Takata K, Singer S J
Department of Biology, University of California at San Diego, La Jolla.
Blood. 1988 Mar;71(3):818-21.
Phosphorylation of tyrosine residues of cellular proteins is a rare event and is considered to be related to the regulation of cellular growth, differentiation, and some forms of neoplastic transformation. Using high-affinity antibodies specific to phosphotyrosine (P-Tyr), we have shown the presence at high concentrations of P-Tyr-modified proteins in mouse bone-marrow megakaryocytes. Immunofluorescence microscopy of semithin frozen sections revealed that P-Tyr labeling was localized in a punctate pattern in the majority of the cytoplasm. The thin outer rim of the cytoplasm and the cell membrane was devoid of the label. Immunogold electron microscopy of ultrathin frozen sections showed that P-Tyr labeling was concentrated mostly on the membranes of the vesicles in the cytoplasm. The membrane demarcation system characteristic of megakaryocytes was not labeled. The intensity of P-Tyr labeling varied from one megakaryocyte to another. These results suggest that tyrosine phosphorylation of specific proteins might be correlated with the developmental stage of megakaryocytes, possibly related to the formation and deposition of the granules.
细胞蛋白质酪氨酸残基的磷酸化是一种罕见事件，被认为与细胞生长、分化以及某些形式的肿瘤转化调控有关。利用对磷酸酪氨酸（P-Tyr）具有高亲和力的抗体，我们已证明在小鼠骨髓巨核细胞中存在高浓度的P-Tyr修饰蛋白。半薄冰冻切片的免疫荧光显微镜检查显示，P-Tyr标记以点状模式定位于大部分细胞质中。细胞质的薄外缘和细胞膜没有标记。超薄冰冻切片的免疫金电子显微镜检查表明，P-Tyr标记主要集中在细胞质中囊泡的膜上。巨核细胞特有的膜分界系统没有被标记。P-Tyr标记的强度在不同巨核细胞之间有所不同。这些结果表明，特定蛋白质的酪氨酸磷酸化可能与巨核细胞的发育阶段相关，可能与颗粒的形成和沉积有关。
