scholarly journals Distinct effects of tubulin isotype mutations on neurite growth in Caenorhabditis elegans

2017 ◽  
Author(s):  
Chaogu Zheng ◽  
Margarete Diaz-Cuadros ◽  
Ken C.Q. Nguyen ◽  
David H. Hall ◽  
Martin Chalfie
Keyword(s):  
Function Analysis ◽  
Critical Role ◽  
Neurite Growth ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Post Translational Modification ◽  
Exterior Surface ◽  
Tubulin Isotypes ◽  
C Elegans ◽  
Tubulin Isotype

AbstractTubulins, the building block of microtubules (MTs), play a critical role in both supporting and regulating neurite growth. Eukaryotic genomes contain multiple tubulin isotypes, and their missense mutations cause a range of neurodevelopmental defects. Using the C. elegans touch receptor neurons, we analyzed the effects of 67 tubulin missense mutations on neurite growth. Three types of mutations emerged: 1) loss-of-function mutations, which cause mild defects in neurite growth; 2) antimorphic mutations, which map to the GTP binding site and intradimer and interdimer interfaces, significantly reduce MT stability, and cause severe neurite growth defects; and 3) neomorphic mutations, which map to the exterior surface, increase MT stability, and cause ectopic neurite growth. Structure-function analysis reveals a causal relationship between tubulin structure and MT stability. This stability affects neuronal morphogenesis. As part of this analysis, we engineered several disease-associated human tubulin mutations into C. elegans genes and examined their impact on neuronal development at the cellular level. We also discovered an α-tubulin (TBA-7) that appears to destabilize MTs. Loss of TBA-7 led to the formation of hyperstable MTs and the generation of ectopic neurites; the lack of potential sites for polyamination and polyglutamination on TBA-7 may be responsible for this destabilization.Table of Content (TOC) Highlight SummaryDifferent tubulin isotypes perform different functions in the regulation of MT structure and neurite growth, and missense mutations of tubulin genes have three types of distinct effects on MT stability and neurite growth. One α-tubulin isotype appears to induce relative instability due to the lack of potential post-translational modification sites.

scholarly journals Distinct effects of tubulin isotype mutations on neurite growth in Caenorhabditis elegans

2017 ◽  
Vol 28 (21) ◽  
pp. 2786-2801 ◽  
Author(s):  
Chaogu Zheng ◽  
Margarete Diaz-Cuadros ◽  
Ken C. Q. Nguyen ◽  
David H. Hall ◽  
Martin Chalfie
Keyword(s):  
Caenorhabditis Elegans ◽  
Neuronal Development ◽  
Function Analysis ◽  
Critical Role ◽  
Neurite Growth ◽  
Cellular Level ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Exterior Surface ◽  
C Elegans

Tubulins, the building block of microtubules (MTs), play a critical role in both supporting and regulating neurite growth. Eukaryotic genomes contain multiple tubulin isotypes, and their missense mutations cause a range of neurodevelopmental defects. Using the Caenorhabditis elegans touch receptor neurons, we analyzed the effects of 67 tubulin missense mutations on neurite growth. Three types of mutations emerged: 1) loss-of-function mutations, which cause mild defects in neurite growth; 2) antimorphic mutations, which map to the GTP binding site and intradimer and interdimer interfaces, significantly reduce MT stability, and cause severe neurite growth defects; and 3) neomorphic mutations, which map to the exterior surface, increase MT stability, and cause ectopic neurite growth. Structure-function analysis reveals a causal relationship between tubulin structure and MT stability. This stability affects neuronal morphogenesis. As part of this analysis, we engineered several disease-associated human tubulin mutations into C. elegans genes and examined their impact on neuronal development at the cellular level. We also discovered an α-tubulin (TBA-7) that appears to destabilize MTs. Loss of TBA-7 led to the formation of hyperstable MTs and the generation of ectopic neurites; the lack of potential sites for polyamination and polyglutamination on TBA-7 may be responsible for this destabilization.

scholarly journals Epistatic, Synthetic, and Balancing Interactions among Tubulin Missense Mutations Affecting Neurite Growth in Caenorhabditis elegans

