Kedlaya Rajendra H, Bhat Kumar M R, Mitchell Julie, Darnell Steven J, Setaluri Vijayasaradhi
Department of Dermatology, University of Wisconsin, Madison, WI 53706, USA.
Arch Biochem Biophys. 2006 Oct 15;454(2):160-9. doi: 10.1016/j.abb.2006.08.010. Epub 2006 Aug 23.
PDZ proteins coordinate assembly of protein complexes that participate in diverse biological processes. GIPC is a multifunctional PDZ protein that interacts with several soluble and membrane proteins. Unlike most PDZ proteins, GIPC contains single PDZ domain and the mechanisms by which GIPC mediates its actions remain unclear. We investigated the possibility that in lieu of multiple PDZ domains, GIPC forms multimers. Here, we demonstrate that GIPC can bind to itself and that the PDZ domain is involved in GIPC-GIPC interaction. Gel filtration, sucrose gradient centrifugation and chemical cross-linking showed that whereas bulk of cytosolic GIPC was present as monomer, oligomers with an estimated molecular mass corresponding to GIPC homotrimer were readily detectable in the membrane fraction. Modeling of GIPC PDZ domain showed feasibility of trimerization. Immunogold electron microscopy showed that GIPC is present in clusters near vesicles. Our data suggest that oligomers of GIPC mediate its functions in melanocytes.
PDZ蛋白协调参与多种生物过程的蛋白质复合物的组装。GIPC是一种多功能PDZ蛋白，可与多种可溶性和膜蛋白相互作用。与大多数PDZ蛋白不同，GIPC包含单个PDZ结构域，其介导作用的机制尚不清楚。我们研究了GIPC形成多聚体以替代多个PDZ结构域的可能性。在此，我们证明GIPC可以自身结合，并且PDZ结构域参与GIPC-GIPC相互作用。凝胶过滤、蔗糖梯度离心和化学交联表明，虽然大部分胞质GIPC以单体形式存在，但在膜部分很容易检测到估计分子量对应于GIPC同三聚体的寡聚体。GIPC PDZ结构域的建模显示了三聚化的可行性。免疫金电子显微镜显示GIPC存在于囊泡附近的簇中。我们的数据表明，GIPC的寡聚体在黑素细胞中介导其功能。
