Tropomodulin's Actin-Binding Abilities Are Required to Modulate Dendrite Development

The Role of Preoperative Chronic Hypertension in Neurocognitive Decline after Cardiac Surgery: A Retrospective Cohort Study

INTRODUCTION

Patients frequently experience transient postoperative neurocognitive decline (NCD) after cardiac surgery with cardiopulmonary bypass. The goal of this study is to describe preoperative high blood pressure as a risk factor for NCD and use genomic expression to uncover its contribution to the pathophysiology of NCD.

METHODS

This is a retrospective analysis of cohort study at a single academic center. Patients undergoing cardiac surgery with the use of cardiopulmonary bypass were administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) preoperatively, at postoperative day four, and four weeks postoperatively. Electronic medical records were reviewed for all recorded blood pressure from the year preceding surgery and intraoperative blood pressures. Blood samples were collected six hours preoperatively and six hours postoperatively to assess messenger ribonucleic acid expression.

RESULTS

Eighty-seven patients completed postoperative day four testing, of whom thirty-seven experienced NCD (42.5%). Chronically elevated systolic blood pressure over the year preceding surgery was correlated with greater negative change in RBANS score at postoperative day four (P=0.03). Upon genomic analysis, macrophage markers were upregulated preoperatively, and anti-inflammatory and neuroprotective genes were downregulated postoperatively among patients who had a mean systolic blood pressure ≥ 130 mmHg.

CONCLUSION

Chronic exposure to elevated preoperative systolic blood pressure may increase the risk of NCD. The contributing role of preoperative hypertension in NCD may be partly explained by reduced attenuation of oxidative stress, increased inflammation, and reduced neuroprotection and heme metabolism postoperatively. This must be considered when assessing patient risks for cardiac surgery.

Intra-amniotic delivery of tropomodulin 3 rescues cell apoptosis induced by miR-200b-3p upregulation via non-canonical nuclear factor kappa B pathways in ethylene thiourea induced anorectal malformations fetal rat

Ethylene thiourea (ETU), a metabolite of the fungicide ethylene bisdithiocarbamate (EBDC), has received great concern because of its harmful effects. ETU-induced anorectal malformations (ARMs) in rat models have been reported and widely used in the study of ARMs embryogenesis. Dysplasia of the lumbosacral spinal cord (LSSC), pelvic floor muscles (PFMs), and hindgut (HG) during intrauterine life affects postoperative defecation in patients with ARMs. However, the underlying toxic effects of ETU and pathological mechanisms in the three defecation-related tissues of fetuses with ARMs have not been reported. Thus, this study aimed to elucidate the molecular mechanisms involved in ARMs, with a focus on the dysregulation of miR-200b-3p and its downstream target tropomodulin 3 (TMOD3). The mRNA and protein levels of miR-200b-3p and TMOD3 in LSSC, PFMs, and HG of fetal rats with ARMs were evaluated by reverse transcription quantitative polymerase chain reaction and Western blotting (WB) on embryonic day 17 (E17). Further, a dual-luciferase reporter assay confirmed their targeting relationship. Gene silencing and overexpression of miR-200b-3p and TMOD3 were performed to verify their functions in HEK-293 T cells. Fetal rats with ARMs also received intra-amniotic microinjection of Ad-TMOD3 on E15, and key molecules in nuclear factor kappa (NF-κB) signaling and apoptosis were evaluated by WB on E21. Abnormally high levels of miR-200b-3p inhibited TMOD3 expression by binding with its 3'-untranslated region, leading to the activation of the non-canonical NF-κB signaling pathway, which is critical in the maldevelopment of LSSC, PFMs, and HG in ARMs rats. Furthermore, miR-200b-3p triggered apoptosis by directly targeting TMOD3. Notably, intra-amniotic Ad-TMOD3 microinjection revealed that the upregulation of TMOD3 expression mitigates the effects of miR-200b-3p on the activation of non-canonical NF-κB signaling and apoptosis in fetal rat model of ARMs. A novel miR-200b-3p/TMOD3/non-canonical NF-κB signaling axis triggered the massive apoptosis in LSSC, PFMs, and HG of ARMs, which was restored by the intra-amniotic injection of Ad-TMOD3 during embryogenesis. Our results indicate the potential of TMOD3 as a treatment target to restore defecation.

