Morita Tsuyoshi, Amagai Aiko, Maeda Yasuo
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Exp Cell Res. 2002 Oct 15;280(1):45-54. doi: 10.1006/excr.2002.5620.
Dd-TRAP1 is a Dictyostelium homologue of TRAP-1, a human protein that binds to the type 1 tumor necrosis factor (TNF) receptor. TRAP-1 has a putative mitochondrial localization sequence and shows significant homology to members of the HSP90 family. Although TRAP-1 is mainly localized to mitochondria in several mammalian cells, in certain tissues it is also localized at specific extramitochondrial sites. In Dictyostelium cells, Dd-TRAP1 is predominantly located in the cell membrane/cortex during growth and just after starvation. Double staining of vegetatively growing cells with the anti-Dd-TRAP1 antibody and TRITC-phalloidin has demonstrated colocalization of Dd-TRAP1 and F-actin at the leading edge of cortical protrusions such as pseudopodes. Coupled with differentiation, however, Dd-TRAP1 located at the cortical region is translocated to mitochondria in spite of the absence of the mitochondrial localization sequence at its N-terminus. The translocation of this protein raises interesting and fundamental questions regarding possible mechanisms by which Dd-TRAP1 is involved in cellular differentiation.
Dd-TRAP1是TRAP-1的盘基网柄菌同源物，TRAP-1是一种与1型肿瘤坏死因子（TNF）受体结合的人类蛋白质。TRAP-1具有一个假定的线粒体定位序列，并且与HSP90家族成员具有显著的同源性。尽管TRAP-1在几种哺乳动物细胞中主要定位于线粒体，但在某些组织中它也定位于特定的线粒体外位点。在盘基网柄菌细胞中，Dd-TRAP1在生长期间和饥饿后主要位于细胞膜/皮质中。用抗Dd-TRAP1抗体和TRITC-鬼笔环肽对营养生长细胞进行双重染色，已证明Dd-TRAP1和F-肌动蛋白在皮质突起（如伪足）的前缘共定位。然而，随着分化的进行，位于皮质区域的Dd-TRAP1尽管在其N端没有线粒体定位序列，但仍会转移到线粒体中。这种蛋白质的转移引发了关于Dd-TRAP1参与细胞分化的可能机制的有趣而基本的问题。
