Aspects of the Role of the Endoplasmic Reticulum in Protein Synthesis

Svardal, Asbjørn; Pryme, Ian F.

doi:10.1007/978-1-4615-7948-9_3

Cited by 17 publications

(4 citation statements)

References 230 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is considerable morphological and biochemical evidence showing that changes occur in the ER during the process of carcinogenesis (26) and that the functional aspects of the ER are subject to considerable alteration according to the physiological conditions (27,28,29). For example, differences between microsomes of normal mouse liver and hepatomas in a variety of respects have been reported: altered phospholipid synthesis (30), minor changes in electrophoretic patterns of membrane proteins (31), diversion of synthesis of albumin from membrane-bound polysomes to free polysomes in the hepatoma line 5123 (32), and differences in enzyme activities (33,34).…”

Section: B)mentioning

confidence: 99%

Variation in microsomal subfractions obtained from normal animal tissues and transformed cells following cell disruption by nitrogen cavitation

1981

Self Cite

View full text Add to dashboard Cite

Microsomal membranes were obtained from MPC-11 cells, L-cells, Krebs II ascites cells and various normal animal tissues following cell disruption by nitrogen cavitation. Membrane preparations were applied to discontinuous sucrose gradients designed to separate three fractions--heavy rough (HR), light rough (LR) and smooth (S) microsomes. In each of the transformed cell lines all three fractions were found whilst in the normal tissues tested the HR fraction was absent. Of the normal tissues liver and pancreas were rich in both LR and S microsomes, the presence of large amounts of LR indicating a rich protein synthesizing activity on membrane-bound polysomes. Kidney also contained appreciable LR but much less than both liver and pancreas. Both heart and lung contained virtually only S microsomal material--a reflection of low protein synthetic activity on membrane-bound polysomes. Attempts to promote the appearance of the HR fraction in liver, kidney and pancreas by incubation in tissue culture medium, or, in the case of pancreas, by cholecystokinin/pancreozymin/secretin stimulation both in vivo and in vitro were unsuccessful.

show abstract

Section: B)mentioning

confidence: 99%

Variation in microsomal subfractions obtained from normal animal tissues and transformed cells following cell disruption by nitrogen cavitation

1981

Self Cite

View full text Add to dashboard Cite

show abstract

“…This clearly indicated that other proteins than light chain were synthesized on membrane-bound polysomes during the various phases of the cell cycle. That membrane-bound polysomes are involved in the synthesis of proteins other than those to be secreted from the cell is now well established (5). In order to examine more closely the membranebound polysome population it was necessary to introduce a technique that allowed for disruption of cells without the use of detergents, since an initial solubilization of endoplasmic reticulum membranes had to be avoided.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructure and polysome content of the microsomal subfractions of mouse plasmacytoma cells

1981

Self Cite

View full text Add to dashboard Cite

The endoplasmic reticulum (ER) of MPC-11 cells released as vesicles upon cell disruption by nitrogen cavitation was separated from the bulk of mitochondria, lysosomes and plasma membranes by a low speed centrifugation. The ER membranes were fractionated on discontinuous sucrose gradients into heavy rough (HR), light rough (LR) and smooth (S) membranes. The morphology of subcellular fractions was studied by electron microscopy and the ER membranes were shown to be virtually free of contaminating organelles. The S fraction was easily distinguishable because of the lack or ribosomes but there were no apparent morphological differences between the HR and LR fractions. Of total activity in the microsomal subfractions, 70% of the UDPase and 67% of the 5'-nucleotidase activity was associated with the S fraction. Polysomes were present in the HR, LR and nuclear-associated ER fractions but not in the S fraction. The HR and LR fractions did not appear to be contaminated to any great extent with free polysomes. RNA/protein and RNA/phospholipid ratios of the HR fraction were higher than those of the LR fraction, indicating a greater density of ribosomes in the former fraction. These ratios were much lower in the S fraction reflecting the low ribosome content.

show abstract

“…In the case of membrane and secretory proteins it is known that the first step in such targeting is achieved by synthesis in a distinct polyribosome (polysome) compartment. It is well documented that membrane and secreted proteins are synthesized on polysomes bound to rough endoplasmic reticulum (ER) membranes (membrane-bound polysomes; MBP) and it has been proposed that the other cell proteins are made on the so-called 'free' cytosolic polysomes (FP) (see reviews by Shires & Pitot, 1973;Svardal & Pryme, 1980). Thus, mRNAs were envisaged as being segregated into two distinct populations of polysomes depending on the ultimate cellular localization of the encoded protein (the signal hypothesis; see Blobel & Dobberstein, 1975).…”

Section: Introductionmentioning

confidence: 99%