Identification of alpha-tubulin as an hsp105alpha-binding protein by the yeast two-hybrid system

Hsp105alpha is a mammalian stress protein that belongs to the HSP105/110 family. Hsp105alpha prevents stress-induced apoptosis in neuronal cells and binds to Hsp70/Hsc70 and suppresses the Hsp70 chaperone activity in vitro. In this study, to further elucidate the function of Hsp105alpha, we searched for Hsp105alpha-binding proteins by screening a mouse FM3A cell cDNA library with full-length Hsp105alpha using the yeast two-hybrid system and obtained alpha-tubulin as an Hsp105alpha-binding protein. Hsp105alpha bound directly to alpha-tubulin both in vitro and in vivo. Indirect immunofluorescence analysis with anti-Hsp105 and anti-alpha-tubulin antibodies indicated that Hsp105alpha was colocalized with microtubules. Furthermore, the disorganization of microtubules induced by heat shock was prevented in Hsp105alpha-overexpressing COS-7 cells. These findings suggested that Hsp105alpha associates with alpha-tubulin and microtubules in cells and plays a role in protection of microtubules under conditions of stress.     

Circadian rhythm of atrioventricular conduction predicts long-term survival in patients with chronic atrial fibrillation

The R-R interval of the electrocardiogram during atrial fibrillation (AF) appears absolutely irregular. However, the Poincaré plot of the R-R interval reveals a sector shape of distribution that is unique to AF. Furthermore, the height of lower envelope (LE1.0) of the distribution and the degree of scatter above the envelope (scattering index) may reflect the refractoriness and concealment of atrioventricular (AV) conduction, respectively. We previously observed that both the LE1.0 and scattering index show clear circadian rhythms in patients with chronic AF and that the rhythms are blunted in those with congestive heart failure and chronic AF. In the present study, we examined if the blunted circadian rhythm of the AV conduction has prognostic value in patients with chronic AF. We studied a retrospective cohort of 120 patients who underwent 24h Holter monitoring at baseline. During an observation period of 33 +/- 16 mon, there were 25 deaths (21%) including 13 cardiac and 8 stroke deaths. All patients showed significant circadian rhythms in both LE1.0 and scattering index with acrophases occurring at night; however, patients dying subsequently from cardiac causes, but not those from fatal stroke were blunted in the circadian rhythms (the amplitudes were < 55% of those in surviving patients). Furthermore, the reduced circadian amplitude of scattering index was an increased risk for cardiac death even after adjustment of coexisting cardiovascular risks [adjusted relative risk (95% confidence interval) per 1-SD decrement, 4.24 (1.54-11.6)]. When patients were divided by the circadian amplitude of the scattering index of 36.5 msec (mean minus 1-SD), the 5yr cardiac mortality below and above the cutoff was 57 and 6%, respectively (log-rank test, p < 0.001). We conclude that the blunted circadian rhythm of AV conduction is an independent risk for cardiac death in patients with chronic AF.     

Identification of newly isolated Babesia parasites from cattle in Korea by using the Bo-RBC-SCID mice

Attempts were made to isolate and identify Korean bovine Babesia parasite. Blood samples were collected from Holstein cows in Korea, and Babesia parasites were propagated in SCID mice with circulating bovine red blood cells for isolation. The isolate was then antigenically and genotypically compared with several Japanese isolates. The Korean parasite was found to be nearly identical to the Oshima strain isolated from Japanese cattle, which was recently designated as Babesia ovata oshimensis n. var. Haemaphysalis longicornis was the most probable tick species that transmitted the parasite.     

Identification of human Kir2.2 (KCNJ12) gene encoding functional inward rectifier potassium channel in both mammalian cells and Xenopus oocytes

Arginine residue at position 285 (R285) in the intracellular C-terminal domain of inward rectifier potassium channel Kir2.2 is conserved in many species, but missing in previously reported human Kir2.2 sequences. We here identified the human Kir2.2 gene in normal individuals, which contained R285 in the deduced amino-acid sequence (hKir2.2/R285). All 30 individuals we examined were homozygous for Kir2.2/R285 gene. The hKir2.2/R285 was electrophysiologically functional in both mammalian cells and Xenopus oocytes. However, the hKir2.2 missing R285 was functional only in Xenopus oocytes, but not in mammalian cells. Thus, R285 in Kir2.2 is important for its functional expression in mammalian cells.     

Dissection of upstream regulatory components of the Rho1p effector, 1,3-beta-glucan synthase,in Saccharomyces cerevisiae

In the budding yeast Saccharomyces cerevisiae, one of the main structural components of the cell wall is 1,3-beta-glucan produced by 1,3-beta-glucan synthase (GS). Yeast GS is composed of a putative catalytic subunit encoded by FKS1 and FKS2 and a regulatory subunit encoded by RHO1. A combination of amino acid alterations in the putative catalytic domain of Fks1p was found to result in a loss of the catalytic activity. To identify upstream regulators of 1,3-beta-glucan synthesis, we isolated multicopy suppressors of the GS mutation. We demonstrate that all of the multicopy suppressors obtained (WSC1, WSC3, MTL1, ROM2, LRE1, ZDS1, and MSB1) and the constitutively active RHO1 mutations tested restore 1,3-beta-glucan synthesis in the GS mutant. A deletion of either ROM2 or WSC1 leads to a significant defect of 1,3-beta-glucan synthesis. Analyses of the degree of Mpk1p phosphorylation revealed that among the multicopy suppressors, WSC1, ROM2, LRE1, MSB1, and MTL1 act positively on the Pkc1p-MAPK pathway, another signaling pathway regulated by Rho1p, while WSC3 and ZDS1 do not. We have also found that MID2 acts positively on Pkc1p without affecting 1,3-beta-glucan synthesis. These results suggest that distinct networks regulate the two effector proteins of Rho1p, Fks1p and Pkc1p.     