Proteomic changes in the hippocampus of large mammals after total-body low dose radiation

There is a growing interest in low dose radiation (LDR) to counteract neurodegeneration. However, LDR effects on normal brain have not been completely explored yet. Recent analyses showed that LDR exposure to normal brain tissue causes expression level changes of different proteins including neurodegeneration-associated proteins. We assessed the proteomic changes occurring in radiated vs. sham normal swine brains. Due to its involvement in various neurodegenerative processes, including those associated with cognitive changes after high dose radiation exposure, we focused on the hippocampus first. We observed significant proteomic changes in the hippocampus of radiated vs. sham swine after LDR (1.79Gy). Mass spectrometry results showed 190 up-regulated and 120 down-regulated proteins after LDR. Western blotting analyses confirmed increased levels of TPM1, TPM4, PCP4 and NPY (all proteins decreased in various neurodegenerative processes, with NPY and PCP4 known to be neuroprotective) in radiated vs. sham swine. These data support the use of LDR as a potential beneficial tool to interfere with neurodegenerative processes and perhaps other brain-related disorders, including behavioral disorders.

Effects of Tropomodulin 2 on Dendritic Spine Reorganization and Dynamics

Dendritic spines are actin-rich protrusions that receive a signal from the axon at the synapse. Remodeling of cytoskeletal actin is tightly connected to dendritic spine morphology-mediated synaptic plasticity of the neuron. Remodeling of cytoskeletal actin is required for the formation, development, maturation, and reorganization of dendritic spines. Actin filaments are highly dynamic structures with slow-growing/pointed and fast-growing/barbed ends. Very few studies have been conducted on the role of pointed-end binding proteins in the regulation of dendritic spine morphology. In this study, we evaluated the role played by tropomodulin 2 (Tmod2)-a brain-specific isoform, on the dendritic spine re-organization. Tmod2 regulates actin nucleation and polymerization by binding to the pointed end via actin and tropomyosin (Tpm) binding sites. We studied the effects of Tmod2 overexpression in primary hippocampal neurons on spine morphology using confocal microscopy and image analysis. Tmod2 overexpression decreased the spine number and increased spine length. Destroying Tpm-binding ability increased the number of shaft synapses and thin spine motility. Eliminating the actin-binding abilities of Tmod2 increased the number of mushroom spines. Tpm-mediated pointed-end binding decreased F-actin depolymerization, which may positively affect spine stabilization; the nucleation ability of Tmod2 appeared to increase shaft synapses.

Alterations in the Proteome of Developing Neocortical Synaptosomes in the Absence of MET Signaling Revealed by Comparative Proteomics

Alterations in the expression of genes encoding proteins involved in synapse formation, maturation, and function are a hallmark of many neurodevelopmental and psychiatric disorders. For example, there is reduced neocortical expression of the MET receptor tyrosine kinase (MET) transcript and protein in Autism Spectrum Disorder (ASD) and Rett syndrome. Preclinical in vivo and in vitro models manipulating MET signaling reveal that the receptor modulates excitatory synapse development and maturation in select forebrain circuits. The molecular adaptations underlying the altered synaptic development remain unknown. We performed a comparative mass spectrometry analysis of synaptosomes generated from the neocortex of wild type and Met null mice during the peak of synaptogenesis (postnatal day 14; data are available from ProteomeXchange with identifier PXD033204). The analyses revealed broad disruption of the developing synaptic proteome in the absence of MET, consistent with the localization of MET protein in pre- and postsynaptic compartments, including proteins associated with the neocortical synaptic MET interactome and those encoded by syndromic and ASD risk genes. In addition to an overrepresentation of altered proteins associated with the SNARE complex, multiple proteins in the ubiquitin-proteasome system and associated with the synaptic vesicle, as well as proteins that regulate actin filament organization and synaptic vesicle exocytosis/endocytosis, were disrupted. Taken together, the proteomic changes are consistent with structural and functional changes observed following alterations in MET signaling. We hypothesize that the molecular adaptations following Met deletion may reflect a general mechanism that produces circuit-specific molecular changes due to loss or reduction of synaptic signaling proteins.

