Factors related to a sense of economic insecurity among older adults who participate in social activities.

Japan has the highest life expectancy worldwide. Older adults who experience economic insecurity may refrain from seeking medical consultation or using long-term care insurance, and these behaviors may increase the incidence and progression of frailty. This study conducted a cross-sectional survey to identify factors related to a sense of economic insecurity among older adults who participate in social activities, and identified support measures. In total, 1,351 older adults aged ≥65 years who had participated in social activities voluntarily completed an anonymous self-administered questionnaire. The questionnaire encompassed their physical, cognitive, social, and psychological conditions, and economic insecurity. We performed univariate analysis considering a sense of economic insecurity as the dependent variable, and conducted multiple logistic regression analysis (forced entry method) considering the independent variables with p<0.1 as the covariates. Among the 872 filled questionnaires, 717 were analyzed as they had no missing data with respect to the responses to survey questions (valid response rate was 53.1%). Analysis results showed that 43.6% of the older adults had a sense of economic insecurity, which was most common among those aged 75-84 years, accounting for 47.3%, followed by those aged 65-74 years accounting for 44.1%, and those aged ≥85 years accounting for 31.5% (p<0.05). The sense of economic insecurity was not associated with physical conditions, subjective symptoms of dementia, or social conditions; however, it grew with increased loneliness (OR: 1.71, 1.002-2.92, p = 0.049) and decreased with an increased subjective sense of well-being (OR: 0.86, 0.81-0.92, <0.001). Economic insecurity among older adults was not associated with physical, cognitive, or social aspects, as reported in previous studies. The survey respondents constituted older adults who participate in social activities. Maintaining interactions within the community, even in old age, may prevent loneliness and improve subjective health.

Developing a scale for examining the perspective of university students on parental care.

Introduction: With the declining birth rate and increasingly aging population in Japan, an increased care burden may be placed on the family and the younger generation will address challenging circumstances when they can care for their parents. This study aimed to develop a scale for examining the perspectives of Japanese university students on parental care and determines its reliability and validity. Methods: A web-based survey on a total of 408 Japanese students was adopted. This study performed exploratory and confirmatory factor analyses to obtain the underlying factors of the scale. Reliability was verified using Cronbach's α coefficient and Spearman-Brown's split-half reliability α coefficient. Validity was verified through sample, criterion-related, and convergent and discriminant validity. Results: In total, the study identified a three-factor 11 item-scale. Cronbach's α for the scale was 0.901, and the Cronbach's α and split-half reliability α coefficients of each factor were greater than 0.7. Three factors explained 64.6% of the total variance. The model indicators were χ2/df = 2.241, comparative fit index (CFI) = 0.951, incremental fit index (IFI) = 0.951, TLI = 0.942, root mean square error of approximation (RMSEA) = 0.078 (p < 0.001). Thus, the study confirmed that the convergent and discriminant validity is acceptable. Correlations were noted for criterion-related validity (r = 0.675, p < 0.001). Discussion: The results show that the scale for examining the perspective of Japanese university students on parental care was confirmed with good reliability and validity.

Cross-cultural metathemes of Chinese and Japanese university students' perspective on parental care.

Introduction: Due to declining birthrates and aging populations, parental care is going to place a greater burden on younger generations in the future, especially in East Asia where it is more common for children to provide care regardless of whether there is a national long-term care insurance program. Therefore, it has become important to understand the younger generation's views on parental care. Methods: An explorative, metathematic qualitative study design was used. Data collection relied on semi-structured interviews, of which 19 Chinese and 19 Japanese university students were conducted from December 2021 to July 2022 using a snowball sampling method. Metatheme analysis was then used to identify broad cross-cultural metathemes and inter-relationships on parental care. Results: Three parental care metathemes were identified for the perspectives of parental care: distrust of leaving parental care to others, responsibility to care for their parents, and importance of parent-child interactions about parental care. Conclusion: To improve social support for care, both countries must improve long-term care service delivery and healthcare systems and ensure that there is a trusting relationship between healthcare professionals and the public. Governments should also ensure that adult children receive assistance to balance their work, life, and parental care responsibilities. The findings provide several practical suggestions for improving healthcare systems in China and Japan through the younger generations' views.

