Biophysics Institute, Johannes Kepler University Linz, Austria.
Cell Biol Int. 2010 Nov;34(11):1109-12. doi: 10.1042/CBI20100408.
The cationic antimicrobial immunomodulatory peptide, KLK (KLKL₅KLK), exerts profound membrane interacting properties, impacting on ultrastructure and fluidity. KLK-membrane interactions that lead to these alterations require the ability of the peptide to move into an α-helical conformation. We show that KLK induces an increase of the intracellular Ca²(+) concentration in human T24 cells. The effect of KLK is buffer-sensitive, as it is detected when HBSS buffer is used, but not with PBS. This, together with the lack of effect of the middle leucine-to-proline-substituted peptide derivative [KPK (KLKLLPLLKLK)], indicates that it is the conformational propensity rather than the net positive charge that contributes to the effect of KLK on intracellular Ca²(+) level of T24 cells. We show that, although KLK slightly stimulates Ca²(+) influx into the cell, the bulk increase of Ca²(+) levels is due to KLK-induced depletion of intracellular Ca²(+) stores. Finally, we demonstrate a KLK-induced switch of PS (phosphatidylserine) from the inner to the outer plasma membrane leaflet that contributes to the onset of early apoptotic changes in these cells.
阳离子抗菌免疫调节肽 KLK（KLKL₅KLK）具有深刻的膜相互作用特性，影响超微结构和流动性。导致这些改变的 KLK-膜相互作用需要肽具有进入α-螺旋构象的能力。我们表明 KLK 诱导人 T24 细胞内 Ca²(+)浓度增加。KLK 的作用对缓冲液敏感，因为当使用 HBSS 缓冲液时可以检测到，但使用 PBS 时则不能。这一点，以及中间亮氨酸到脯氨酸取代肽衍生物 [KPK（KLKLLPLLKLK）] 没有作用，表明是构象倾向而不是净正电荷导致 KLK 对 T24 细胞内 Ca²(+)水平的影响。我们表明，尽管 KLK 轻微刺激 Ca²(+)内流入细胞，但 Ca²(+)水平的大量增加是由于 KLK 诱导的细胞内 Ca²(+)储存耗尽所致。最后，我们证明 KLK 诱导 PS（磷脂酰丝氨酸）从内到外质膜小叶的转换，这有助于这些细胞早期凋亡变化的发生。
