Specific conserved C-terminal amino acids of Caenorhabditis elegans HMP-1/α-catenin modulate F-actin binding independently of vinculin.

Stable intercellular adhesions formed through the cadherin-catenin complex are important determinants of proper tissue architecture and help maintain tissue integrity during morphogenetic movements in developing embryos. A key regulator of this stability is α-catenin, which connects the cadherin-catenin complex to the actin cytoskeleton. Although the C-terminal F-actin-binding domain of α-catenin has been shown to be crucial for its function, a more detailed in vivo analysis of discrete regions and residues required for actin binding has not been performed. Using Caenorhabditis elegans as a model system, we have characterized mutations in hmp-1/α-catenin that identify HMP-1 residues 687-742 and 826-927, as well as amino acid 802, as critical to the localization of junctional proximal actin during epidermal morphogenesis. We also find that the S823F transition in a hypomorphic allele, hmp-1(fe4), decreases actin binding in vitro. Using hmp-1(fe4) animals in a mutagenesis screen, we were then able to identify 11 intragenic suppressors of hmp-1(fe4) that revert actin binding to wild-type levels. Using homology modeling, we show that these amino acids are positioned at key conserved sites within predicted α-helices in the C terminus. Through the use of transgenic animals, we also demonstrate that HMP-1 residues 315-494, which correspond to a putative mechanotransduction domain that binds vinculin in vertebrate αE-catenin, are not required during epidermal morphogenesis but may aid efficient recruitment of HMP-1 to the junction. Our studies are the first to identify key conserved amino acids in the C terminus of α-catenin that modulate F-actin binding in living embryos of a simple metazoan.

Toxigenic Clostridioides difficile colonization as a risk factor for development of C. difficile infection in solid-organ transplant patients.

BACKGROUND: The association between Clostridioides difficile colonization and C. difficile infection (CDI) is unknown in solid-organ transplant (SOT) patients. We examined C. difficile colonization and healthcare-associated exposures as risk factors for development of CDI in SOT patients. METHODS: The retrospective study cohort included all consecutive SOT patients with at least 1 screening test between May 2017 and April 2018. CDI was defined as the presence of diarrhea (without laxatives), a positive C. difficile clinical test, and the use of C. difficile-directed antimicrobial therapy as ordered by managing clinicians. In addition to demographic variables, exposures to antimicrobials, immunosuppressants, and gastric acid suppressants were evaluated from the time of first screening test to the time of CDI, death, or final discharge. RESULTS: Of the 348 SOT patients included in our study, 33 (9.5%) were colonized with toxigenic C. difficile. In total, 11 patients (3.2%) developed CDI. Only C. difficile colonization (odds ratio [OR], 13.52; 95% CI, 3.46-52.83; P = .0002), age (OR, 1.09; CI, 1.02-1.17; P = .0135), and hospital days (OR, 1.05; 95% CI, 1.02-1.08; P = .0017) were independently associated with CDI. CONCLUSIONS: Although CDI was more frequent in C. difficile colonized SOT patients, the overall incidence of CDI was low in this cohort.

Corticotrophin releasing factor receptor 1 antagonists prevent chronic stress-induced behavioral changes and synapse loss in aged rats.

Mounting evidence suggests that chronic stress can alter brain structure and function and promote the development of neuropsychiatric disorders, such as depression and Alzheimer's disease. Although the results of several studies have indicated that aged brains are more vulnerable to chronic stress, it remains unknown whether antagonists of a key stress regulator, the corticotrophin releasing factor receptor 1 (CRF1), can prevent stress-induced anxiety and memory deficits in animal models. In this study, we evaluated the potential benefits of two CRF1 antagonists, R121919 and antalarmin, for preventing stress-induced anxiety-related behavioral and memory deficits and neurodegeneration in aged rats. We stressed rats using isolation-restraint for 3 months starting from the 18 months of age. Subsets of animals were administrated either R121919 or antalarmin through food chow for 3 months, followed by a series of behavioral, biochemical and morphological analyses. We found that stressed aged rats displayed body weight losses and increased corticosterone levels, as well as anxiety-related behaviors and memory deficits. Additionally, chronic stress induced a loss of cortical dendritic spines and synapses. However, R121919 and antalarmin both prevented stress-induced behavioral changes including anxiety-related behaviors and memory deficits and prevented synapse loss, perhaps through reversing HPA axis dysfunction. These results suggest that CRF1 antagonists may hold promise as a potential therapy for preventing stress-induced anxiety and memory deficits in aged individuals.

HDAC inhibitors restore the capacity of aged mice to respond to haloperidol through modulation of histone acetylation.

Antipsychotic drugs are widely prescribed to elderly patients for the treatment of a variety of psychopathological conditions, including psychosis and the behavioral disturbances associated with dementia. However, clinical experience suggests that these drugs may be less efficacious in the elderly individuals than in the young. Recent studies suggest that aging may be associated with epigenetic changes and that valproic acid (VPA), a histone deacetylase inhibitor, may reverse such changes. However, it is not yet known whether HDAC inhibitors can modulate age-related epigenetic changes that may impact antipsychotic drug action. In this study, we analyzed conditioned avoidance response (CAR) and c-Fos expression patterns to elucidate the effect of HDAC inhibitors VPA and entinostat (MS-275) on behavioral and molecular markers of the effects of haloperidol (HAL) in aged mice. Our results showed that HAL administration failed to suppress the avoidance response during the CAR test, suggesting an age-related decrease in drug efficacy. In addition, HAL-induced c-Fos expression in the nucleus accumbens shell and prefrontal cortex was significantly lower in aged mice as compared with young mice. Pretreatment with VPA and MS-275 significantly improved HAL effects on the CAR test in aged mice. Also, VPA and MS-275 pretreatment restored HAL-induced increases in c-Fos expression in the nucleus accumbens shell and prefrontal cortex of aged mice to levels comparable with those observed in young mice. Lastly, but most importantly, increases in c-Fos expression and HAL efficacy in the CAR test of the HAL+VPA and HAL+MS-275 groups were correlated with elevated histone acetylation at the c-fos promoter region in aged mice. These findings suggest that pretreatment with VPA or MS-275 increases the behavioral and molecular effects of HAL in aged mice and that these effects occur via modulation of age-related histone hypoacetylation in the nucleus accumbens shell and prefrontal cortex.

Electro-acupuncture upregulates CGRP expression after rat spinal cord transection.

Calcitonin gene-related peptide (CGRP) plays a variety of important roles within the nervous system. Increasing CGRP expression could improve the survival of injured neurons and prevent neuronal loss. In this study, we first evaluated in vitro the neuroprotective function of CGRP on mechanically injured cerebellar granule neurons (CGNs) of rats. We then verified this result through exogenous administration of CGRP in a spinal cord transected completely in rats. Finally, we investigated the effect of electro-acupuncture (EA) on CGRP expression following the spinal cord transected completely in rats. We found that EA can improve CGRP expression, and exogenous CGRP may promote the survival of injured neurons, both in vivo and in vitro. Our results suggest that CGRP may be a specific neuropeptide expressed in GV-EA treatment of spinal cord injuries (SCI), and that CGRP may play a neuroprotective role in survival of neurons injured mechanically.