Channel openings are necessary but not sufficient for use-dependent block of cardiac Na(+) channels by flecainide: evidence from the analysis of disease-linked mutations

Na(+) channel blockers such as flecainide have found renewed usefulness in the diagnosis and treatment of two clinical syndromes arising from inherited mutations in SCN5A, the gene encoding the alpha subunit of the cardiac voltage-gated Na(+) channel. The Brugada syndrome (BrS) and the LQT-3 variant of the Long QT syndrome are caused by disease-linked SCN5A mutations that act to change functional and pharmacological properties of the channel. Here we have explored a set of SCN5A mutations linked both to BrS and LQT-3 to determine what disease-modified channel properties underlie distinct responses to the Na(+) channel blocker flecainide. We focused on flecainide block that develops with repetitive channel activity, so-called use-dependent block (UDB). Our results indicate that mutation-induced changes in the voltage-dependence of channel availability (inactivation) may act as determinants of flecainide block. The data further indicate that UDB by flecainide requires channel opening, but is not likely due to open channel block. Rather, flecainide appears to interact with inactivation states that follow depolarization-induced channel opening, and mutation-induced changes in channel inactivation will alter flecainide block independent of the disease to which the mutation is linked. Analysis of flecainide block of mutant channels linked to these rare disorders has provided novel insight into the molecular determinants of drug action.     

Transgenic mouse model of tauopathies with glial pathology and nervous system degeneration

Frontotemporal dementias (FTDs), including corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), are neurodegenerative tauopathies characterized by widespread CNS neuronal and glial tau pathologies, but there are no tau transgenic (Tg) mice that model neurodegeneration with glia tau lesions. Thus, we generated Tg mice overexpressing human tau in neurons and glia. No neuronal tau aggregates were detected, but old mice developed Thioflavin S- and Gallyas-positive glial tau pathology resembling CBD astrocytic plaques. Tau-immunoreactive and Gallyas-positive oligodendroglial coiled bodies (similar to CBD and PSP), glial degeneration, and motor deficits were associated with age-dependent accumulations of insoluble hyperphosphorylated human tau and tau immunopositive filaments in degenerating glial cells. Thus, tau-positive glial lesions similar to human FTDs occur in these Tg mice, and these pathologies are linked to glial and axonal degeneration.     

Differential expression of tissue factor and tissue factor pathway inhibitor in metastatic melanoma lesions

Tissue factor (TF) is involved in tumor progression and metastatic potency in some malignant tumors and its function is regulated by tissue factor pathway inhibitor (TFPI) therefore the interaction of both molecules is crucial for their functional role. We evaluated the clinical relevance of TF and TFPI expression in benign and malignant melanocytic lesions. Expression of both was examined by immunoperoxidase staining using serial tissue sections in 16 nevi, 34 primary and 15 metastatic melanoma lesions. TF and TFPI were ubiquitously expressed in benign and malignant melanocytic lesions. This finding was confirmed by Western blot analysis using cultured human melanocytes, nevi cells (NCN) and melanoma cell lines. Although TF expression was not associated with malignant transformation and disease progression, TFPI expression in primary and metastatic melanoma lesions was significantly lower and weaker than that in nevi lesions in terms of intensity and percentage of stained cells. In addition, TFPI expression in metastatic lesions was significantly lower and weaker than that of TF. These results suggest that the relative expression of TF to TFPI may play a crucial role in the malignant transformation and metastatic potency in melanocytic cells.     

Use of 13C-labeled glucose for measuring exogenous glucose oxidation in mice

The author modified a respiratory gas analyzer to analyze the respiratory 13CO2 of 12 small laboratory animals all at once. To investigate the practical use of this system, mice were orally (OR) or intravenously (i.v.) given glucose solutions containing three different amounts of 13C-labeled glucose. Expired 13CO2 derived from exogenous glucose was detected within 10 minutes after administration in OR mice, but about 30 minutes in i.v. mice. The height of the peak of 13CO2 expiration was correlated with the administered 13C-glucose mass.     

Endometriosis: the pathophysiology as an estrogen-dependent disease

Endometriosis, defined as the presence of endometrial glands and stroma outside of the uterine cavity, develops mostly in women of reproductive age and regresses after menopause or ovariectomy, suggesting that the growth is estrogen-dependent. Indeed, the lesions contain estrogen receptors (ER) as well as aromatase, an enzyme that catalyses the conversion of androgens to estrogens, suggesting that local estrogen production may stimulate the growth of lesions. The expression patterns of ER and progesterone receptors in endometriotic lesions are different from those in the eutopic endometrium. Moreover, estrogen metabolism, including the expression pattern of aromatase and the regulation of 17β-hydroxysteroid dehydrogenase type 2 (an enzyme responsible for the inactivation of estradiol to estrone), is altered in the eutopic endometrium of women with endometriosis, adenomyosis, and/or leiomyomas compared to that in the eutopic endometrium of women without disease. Immunostaining for P450arom in endometrial biopsy specimens diagnosed these diseases with sensitivity and specificity of 91 and 100%, respectively. This is applicable to the clinical diagnosis of endometriosis. The polymorphisms in the ER- gene, the CYP19 gene encoding aromatase, and several other genes are associated with the risk of endometriosis. Studies of these will lead to better understandings of the etiology and pathophysiology of endometriosis.