Liu A Y, Fiske W W, Chen K Y
Cancer Res. 1980 Nov;40(11):4100-8.
The regulation of cyclic adenosine 3':5'-monophosphate (cAMP)-binding protein in N-18 neuroblastoma cells in tissue culture was studied by the covalent incorporation of 8-azido-cyclic adenosine 3':5'-[32P]monophosphate, together with the techniques of sodium dodecyl sulfate:polyacrylamide gel electrophoresis and autoradiography. Greater than 95% of the total cAMP binding activity of N-18 neuroblastoma cells was identified as being regulatory subunits of the type I (RI) and type II (RII) species, with RI being the predominant form of the two (RI:RII = 3:1). The specific activity of RI but not of RII increased 3-fold when cells were grown in medium containing 1% rather than 10% fetal calf serum. Under the same conditions, the specific activity of acetylcholinesterase increased 3- to 5-fold. The increase in RI was inversely related to the serum concentration in the medium and was specific for cells at the stationary phase of growth. An increase in intracellular cAMP, concomitant with the increase in RI, was also observed. Morphological examination of stationary-phase neuroblastoma cells maintained in medium containing 1% fetal calf serum suggested the presence of a high proportion of highly-differentiated cells. It is proposed that the regulatory control of RI cAMP-binding protein by serum may involve modulation of intracellular cAMP and that the expression RI may be used as a biochemical index of differentiation in mouse neuroblastoma cells.
通过8-叠氮基环腺苷3':5'-[32P]单磷酸的共价掺入，以及十二烷基硫酸钠：聚丙烯酰胺凝胶电泳和放射自显影技术，研究了组织培养的N-18神经母细胞瘤细胞中环腺苷3':5'-单磷酸（cAMP）结合蛋白的调节。N-18神经母细胞瘤细胞总cAMP结合活性的95%以上被鉴定为I型（RI）和II型（RII）调节亚基，其中RI是两者中的主要形式（RI:RII = 3:1）。当细胞在含1%而非10%胎牛血清的培养基中生长时，RI的比活性增加了3倍，而RII的比活性未增加。在相同条件下，乙酰胆碱酯酶的比活性增加了3至5倍。RI的增加与培养基中的血清浓度呈负相关，且对生长静止期的细胞具有特异性。同时还观察到细胞内cAMP增加，与RI增加相伴。对在含1%胎牛血清的培养基中维持的静止期神经母细胞瘤细胞进行形态学检查，提示存在高比例的高度分化细胞。有人提出，血清对RI cAMP结合蛋白的调节控制可能涉及细胞内cAMP的调节，并且RI的表达可作为小鼠神经母细胞瘤细胞分化的生化指标。