2020 ◽  
pp. mbc.E20-07-0492
Author(s):  
Ho Ming Terence Lee ◽  
Natalie Yvonne Sayegh ◽  
A. Sophia Gayek ◽  
Susan Laura Javier Jao ◽  
Martin Chalfie ◽  
...  
Keyword(s):  
Genetic Interaction ◽  
Neurite Growth ◽  
Phenotypic Characterization ◽  
Missense Mutations ◽  
Loss Of Function ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
Receptor Neurons ◽  
Tubulin Mutations

Mutations in tubulins affect microtubule (MT) dynamics and functions during neuronal differentiation and their genetic interaction provides insights into the regulation of MT functions. We previously used C. elegans touch receptor neurons to analyze the cellular impact of tubulin mutations and reported the phenotypes of 67 tubulin missense mutations, categorized into three classes: loss-of-function ( lf), antimorphic ( anti), and neomorphic ( neo) alleles. In this study, we isolated 54 additional tubulin alleles through suppressor screens in sensitized backgrounds that caused excessive neurite growth. These alleles included 32 missense mutations not analyzed before, bringing the total number of mutations in our collection to 99. Phenotypic characterization of these newly isolated mutations identified three new types of alleles: partial lf and weak neo alleles of mec-7/β-tubulin that had subtle effects and strong anti alleles of mec-12/α-tubulin. We also discovered complex genetic interactions among the tubulin mutations, including the suppression of neo mutations by intragenic lf and anti alleles, additive and synthetic effects between mec-7 neo alleles, and unexpected epistasis, in which weaker neo alleles masked the effects of stronger neo alleles in inducing ectopic neurite growth. We also observed balancing between neo and anti alleles, whose respective MT-hyperstablizing and -destabilizing effects neutralized each other.

scholarly journals HMGB1 Promotes Systemic Lupus Erythematosus by Enhancing Macrophage Inflammatory Response

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Mudan Lu ◽  
Shanshan Yu ◽  
Wei Xu ◽  
Bo Gao ◽  
Sidong Xiong
Keyword(s):  
Systemic Lupus Erythematosus ◽  
Inflammatory Response ◽  
Proinflammatory Cytokines ◽  
Lupus Erythematosus ◽  
Function Analysis ◽  
Critical Role ◽  
Loss Of Function ◽  
Systemic Lupus ◽  
Glycation End Products ◽  
Hmgb1 Expression

Background/Purpose. HMGB1, which may act as a proinflammatory mediator, has been proposed to contribute to the pathogenesis of multiple chronic inflammatory and autoimmune diseases including systemic lupus erythematosus (SLE); however, the precise mechanism of HMGB1 in the pathogenic process of SLE remains obscure.Method. The expression of HMGB1 was measured by ELISA and western blot. The ELISA was also applied to detect proinflammatory cytokines levels. Furthermore, nephritic pathology was evaluated by H&E staining of renal tissues.Results. In this study, we found that HMGB1 levels were significantly increased and correlated with SLE disease activity in both clinical patients and murine model. Furthermore, gain- and loss-of-function analysis showed that HMGB1 exacerbated the severity of SLE. Of note, the HMGB1 levels were found to be associated with the levels of proinflammatory cytokines such as TNF-αand IL-6 in SLE patients. Further study demonstrated that increased HMGB1 expression deteriorated the severity of SLE via enhancing macrophage inflammatory response. Moreover, we found that receptor of advanced glycation end products played a critical role in HMGB1-mediated macrophage inflammatory response.Conclusion. These findings suggested that HMGB1 might be a risk factor for SLE, and manipulation of HMGB1 signaling might provide a therapeutic strategy for SLE.

Functional expression of heterologous proteins in yeast: insights into Ca2+ signaling and Ca2+-transporting ATPases

2004 ◽  
Vol 287 (3) ◽  
pp. C580-C589 ◽  
Author(s):  
Van-Khue Ton ◽  
Rajini Rao
Keyword(s):  
Secretory Pathway ◽  
Function Analysis ◽  
Model Organism ◽  
Functional Expression ◽  
Missense Mutations ◽  
Heterologous Proteins ◽  
Loss Of Function ◽  
Yeast Saccharomyces Cerevisiae ◽  
Culturing Conditions ◽  
Mutant Phenotypes

