Syndecan-4 regulates localization, activity and stability of protein kinase C-α
Syndecan-4 regulates localization, activity and stability of protein kinase C-α
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DOI：
10.1042/bj20031734
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发表时间：
2004-03-15
影响因子：
4.1
通讯作者：
Oh, ES
中科院分区：
文献类型：
--
作者：
Keum, E;Kim, Y;Oh, ES
在细胞-基质粘附过程中，多配体蛋白聚糖-4跨膜硫酸乙酰肝素蛋白聚糖在粘着斑和应力纤维的形成中起关键作用。我们先前已经表明，多配体蛋白聚糖-4胞质结构域在体外直接结合并激活PKC-α（蛋白激酶Goi）[Oh，Woods和Couchman（1997）J.Biol.Chem.272，8133-8136]。然而，syndecan-4是否在体内具有相同的活性需要解决。使用哺乳动物双杂交试验，我们表明，syndecan-4与PKC-α在体内相互作用，这种相互作用是通过syndecan-4胞质结构域介导的。此外，PKC的激活增加了syndecan-4和PKC-α之间的相互作用的程度。syndecan-4的过表达，但不是缺乏其胞质结构域的突变体，特异性地增加了内源性PKC-α的水平，并增强了PKC-α向洗涤剂不溶性组分和膜组分的易位。此外，大鼠胚胎成纤维细胞过度表达syndecan-4表现出一个缓慢的下调PKC-α的反应，无论是长期治疗PMA或维持细胞悬浮培养。PKC-α免疫复合物激酶测定也表明syndecan-4过表达增加了膜PKC-α的活性。总之，这些结果表明，syndecan-4与PKC-α在体内相互作用，并调节其定位，活性和稳定性。
During cell-matrix adhesion, syndecan-4 transmembrane heparan sulphate proteoglycan plays a critical role in the formation of focal adhesions and stress fibres. We have shown previously that the syndecan-4 cytoplasmic domain directly binds to and activates PKC-alpha (protein kinase Goi) in vitro [Oh, Woods and Couchman (1997) J. Biol. Chem. 272, 8133-8136]. However, whether syndecan-4 has the same activity in vivo needs to be addressed. Using mammalian two-hybrid assays, we showed that syndecan-4 interacted with PKC-alpha in vivo and that this interaction was mediated through syndecan-4 cytoplasmic domain. Furthermore, the activation of PKC increased the extent of interaction between syndecan-4 and PKC-alpha. Overexpression of syndecan-4, but not a mutant lacking its cytoplasmic domain, specifically increased the level of endogenous PKC-alpha and enhanced the translocation of PKC-alpha into both detergent-insoluble and membrane fractions. In addition, rat embryo fibroblasts overexpressing syndecan-4 exhibited a slowed down-regulation of PKC-alpha in response either to a prolonged treatment with PMA or to maintaining cells in suspension culture. PKC-alpha immunocomplex kinase assays also showed that syndecan-4 overexpression increased the activity of membrane PKC-alpha. Taken together, these results suggest that syndecan-4 interacts with PKC-alpha in vivo and regulates its localization, activity and stability.