Villa-Moruzzi E, Tognarini M, Cecchini G, Marchisio P C
Department of Biomedicine, University of Pisa, Italy.
Cell Adhes Commun. 1998 Jun;5(4):297-305. doi: 10.3109/15419069809040299.
In all mammalian cells protein phosphatase-1 (PP1) exists in three isoforms, defined as alpha, gamma 1 and delta. Immunofluorescence studies with isoform-specific antibodies indicated that delta, but not alpha or gamma 1, is enriched at focal adhesions in HeLa cells, fibroblasts, endothelial cells and keratinocytes. This was confirmed also by interference reflection microscopy, which indicated that PP1 delta was in areas of tight adhesion of the membrane to the extracellular matrix at sites where the microfilament cytoskeleton is organized. In all the cell types so far considered the PP1 delta in focal adhesions represented only a small aliquot of the total PP1 delta, which was predominantly localized to the nucleus. The association of PP1 delta to focal adhesions was confirmed by the co-immunoprecipitation of PP1 delta with the focal adhesion kinase pp125FAK and with the alpha v integrin. Comparison between the amount of PP1 delta associated with focal adhesion proteins and that of PP1 delta recovered in an anti-PP1 delta immunoprecipitate confirmed that only a minor amount of the enzyme was associated with the focal adhesions. Since some focal adhesion proteins are phosphorylated on Ser/Thr, it is likely that PP1 delta may be involved in the regulation of focal adhesion functions and particularly in the signaling pathway generated by cell-substratum adhesion.
在所有哺乳动物细胞中，蛋白磷酸酶-1（PP1）以三种同工型存在，分别定义为α、γ1和δ。用同工型特异性抗体进行的免疫荧光研究表明，在HeLa细胞、成纤维细胞、内皮细胞和角质形成细胞中，δ而非α或γ1在粘着斑处富集。干涉反射显微镜也证实了这一点，其表明PP1δ位于微丝细胞骨架组织部位的细胞膜与细胞外基质紧密粘附的区域。在目前所研究的所有细胞类型中，粘着斑中的PP1δ仅占总PP1δ的一小部分，而总PP1δ主要定位于细胞核。通过PP1δ与粘着斑激酶pp125FAK以及αv整合素的共免疫沉淀，证实了PP1δ与粘着斑的关联。将与粘着斑蛋白相关的PP1δ量与抗PP1δ免疫沉淀物中回收的PP1δ量进行比较，证实只有少量该酶与粘着斑相关。由于一些粘着斑蛋白在丝氨酸/苏氨酸上被磷酸化，PP1δ可能参与粘着斑功能的调节，尤其是参与由细胞-基质粘附产生的信号通路。
