Institute of Pathology, University of Regensburg, Franz-Josef-Strauss-Allee 11, D-93053 Regensburg, Germany.
Cell Res. 2010 Nov;20(11):1224-38. doi: 10.1038/cr.2010.121. Epub 2010 Aug 24.
Malignant melanoma, characterized by invasive local growth and early formation of metastases, is the most aggressive type of skin cancer. Melanoma inhibitory activity (MIA), secreted by malignant melanoma cells, interacts with the cell adhesion receptors, integrins α(4)β(1) and α(5)β(1), facilitating cell detachment and promoting formation of metastases. In the present study, we demonstrate that MIA secretion is confined to the rear end of migrating cells, while in non-migrating cells MIA accumulates in the actin cortex. MIA protein takes a conventional secretory pathway including coat protein complex I (COPI)- and coat protein complex II (COPII)-dependent protein transport to the cell periphery, where its final release depends on intracellular Ca(2+) ions. Interestingly, the Ca(2+)-activated K(+)-channel, subfamily N, member 4 (KCa3.1), known to be active at the rear end of migrating cells, was found to support MIA secretion. Secretion was diminished by the specific KCa3.1 channel inhibitor TRAM-34 and by expression of dominant-negative mutants of the channel. In summary, we have elucidated the migration-associated transport of MIA protein to the cell rear and also disclosed a new mechanism by which KCa3.1 potassium channels promote cell migration.
恶性黑色素瘤的特征是局部侵袭性生长和早期形成转移，是最具侵袭性的皮肤癌类型。黑色素瘤抑制活性（MIA）由恶性黑色素瘤细胞分泌，与细胞粘附受体整合素α(4)β(1)和α(5)β(1)相互作用，促进细胞脱落并促进转移的形成。在本研究中，我们证明了 MIA 的分泌仅限于迁移细胞的后端，而在非迁移细胞中，MIA 则在肌动蛋白皮层中积累。MIA 蛋白通过传统的分泌途径，包括衣被蛋白复合物 I（COPI）和衣被蛋白复合物 II（COPII）依赖性蛋白质运输到细胞外周，其最终释放取决于细胞内 Ca(2+)离子。有趣的是，已知在迁移细胞的后端活跃的 Ca(2+)-激活的 K(+)通道，亚家族 N，成员 4（KCa3.1）被发现支持 MIA 的分泌。特异性 KCa3.1 通道抑制剂 TRAM-34 和通道的显性负突变体的表达降低了分泌。总之，我们阐明了 MIA 蛋白向细胞后端的迁移相关运输，也揭示了 KCa3.1 钾通道促进细胞迁移的新机制。
