Yamashita Tetsuji, Miyagi Yohei, Ono Michio, Ito Hiroaki, Watanabe Keiko, Sonoda Tomoko, Tsuzuki Keisuke, Ozawa Seiji, Aoki Ichiro, Okuda Kenji, Mishina Masayoshi, Kawamoto Susumu
Department of Bacteriology, Yokohama City University School of Medicine, 3-9 Fukuura, Yokohama 236-0004, Japan.
Brain Res Mol Brain Res. 2005 Nov 18;141(1):83-94. doi: 10.1016/j.molbrainres.2005.08.006. Epub 2005 Sep 15.
Delphilin is identified as a Glutamate receptor delta2 (GluRdelta2) subunit interacting protein, consisting of a PDZ domain and formin homology (FH) domains 1 and 2, in addition to a C-terminal coiled-coil structure. Delphilin has been shown to be selectively expressed in cerebellar Purkinje cells where it co-localizes with the GluRdelta2 subunit at the Purkinje cell-parallel fiber synapses. Although Delphilin specifically interacts with the GluRdelta2 C-terminus via its PDZ domain, the physiological role of the interaction is not yet understood. Here, we report that the Delphilin protein exhibits diversity at its N-terminus by variable usage of the first several exons. Interestingly, the two Delphilin mRNAs which correspond to the first one initially identified (now designated as Delphilin alpha) and the second that contains a newly identified first exon (designated as Delphilin beta), show different chronological expression profiles. Delphilin beta mRNA was not decreased throughout the cerebellar development in vivo and in vitro, while in vivo Delphilin alpha mRNA gradually decreases following the first postnatal week. Delphilins alpha and beta also revealed different subcellular distribution with some overlap. Specifically, the cerebellar synaptosomal membrane fraction contained the Delphilin beta protein. Both Delphilin alpha and beta localized at the dendritic spines with GluRdelta2; however, dendritic shafts in cultured Purkinje cells also included Delphilin beta. In MDCK cells upon becoming confluent, Delphilin alpha moved to the cell-cell junction area, whereas Delphilin beta maintained a diffuse distribution pattern throughout the cytoplasm. Taken as a whole, these two different Delphilins seemed to play functionally different roles in developing and matured cerebellar Purkinje cells.
德尔菲林被鉴定为一种与谷氨酸受体δ2（GluRδ2）亚基相互作用的蛋白，它除了具有一个C末端卷曲螺旋结构外，还包含一个PDZ结构域以及formin同源（FH）结构域1和2。研究表明，德尔菲林在小脑浦肯野细胞中选择性表达，并在浦肯野细胞 - 平行纤维突触处与GluRδ2亚基共定位。尽管德尔菲林通过其PDZ结构域与GluRδ2的C末端特异性相互作用，但这种相互作用的生理作用尚不清楚。在此，我们报告德尔菲林蛋白在其N末端通过前几个外显子的可变使用表现出多样性。有趣的是，与最初鉴定的第一个（现称为德尔菲林α）和包含新鉴定的第一个外显子的第二个（称为德尔菲林β）相对应的两种德尔菲林mRNA，显示出不同的时间表达谱。在体内和体外，德尔菲林β mRNA在整个小脑发育过程中均未减少，而在体内，德尔菲林α mRNA在出生后第一周后逐渐减少。德尔菲林α和β也显示出不同的亚细胞分布，有一些重叠。具体而言，小脑突触体膜部分含有德尔菲林β蛋白。德尔菲林α和β都与GluRδ2一起定位于树突棘；然而，培养的浦肯野细胞中的树突轴也包含德尔菲林β。在汇合的MDCK细胞中，德尔菲林α移动到细胞 - 细胞连接区域，而德尔菲林β在整个细胞质中保持弥散分布模式。总体而言，这两种不同的德尔菲林似乎在发育中和成熟的小脑浦肯野细胞中发挥着不同的功能作用。