A novel technique of STEM observation of TEM section using LVSEM and application of pathological diagnosis of renal biopsy.

The usefulness of the transmission electron microscope (TEM) for pathological diagnosis is apparent. However, high operating costs and other disadvantages have limited the ability to maintain and operate a TEM. In recent years, a general-purpose benchtop low-vacuum scanning electron microscope (LVSEM), which is inexpensive and easy to operate, has been developed and is expected to be applied in electron microscopic pathological diagnosis. To date, we have previously observed TEM ultrathin sections of Immunoglobulin A (IgA) nephropathy with a benchtop LVSEM using an ultra variable-pressure detector (UVD) and a newly developed holder for observing scanning transmission electron microscope (STEM) images (UVD-STEM holder) and compared the images with those obtained with typical TEM observations. We reported the results in the 53rd Annual Meeting of the Japanese Society for Clinical Molecular Morphology and the 64th Symposium of The Japanese Society of Microscopy and discussed the validity of the methods in the pathological diagnosis of IgA nephropathy and other renal diseases. As a result, we demonstrated the potential for pathological diagnosis using benchtop LVSEM. In this study, we similarly examined typical kidney diseases such as membranous nephropathy, lupus nephritis and amyloidosis. We could obtain sufficient data for the pathological diagnosis of IgA nephropathy, membranous nephropathy and lupus nephritis. However, it is difficult to detect amyloid fibres that are characteristic of amyloidosis. The development of this method is expected to expand the possibilities for pathological diagnosis using electron microscopy, including its application to other diseases.

High concentration of extracellular nucleotides suppresses cell growth via delayed cell cycle progression in cancer and noncancer cell lines.

Tumor necrosis frequently occurs in malignant tumors, showing rapid growth and invasion. This phenomenon is generally regarded as simple ischemic necrosis due to insufficient tumor vessels and blood supply. However, the necrotic tissue contains high amount of nuclear substances, DNA, and nucleoproteins that may affect the surrounding tumor cells by promoting or suppressing the tumor cell growth in vivo. This study focused on the effects of an externally administered water-soluble nuclear crude extract (SNE) containing nuclear protein and oligonucleotides on several human cancer and noncancer cell lines. The results demonstrated that the SNE suppressed cell growth in cancer and noncancer cells in vitro. Through the flow cytometry analysis of the nuclear DNA content, it was observed that the SNE increased and decreased cell proportion in the S and G2/M phases, respectively, thereby suggesting that the cell growth inhibition was due to cell cycle delay, and not due to apoptosis. These studies suggest that the high-concentration of extracellular nucleotides generated as a result of tumor necrosis and/or released from infiltrated neutrophils could suppress the growth of surrounding cancer and intrinsic cells, which provides us some insights into an alternative anticancer strategy for patients with highly malignant necrotic tumor.

Prognostic evaluation of branch atheromatous disease in the pons using carotid artery ultrasonography.

