Institut für Biochemie (Emil-Fischer-Zentrum), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
J Neurochem. 2011 Sep;118(5):737-48. doi: 10.1111/j.1471-4159.2011.07367.x. Epub 2011 Jul 21.
Protein kinase C-ζ interacting proteins (ZIP1-3) recruit the enzymatic activity of the atypical protein kinase C isoforms PKC-λ/ι or PKC-ζ to target proteins. In this study, we searched for binding partners of ZIP3 in the CNS and identified spartin, a multifunctional protein that is mutated in spastic paraplegia type 20. In transfected cells, spartin was present on the surface of lipid droplets (LD), whereas ZIP proteins appeared in intracellular speckles. In the presence of spartin, ZIP1 and ZIP3 were translocated to spartin-positive LD. This translocation was mediated by amino acids 196-393 of spartin that interacted with an N-terminal region of ZIP proteins. Furthermore, ZIP proteins interacted simultaneously with spartin and PKC-ζ, resulting in an enrichment of PKC-ζ on spartin/ZIP-labelled LD. Without spartin, neither ZIP proteins nor PKC-ζ were detected on LD. Interestingly, the presence of the spartin/ZIP/PKC-ζ complex increased LD size. This effect was most pronounced upon incorporation of the ZIP3 isoform into the trimer. Finally, we co-localized spartin, ZIP proteins and PKC-ζ in axon terminals of neurons in the mammalian retina. In summary, we describe spartin as new binding partner of the ZIP/PKC-ζ dimer that recruits PKC-ζ to LD and show that the expressed ZIP isoform regulates LD size.
蛋白激酶 C-ζ 相互作用蛋白（ZIP1-3）将非典型蛋白激酶 C 同工型 PKC-λ/ι 或 PKC-ζ 的酶活性募集到靶蛋白上。在这项研究中，我们在中枢神经系统中搜索 ZIP3 的结合伙伴，并鉴定出 spartin，这是一种在痉挛性截瘫 20 型中发生突变的多功能蛋白。在转染细胞中，spartin 存在于脂滴（LD）的表面，而 ZIP 蛋白则存在于细胞内斑点中。在 spartin 的存在下，ZIP1 和 ZIP3 被转运到 spartin 阳性 LD。这种易位是由 spartin 与 ZIP 蛋白的 N 端区域相互作用的 196-393 个氨基酸介导的。此外，ZIP 蛋白与 spartin 和 PKC-ζ 同时相互作用，导致 PKC-ζ 在 spartin/ZIP 标记的 LD 上富集。没有 spartin，LD 上既没有 ZIP 蛋白，也没有 PKC-ζ。有趣的是，spartin/ZIP/PKC-ζ 复合物的存在增加了 LD 的大小。这种效应在将 ZIP3 同工型掺入三聚体时最为明显。最后，我们在哺乳动物视网膜神经元的轴突末端共定位了 spartin、ZIP 蛋白和 PKC-ζ。总之，我们将 spartin 描述为 ZIP/PKC-ζ 二聚体的新结合伙伴，它将 PKC-ζ 募集到 LD，并表明表达的 ZIP 同工型调节 LD 的大小。