The baker's yeast Saccharomyces cerevisiae is a well-developed, versatile, and widely used model organism. It offers a compact and fully sequenced genome, tractable genetics, simple and inexpensive culturing conditions, and, importantly, a conservation of basic cellular machinery and signal transducing pathways with higher eukaryotes. In this review, we describe recent technical advances in the heterologous expression of proteins in yeast and illustrate their application to the study of the Ca2+ homeostasis machinery, with particular emphasis on Ca2+-transporting ATPases. Putative Ca2+-ATPases in the newly sequenced genomes of organisms such as parasites, plants, and vertebrates have been investigated by functional complementation of an engineered yeast strain lacking endogenous Ca2+ pumps. High-throughput screens of mutant phenotypes to identify side chains critical for ion transport and selectivity have facilitated structure-function analysis, and genomewide approaches may be used to dissect cellular pathways involved in Ca2+ transport and trafficking. The utility of the yeast system is demonstrated by rapid advances in the study of the emerging family of Golgi/secretory pathway Ca2+,Mn2+-ATPases (SPCA). Functional expression of human SPCA1 in yeast has provided insight into the physiology, novel biochemical characteristics, and subcellular localization of this pump. Haploinsufficiency of SPCA1 leads to Hailey-Hailey disease (HDD), a debilitating blistering disorder of the skin. Missense mutations, identified in patients with HHD, may be conveniently assessed in yeast for loss-of-function phenotypes associated with the disease.

scholarly journals Calcineurin homologous proteins regulate the membrane localization and activity of sodium/proton exchangers in C. elegans

2016 ◽  
Vol 310 (3) ◽  
pp. C233-C242 ◽  
Author(s):  
Erik Allman ◽  
Qian Wang ◽  
Rachel L. Walker ◽  
Molly Austen ◽  
Maureen A. Peters ◽  
...  
Keyword(s):  
Genetic Model ◽  
Expression Patterns ◽  
Critical Role ◽  
Model Organism ◽  
Loss Of Function ◽  
Homologous Proteins ◽  
Relative Significance ◽  
C Elegans ◽  
Fluorescent Tags

Calcineurin B homologous proteins (CHP) are N-myristoylated, EF-hand Ca2+-binding proteins that bind to and regulate Na+/H+ exchangers, which occurs through a variety of mechanisms whose relative significance is incompletely understood. Like mammals, Caenorhabditis elegans has three CHP paralogs, but unlike mammals, worms can survive CHP loss-of-function. However, mutants for the CHP ortholog PBO-1 are unfit, and PBO-1 has been shown to be required for proton signaling by the basolateral Na+/H+ exchanger NHX-7 and for proton-coupled intestinal nutrient uptake by the apical Na+/H+ exchanger NHX-2. Here, we have used this genetic model organism to interrogate PBO-1's mechanism of action. Using fluorescent tags to monitor Na+/H+ exchanger trafficking and localization, we found that loss of either PBO-1 binding or activity caused NHX-7 to accumulate in late endosomes/lysosomes. In contrast, NHX-2 was stabilized at the apical membrane by a nonfunctional PBO-1 protein and was only internalized following its complete loss. Additionally, two pbo-1 paralogs were identified, and their expression patterns were analyzed. One of these contributed to the function of the excretory cell, which acts like a kidney in worms, establishing an alternative model for testing the role of this protein in membrane transporter trafficking and regulation. These results lead us to conclude that the role of CHP in Na+/H+ exchanger regulation differs between apical and basolateral transporters. This further emphasizes the importance of proper targeting of Na+/H+ exchangers and the critical role of CHP family proteins in this process.

Determinating the role of the E3 Ubiquitin Ligase Ariadne 2 in mammalian systemss

2007 ◽  
Vol 30 (4) ◽  
pp. 87
Author(s):  
A. E. Lin ◽  
A. Wakeham ◽  
A. You-Ten ◽  
G. Wood ◽  
T. W. Mak
Keyword(s):  
Function Analysis ◽  
Critical Role ◽  
Ring Finger ◽  
E3 Ligase ◽  
Signalling Pathways ◽  
Loss Of Function ◽  
In Vivo Models