BACKGROUND: Branch atheromatous disease is an ischemic stroke, involving occlusion or severe stenosis of the perforating artery, causing neurologic symptoms and serious sequelae. We aimed to investigate initial morphometric and hemodynamic characteristics of the vertebral artery immediately post-onset to predict lesion expanding. METHODS: This case-control study collected demographic, historical, and physical examination data from 44 patients with branch atheromatous disease in the pons at admission. The maximum ischemic pons area and stenosis rate in the basilar artery were calculated using magnetic resonance images. Diameter, velocity, and flow volume of the vertebral arteries were measured using carotid artery ultrasonography. Correlations between ischemic lesion extent and these parameters were investigated. RESULTS: Patients were assigned to groups of less (Group 1) or more (Group 2) than the median maximum ischemic area in the pons, calculated from magnetic resonance images (121.6 mm2). Modified Rankin scale scores were significantly worse in Group 2. Blood pressure and blood findings were similar between groups. Group 2 showed significantly higher basilar artery stenosis rates. Flow volume, velocity, peak systolic velocity, and end-diastolic velocity in the vertebral artery on both sides were significantly decreased in Group 2. CONCLUSIONS: Deteriorated vertebral artery hemodynamics caused a more extensive ischemic lesion in branch atheromatous disease in the pons. Evaluation of the vertebral using carotid artery ultrasonography in the acute phase may be useful for predicting disease progression.

The role of caregiver burden in the familial functioning, social support, and quality of family life of family caregivers of elders with dementia.

Objective: The present study aimed to examine the role that caregiver burden plays in the familial functioning, social support, and quality of family life (QOFL) of caregivers of elderly family members with dementia. Methods: A survey was conducted with 200 primary caregivers of elderly dementia patients who resided in prefecture "S". The questionnaire consisted of items that required demographic information, the Japanese versions of the Zarit Burden Inventory (ZBI) and the Family Adaptability and Cohesion Evaluation Scales (FACES II), and scales that measure quality of family life and social support. On the basis of the median ZBI score (i.e., 30.8), participants were divided into two groups: group A (i.e., ZBI score < 30) and group B (i.e., ZBI score > 30). Stepwise multiple regression analysis was conducted with QOFL as the dependent variable. Version 24 of the Statistical Package for the Social Sciences for Windows was used to conduct all the statistical analyses; the statistical significance level was specified as 0.05. Results: Group A and B obtained average ZBI scores of 18.5 and 43.8, respectively. The study targeted 81 patients from group A (average age = 61.0 years) and 77 patients from group B (average age = 61.7 years). Time that was spent on caregiving tasks was significantly higher for group B, when compared to group A. In addition, significant differences in cohesion and adaptability, which are two dimensions that are measured by the FACES II, and QOFL emerged between the two groups. The results of the multiple regression analysis showed that cohesion (ß = 0.38), practical support (ß = 0.32), adaptability (ß = 0.30), and living arrangement (ß = -0.12) significantly predicted QOFL. Conclusion: Family cohesion and adaptability are indicators of healthy familial functioning. In order to improve the QOFL of caregivers of elderly dementia patients, it is necessary to strengthen emotional ties, maintain emotional attachment, and flexibly respond to the burden of nursing care and changes in power structures and role relationships.

Quantitative analysis of the elastic fiber in the tunica media at the carotid bifurcation.

In this study, the results of our previously reported technique of quantitative analysis by using microscopic image analysis of tissue image slices to calculate the proportion of the area of the tunica media occupied by of elastic fibers was compared with Janzen et al.'s technique at the carotid bifurcation. This particularly analyzed the area of transition between the common carotid and the internal carotid, to observe the quantitative changes in elastic fiber content. The data obtained from our quantitative analysis of elastic fibers were clearly at variance with those obtained by counting the number of elastic fibers. The amount of elastic fibers in the tunica media (the elastic fiber ratio) decreased from the proximal carotid artery (the common carotid) to the bifurcation, then peaked in the internal carotid immediately after the bifurcation before declining again.

Intracranial Bony Canal of the Middle Meningeal Artery - Morphological and Histological Analysis.

