Cell type specificity of signaling:view from membrane receptors distribution and their downstream transduction networks

Studies on cell signaling pay more attention to spatial dynamics and how such diverse organization can relate to high order of cellular capabilities.To overview the specificity of cell signaling,we integrated human receptome data with proteome spatial expression profiles to systematically investigate the specificity of receptors and receptor-triggered transduction networks across 62 normal cell types and 14 cancer types.Six percent receptors showed cell-type-specific expression,and 4% signaling networks presented enriched cell-specific proteins induced by the receptors.We introduced a concept of“response context”to annotate the cell-type dependent signaling networks.We found that most cells respond similarly to the same stimulus,as the“response contexts”presented high functional similarity.Despite this,the subtle spatial diversity can be observed from the difference in network architectures.The architecture of the signaling networks in nerve cells displayed less completeness than that in glandular cells,which indicated cellular-context dependent signaling patterns are elaborately spatially organized.Likewise,in cancer cells most signaling networks were generally dysfunctional and less complete than that in normal cells.However,glioma emerged hyper-activated transduction mechanism in malignant state.Receptor ATP6AP2 and TNFRSF21 induced rennin-angiotensin and apoptosis signaling were found likely to explain the glioma-specific mechanism.This work represents an effort to decipher context-specific signaling network from spatial dimension.Our results indicated that although a majority of cells engage general signaling response with subtle differences,the spatial dynamics of cell signaling can not only deepen our insights into different signaling mechanisms,but also help understand cell signaling in disease.

Cell Type Specific Expression of CD80 （B7-1） Gene in Murine

The CD80 （B7-1） costimulatory molecule is expressed on the surface of B cells and its expression is transcriptionally upregulated upon stimuli. To identify the region of murine CD80 promoter that direct cell type specific gene expression, four promoters construct of CD80 gene were generated with DNA fragments fused to the GFP reporter gene. In the present study, significant promoter activity was detected with all four promoter constructs only in the murine B lymphocyte. Further, the CD80 promoter region extending from -3,005 bp to ＋273 bp in relation to the previously reported transcription start site, was identified as tissue specific region. Interestingly, the shortest 700 bp （-427/＋273） of promoter fragment was sufficient to direct the CD80 gene expression. The level of CD80 expression was also found to be modulated by exogenous stimuli in B lymphocyte. Additionally, it was demonstrated that the CD80 gene expression is regulated at the level of transcription where the inducible CD80 gene transcript was detected in B lymphocyte with increasing time.