Hashimoto Muneaki, Nara Takeshi, Enomoto Masahiro, Kurebayashi Nagomi, Yoshida Mitsutaka, Sakurai Takashi, Mita Toshihiro, Mikoshiba Katsuhiko
Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Saitama, 351-0198, Japan; Princess Margaret Cancer Centre, Department of Medical Biophysics, University of Toronto, M5G1L7, Toronto, Ontario, Canada.
Biochem Biophys Res Commun. 2015 Oct 23;466(3):475-80. doi: 10.1016/j.bbrc.2015.09.053. Epub 2015 Sep 12.
Inositol 1,4,5-trisphosphate receptor (IP3R) is a key regulator of intracellular Ca(2+) concentration that release Ca(2+) from Ca(2+) stores in response to various external stimuli. IP3R also works as a signal hub which form a platform for interacting with various proteins involved in diverse cell signaling. Previously, we have identified an IP3R homolog in the parasitic protist, Trypanosoma cruzi (TcIP3R). Parasites expressing reduced or increased levels of TcIP3R displayed defects in growth, transformation, and infectivity. In the present study, we established parasitic strains expressing a dominant negative form of TcIP3R, named DN-TcIP3R, to further investigate the physiological role(s) of TcIP3R. We found that the growth of epimastigotes expressing DN-TcIP3R was significantly slower than that of parasites with TcIP3R expression levels that were approximately 65% of wild-type levels. The expression of DN-TcIP3R in epimastigotes induced metacyclogenesis even in the normal growth medium. Furthermore, these epimastigotes showed the presence of dense mitochondria under a transmission electron microscope. Our findings confirm that TcIP3R is crucial for epimastigote growth, as previously reported. They also suggest that a strong inhibition of the IP3R-mediated signaling induces metacyclogenesis and that mitochondrial integrity is closely associated with this signaling.
肌醇1,4,5-三磷酸受体（IP3R）是细胞内钙离子浓度的关键调节因子，可响应各种外部刺激从钙库中释放钙离子。IP3R还作为信号枢纽，形成一个与参与多种细胞信号传导的各种蛋白质相互作用的平台。此前，我们在寄生原生生物克氏锥虫（TcIP3R）中鉴定出一种IP3R同源物。表达水平降低或升高的TcIP3R的寄生虫在生长、转化和感染性方面表现出缺陷。在本研究中，我们建立了表达显性负性形式的TcIP3R（命名为DN-TcIP3R）的寄生菌株，以进一步研究TcIP3R的生理作用。我们发现，表达DN-TcIP3R的无鞭毛体的生长明显慢于TcIP3R表达水平约为野生型水平65%的寄生虫。即使在正常生长培养基中，无鞭毛体中DN-TcIP3R的表达也会诱导后循环发育。此外，在透射电子显微镜下，这些无鞭毛体显示出线粒体致密。我们的研究结果证实，如先前报道的那样，TcIP3R对无鞭毛体生长至关重要。它们还表明，对IP3R介导的信号传导的强烈抑制会诱导后循环发育，并且线粒体完整性与该信号传导密切相关。
