Spoerl Ziqiang, Stumpf Maria, Noegel Angelika A, Hasse Andreas
Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 52, D-50931 Köln, Germany.
J Biol Chem. 2002 Dec 13;277(50):48858-67. doi: 10.1074/jbc.M205136200. Epub 2002 Oct 10.
Coronin 3 is a ubiquitously expressed member of the coronin protein family in mammals. In fibroblasts and HEK 293 cells, it is localized both in the cytosol and in the submembranous cytoskeleton, especially at lamellipodia and membrane ruffles. The carboxyl terminus of all coronins contains a coiled coil suggested to mediate dimerization. We show here that in contrast to other coronin homologues, the recombinant human coronin 3 carboxyl terminus forms oligomers rather than dimers, and that this part is sufficient to bind to and cross-link F-actin in vitro. The carboxyl terminus alone also conferred membrane association in vivo, and removal of the coiled coil abolished membrane localization but not in vitro F-actin binding. Coronin 3 is exclusively extracted as an oligomer from both the cytosol and the membrane fraction. Because oligomerization was not reported for other coronins, it might be a key feature governing coronin 3-specific functions. Cytosolic coronin 3 showed a high degree of phosphorylation, which is likely to regulate the subcellular localization of the protein.
冠蛋白3是哺乳动物中冠蛋白家族普遍表达的成员。在成纤维细胞和HEK 293细胞中，它定位于细胞质和膜下细胞骨架中，特别是在片状伪足和膜皱褶处。所有冠蛋白的羧基末端都含有一个卷曲螺旋结构，推测其介导二聚化。我们在此表明，与其他冠蛋白同源物不同，重组人冠蛋白3的羧基末端形成寡聚体而非二聚体，并且这一部分足以在体外结合并交联F-肌动蛋白。单独的羧基末端在体内也赋予了膜结合能力，去除卷曲螺旋结构消除了膜定位，但并未消除体外F-肌动蛋白结合。冠蛋白3仅作为寡聚体从细胞质和膜组分中提取出来。由于其他冠蛋白未报道有寡聚化现象，这可能是决定冠蛋白3特异性功能的关键特征。细胞质中的冠蛋白3表现出高度磷酸化，这可能调节该蛋白的亚细胞定位。
