Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D02003 (NBT)
 1,323 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Major histocompatibility complex (MHC) class I antigens are constituted of dimers consisting of a peripheral light chain, beta 2-microglobulin (beta 2m) and a transmembrane heavy chain whose cell surface expression depends on its assembly with beta 2m. In contrast, soluble beta 2m can be secreted in the absence of heavy chain expression. The presence of beta 2m in medium conditioned by a rat thymic epithelial cell line, IT45-R1 (IT45) prompted us to investigate whether beta 2m could be secreted by cells that express MHC class I antigens. IT45 cells produce three to five times more beta 2m in the culture supernatant than another rat thymic epithelial cell line, IT26-R21 (IT26). The IT45 cell line exported beta 2m through a constitutive pathway of secretion, as indicated by the kinetics of production and localization of intracellular beta 2m. Although cells from the IT45 cell line expressed a much higher amount of beta 2m as compared to IT26 and NBT II cells (a rat bladder epithelial cell line), all three of these cell lines expressed the same amount of membrane and intracellular MHC class I heavy chain. These data are thus consistent with a constitutive secretion of beta 2m dependent upon an overexpression of MHC class I light chain as compared to the heavy chain. The amount of beta 2m mRNA and the ratio of beta 2m versus MHC class I heavy chain transcripts were higher in IT45 than in IT26 cells, indicating that overexpression of beta 2m in IT45 cells could be due to an enhanced level of beta 2m mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Overproduction and secretion of beta 2-microglobulin by a rat thymic epithelial cell line that expresses MHC class I heavy chain. 186 Sep 2

The laminin family of extracellular matrix glycoproteins plays a major role in cell migration and differentiation and in tumor cell invasion. As previously shown, the laminin deposited by normal and malignant rat liver epithelial cells in their extracellular matrix (ECM) and into their ECM migration tracks does not contain a typical (EHS-like) alpha 1 heavy chain. By RT-PCR screening we have now identified two alpha chains among a total of five additional laminin chains produced by these cells. Three of the newly identified chains were not previously known for the rat. Their sequences have been deposited in the EMBL nucleotide sequence data bank. The alpha 5 chain now identified is expressed at comparably high levels by both the normal and the malignant liver epithelial cells. The chain is also expressed in fetal liver together with the alpha 2 and beta 2 chains, but it is only vestigially expressed in the mature organ as shown by RT-PCR. These results suggest for alpha 5 a role in development and production of the chain by only a small subset of cells in adult liver. At the level of detection used, no changes were observed in regenerating liver after partial hepatectomy. In addition to the alpha 5 chain, the cultured cells express the beta 1 and beta 2 light chains, indicating the expression of more than one laminin isoform by the same cell line. The expression of the alpha 5 chain and of the other new non-EHS isoform chains was also analyzed in various tissues. The malignant liver epithelial cells, but not their nontumorigenic parental cells, also express, in addition to the alpha 5 chain the alpha 2 chain, which is expressed at high level by the NBT II bladder carcinoma cell line, suggesting a relationship with malignancy.
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PMID:Laminin alpha 5, a major transcript of normal and malignant rat liver epithelial cells, is differentially expressed in developing and adult liver. 941 68