Zhou Qing, Nguyen Phu Van, Li Ziyin
Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
J Biol Chem. 2024 Nov;300(11):107856. doi: 10.1016/j.jbc.2024.107856. Epub 2024 Oct 5.
Trypanosoma brucei is a flagellated parasitic protozoan, and within the insect vector the parasite transitions from the trypomastigote form to the epimastigote form by repositioning its mitochondrial genome and relocating the flagellum. The mechanisms underlying such morphology changes are still poorly understood, but several flagellum-localized proteins are involved in this process by modulating the flagellum attachment zone (FAZ) that adheres the flagellum to the cell membrane. We report here a putative cAMP-binding protein named cAMP-BP1, which promotes flagellar connection and morphology transition. cAMP-BP1 contains two cyclic nucleotide-binding domains and five calcium-binding C2 domains and localizes to the flagella connector and the new FAZ tip. Depletion of cAMP-BP1 in the trypomastigote form of T. brucei causes major morphology changes, generating epimastigote-like cells with repositioned kinetoplast and relocated flagellum. At the flagella connector and the new FAZ tip, cAMP-BP1 associates with FLAM3, a regulator of morphology transition, depends on the latter for localization, and is required for FLAM3 localization to the flagella connector. Knockdown of cAMP-BP1 inhibits FAZ elongation and disrupts flagellar connection by impairing flagella connector structural integrity. These results identify a flagella connector- and new FAZ tip-localized protein as a regulator of morphology transition and flagellar connection in trypanosomes and uncover its functional interplay with FLAM3 to promote FAZ elongation for maintaining trypomastigote morphology.
布氏锥虫是一种有鞭毛的寄生原生动物，在昆虫媒介体内，该寄生虫通过重新定位其线粒体基因组和移动鞭毛，从锥鞭毛体形式转变为上鞭毛体形式。这种形态变化背后的机制仍知之甚少，但几种鞭毛定位蛋白通过调节将鞭毛附着到细胞膜的鞭毛附着区（FAZ）参与了这一过程。我们在此报告一种名为cAMP-BP1的假定cAMP结合蛋白，它促进鞭毛连接和形态转变。cAMP-BP1包含两个环核苷酸结合结构域和五个钙结合C2结构域，并定位于鞭毛连接器和新的FAZ尖端。在布氏锥虫的锥鞭毛体形式中耗尽cAMP-BP1会导致主要的形态变化，产生具有重新定位的动基体和重新定位的鞭毛的类似上鞭毛体的细胞。在鞭毛连接器和新的FAZ尖端，cAMP-BP1与形态转变调节因子FLAM3结合，依赖后者进行定位，并且是FLAM3定位于鞭毛连接器所必需的。敲低cAMP-BP1会抑制FAZ伸长，并通过损害鞭毛连接器的结构完整性破坏鞭毛连接。这些结果确定了一种定位于鞭毛连接器和新的FAZ尖端的蛋白作为锥虫形态转变和鞭毛连接的调节因子，并揭示了其与FLAM3的功能相互作用，以促进FAZ伸长以维持锥鞭毛体形态。
