 21(4.000): 221-235]
Endoplasmic Reticulum Stress and Diabetic Cardiomyopathy
Jiancheng Xu,Qi Zhou,Wei Xu,Lu Cai
Experimental Diabetes Research , 2012, DOI: 10.1155/2012/827971
Abstract: The endoplasmic reticulum (ER) is an organelle entrusted with lipid synthesis, calcium homeostasis, protein folding, and maturation. Perturbation of ER-associated functions results in an evolutionarily conserved cell stress response, the unfolded protein response (UPR) that is also called ER stress. ER stress is aimed initially at compensating for damage but can eventually trigger cell death if ER stress is excessive or prolonged. Now the ER stress has been associated with numerous diseases. For instance, our recent studies have demonstrated the important role of ER stress in diabetes-induced cardiac cell death. It is known that apoptosis has been considered to play a critical role in diabetic cardiomyopathy. Therefore, this paper will summarize the information from the literature and our own studies to focus on the pathological role of ER stress in the development of diabetic cardiomyopathy. Improved understanding of the molecular mechanisms underlying UPR activation and ER-initiated apoptosis in diabetic cardiomyopathy will provide us with new targets for drug discovery and therapeutic intervention.
Mechanisms of CFTR Folding at the Endoplasmic Reticulum  [PDF]
Soo Jung Kim,William R. Skach
Frontiers in Pharmacology , 2012, DOI: 10.3389/fphar.2012.00201
Abstract: In the past decade much has been learned about how Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) folds and misfolds as the etiologic cause of cystic fibrosis (CF). CFTR folding is complex and hierarchical, takes place in multiple cellular compartments and physical environments, and involves several large networks of folding machineries. Insertion of transmembrane (TM) segments into the endoplasmic reticulum (ER) membrane and tertiary folding of cytosolic domains begin cotranslationally as the nascent polypeptide emerges from the ribosome, whereas posttranslational folding establishes critical domain–domain contacts needed to form a physiologically stable structure. Within the membrane, N- and C-terminal TM helices are sorted into bundles that project from the cytosol to form docking sites for nucleotide binding domains, NBD1 and NBD2, which in turn form a sandwich dimer for ATP binding. While tertiary folding is required for domain assembly, proper domain assembly also reciprocally affects folding of individual domains analogous to a jig-saw puzzle wherein the structure of each interlocking piece influences its neighbors. Superimposed on this process is an elaborate proteostatic network of cellular chaperones and folding machineries that facilitate the timing and coordination of specific folding steps in and across the ER membrane. While the details of this process require further refinement, we finally have a useful framework to understand key folding defect(s) caused by ΔF508 that provides a molecular target(s) for the next generation of CFTR small molecule correctors aimed at the specific defect present in the majority of CF patients.
ULTRASTRUCTURAL STUDY OF THE COAGULATING GLAND EPITHELIUM OF THE RAT (Rattus norvegicus) AFTER VASECTOMY
Melo,S. R.; Mello Jr.,W.; Garcia,P. J.; Cagnon,V. H. A.;
Revista chilena de anatomía , 1997, DOI: 10.4067/S0716-98681997000200008
Abstract: morphological alterations of the coagulating gland of vasectomized rats were observed using light and transmission electron microscopy. the results demonstrated atrophy of the height of the secretory epithelium. ultrastructural observations showed atrophy of the rough endoplasmic reticulum cisternae
Endoplasmic reticulum quality control and congenital pathology
Marek Michalak
Journal of Applied Biomedicine , 2005,
Abstract: Quality control of the endoplasmic reticulum plays a critical role in protein folding, modification andmodification of a secretory pathway. As endoplasmic reticulum chaperones, calreticulin and calnexinhave similar substrate specificity and share several common features. Yet, surprisingly, mice bearing adisruption in the calreticulin gene die from a lesion in cardiac development and develop significantmetabolic problems whereas calnexin-deficient mice are born alive with, yet not understood, neurologicalproblems. Studies with calreticulin and calnexin gene knockout mice and calreticulin- and calnexindeficientcell lines indicate that calnexin is unable to compensate for the loss of calreticulin andconversely, calreticulin cannot compensate for the loss of calnexin. Calreticulin or calnexin deficiency orreduction in the level of ERp57 protein (ERp57 heterozygote mice) leads to development of metabolicdisorders as documented by sever changes serum lipids and carbohydrates composition in these animals.These observations indicate that calreticulin, calnexin and ERp57, in addition of being involved inmaturation of glycoproteins in the endoplasmic reticulum, perform other distinct functions includingaffecting energy metabolism.
Endoplasmic Reticulum Calcium Pumps and Cancer Cell Differentiation  [PDF]
Béla Papp,Jean-Philippe Brouland,Atousa Arbabian,Pascal Gélébart,Tünde Kovács,Régis Bobe,Jocelyne Enouf,Nadine Varin-Blank,ágota Apáti
Biomolecules , 2012, DOI: 10.3390/biom2010165
Abstract: The endoplasmic reticulum (ER) is a major intracellular calcium storage pool and a multifunctional organelle that accomplishes several calcium-dependent functions involved in many homeostatic and signaling mechanisms. Calcium is accumulated in the ER by Sarco/Endoplasmic Reticulum Calcium ATPase (SERCA)-type calcium pumps. SERCA activity can determine ER calcium content available for intra-ER functions and for calcium release into the cytosol, and can shape the spatiotemporal characteristics of calcium signals. SERCA function therefore constitutes an important nodal point in the regulation of cellular calcium homeostasis and signaling, and can exert important effects on cell growth, differentiation and survival. In several cell types such as cells of hematopoietic origin, mammary, gastric and colonic epithelium, SERCA2 and SERCA3-type calcium pumps are simultaneously expressed, and SERCA3 expression levels undergo significant changes during cell differentiation, activation or immortalization. In addition, SERCA3 expression is decreased or lost in several tumor types when compared to the corresponding normal tissue. These observations indicate that ER calcium homeostasis is remodeled during cell differentiation, and may present defects due to decreased SERCA3 expression in tumors. Modulation of the state of differentiation of the ER reflected by SERCA3 expression constitutes an interesting new aspect of cell differentiation and tumor biology.
Unfolded protein stress in the endoplasmic reticulum and mitochondria: a role in neurodegeneration  [PDF]
Marisol Morales Soto
Frontiers in Aging Neuroscience , 2012, DOI: 10.3389/fnagi.2012.00005
Abstract: Protein-folding occurs in several intracellular locations including the endoplasmic reticulum and mitochondria. In normal conditions there is a balance between the levels of unfolded proteins and protein folding machinery. Disruption of homeostasis and an accumulation of unfolded proteins trigger stress responses, or unfolded protein responses (UPR), in these organelles. These pathways signal to increase the folding capacity, inhibit protein import or expression, increase protein degradation, and potentially trigger cell death. Many aging-related neurodegenerative diseases involve the accumulation of misfolded proteins in both the endoplasmic reticulum and mitochondria. The exact participation of the UPRs in the onset of neurodegeneration is unclear, but there is significant evidence for the alteration of these pathways in the endoplasmic reticulum and mitochondria. Here we will discuss the involvement of endoplasmic reticulum and mitochondrial stress and the possible contributions of the UPR in these organelles to the development of two neurodegenerative diseases, Parkinson's disease (PD) and Alzheimer's disease (AD).
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