The middle meningeal artery (MMA) can play an important role in the surgical revascularization. However, the MMA can be easily injured if it passes through a bony canal. We investigated the morphological and histological features of the bony canal to improve surgical results. MATERIALS AND METHODS: Fifty adult dry skulls were investigated. The length of the bony canal and the distance from the orbital rim to the bony canal were measured. Additionally, 28 cadaveric heads were examined histologically. RESULTS: Sixty-three bony canals were found in 43 skulls. The mean length of bony canals was 9.2 mm, and the mean distance from the orbital rim was 24.0 mm. The bony canal ran mainly from the sphenoid bone (69.8%) to the parietal bone (73.0%). Histologically, both sides of the meningeal grooves gradually closed the distance, and formed the bony canal. The MMA inside the bony canal was enveloped with collagen tissues, divided into branches, and was accompanied by the vein. CONCLUSIONS: The bony canal is located around the pterion and is formed during bone growth. The MMA is covered with collagen tissues inside the bony canal. It is possible to safely expose and preserve the MMA during craniotomy with careful drilling.

Sex differences in morphometric aspects of the peripheral nerves and related diseases.

BACKGROUND: The elucidation of the relationship between the morphology of the peripheral nerves and the diseases would be valuable in developing new medical treatments on the assumption that characteristics of the peripheral nerves in females are different from those in males. METHODS: We used 13 kinds of the peripheral nerve. The materials were obtained from 10 Japanese female and male cadavers. We performed a morphometric analysis of nerve fibers. We estimated the total number of myelinated axons, and calculated the average transverse area and average circularity ratio of myelinated axons in the peripheral nerves. RESULTS: There was no statistically significant difference in the total number, average transverse area, or average circularity ratio of myelinated axons between the female and male specimens except for the total number of myelinated axons in the vestibular nerve and the average circularity ratio of myelinated axons in the vagus nerve. CONCLUSIONS: The lower number of myelinated axons in the female vestibular nerve may be one of the reasons why vestibular disorders have a female preponderance. Moreover, the higher average circularity ratio of myelinated axons in the male vagus nerve may be one reason why vagus nerve activity to modulate pain has a male preponderance.

Presynaptic protein Synaptotagmin1 regulates the neuronal polarity and axon differentiation in cultured hippocampal neurons.

BACKGROUND: Hippocampal neurons in the brain polarize to form multiple dendrites and one long axon. The formation of central synapses remains poorly understood. Although several of the intracellular proteins involved in the clustering of central neurotransmitter receptors and ion channels have been identified, the signals involved in pre- and postsynaptic differentiation remain elusive. Synaptotagmin1 is an abundant and important presynaptic vesicle protein that binds Ca(2+) (J Biol Chem 277:7629-7632, 2002) in regulation of synaptic vesicle exocytosis at the synapse. Synapse consists of the formation of synaptic connections and requires precise coordination of Synaptotagmin1. It was reported Synaptotagmin1 plays an important roles in the formation of axonal filopodia and branches in chicken forebrain neurons (Dev Neurobiol 73:27-44, 2013). To determine if Synaptotagmin1 could have a role in formation of axon in hippocampal neurons, we investigated the effects of Synaptotagmin1 overexpression and knockdown using the shRNA on the growth and branching of the axons of primary hippocampal neurons. We showed that overexpression of Synaptotagmin1 leads to abnormal multiple axon formation in cultured rat hippocampal neurons. RESULTS: We first examined the effects of Synaptotagmin1 on the numbers of axon and dendrites. We found that the overexpression of Synaptotagmin1 led to the formation of multiple axons and induced an increase in the number of endogenous postsynaptic protein Homer1c clusters in cultured hippocampal neurons. Endogenous initial segment of axon was detected with anti-sodium channel (anti-NaCh) antibody and with anti-Tau1 (J Neurosci 24: 4605-4613, 2004). The endogenous initial segment of axon was stained with anti-NaCh antibodies and with anti-Tau1 antibodies. Then the numbers of prominence dyed positive were counted as axon. We attempted to specifically knockdown the endogenous Synaptotagmin1 with small hairpin RNAs (shRNAs). To further dissect the functions of endogenous Synaptotagmin1 in neuronal polarity, we used the shRNA of Synaptotagmin1 that specifically blocks the existence of endogenous Synaptotagmin1. When the shRNA of Synaptotagmin1 was introduced to the cells, the number of axons and dendrites did not change. CONCLUSIONS: These results indicate that the accumulation of Synaptotagmin1 may play an important role in axon/dendrite differentiation.

