scholarly journals Hierarchical regulation of mRNA partitioning between the cytoplasm and the endoplasmic reticulum of mammalian cells

2011 ◽  
Vol 22 (14) ◽  
pp. 2646-2658 ◽  
Author(s):  
Qiang Chen ◽  
Sujatha Jagannathan ◽  
David W. Reid ◽  
Tianli Zheng ◽  
Christopher V. Nicchitta
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Signal Recognition Particle ◽  
Signal Recognition ◽  
Endomembrane System ◽  
Genomic Analyses ◽  
Specific Manner ◽  
Signal Encoding ◽  
Mrna Transcriptome

The mRNA transcriptome is currently thought to be partitioned between the cytosol and endoplasmic reticulum (ER) compartments by binary selection; mRNAs encoding cytosolic/nucleoplasmic proteins are translated on free ribosomes, and mRNAs encoding topogenic signal-bearing proteins are translated on ER-bound ribosomes, with ER localization being conferred by the signal-recognition particle pathway. In subgenomic and genomic analyses of subcellular mRNA partitioning, we report an overlapping subcellular distribution of cytosolic/nucleoplasmic and topogenic signal-encoding mRNAs, with mRNAs of both cohorts displaying noncanonical subcellular partitioning patterns. Unexpectedly, the topogenic signal-encoding mRNA transcriptome was observed to partition in a hierarchical, cohort-specific manner. mRNAs encoding resident proteins of the endomembrane system were clustered at high ER-enrichment values, whereas mRNAs encoding secretory pathway cargo were broadly represented on free and ER-bound ribosomes. Two distinct modes of mRNA association with the ER were identified. mRNAs encoding endomembrane-resident proteins were bound via direct, ribosome-independent interactions, whereas mRNAs encoding secretory cargo displayed predominantly ribosome-dependent modes of ER association. These data indicate that mRNAs are partitioned between the cytosol and ER compartments via a hierarchical system of intrinsic and encoded topogenic signals and identify mRNA cohort-restricted modes of mRNA association with the ER.

Nuclear export of signal recognition particle RNA in mammalian cells

2004 ◽  
Vol 313 (2) ◽  
pp. 351-355 ◽  
Author(s):  
Christina N. Alavian ◽  
Joan C. Ritland Politz ◽  
Laura B. Lewandowski ◽  
Christine M. Powers ◽  
Thoru Pederson
Keyword(s):  
Nuclear Export ◽  
Mammalian Cells ◽  
Signal Recognition Particle ◽  
Signal Recognition

scholarly journals Rab1b regulates vesicular transport between the endoplasmic reticulum and successive Golgi compartments.

1991 ◽  
Vol 115 (1) ◽  
pp. 31-43 ◽  
Author(s):  
H Plutner ◽  
A D Cox ◽  
S Pind ◽  
R Khosravi-Far ◽  
J R Bourne ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Essential Role ◽  
Secretory Pathway ◽  
Binding Protein ◽  
Vesicular Transport ◽  
Initial Step ◽  
Gtp Binding Protein ◽  
Gtp Binding ◽  
Golgi Compartment

We report an essential role for the ras-related small GTP-binding protein rab1b in vesicular transport in mammalian cells. mAbs detect rab1b in both the ER and Golgi compartments. Using an assay which reconstitutes transport between the ER and the cis-Golgi compartment, we find that rab1b is required during an initial step in export of protein from the ER. In addition, it is also required for transport of protein between successive cis- and medial-Golgi compartments. We suggest that rab1b may provide a common link between upstream and downstream components of the vesicular fission and fusion machinery functioning in early compartments of the secretory pathway.

scholarly journals GTP-binding proteins may stimulate insulin biosynthesis in rat pancreatic islets by enhancing the signal-recognition-particle-dependent translocation of the insulin mRNA poly-/mono-some complex to the endoplasmic reticulum

1991 ◽  
Vol 275 (1) ◽  
pp. 23-28 ◽  
Author(s):  
N Welsh ◽  
C Oberg ◽  
M Welsh
Keyword(s):  
Endoplasmic Reticulum ◽  
Binding Proteins ◽  
Specific Binding ◽  
Signal Recognition Particle ◽  
Insulin Biosynthesis ◽  
Signal Recognition ◽  
Insulin Synthesis ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Insulin Mrna

