scholarly journals Determination of the Transmembrane Topology of Yeast Sec61p, an Essential Component of the Endoplasmic Reticulum Translocation Complex

1996 ◽  
Vol 271 (41) ◽  
pp. 25590-25597 ◽  
Author(s):  
Barrie M. Wilkinson ◽  
Angela J. Critchley ◽  
Colin J. Stirling
Keyword(s):  
Endoplasmic Reticulum ◽  
Transmembrane Topology ◽  
Essential Component

Studies on the site of addition of sialic acid and glucosamine to rat α1-acid glycoprotein

1977 ◽  
Vol 55 (4) ◽  
pp. 408-414 ◽  
Author(s):  
J. C. Jamieson
Keyword(s):  
Endoplasmic Reticulum ◽  
Sialic Acid ◽  
Rat Liver ◽  
Golgi Complex ◽  
Smooth Endoplasmic Reticulum ◽  
Main Site ◽  
Acid Glycoprotein ◽  
Membrane Bound ◽  
Polypeptide Chains

Ultrasonic extracts of rough and smooth endoplasmic reticulum fractions and Golgi fractions from rat liver were examined by immunoelectrophoresis using antiserum to α1-acid glycoprotein. Rough endoplasmic reticulum fractions contained only sialic acid free α1-acid glycoprotein, whereas smooth endoplasmic reticulum and Golgi fractions also contained sialic acid containing α1-acid glycoprotein. Determination of the sialic acid contents of immune precipitates isolated from the extracts suggested that the Golgi complex was the main site of addition of sialic acid to α1-acid glycoprotein. Immunological studies on puromycin extracts of polyribosomes showed that polypeptide chains of α1-acid glycoprotein and albumin were assembled mainly on membrane-bound polyribosomes. Evidence is presented from incorporation studies with labelled leucine and glucosamine that initial glycosylation of α1-acid glycoprotein occurs mainly or entirely after release of nascent polypeptide from the ribosomal site.

Cytochemical studies of protein transport in the nervous system

1971 ◽  
Vol 261 (839) ◽  
pp. 407-421 ◽  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nervous System ◽  
Golgi Apparatus ◽  
Metabolic Activity ◽  
Nervous Tissue ◽  
Protein Transport ◽  
Division Of Labour ◽  
Central Importance ◽  
Transport Pathways

The transport of materials within the nervous system has received much attention in recent years. Considerable information has accumulated concerning such subjects as the exchange of substances between the circulation and nervous tissue, the passage down axons of molecules and organelles originating in perikarya and the release and fate of neurotransmitters and neurosecretory agents at synapses and other neuron endings (see, for example, Wolstenholme & Porter 1968; Barondes 1969). Many investigations are underway on modulations of transport during nerve growth and regeneration and in tissue responding to injury or to other experimental alterations. However, numerous gaps remain. Of central importance to future analysis of intraneuronal transport will be the determination of details of the routes and mechanisms by which various components synthesized in the perikaryon become distributed throughout the cell. It is becoming increasingly clear that different components move along axons at quite different rates (see, for example, McEwen & Grafstein 1968). This heterogeneity may reflect the existence of a variety of intraaxonal transport pathways. Important clues derive from such work as the studies on microtubules reported by D. S. Smith in the present proceedings but much remains to be learned about possible compartmentalization of movement within axons. Similarly, the organization of perikarya must be further investigated. Neurons possess abundant rough endoplasmic reticulum, many free ribosomes, a well-developed Golgi apparatus and other features consonant with their intensive metabolic activity. Remarkably little is known, however, about most of the molecules synthesized within perikarya and about the division of labour among the organelles of the perikaryal cytoplasm.

scholarly journals Ghrelin Alleviates Endoplasmic Reticulum Stress in MC3T3E1 Cells by Inhibiting AMPK Phosphorylation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xue Lv ◽  
Qianping Zhang ◽  
Bingfei Cheng ◽  
Ying Xin ◽  
Jun Wang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Energy Homeostasis ◽  
Marker Genes ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Expression Of Genes ◽  
Species Production ◽  
Related Proteins

