Wang Wei, Kirsch Thorsten
Musculoskeletal Research Laboratories, Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
J Biol Chem. 2006 Oct 13;281(41):30848-56. doi: 10.1074/jbc.M605937200. Epub 2006 Aug 16.
Apoptosis of terminally differentiated chondrocytes allows the replacement of growth plate cartilage by bone. Despite its importance, little is known about the regulation of chondrocyte apoptosis. We show that overexpression of annexin V, which binds to the cytoplasmic domain of beta5 integrin and protein kinase C alpha (PKCalpha), stimulates apoptotic events in hypertrophic growth plate chondrocytes. To determine whether the balance between the interactions of annexin V/beta5 integrin and annexin V/active PKCalpha play a role in the regulation of terminally differentiated growth plate chondrocyte apoptosis, a peptide mimic of annexin V (Penetratin (Pen)-VVISYSMPD) that binds to beta5 integrin but not to PKCalpha was used. This peptide stimulated apoptotic events in growth plate chondrocytes. Suppression of annexin V expression using small interfering ribonucleic acid decreased caspase-3 activity and increased cell viability in Pen-VVISYSMPD-treated growth plate chondrocytes. An activator of PKC resulted in a further decrease of cell viability and further increase of caspase-3 activity in Pen-VVISYSMPD-treated growth plate chondrocytes, whereas inhibitors of PKCalpha led to an increase of cell viability and decrease of caspase-3 activity of Pen-VVISYSMPD-treated cells. These findings suggest that binding of annexin V to active PKCalpha stimulates apoptotic events in growth plate chondrocytes and that binding of annexin Vto beta5 integrin controls these interactions and ultimately apoptosis.
终末分化软骨细胞的凋亡使得生长板软骨被骨替代。尽管其很重要，但关于软骨细胞凋亡的调控却知之甚少。我们发现，膜联蛋白V的过表达会刺激肥大生长板软骨细胞发生凋亡事件，膜联蛋白V可与β5整合素的胞质结构域及蛋白激酶Cα（PKCα）结合。为了确定膜联蛋白V/β5整合素与膜联蛋白V/活性PKCα之间相互作用的平衡是否在终末分化生长板软骨细胞凋亡的调控中发挥作用，我们使用了一种膜联蛋白V的肽模拟物（穿膜肽（Pen）-VVISYSMPD），它能与β5整合素结合，但不与PKCα结合。这种肽刺激了生长板软骨细胞的凋亡事件。在经Pen-VVISYSMPD处理的生长板软骨细胞中，使用小干扰核糖核酸抑制膜联蛋白V的表达可降低半胱天冬酶-3活性并提高细胞活力。PKC激活剂导致经Pen-VVISYSMPD处理的生长板软骨细胞的细胞活力进一步降低，半胱天冬酶-3活性进一步升高，而PKCα抑制剂则导致经Pen-VVISYSMPD处理的细胞的细胞活力增加，半胱天冬酶-3活性降低。这些发现表明，膜联蛋白V与活性PKCα的结合刺激了生长板软骨细胞的凋亡事件，而膜联蛋白V与β5整合素的结合控制了这些相互作用并最终调控了凋亡。