We aimed to elucidate the putative role of GTP-binding proteins in the regulation of insulin biosynthesis. For this purpose, freshly isolated rat islets were incubated in the presence of liposomes containing GDP, guanosine 5′-[beta-thio]diphosphate (GDP[S]), GTP, guanosine 5′-[gamma-thio]triphosphate (GTP[S]), guanosine 5′-[beta gamma-methylene]triphosphate (p[CH2]ppG), guanosine 5′[beta gamma-imido]triphosphate (p[NH]ppG) and ATP, and the effects of the liposomal delivery of these substances on rates of biosynthesis of insulin and total protein were determined. Insulin biosynthesis during a 1 h incubation at 1.67 mM-glucose was stimulated by ATP- and GTP[S]-containing liposomes as compared with control liposomes. At 16.7 mM-glucose, only the GTP[S]-containing liposomes stimulated insulin biosynthesis. No inhibition of islet protein and insulin synthesis was observed with GDP-, GDP[S]-, p[CH2]ppG- and p[NH]ppG-containing liposomes. By determining the subcellular distribution of insulin mRNA, it was found that the mRNA content associated with microsomes was increased and that associated with the cytosolic mono-/poly-somes decreased when the islets were incubated with GTP[S]-containing liposomes, resulting in an approximate doubling of the ratio of microsomal to polysomal-associated insulin mRNA. ATP-containing liposomes produced no effects on the association of insulin mRNA with microsomes. By using photoaffinity labelling and immunoprecipitation techniques, specific binding of GTP[35S] to the alpha-subunit of the signal-recognition particle (SRP) receptor in islet homogenates containing physiological concentrations of GTP and GDP was demonstrated. These findings suggest that the GTP-binding subunit(s) of the SRP receptor, and possibly also of other GTP-binding proteins involved in this process, may regulate insulin biosynthesis by stimulating the translocation of insulin mRNA to the endoplasmic reticulum and by increasing preproinsulin-peptide translocation into the lumen of the reticulum.

scholarly journals Cotranslational Intersection between the SRP and GET Targeting Pathways to the Endoplasmic Reticulum of Saccharomyces cerevisiae

2016 ◽  
Vol 36 (18) ◽  
pp. 2374-2383 ◽  
Author(s):  
Ying Zhang ◽  
Thea Schäffer ◽  
Tina Wölfle ◽  
Edith Fitzke ◽  
Gerhard Thiel ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Transmembrane Domain ◽  
Signal Recognition Particle ◽  
Transmembrane Proteins ◽  
Signal Recognition ◽  
Ribosome Binding ◽  
Channel Proteins ◽  
Membrane Spanning ◽  
Combined Data

Targeting of transmembrane proteins to the endoplasmic reticulum (ER) proceeds via either the signal recognition particle (SRP) or the guided entry of tail-anchored proteins (GET) pathway, consisting of Get1 to -5 and Sgt2. While SRP cotranslationally targets membrane proteins containing one or multiple transmembrane domains, the GET pathway posttranslationally targets proteins containing a single C-terminal transmembrane domain termed the tail anchor. Here, we dissect the roles of the SRP and GET pathways in the sorting of homologous, two-membrane-spanning K+channel proteins termed Kcv, Kesv, and Kesv-VV. We show that Kcv is targeted to the ER cotranslationally via its N-terminal transmembrane domain, while Kesv-VV is targeted posttranslationally via its C-terminal transmembrane domain, which recruits Get4-5/Sgt2 and Get3. Unexpectedly, nascent Kcv recruited not only SRP but also the Get4-5 module of the GET pathway to ribosomes. Ribosome binding of Get4-5 was independent of Sgt2 and was strongly outcompeted by SRP. The combined data indicate a previously unrecognized cotranslational interplay between the SRP and GET pathways.

scholarly journals The organization of engaged and quiescent translocons in the endoplasmic reticulum of mammalian cells

2004 ◽  
Vol 164 (7) ◽  
pp. 997-1007 ◽  
Author(s):  
Erik L. Snapp ◽  
Gretchen A. Reinhart ◽  
Brigitte A. Bogert ◽  
Jennifer Lippincott-Schwartz ◽  
Ramanujan S. Hegde
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Signal Recognition Particle ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Cellular Environment ◽  
Essential Components ◽  
Nascent Chain ◽  
Functional Components

Protein translocons of the mammalian endoplasmic reticulum are composed of numerous functional components whose organization during different stages of the transport cycle in vivo remains poorly understood. We have developed generally applicable methods based on fluorescence resonance energy transfer (FRET) to probe the relative proximities of endogenously expressed translocon components in cells. Examination of substrate-engaged translocons revealed oligomeric assemblies of the Sec61 complex that were associated to varying degrees with other essential components including the signal recognition particle receptor TRAM and the TRAP complex. Remarkably, these components not only remained assembled but also had a similar, yet distinguishable, organization both during and after nascent chain translocation. The persistence of preassembled and complete translocons between successive rounds of transport may facilitate highly efficient translocation in vivo despite temporal constraints imposed by ongoing translation and a crowded cellular environment.

