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Membrane biogenesis during B cell differentiation: most endoplasmic reticulum proteins are expressed coordinately
D L Wiest1, J K Burkhardt, S Hester
1Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710.
The Journal of Cell Biology
|May 1, 1990
Summary
Stimulating B cells with lipopolysaccharide (LPS) dramatically increased immunoglobulin (Ig) secretion by expanding the endoplasmic reticulum (ER) and Golgi complex. This organelle expansion supports high-rate protein synthesis and secretion.
Area of Science:
- Cell biology
- Molecular biology
- Immunology
Background:
- High-rate protein secretion requires significant biogenesis of secretory apparatus organelles.
- B cells, like the CH12 cell line, can be induced to secrete immunoglobulin (Ig).
Purpose of the Study:
- To investigate the biogenesis of the secretory apparatus in CH12 B cells during induced immunoglobulin M (IgM) secretion.
- To quantify changes in the endoplasmic reticulum (ER) and Golgi complex upon stimulation.
Main Methods:
- CH12 B cells were stimulated with lipopolysaccharide (LPS) to induce IgM secretion.
- Quantitative analysis of ER and Golgi complex parameters (area, volume, ribosome density) was performed.
Main Results:
- LPS stimulation led to a 12-fold increase in IgM secretion.
- The ER and Golgi complex showed significant expansion: ER area/volume increased 3.3-/3.7-fold, Golgi area/volume increased 3.3-/4.1-fold.
- Rough ER ribosome density increased 3.5-fold, and resident protein expression varied, with some increasing proportionally and others preferentially.
Conclusions:
- The observed expansion of the ER and Golgi complex provides the necessary biosynthetic capacity for increased IgM secretion.
- ER expansion involves proportional increases in most proteins and preferential increases in a few key resident proteins.
- Despite increased IgM synthesis, ER IgM concentration remained relatively stable due to ER expansion.