Ubiquitination is a eukaryotic process of selective proteolysis, where a highly conserved ubiquitin protein is selectively added as a chain to the targeted to a protein for degradation. In recent years, the process of ubiquitination has been shown to be a critical mechanism that can affect essential signalling pathways, including apoptosis, cell cycle arrest and induction of the inflammatory response. Thus, alterations in the ubiquitination process can alter signalling pathways pivotal to numerous disease pathologies. This is clearly demonstrated in perturbations of ubiquitination in the NFκB giving rise to cancer and other immunological disease processes. To gain insight into pathways that require regulation by ubiquitination, our lab has directed focus on the highly conserved E3 ligase, Ariadne 2. Ariadne 2 is characterized as a putative RING finger E3 ligase and is part of the family of highly conserved RBR (RING-B-Box-RING) superfamily. The role of Ariadne 2 has been well studied in Drosophila melanogaster, however, little is known of the function of Ariadne 2 in mammalian systems. Therefore, the main objectives of the project are as follows: To determine the biological role of Ariadne 2, the role of Ariadne 2 in development and differentiation, and the consequences of in vivo loss of Ariadne 2 expression. We are currently investigating the role of Ariadne 2 as an E3 ligase and its involvement in the immune response. To date, we have shown that Ariadne 2 is ubiquitously expressed, especially in the brain, heart, spleen and thymus. For in vivo loss of function analysis, mice were generated by homologous recombination to be deficient for Ariadne 2. These deficient mice die prematurely soon after birth, suggesting a critical role for Ariadne 2 in development and survival. We are currently focusing on the role of Ariadne 2 in development and it’s role in immune pathologies, in particular, spontaneous autoimmunity, using both in vitro studies and in vivo models.

scholarly journals Loss-of-Function Mutations in the Genes Encoding Prokineticin-2 or Prokineticin Receptor-2 Cause Autosomal Recessive Kallmann Syndrome

2008 ◽  
Vol 93 (10) ◽  
pp. 4113-4118 ◽  
Author(s):  
Ana Paula Abreu ◽  
Ericka Barbosa Trarbach ◽  
Margaret de Castro ◽  
Elaine Maria Frade Costa ◽  
Beatriz Versiani ◽  
...  
Keyword(s):  
Hypogonadotropic Hypogonadism ◽  
Critical Role ◽  
Kallmann Syndrome ◽  
Control Group ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Coding Regions ◽  
Prokineticin 2 ◽  
Bilateral Cryptorchidism ◽  
Genes Encoding

Context: Physiological activation of the prokineticin pathway has a critical role in olfactory bulb morphogenesis and GnRH secretion in mice. Objective: To investigate PROK2 and PROKR2 mutations in patients with hypogonadotropic hypogonadism (HH) associated or not with olfactory abnormalities. Design: We studied 107 Brazilian patients with HH (63 with Kallmann syndrome and 44 with normosmic HH) and 100 control individuals. The coding regions of PROK2 and PROKR2 were amplified by PCR followed by direct automatic sequencing. Results: In PROK2, two known frameshift mutations were identified. Two brothers with Kallmann syndrome harbored the homozygous p.G100fsX121 mutation, whereas one male with normosmic HH harbored the heterozygous p.I55fsX56 mutation. In PROKR2, four distinct mutations (p.R80C, p.Y140X, p.L173R, and p.R268C) were identified in five patients with Kallmann syndrome and in one patient with normosmic HH. These mutations were not found in the control group. The p.R80C, p.L173R, and p.R268C missense mutations were identified in the heterozygous state in the HH patients and in their asymptomatic first-degree relatives. In addition, no mutations of FGFR1, KAL1, GnRHR, KiSS-1, or GPR54 were identified in these patients. Notably, the new nonsense mutation (p.Y140X) was identified in the homozygous state in an anosmic boy with micropenis, bilateral cryptorchidism, and high-arched palate. His asymptomatic parents were heterozygous for this severe defect. Conclusion: We expanded the repertoire of PROK2 and PROKR2 mutations in patients with HH. In addition, we show that PROKR2 haploinsufficiency is not sufficient to cause Kallmann syndrome or normosmic HH, whereas homozygous loss-of-function mutations either in PROKR2 or PROK2 are sufficient to cause disease phenotype, in accordance with the Prokr2 and Prok2 knockout mouse models.