Cell Membrane Perforation with Photosensitizer and a Brush-shaped Soft-polymer Sheet Using a Malignant Glioma Cell Line.

BACKGROUND: Transduction of foreign molecules into cells is an important technique to investigate the functions of corresponding molecules and/or targets. Recently, a mass-producible nanoprinting perforator was devised enabling for large-scale, high-performance drug or nucleic-acid transfer into cells without cell damage. Since little is known on the performance of the system, we investigated its effects on a malignant glioma cell line. MATERIALS AND METHODS: Photosensitization was performed by the Cell Stamper CP-01. The malignant U373MG glioma cell line was used for transduction. RESULTS: Photosensitization transduced FITC-conjugated albumin into cells. Trypan blue inclusion test demonstrated membrane disintegration by the procedure and scanning electron microscopy disclosed perforation of the cell membrane. CONCLUSION: Local oxidation reaction during the nanoprinting caused reversible membrane perforation. Morphological findings from the current study support the above mechanism, therefore the specific printing system might be convenient for transduction of foreign molecules into malignant glioma cells.

Effects of silica and titanium oxide particles on a human neural stem cell line: morphology, mitochondrial activity, and gene expression of differentiation markers.

Several in vivo studies suggest that nanoparticles (smaller than 100 nm) have the ability to reach the brain tissue. Moreover, some nanoparticles can penetrate into the brains of murine fetuses through the placenta by intravenous administration to pregnant mice. However, it is not clear whether the penetrated nanoparticles affect neurogenesis or brain function. To evaluate its effects on neural stem cells, we assayed a human neural stem cell (hNSCs) line exposed in vitro to three types of silica particles (30 nm, 70 nm, and <44 µm) and two types of titanium oxide particles (80 nm and < 44 µm). Our results show that hNSCs aggregated and exhibited abnormal morphology when exposed to the particles at concentrations = 0.1 mg/mL for 7 days. Moreover, all the particles affected the gene expression of Nestin (stem cell marker) and neurofilament heavy polypeptide (NF-H, neuron marker) at 0.1 mg/mL. In contrast, only 30-nm silica particles at 1.0 mg/mL significantly reduced mitochondrial activity. Notably, 30-nm silica particles exhibited acute membrane permeability at concentrations =62.5 µg/mL in 24 h. Although these concentrations are higher than the expected concentrations of nanoparticles in the brain from in vivo experiments in a short period, these thresholds may indicate the potential toxicity of accumulated particles for long-term usage or continuous exposure.

Cell-based in vitro blood-brain barrier model can rapidly evaluate nanoparticles' brain permeability in association with particle size and surface modification.

The possibility of nanoparticle (NP) uptake to the human central nervous system is a major concern. Recent reports showed that in animal models, nanoparticles (NPs) passed through the blood-brain barrier (BBB). For the safe use of NPs, it is imperative to evaluate the permeability of NPs through the BBB. Here we used a commercially available in vitro BBB model to evaluate the permeability of NPs for a rapid, easy and reproducible assay. The model is reconstructed by culturing both primary rat brain endothelial cells and pericytes to support the tight junctions of endothelial cells. We used the permeability coefficient (P(app)) to determine the permeability of NPs. The size dependency results, using fluorescent silica NPs (30, 100, and 400 nm), revealed that the Papp for the 30 nm NPs was higher than those of the larger silica. The surface charge dependency results using Qdots® (amino-, carboxyl-, and PEGylated-Qdots), showed that more amino-Qdots passed through the model than the other Qdots. Usage of serum-containing buffer in the model resulted in an overall reduction of permeability. In conclusion, although additional developments are desired to elucidate the NPs transportation, we showed that the BBB model could be useful as a tool to test the permeability of nanoparticles.

