About the Cover
The Journal of Experimental Medicine
194
11
To test the hypothesis that there are both ligand-independent as well as ligand-dependent signaling functions for the B cell antigen receptor (BCR), a targeting strategy was devised to allow localization of the cytoplasmic domains of immunoglobulin (Ig)alpha/Igbeta to the inner leaflet of the B cell plasma membrane in a manner that obviated the possibility of encounter with extracellular ligand. The cover image shows primary bone marrowderived murine pro/pre-B lymphocytes coexpressing the Igalpha/Igbeta cytoplasmic domain chimeric protein (red fluorescence) and green fluorescent protein (GFP; green fluorescence). The top right image depicts B cells expressing the plasma membrane targeted Igalpha/Igbeta protein, while the bottom images depict expression of the same molecule, however in this case, lacking the plasma membrane targeting sequence. The basal ligand-independent signaling is sufficient to facilitate the pro-B -> pre-B cell transition. See related article by Bannish et al., pp.
1583-1596
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