The Anaphase-Promoting Complex (APC) ubiquitin ligase affects chemosensory behavior in \u3cem\u3eC. elegans\u3c/em\u3e

The regulation of fundamental aspects of neurobiological function has been linked to the ubiquitin signaling system (USS), which regulates the degradation and activity of proteins and is catalyzed by E1, E2, and E3 enzymes. The Anaphase-Promoting Complex (APC) is a multi-subunit E3 ubiquitin ligase that controls diverse developmental and signaling processes in post-mitotic neurons; however, potential roles for the APC in sensory function have yet to be explored. In this study, we examined the effect of the APC ubiquitin ligase on chemosensation in Caenorhabditis elegans by testing chemotaxis to the volatile odorants, diacetyl, pyrazine, and isoamyl alcohol, to which wild-type worms are attracted. Animals with loss of function mutations in either of two alleles (g48 and ye143) of the gene encoding the APC subunit EMB-27 APC6 showed increased chemotaxis towards diacetyl and pyrazine, odorants sensed by AWA neurons, but exhibited normal chemotaxis to isoamyl alcohol, which is sensed by AWC neurons. The statistically significant increase in chemotaxis in the emb-27 APC6 mutants suggests that the APC inhibits AWA-mediated chemosensation in C. elegans. Increased chemotaxis to pyrazine was also seen with mutants lacking another essential APC subunit, MAT-2 APC1; however, mat-2 APC1 mutants exhibited wild type responses to diacetyl. The difference in responsiveness of these two APC subunit mutants may be due to differential strength of these hypomorphic alleles or may indicate the presence of functional sub-complexes of the APC at work in this process. These findings are the first evidence for APC-mediated regulation of chemosensation and lay the groundwork for further studies aimed at identifying the expression levels, function, and targets of the APC in specific sensory neurons. Because of the similarity between human and C. elegans nervous systems, the role of the APC in sensory neurons may also advance our understanding of human sensory function and disease

Caenorhabditis elegans : Señalización de CA2+ en la faringe

Nuestro objetivo es medir variaciones de Ca2+ en la faringe en condiciones de experimentación. Observar posibles diferencias en el patrón de calcio citosólico en la faringe a lo largo de la vida del C. elegans. Y la obtención de líneas mutantes que expresen el colorante YC2.1 en gusanos que llevan las mutaciones eat-2, nuo-6 y daf-2 ya descritas, para ver si dichas mutaciones afectan al patrón de Ca2+ observado en el gusano silvestre.Máster en Investigación Biomédic

High interindividual variability in dose-dependent reduction in speed of movement after exposing C. elegans to shock waves

In blast-related mild traumatic brain injury (br-mTBI) little is known about the connections between initial trauma and expression of individual clinical symptoms. Partly due to limitations of current in vitro and in vivo models of br-mTBI, reliable prediction of individual short-and long-term symptoms based on known blast input has not yet been possible. Here we demonstrate a dose-dependent effect of shock wave exposure on C. elegans using shock waves that share physical characteristics with those hypothesized to induce br-mTBI in humans. Increased exposure to shock waves resulted in decreased mean speed of movement while increasing the proportion of worms rendered paralyzed. Recovery of these two behavioral symptoms was observed during increasing post-traumatic waiting periods. Although effects were observed on a population-wide basis, large interindividual variability was present between organisms exposed to the same highly controlled conditions. Reduction of cavitation by exposing worms to shock waves in polyvinyl alcohol resulted in reduced effect, implicating primary blast effects as damaging components in shock wave induced trauma. Growing worms on NGM agar plates led to the same general results in initial shock wave effect in a standard medium, namely dose-dependence and high interindividual variability, as raising worms in liquid cultures. Taken together, these data indicate that reliable prediction of individual clinical symptoms based on known blast input as well as drawing conclusions on blast input from individual clinical symptoms is not feasible in br-mTBI

The effects of Rapamycin on Lifespan and Healthspan in Caenorhabditis elegans atg-18 mutants

Aging is a biological process causing loss of physical integrity, reduced function, and higher vulnerability to death. Aging also increases the risk of major human diseases including cancer, diabetes, cardiovascular disorders, and neurodegenerative disorders like dementia. Research on aging and age-related diseases is important to improve human health during aging to minimize the global socioeconomic burden and challenges in healthcare. Autophagy is a cellular clearance pathway which promotes homeostasis in the cells and is proposed as a hallmark of aging. A disruption of autophagy is shown to accelerate age-related aggregation of proteins and shorten lifespan in several model organisms. An increase in autophagy e.g., by the autophagy-inducer rapamycin has shown suppressed protein aggregation as well as promoted health and longevity. Studies have shown that induction of autophagy by treatment with rapamycin in the widely used nematode Caenorhabditis elegans extends lifespan and healthspan parameters. This study aimed to investigate the effects of rapamycin treatment with a malfunctioning autophagy-machinery to see whether the treatment can affect lifespan and/or healthspan without affecting autophagy. C. elegans atg-18(gk378) with a loss-of-function mutation causing a malfunctional autophagy-machinery were investigated. Lifespan assay, as well as the healthspan assays pharyngeal pumping and thrashing were performed in the mutant and in a WT strain to examine the effects of the treatment. The lifespan assay showed a decreased lifespan for the mutants treated with rapamycin, suggesting that rapamycin might affect other mechanisms related to the process of aging with a negative effect. Considering that the thrashing assay might be a more reliable healthspan parameter than the pumping assay, rapamycin-treatment seemed to increase healthspan of the mutants as well as for the WT. To validate the effect of rapamycin on autophagy and the mammalian ATG-18 homolog WIPI2, HeLa cells with GFP-tagged WIPI2B were treated with rapamycin. Imaging of the cells clearly showed an increase in autophagy after 24 hours of treatment. Imaging as well as Western Blots suggested that 2 hours of treatment is not sufficient to show an effect of rapamycin-treatment. This study suggests that rapamycin decreases the lifespan of C. elegans atg-18(gk378) mutants, but to some degree promote healthier aging. The mechanisms seemingly affected by rapamycin in the C. elegans mutants may be interesting for further investigation. Not only in C. elegans, but also using other model organisms to investigate the replicability of the results in other models