Presynaptic protein synaptotagmin1 regulates the activity-induced remodeling of synaptic structures in cultured hippocampal neurons.

Activity-dependent reorganizations of central neuronal synapses are thought to play important roles in learning and memory. Although the precise mechanisms of how neuronal activities modify synaptic connections in neurons remain to be clarified, the activity-induced neuronal presynaptic proteins such as synaptotagmin1 may contribute to the onset of synaptic remodeling. To understand better the physiological roles of synaptotagmin1, we first examined the prolonged effects of neuronal stimulation capable of inducing synaptotagmin1 on the distribution of a postsynaptic proteins (PSD) protein Homer1c by immunostaining. Previously we found that glutamate stimulation induced other postsynaptic proteins, such as postsynaptic density-95 (PSD95), a biphasic change with an initially diffuse distribution after 30 min to 1 hr, followed by reassembly to more than the original level after 4-8 hr, suggesting that glutamate stimulation induces a global biphasic alteration in synaptic structures. To dissect further the functions of synaptotagmin1 in the activity-induced synaptic remodeling, short hairpin RNA (shRNA) vectors that specifically block the expression of endogenous synaptotagmin1 were constructed. When the shRNA of synaptotagmin1 was introduced to the neurons, the activity-induced changes were almost completely suppressed. We found that synaptotagmin1 contributes to the postsynaptic remodeling in a retrograde manner. Our data indicate that synaptotagmin1 regulates the activity-induced biphasic changes of post- and presynaptic sites.

Expression of mRNAs of urocortin and corticotropin-releasing factor receptors in malignant glioma cell lines.

BACKGROUND: Urocortin and corticotropin-releasing factors (CRFs) and their receptors are expressed in many organs, including the central nervous system. In this study, the expression of mRNAs of urocortin 1, 2, 3, and CRF and CRF receptors 1 and 2 in malignant glioma, was examined. MATERIALS AND METHODS: The RNAs of human and rat glioma cell lines were isolated. Transcripts in these cells were analyzed using cDNA. In addition, the effects of proliferative and cytotoxic stimulation by serum supplementation, ionizing radiation, and the antineoplastic agent temozolomide were investigated. RESULTS: Human and rat cells transcribed urocortin. CRF receptors were detected in human glioma cells. When human KNS42 cells were exposed to stimulation, transcription was altered according to the specific condition. CONCLUSION: Expression of mRNAs of urocortin and CRF receptors was confirmed in human glioma cell lines. Although the quantities of transcripts varied with the proliferative and cytotoxic stimulation, the overall transcription pattern was not influenced by these stimuli.

Down-regulation of EGFR prolonged cell growth of glioma but did not increase the sensitivity to temozolomide.

BACKGROUND: Malignant glioma is an invasive disease of the central nervous system. One of the factors that regulate growth of these tumors is expression of epidermal growth factor receptor (EGFR) in the cells. This study investigated the effects of down-regulation of EGFR on cell proliferation, cell cycle and cytotoxicity to antineoplastic agent. MATERIALS AND METHODS: A short hairpin RNA transcription vector targeting EGFR was transfected into KNS42 cells. Growth curve, cell cycle and sensitivity to temozolomide of the cells were assessed. RESULTS: Transfection inhibited EGFR expression by 50.5%. It prolonged cell doubling time by 25.7%. However, it did not meaningfully alter the cell cycle populations nor increase sensitivity to temozolomide. CONCLUSION: Suppressing expression of EGFR inhibited cell proliferation. However, unlike PTEN expression or ROCK1 down-regulation, it did not alter the cell cycle or increase sensitivity to temozolomide.

The effect of PTEN on proliferation and drug-, and radiosensitivity in malignant glioma cells.

