Mohiti J, Caswell A M, Walker J H
Department of Biochemistry and Molecular Biology, University of Leeds, UK.
Mol Membr Biol. 1995 Oct-Dec;12(4):321-9. doi: 10.3109/09687689509072434.
In cell culture, human osteoblasts and the osteosarcoma cell line MG-63 express annexins I, II, IV, V and VI. Small proportions of annexins IV and V are lost from MG-63 cells into the culture medium in a sedimentable form. however, the bulk of these annexins is intracellular. In non-confluent cells 3 days after passaging, annexin IV and annexin V are strongly present throughout the nucleus and are also present in the cytoplasm. On elevation of the intracellular calcium concentration with the lonophore ionomycin, the intranuclear pools of annexin IV in 38 +/- 4% of cells and annexin V in 70 +/- 5% of cells show relocation to the nuclear membrane within 40 s. Extracellular ATP, which causes a transient increase in the cytosolic free calcium concentration by acting at P2-purinoceptors, also causes relocation of the intranuclear pool of annexin IV in 22 +/- 4% of cells and of annexin V in 38 +/- 8% of cells. After stimulation no significant reversal of the relocation is observed. Elevation of intracellular calcium with ionophore and ATP also causes relocation of the cytoplasmic pools of annexins IV and V. The results support a role for annexins at cellular membranes in response to elevation of cytosolic calcium levels.
在细胞培养中，人成骨细胞和骨肉瘤细胞系MG-63表达膜联蛋白I、II、IV、V和VI。少量的膜联蛋白IV和V以可沉降的形式从MG-63细胞中释放到培养基中。然而，这些膜联蛋白大部分存在于细胞内。传代后3天的未汇合细胞中，膜联蛋白IV和膜联蛋白V在整个细胞核中大量存在，也存在于细胞质中。用离子载体离子霉素提高细胞内钙浓度后，38±4%的细胞中膜联蛋白IV的核内池和70±5%的细胞中膜联蛋白V的核内池在40秒内重新定位到核膜。细胞外ATP通过作用于P2嘌呤受体导致胞质游离钙浓度短暂升高，也导致22±4%的细胞中膜联蛋白IV的核内池和38±8%的细胞中膜联蛋白V的核内池重新定位。刺激后未观察到重新定位的显著逆转。用离子霉素和ATP提高细胞内钙浓度也会导致膜联蛋白IV和V的细胞质池重新定位。这些结果支持膜联蛋白在细胞膜上响应胞质钙水平升高发挥作用。