Ghrelin is a gastric endocrine peptide that has been found to be involved in the process of energy homeostasis and bone physiology in recent years. To explore the effects of ghrelin on endoplasmic reticulum stress (ERS) in MC3T3E1 cells and its possible mechanism, an ERS model was induced by tunicamycin (TM) in the osteoblast line MC3T3E1. TM at 1.5 μg/mL was selected as the experimental concentration found by CCK8 assay. Through the determination of apoptosis, reactive oxygen species production, and endoplasmic reticulum stress-related gene expression, we found that ERS induced by TM can be relieved by ghrelin in a concentration-dependent manner ( P < 0.001 ). Compared with the TM group, ghrelin reduced the expression of ERS-related marker genes induced by TM. Compared with the GSK621 + TM group without ghrelin pretreatment, the mRNA expression of genes in the ghrelin pretreatment group decreased significantly ( P < 0.001 ). The results of protein analysis showed that the levels of BIP, p-AMPK, and cleaved-caspase3 in the TM group increased significantly, while the levels decreased after ghrelin pretreatment. In group GSK621 + TM compared with group GSK621 + ghrelin+TM, ghrelin pretreatment significantly reduced the level of p-AMPK, which is consistent with the trend of the ERS-related proteins BIP and cleaved-caspase3. In conclusion, ghrelin alleviates the ERS induced by TM in a concentration-dependent manner and may or at least partly alleviate the apoptosis induced by ERS in MC3T3E1 cells by inhibiting the phosphorylation of AMPK.

scholarly journals Mechanism of Residence of Cytochrome B(5), a Tail-Anchored Protein, in the Endoplasmic Reticulum

2000 ◽  
Vol 148 (5) ◽  
pp. 899-914 ◽  
Author(s):  
Emanuela Pedrazzini ◽  
Antonello Villa ◽  
Renato Longhi ◽  
Alessandra Bulbarelli ◽  
Nica Borgese
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Bilayer ◽  
Cytochrome B ◽  
Golgi Complex ◽  
Intracellular Trafficking ◽  
Secretory Pathway ◽  
Transmembrane Topology ◽  
Glycosylation Sites ◽  
Cytosolic Domain

Endoplasmic reticulum (ER) proteins maintain their residency by static retention, dynamic retrieval, or a combination of the two. Tail-anchored proteins that contain a cytosolic domain associated with the lipid bilayer via a hydrophobic stretch close to the COOH terminus are sorted within the secretory pathway by largely unknown mechanisms. Here, we have investigated the mode of insertion in the bilayer and the intracellular trafficking of cytochrome b(5) (b[5]), taken as a model for ER-resident tail-anchored proteins. We first demonstrated that b(5) can acquire a transmembrane topology posttranslationally, and then used two tagged versions of b(5), N-glyc and O-glyc b(5), containing potential N- and O-glycosylation sites, respectively, at the COOH-terminal lumenal extremity, to discriminate between retention and retrieval mechanisms. Whereas the N-linked oligosaccharide provided no evidence for retrieval from a downstream compartment, a more stringent assay based on carbohydrate acquisition by O-glyc b(5) showed that b(5) gains access to enzymes catalyzing the first steps of O-glycosylation. These results suggest that b(5) slowly recycles between the ER and the cis-Golgi complex and that dynamic retrieval as well as retention are involved in sorting of tail-anchored proteins.

scholarly journals Selective Protein Exit from Yeast Endoplasmic Reticulum in Absence of Functional COPII Coat Component Sec13p

2002 ◽  
Vol 13 (12) ◽  
pp. 4130-4140 ◽  
Author(s):  
Netta Fatal ◽  
Taina Suntio ◽  
Marja Makarow
Keyword(s):  
Endoplasmic Reticulum ◽  
Functional Form ◽  
Protein S ◽  
Normal Function ◽  
Essential Component ◽  
Exchange Factor ◽  
Terminal Domain ◽  
Golgi Transport ◽  
Transport Vesicles ◽  
Cargo Protein

Sec13p has been thought to be an essential component of the COPII coat, required for exit of proteins from the yeast endoplasmic reticulum (ER). We show herein that normal function of Sec13p was not required for ER exit of the Hsp150 glycoprotein. Hsp150 was secreted to the medium under restrictive conditions in a sec13-1mutant. The COPII components Sec23p and Sec31p and the GTP/GDP exchange factor Sec12p were required in functional form for secretion of Hsp150. Hsp150 leaves the ER in the absence of retrograde COPI traffic, and the responsible determinant is a peptide repeated 11 times in the middle of the Hsp150 sequence. Herein, we localized the sorting determinant for Sec13p-independent ER exit to the C-terminal domain. Sec13p-dependent invertase left the ER in the absence of normal Sec13p function, when fused to the C-terminal domain of Hsp150, demonstrating that this domain contained an active mediator of Sec13p-independent secretion. Thus, Hsp150 harbors two different signatures that regulate its ER exit. Our data show that transport vesicles lacking functional Sec13p can carry out ER-to-Golgi transport, but select only specific cargo protein(s) for ER exit.

scholarly journals Determination of Transmembrane Topology of theEscherichia coliNatural Resistance-associated Macrophage Protein (Nramp) Ortholog

2003 ◽  
Vol 279 (5) ◽  
pp. 3318-3326 ◽  
Author(s):  
Pascal Courville ◽  
Roman Chaloupka ◽  
Frédéric Veyrier ◽  
Mathieu F. M. Cellier
Keyword(s):  
Transmembrane Topology ◽  
Macrophage Protein
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