BACKGROUND: Deletions or mutations of the phosphatase and tensin homolog (PTEN) are frequently observed in malignant glioma and are responsible for progression of the disease. Since the molecule is a promising target for gene therapy, the effects of PTEN on glioma proliferation in combination with the anti-neoplastic agent, temozolomide, and ionizing radiation were investigated. MATERIALS AND METHODS: An adenoviral vector encoding PTEN was used. After infection, changes in proliferation, the cell cycle, as well as drug- and radiosensitivity were investigated. RESULTS: Expression of PTEN led to a 1.21-fold prolongation of the doubling time of the cells. It reduced G(1) and increased G(2)/M populations. Forced PTEN expression conferred sensitivity to temozolomide and/or ionizing radiation. CONCLUSION: In addition to counteracting cell proliferation, expression of PTEN presented advantages in the chemo- and radiosensitivity of glioma cells. Methods for up-regulation of PTEN may have a role in increasing the efficacy of current adjuvant therapies.

The Na+/Ca2+ exchanger-mediated Ca2+ influx triggers nitric oxide-induced cytotoxicity in cultured astrocytes.

Nitric oxide (NO) is involved in many pathological conditions including neurodegenerative disorders. We have previously found that sodium nitroprusside (SNP), an NO donor, stimulates mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulating kinase (ERK), c-jun N-terminal protein kinase (JNK) and p38 MAPK, leading to caspase-independent apoptosis in cultured astrocytes. In view of the previous observation that NO stimulates the activity of the Na(+)/Ca(2+) exchanger (NCX), this study examines the involvement of NCX in cytotoxicity. The specific NCX inhibitor SEA0400 blocked SNP-induced phosphorylation of ERK, JNK and p38 MAPK, and decrease in cell viability. SNP-induced phosphorylation of ERK, JNK and p38 MAPK was blocked by removal of external Ca(2+), and SNP treatment caused an increase in (45)Ca(2+) influx. This increase in (45)Ca(2+) influx was blocked by SEA0400, but not the Ca(2+) channel blocker nifedipine. In addition, SNP-induced (45)Ca(2+) influx and cytotoxicity were reduced in NCX1-deficient cells which were transfected with NCX1 siRNA. Inhibitors of intracellular Ca(2+)-dependent proteins such as calpain and calmodulin blocked SNP-induced ERK phosphorylation and decrease in cell viability. Furthermore, the guanylate cyclase inhibitor LY83583 and the cGMP-dependent protein kinase inhibitor KT5823 blocked SNP-induced cytotoxicity. These findings suggest that NCX-mediated Ca(2+) influx triggers SNP-induced apoptosis in astrocytes, which may be mediated by a cGMP-dependent pathway.

A novel protein specifically interacting with Homer2 regulates ubiquitin-proteasome systems.

Homer family proteins are encoded by three genes, homer1, 2 and 3. Most of these proteins are expressed constitutively in nervous systems and accumulated in postsynaptic regions. However, the functional significance of these proteins, especially the significance of the distinction among the proteins encoded by homer1, 2 and 3, is still obscure. In the present study, we isolated a cDNA clone encoding a novel protein by two-hybrid system screening using the C-terminal half of Homer2b as the bait. This protein, termed 2B28, has 297 amino acid residues and contains three major domains: a UBA domain, a coiled-coil region, and a UBX domain. When expressed in HEK293T cells, 2B28 showed colocalization with uniquitin and enhanced the expression levels of IkappaB or Homer1a proteins, which are known to be degraded by proteasomes, indicating that 2B28 is involved in ubiquitin-proteasome functions. 2B28 specifically interacted and colocalized with Homer2 proteins, but not with Homer1 proteins. So far, we have identified no counterpart of 2B28 for Homer1 experimentally or in the protein databases. These results suggest that the specific interaction of 2B28 with Homer2 may play a role in regulation of protein degradation by ubiquitin-proteasome systems and that this function may be specific to Homer2 proteins among Homer family proteins.