Interaction between the flagellar pocket collar and the hook complex via a novel microtubule-binding protein in Trypanosoma brucei

We have characterized a cDNA encoding a cysteine-rich, acidic integral membrane protein (CRAM) of the parasitic protozoa Trypanosoma brucei and Trypanosoma equiperdum. Unlike other membrane proteins of T. brucei, which are distributed throughout the cell surface, CRAM is concentrated in the flagellar pocket, an invagination of the cell surface of the trypanosome where endocytosis has been documented. Accordingly, CRAM also locates to vesicles located underneath the pocket, providing evidence of its internalization. CRAM has a predicted molecular mass of 130 kilodaltons and has a signal peptide, a transmembrane domain, and a 41-amino-acid cytoplasmic extension. A characteristic feature of CRAM is a large extracellular domain with a roughly 66-fold acidic, cysteine-rich 12-amino-acid repeat. CRAM is conserved among different protozoan species, including Trypanosoma cruzi, and CRAM has structural similarities with eucaryotic cell surface receptors. The most striking homology of CRAM is to the human low-density-lipoprotein receptor. We propose that CRAM functions as a cell surface receptor of different trypanosome species.

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NDP Kinase 7 Is a Conserved Microtubule-Binding Protein Preferentially Expressed in Ciliated Cells

Cell Structure and Function ◽

10.1247/csf.09016 ◽

2010 ◽

Vol 35 (1) ◽

pp. 23-30 ◽

Cited By ~ 12

Author(s):

Takashi Ikeda

Keyword(s):

Binding Protein ◽

Ciliated Cells ◽

Ndp Kinase ◽

Microtubule Binding

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Smuggle tau through a secret(ory) pathway

Biochemical Journal ◽

10.1042/bcj20210324 ◽

2021 ◽

Vol 478 (14) ◽

pp. 2921-2925

Author(s):

Hao Xu (徐昊)

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Neurodegenerative Diseases ◽

Recent Work ◽

Molecular Mechanisms ◽

Binding Protein ◽

Nerve Cells ◽

Transmembrane Domains ◽

Tau Pathology ◽

Microtubule Binding

Secretion of misfolded tau, a microtubule-binding protein enriched in nerve cells, is linked to the progression of tau pathology. However, the molecular mechanisms underlying tau secretion are poorly understood. Recent work by Lee et al. [Biochemical J. (2021) 478: 1471–1484] demonstrated that the transmembrane domains of syntaxin6 and syntaxin8 could be exploited for tau release, setting a stage for testing a novel hypothesis that has profound implications in tauopathies (e.g. Alzheimer's disease, FTDP-17, and CBD/PSP) and other related neurodegenerative diseases. The present commentary highlights the importance and limitations of the study, and discusses opportunities and directions for future investigations.

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Inscuteable-dependent apical localization of the microtubule-binding protein Cornetto suggests a role in asymmetric cell division

Journal of Cell Science ◽

10.1242/jcs.114.20.3655 ◽

2001 ◽

Vol 114 (20) ◽

pp. 3655-3662 ◽

Cited By ~ 1

Author(s):

Silvia Bulgheresi ◽

Elke Kleiner ◽

Juergen A. Knoblich

Keyword(s):

Cell Fate ◽

Mitotic Spindle ◽

Binding Protein ◽

Protein Localization ◽

Apical Cell ◽

Coiled Coil ◽

Cell Cortex ◽

Dependent Manner ◽

Genetic Redundancy ◽

Microtubule Binding

Drosophila neuroblasts divide asymmetrically along the apical-basal axis. The Inscuteable protein localizes to the apical cell cortex in neuroblasts from interphase to metaphase, but disappears in anaphase. Inscuteable is required for correct spindle orientation and for asymmetric localization of cell fate determinants to the opposite (basal) cell cortex. Here, we show that Inscuteable also directs asymmetric protein localization to the apical cell cortex during later stages of mitosis. In a two-hybrid screen for Inscuteable-binding proteins, we have identified the coiled-coil protein Cornetto, which shows a highly unusual subcellular distribution in neuroblasts. Although the protein is uniformly distributed in the cytoplasm during metaphase, it concentrates apically in anaphase and forms an apical crescent during telophase in an inscuteable-dependent manner. Upon overexpression, Cornetto localizes to astral microtubules and microtubule spin-down experiments demonstrate that Cornetto is a microtubule-binding protein. After disruption of the actin cytoskeleton, Cornetto localizes with microtubules throughout the cell cycle and decorates the mitotic spindle during metaphase. Our results reveal a novel pattern of asymmetric protein localization in Drosophila neuroblasts and are consistent with a function of Cornetto in anchoring the mitotic spindle during late phases of mitosis, even though our cornetto mutant analysis suggests that this function might be obscured by genetic redundancy.

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A potential role for a novel ZC3H5 complex in regulating mRNA translation in Trypanosoma brucei

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014346 ◽

2020 ◽

Vol 295 (42) ◽

pp. 14291-14304

Author(s):

Kathrin Bajak ◽

Kevin Leiss ◽

Christine Clayton ◽

Esteban Erben

Keyword(s):

Gene Expression ◽

Trypanosoma Brucei ◽

Binding Proteins ◽

Rna Binding ◽

Rna Binding Proteins ◽

Binding Protein ◽

Affinity Purification ◽

Critical Role ◽

Rna Binding Protein ◽

Mrna Translation

In Trypanosoma brucei and related kinetoplastids, gene expression regulation occurs mostly posttranscriptionally. Consequently, RNA-binding proteins play a critical role in the regulation of mRNA and protein abundance. Yet, the roles of many RNA-binding proteins are not understood. Our previous research identified the RNA-binding protein ZC3H5 as possibly involved in gene repression, but its role in controlling gene expression was unknown. We here show that ZC3H5 is an essential cytoplasmic RNA-binding protein. RNAi targeting ZC3H5 causes accumulation of precytokinetic cells followed by rapid cell death. Affinity purification and pairwise yeast two-hybrid analysis suggest that ZC3H5 forms a complex with three other proteins, encoded by genes Tb927.11.4900, Tb927.8.1500, and Tb927.7.3040. RNA immunoprecipitation revealed that ZC3H5 is preferentially associated with poorly translated, low-stability mRNAs, the 5′-untranslated regions and coding regions of which are enriched in the motif (U/A)UAG(U/A). As previously found in high-throughput analyses, artificial tethering of ZC3H5 to a reporter mRNA or other complex components repressed reporter expression. However, depletion of ZC3H5 in vivo caused only very minor decreases in a few targets, marked increases in the abundances of very stable mRNAs, an increase in monosomes at the expense of large polysomes, and appearance of “halfmer” disomes containing two 80S subunits and one 40S subunit. We speculate that the ZC3H5 complex might be implicated in quality control during the translation of suboptimal open reading frames.

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