Vitamin B12 Deficiency Does Not Stimulate Amyloid-beta Toxicity in a Ceanorhabditis elegans Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is symptomized by amyloid-beta plaques in the brain and accounts for more than 65 percent of dementia cases. Vitamin B12 (cobalamin) deficiency can result in similar cognitive impairment and roughly 15% of the elderly are vitamin B12 deficient. Vitamin B12 deficiency results in the accumulation of toxic methylmalonic acid and homocysteine. Hyperhomocysteinemia is a strong risk factor for AD. To test if vitamin B12 deficiency stimulates amyloid-beta toxicity, Caenorhabditis elegans expressing amyloid-beta in muscle were fed either vitamin B12-deficient OP50-1 or vitamin B12-rich HT115(DE3) E. coli bacteria. Increased amyloid-beta toxicity was found in worms fed the 0P50-1 diet. Supplementation of the OP50-1 diet with vitamin B12 did not rescue the increased C. elegans toxicity. Knockdown of either of the only two C. elegans vitamin B12-dependent enzymes metr-1 or mmmc-1 protected against toxicity. Therefore, vitamin B12 deficiency does not stimulate Alzheimer’s amyloid-beta-mediated toxicity in C. elegans

Catalpol Modulates Lifespan via DAF-16/FOXO and SKN-1/Nrf2 Activation in

Catalpol is an effective component of rehmannia root and known to possess various pharmacological properties. The present study was aimed at investigating the potential effects of catalpol on the lifespan and stress tolerance using C. elegans model system. Herein, catalpol showed potent lifespan extension of wild-type nematode under normal culture condition. In addition, survival rate of catalpol-fed nematodes was significantly elevated compared to untreated control under heat and oxidative stress but not under hyperosmolality conditions. We also found that elevated antioxidant enzyme activities and expressions of stress resistance proteins were attributed to catalpol-mediated increased stress tolerance of nematode. We further investigated whether catalpol’s longevity effect is related to aging-related factors including reproduction, food intake, and growth. Interestingly, catalpol exposure could attenuate pharyngeal pumping rate, indicating that catalpol may induce dietary restriction of nematode. Moreover, locomotory ability of aged nematode was significantly improved by catalpol treatment, while lipofuscin levels were attenuated, suggesting that catalpol may affect age-associated changes of nematode. Our mechanistic studies revealed that mek-1, daf-2, age-1, daf-16, and skn-1 are involved in catalpol-mediated longevity. These results indicate that catalpol extends lifespan and increases stress tolerance of C. elegans via DAF-16/FOXO and SKN-1/Nrf activation dependent on insulin/IGF signaling and JNK signaling

Virulence behavior of uropathogenic Escherichia coli strains in the host model Caenorhabditis elegans

Urinary tract infections (UTIs) are among the most common bacterial infections in humans. Although a number of bacteria can cause UTIs, most cases are due to infection by uropathogenic Escherichia coli (UPEC). UPEC are a genetically heterogeneous group that exhibit several virulence factors associated with colonization and persistence of bacteria in the urinary tract. Caenorhabditis elegans is a tiny, free-living nematode found worldwide. Because many biological pathways are conserved in C. elegans and humans, the nematode has been increasingly used as a model organism to study virulence mechanisms of microbial infections and innate immunity. The virulence of UPEC strains, characterized for antimicrobial resistance, pathogenicity-related genes associated with virulence and phylogenetic group belonging was evaluated by measuring the survival of C. elegans exposed to pure cultures of these strains. Our results showed that urinary strains can kill the nematode and that the clinical isolate ECP110 was able to efficiently colonize the gut and to inhibit the host oxidative response to infection. Our data support that C. elegans, a free-living nematode found worldwide, could serve as an in vivo model to distinguish, among uropathogenic E. coli, different virulence behavior

Using C. elegans to screen for targets of ethanol and behavior-altering drugs

Caenorhabditis elegans is an attractive model system for determining the targets of neuroactive compounds. Genetic screens in C. elegans provide a relatively unbiased approach to the identification of genes that are essential for behavioral effects of drugs and neuroactive compounds such as alcohol. Much work in vertebrate systems has identified multiple potential targets of ethanol but which, if any, of those candidates are responsible for the behavioral effects of alcohol is uncertain. Here we provide detailed methodology for a genetic screen for mutants of C. elegans that are resistant to the depressive effects of ethanol on locomotion and for the subsequent behavioral analysis of those mutants. The methods we describe should also be applicable for use in screening for mutants that are resistant or hypersensitive to many neuroactive compounds and for identifying the molecular targets or biochemical pathways mediating drug responses