Cleavage of tropomodulin-3 by asparagine endopeptidase promotes cancer malignancy by actin remodeling and SND1/RhoA signaling

Background

Abnormal proliferation and migration of cells are hallmarks of cancer initiation and malignancy. Asparagine endopeptidase (AEP) has specific substrate cleavage ability and plays a pro-cancer role in a variety of cancers. However, the underlying mechanism of AEP in cancer proliferation and migration still remains unclear.

Methods

Co-immunoprecipitation and following mass spectrometry were used to identify the substrate of AEP. Western blotting was applied to measure the expression of proteins. Single cell/nuclear-sequences were done to detect the heterogeneous expression of Tmod3 in tumor tissues. CCK-8 assay, flow cytometry assays, colony formation assay, Transwell assay and scratch wound-healing assay were performed as cellular functional experiments. Mouse intracranial xenograft tumors were studied in in vivo experiments.

Results

Here we showed that AEP cleaved a ubiquitous cytoskeleton regulatory protein, tropomodulin-3 (Tmod3) at asparagine 157 (N157) and produced two functional truncations (tTmod3-N and tTmod3-C). Truncated Tmod3 was detected in diverse tumors and was found to be associated with poor prognosis of high-grade glioma. Functional studies showed that tTmod3-N and tTmod3-C enhanced cancer cell migration and proliferation, respectively. Animal models further revealed the tumor-promoting effects of AEP truncated Tmod3 in vivo. Mechanistically, tTmod3-N was enriched in the cell cortex and competitively inhibited the pointed-end capping effect of wild-type Tmod3 on filamentous actin (F-actin), leading to actin remodeling. tTmod3-C translocated to the nucleus, where it interacted with Staphylococcal Nuclease And Tudor Domain Containing 1 (SND1), facilitating the transcription of Ras Homolog Family Member A/Cyclin Dependent Kinases (RhoA/CDKs).

Conclusion

The newly identified AEP-Tmod3 protease signaling axis is a novel “dual-regulation” mechanism of tumor cell proliferation and migration. Our work provides new clues to the underlying mechanisms of cancer proliferation and invasive progression and evidence for targeting AEP or Tmod3 for therapy.

Vibrio splendidus flagellin C binds tropomodulin to induce p38 MAPK-mediated p53-dependent coelomocyte apoptosis in Echinodermata

As a typical pathogen-associated molecular pattern, bacterial flagellin can bind Toll-like receptor 5 and the intracellular NAIP5 receptor component of the NLRC4 inflammasome to induce immune responses in mammals. However, these flagellin receptors are generally poorly understood in lower animal species. In this study, we found that the isolated flagellum of Vibrio splendidus AJ01 destroyed the integrity of the tissue structure of coelomocytes and promoted apoptosis in the sea cucumber Apostichopus japonicus. To further investigate the molecular mechanism, the novel intracellular LRR domain-containing protein tropomodulin (AjTmod) was identified as a protein that interacts with flagellin C (FliC) with a dissociation constant (K_d) of 0.0086 ± 0.33 μM by microscale thermophoresis assay. We show that knockdown of AjTmod also depressed FliC-induced apoptosis of coelomocytes. Further functional analysis with different inhibitor treatments revealed that the interaction between AjTmod and FliC could specifically activate p38 MAPK, but not JNK or ERK MAP kinases. We demonstrate that the transcription factor p38 is then translocated into the nucleus, where it mediates the expression of p53 to induce coelomocyte apoptosis. Our findings provide the first evidence that intracellular AjTmod serves as a novel receptor of FliC and mediates p53-dependent coelomocyte apoptosis by activating the p38 MAPK signaling pathway in Echinodermata.

Tropomodulin1 Expression Increases Upon Maturation in Dendritic Cells and Promotes Their Maturation and Immune Functions