The role of microtubules in transport between the endoplasmic reticulum and Golgi apparatus in mammalian cells.

2005 ◽  
Vol 72 ◽  
pp. 1-13 ◽  
Author(s):  
Krysten J. Palmer ◽  
Peter Watson ◽  
David J. Stephens
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Motor Proteins ◽  
Microtubule Cytoskeleton ◽  
Early Secretory Pathway ◽  
Golgi Transport ◽  
Intracellular Compartments ◽  
Retrograde Traffic

The organization of intracellular compartments and the transfer of components between them are central to the correct functioning of mammalian cells. Proteins and lipids are transferred between compartments by the formation, movement and subsequent specific fusion of transport intermediates. These vesicles and membrane clusters must be coupled to the cytoskeleton and to motor proteins that drive motility. Anterograde ER (endoplasmic reticulum)-to-Golgi transport, and the converse step of retrograde traffic from the Golgi to the ER, are now known to involve coupling of membranes to the microtubule cytoskeleton. Here we shall discuss our current understanding of the mechanisms that link membrane traffic in the early secretory pathway to the microtubule cytoskeleton in mammalian cells. Recent data have also provided molecular detail of functional co-ordination of motor proteins to specify directionality, as well as mechanisms for regulating motor activity by protein phosphorylation.

Topology of signal recognition particle receptor in endoplasmic reticulum membrane

Nature ◽  
1985 ◽  
Vol 318 (6044) ◽  
pp. 334-338 ◽  
Author(s):  
Leander Lauffer ◽  
Pablo D. Garcia ◽  
Richard N. Harkins ◽  
Lisa Coussens ◽  
Axel Ullrich ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Signal Recognition Particle ◽  
Endoplasmic Reticulum Membrane ◽  
Signal Recognition ◽  
Signal Recognition Particle Receptor

scholarly journals The propeptide of preprosomatostatin mediates intracellular transport and secretion of alpha-globin from mammalian cells.

1989 ◽  
Vol 108 (5) ◽  
pp. 1647-1655 ◽  
Author(s):  
T J Stoller ◽  
D Shields
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Signal Peptide ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Secretory Pathway ◽  
Gh3 Cells ◽  
Alpha Globin ◽  
Regulated Secretory Pathway

We have investigated the role of the somatostatin propeptide in mediating intracellular transport and sorting to the regulated secretory pathway. Using a retroviral expression vector, two fusion proteins were expressed in rat pituitary (GH3) cells: a control protein consisting of the beta-lactamase signal peptide fused to chimpanzee alpha-globin (142 amino acids); and a chimera of the somatostatin signal peptide and proregion (82 amino acids) fused to alpha-globin. Control globin was translocated into the endoplasmic reticulum as determined by accurate cleavage of its signal peptide; however, alpha-globin was not secreted but was rapidly and quantitatively degraded intracellularly with a t 1/2 of 4-5 min. Globin degradation was insensitive to chloroquine, a drug which inhibits lysosomal proteases, but was inhibited at 16 degrees C suggesting proteolysis occurred during transport to the cis-Golgi apparatus. In contrast to the control globin, approximately 30% of the somatostatin propeptide-globin fusion protein was transported to the distal elements of the Golgi apparatus where it was endoproteolytically processed. Processing of the chimera occurred in an acidic intracellular compartment since cleavage was inhibited by 25 microM chloroquine. 60% of the transported chimera was cleaved at the Arg-Lys processing site in native prosomatostatin yielding "mature" alpha-globin. Most significantly, approximately 50% of processed alpha-globin was sorted to the regulated pathway and secreted in response to 8-Br-cAMP. We conclude that the somatostatin propeptide mediated transport of alpha-globin from the endoplasmic reticulum to the trans-Golgi network by protecting molecules from degradation and in addition, facilitated packaging of alpha-globin into vesicles whose secretion was stimulated by cAMP.

Sign in / Sign up

Export Citation Format

Share Document