scholarly journals Proteins and Molecular Pathways Relevant for the Malignant Properties of Tumor-Initiating Pancreatic Cancer Cells

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1397
Author(s):  
Lisa Samonig ◽  
Andrea Loipetzberger ◽  
Constantin Blöchl ◽  
Marc Rurik ◽  
Oliver Kohlbacher ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Function Analysis ◽  
Critical Role ◽  
Three Dimensional ◽  
Small Subset ◽  
Loss Of Function ◽  
Tumor Initiating Cells ◽  
Differential Proteomics ◽  
Pancreatic Cancer Cells

Cancer stem cells (CSCs), a small subset of the tumor bulk with highly malignant properties, are deemed responsible for tumor initiation, growth, metastasis, and relapse. In order to reveal molecular markers and determinants of their tumor-initiating properties, we enriched rare stem-like pancreatic tumor-initiating cells (TICs) by harnessing their clonogenic growth capacity in three-dimensional multicellular spheroid cultures. We compared pancreatic TICs isolated from three-dimensional tumor spheroid cultures with nontumor-initiating cells (non-TICs) enriched in planar cultures. Employing differential proteomics (PTX), we identified more than 400 proteins with significantly different expression in pancreatic TICs and the non-TIC population. By combining the unbiased PTX with mRNA expression analysis and literature-based predictions of pro-malignant functions, we nominated the two calcium-binding proteins S100A8 (MRP8) and S100A9 (MRP14) as well as galactin-3-binding protein LGALS3BP (MAC-2-BP) as putative determinants of pancreatic TICs. In silico pathway analysis followed by candidate-based RNA interference mediated loss-of-function analysis revealed a critical role of S100A8, S100A9, and LGALS3BP as molecular determinants of TIC proliferation, migration, and in vivo tumor growth. Our study highlights the power of combining unbiased proteomics with focused gene expression and functional analyses for the identification of novel key regulators of TICs, an approach that warrants further application to identify proteins and pathways amenable to drug targeting.

scholarly journals Probing small ribosomal subunit RNA helix 45 acetylation across eukaryotic evolution

2021 ◽  
Author(s):  
Marie-line Bortolin-Cavaillé ◽  
Aurélie Quillien ◽  
Supuni Thalalla Gamage ◽  
Justin M Thomas ◽  
Aldema Sas-Chen ◽  
...  
Keyword(s):  
Ribosome Biogenesis ◽  
18S Rrna ◽  
Molecular Mechanisms ◽  
Function Analysis ◽  
Ribosomal Subunit ◽  
Model Organisms ◽  
Loss Of Function ◽  
C Elegans ◽  
Base Modification ◽  
Essential Enzyme

NAT10 is an essential enzyme that catalyzes the formation of N4-acetylcytidine (ac4C) in eukaryotic transfer RNA (tRNA) and 18S ribosomal RNA (rRNA). Recent studies in human cells suggested that rRNA acetylation is dependent on SNORD13, a non-canonical box C/D small nucleolar RNA (SNORD) predicted to base-pair with 18S rRNA via two antisense elements. However, the selectivity of SNORD13-dependent cytidine acetylation and its relationship to NAT10 essential function in pre-rRNA processing remain to be defined. Here, we used CRISPR-Cas9 genome editing to formally demonstrate that SNORD13 is required for acetylation of a single cytidine residue of human and zebrafish 18S rRNA. In-depth characterization revealed that SNORD13-dependent ac4C is dispensable for yeast or human cell growth, ribosome biogenesis, translation, and the development of multicellular metazoan model organisms. This loss of function analysis inspired a cross-evolutionary survey of the eukaryotic rRNA acetylation machinery that led to the characterization of many novel SNORD13 genes in phylogenetically-distant metazoans and more deeply rooted photosynthetic organisms. This includes an atypical SNORD13-like RNA in D. melanogaster which appears to guide ac4C to 18S rRNA helix 45 despite lacking one of the two rRNA antisense elements. Finally, we discover that C. elegans 18S rRNA is not acetylated despite the presence of an essential NAT10 homolog. Altogether, our findings shed light on the molecular mechanisms underlying SNORD13-mediated rRNA acetylation across the eukaryotic tree of life and raise new questions regarding the biological function and evolutionary persistence of this highly conserved rRNA base modification.

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