Dendritic cells (DCs) are the most potent antigen-presenting cells. Upon maturation, DCs express costimulatory molecules and migrate to the lymph nodes to present antigens to T cells. The actin cytoskeleton plays key roles in multiple aspects of DC functions. However, little is known about the mechanisms and identities of actin-binding proteins that control DC maturation and maturation-associated functional changes. Tropomodulin1 (Tmod1), an actin-capping protein, controls actin depolymerization and nucleation. We found that Tmod1 was expressed in bone marrow-derived immature DCs and was significantly upregulated upon lipopolysaccharide (LPS)-induced DC maturation. By characterizing LPS-induced mature DCs (mDCs) from Tmod1 knockout mice, we found that compared with Tmod1+/+ mDCs, Tmod1-deficient mDCs exhibited lower surface expression of costimulatory molecules and chemokine receptors and reduced secretion of inflammatory cytokines, suggesting that Tmod1 deficiency retarded DC maturation. Tmod1-deficient mDCs also showed impaired random and chemotactic migration, deteriorated T-cell stimulatory ability, and reduced F-actin content and cell stiffness. Furthermore, Tmod1-deficient mDCs secreted high levels of IFN-β and IL-10 and induced immune tolerance in an experimental autoimmune encephalomyelitis (EAE) mouse model. Mechanistically, Tmod1 deficiency affected TLR4 signaling transduction, resulting in the decreased activity of MyD88-dependent NFκB and MAPK pathways but the increased activity of the TRIF/IRF3 pathway. Rescue with exogenous Tmod1 reversed the effect of Tmod1 deficiency on TLR4 signaling. Therefore, Tmod1 is critical in regulating DC maturation and immune functions by regulating TLR4 signaling and the actin cytoskeleton. Tmod1 may be a potential target for modulating DC functions, a strategy that would be beneficial for immunotherapy for several diseases.

Comparative Proteomic Analysis of Differentially Expressed Proteins between Injured Sensory and Motor Nerves after Peripheral Nerve Transection

Peripheral nerve repair and functional recovery depend on the rate of nerve regeneration and the quality of target reinnervation. It is important to fully understand the cellular and molecular basis underlying the specificity of peripheral nerve regeneration, which means achieving corresponding correct pathfinding and accurate target reinnervation for regrowing motor and sensory axons. In this study, a quantitative proteomic technique, based on isobaric tags for relative and absolute quantitation (iTRAQ), was used to profile the protein expression pattern between single motor and sensory nerves at 14 days after peripheral nerve transection. Among a total of 1259 proteins identified, 176 proteins showed the differential expressions between injured motor and sensory nerves. Quantitative RT-PCR and western blot analysis were applied to validate the proteomic data on representative differentially expressed proteins. Functional categorization indicated that differentially expressed proteins were linked to a diverse array of molecular functions, including axonogenesis, response to axon injury, tissue remodeling, axon ensheathment, cell proliferation and adhesion, vesicle-mediated transport, response to oxidative stress, internal signal cascade, and macromolecular complex assembly, which might play an essential role in peripheral motor and sensory nerve regeneration. Overall, we hope that the proteomic database obtained in this study could serve as a solid foundation for the comprehensive investigation of differentially expressed proteins between injured motor and sensory nerves and for the mechanism elucidation of the specificity of peripheral nerve regeneration. Data are available via ProteomeXchange with identifier PXD022097.

Roles of the actin cytoskeleton in aging and age-associated diseases

The integrity of the cytoskeleton is essential to diverse cellular processes such as phagocytosis and intracellular trafficking. Disruption of the organization and dynamics of the actin cytoskeleton leads to age-associated symptoms and diseases, ranging from cancer to neurodegeneration. In addition, changes in the integrity of the actin cytoskeleton disrupt the functioning of not only somatic and stem cells but also gametes, resulting in aberrant embryonic development. Strategies to preserve the integrity and dynamics of the cytoskeleton are, therefore, potentially therapeutic to age-related disorders. The objective of this article is to revisit the current understanding of the roles played by the actin cytoskeleton in aging, and to review the opportunities and challenges for the transition of basic research into intervention development. It is hoped that, with the snapshot of evidence regarding changes in actin dynamics with advanced age, insights into future research directions can be attained.

Network Medicine Approach for Analysis of Alzheimer's Disease Gene Expression Data

Alzheimer’s disease (AD) is the most widespread diagnosed cause of dementia in the elderly. It is a progressive neurodegenerative disease that causes memory loss as well as other detrimental symptoms that are ultimately fatal. Due to the urgent nature of this disease, and the current lack of success in treatment and prevention, it is vital that different methods and approaches are applied to its study in order to better understand its underlying mechanisms. To this end, we have conducted network-based gene co-expression analysis on data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. By processing and filtering gene expression data taken from the blood samples of subjects with varying disease states and constructing networks based on that data to evaluate gene relationships, we have been able to learn about gene expression correlated with the disease, and we have identified several areas of potential research interest.