Goodnight J, Mischak H, Mushinski J F
Molecular Genetics Section, National Cancer Institute, Bethesda, MD 20892.
Mol Carcinog. 1994 Nov;11(3):131-7. doi: 10.1002/mc.2940110303.
Expression of mRNA for protein kinase C (PKC)-alpha, -beta, -gamma, -delta, -epsilon, -zeta, and -eta has been shown, by polymerase chain reaction-generated isozyme-specific probes, to be cell-type -and differentiation-stage-specific in mouse hemopoietic cells. Recently, we cloned a 2.2-kb mouse PKC -zeta cDNA. In this study, we used the nearly full-length cDNA PKC-zeta probe to demonstrate that expression of PKC-zeta was significantly elevated in lymphocytic neoplasms at both the mRNA and protein levels. Normal brain, kidney, and liver contain 2.4- and 4.4-kb mRNAs, whereas normal lymphoid organs (spleen, thymus, and lymph nodes) express barely detectable amounts of PKC-zeta. These vanishingly small levels of PKC-zeta mRNA did not increase when polyclonal spleen B-cell proliferation and differentiation were induced in vivo with anti-immunoglobulin D antiserum or in vitro with lipopolysaccharide. In contrast, 2.4-kb transcripts of PKC-zeta are abundant in virtually all neoplastic B-lymphocytic cell lines. Furthermore, additional transcripts of a novel size, about 7 and 8 kb, were found in several mature B-cell lymphomas and plasma cell tumors. Western blot analysis of protein extracts from normal B cells and hemopoietic tumors confirmed that these quantitative differences in PKC-zeta mRNA also exist at the protein level. That is, only trace amounts of PKC-zeta protein were detectable in pro-B cells and pre-B cells, but abundant amounts of this isoform were found in protein extracts from most B-cell lymphomas and plasma cell tumors. These findings suggest that this atypical member of the PKC multigene family participate in the multistep process of malignant transformation of lymphocytes.
通过聚合酶链反应生成的同工酶特异性探针已表明，蛋白激酶C（PKC）的α、β、γ、δ、ε、ζ和η亚型的mRNA在小鼠造血细胞中呈现细胞类型和分化阶段特异性表达。最近，我们克隆了一个2.2 kb的小鼠PKC-ζ cDNA。在本研究中，我们使用近乎全长的PKC-ζ cDNA探针来证明PKC-ζ在淋巴细胞肿瘤中的mRNA和蛋白水平均显著升高。正常脑、肾和肝含有2.4 kb和4.4 kb的mRNA，而正常淋巴器官（脾脏、胸腺和淋巴结）中PKC-ζ的表达量几乎检测不到。当用抗免疫球蛋白D抗血清在体内诱导多克隆脾B细胞增殖和分化，或用脂多糖在体外诱导时，PKC-ζ mRNA这些极低的水平并未增加。相反，PKC-ζ的2.4 kb转录本在几乎所有肿瘤性B淋巴细胞系中都很丰富。此外，在几种成熟B细胞淋巴瘤和浆细胞瘤中发现了新大小的额外转录本，约7 kb和8 kb。对正常B细胞和造血肿瘤蛋白提取物的蛋白质印迹分析证实，PKC-ζ mRNA的这些定量差异在蛋白水平也存在。也就是说，在前B细胞和前B细胞中仅可检测到痕量的PKC-ζ蛋白，但在大多数B细胞淋巴瘤和浆细胞瘤的蛋白提取物中发现了大量的这种同工型。这些发现表明，PKC多基因家族的这个非典型成员参与了淋巴细胞恶性转化的多步骤过程。
