Hendershot L, Levitt D
J Exp Med. 1982 Dec 1;156(6):1622-34. doi: 10.1084/jem.156.6.1622.
Regulation of membrane and secretory mu synthesis was examined in human lymphoblastoid cell lines representing various stages of differentiation. Immunoglobulin phenotype was determined by surface and cytoplasmic staining with fluorochrome-conjugated antibodies and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of anti-mu precipitable cellular products. The thymidine analogue, 5-bromo-2'-deoxyuridine (BUdR), which inhibits differentiation-specific proteins in a variety of systems, was used to examine regulation of immunoglobulin synthesis. We found that BUdR had a differential effect on membrane (mum) and secretory (mus) type mu heavy chains. Ig production in pre-B and plasma cell-like lines, which make mus, was unaffected by BUdR. However, surface expression of IgM (mum) in B cell lines was drastically inhibited at similar doses of BUdR without diminishing total Ig or protein synthesis. Examination of labeled mu chains from control and BUdR-treated B cell lines by SDS-PAGE revealed the production of two sizes of mu (mum and mus) in control cells and only the smaller size (mus) in BUdR-treated cells. This size difference could not be attributed to alterations in glycosylation of the molecules. These data show that BUdR inhibits the production of membrane mu chains without diminishing secretory mu chain synthesis in the same cell. Our findings suggest that thymidine-rich regions of the genome are involved in the regulation of mum vs. mus during B cell differentiation.
在代表不同分化阶段的人淋巴母细胞系中研究了膜结合型和分泌型μ链合成的调控。通过用荧光染料偶联抗体进行表面和胞质染色以及对抗μ可沉淀细胞产物进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）分析来确定免疫球蛋白表型。胸腺嘧啶类似物5-溴-2'-脱氧尿苷（BUdR）可在多种系统中抑制分化特异性蛋白，用其来研究免疫球蛋白合成的调控。我们发现BUdR对膜结合型（μm）和分泌型（μs）μ重链有不同影响。产生μs的前B细胞系和浆细胞样细胞系中的Ig产生不受BUdR影响。然而，在相似剂量的BUdR作用下，B细胞系中IgM（μm）的表面表达受到显著抑制，而总Ig或蛋白质合成并未减少。通过SDS-PAGE对对照和BUdR处理的B细胞系中标记的μ链进行检测，发现在对照细胞中产生了两种大小的μ链（μm和μs），而在BUdR处理的细胞中只产生了较小的μ链（μs）。这种大小差异不能归因于分子糖基化的改变。这些数据表明，BUdR在同一细胞中抑制膜结合型μ链的产生，而不减少分泌型μ链的合成。我们的研究结果表明，基因组中富含胸腺嘧啶的区域参与了B细胞分化过程中μm与μs的调控。
