Decrease in the density of t-tubular L-type Ca2+ channel currents in failing ventricular myocytes

In some forms of cardiac hypertrophy and failure, the gain of Ca(2+)-induced Ca(2+) release [CICR; i.e., the amount of Ca(2+) released from the sarcoplasmic reticulum normalized to Ca(2+) influx through L-type Ca(2+) channels (LTCCs)] decreases despite the normal whole cell LTCC current density, ryanodine receptor number, and sarcoplasmic reticulum Ca(2+) content. This decrease in CICR gain has been proposed to arise from a change in dyad architecture or derangement of the t-tubular (TT) structure. However, the activity of surface sarcolemmal LTCCs has been reported to increase despite the unaltered whole cell LTCC current density in failing human ventricular myocytes, indicating that the "decreased CICR gain" may reflect a decrease in the TT LTCC current density in heart failure. Thus, we analyzed LTCC currents of failing ventricular myocytes of mice chronically treated with isoproterenol (Iso). Although Iso-treated mice exhibited intact t-tubules and normal LTCC subunit expression, acute occlusion of t-tubules of isolated ventricular myocytes with osmotic shock (detubulation) revealed that the TT LTCC current density was halved in Iso-treated versus control myocytes. Pharmacological analysis indicated that kinases other than PKA or Ca(2+)/calmodulin-dependent protein kinase II insufficiently activated, whereas protein phosphatase 1/2A excessively suppressed, TT LTCCs in Iso-treated versus control myocytes. These results indicate that excessive β-adrenergic stimulation causes the decrease in TT LTCC current density by altering the regulation of TT LTCCs by protein kinases and phosphatases in heart failure. This phenomenon might underlie the decreased CICR gain in heart failure.     

Identification and conformer analysis of a novel redox-active motif, Pro-Ala-Ser-Cys-Cys-Ser, in Drosophila thioredoxin reductase by semiempirical molecular orbital calculation

Mammalian thioredoxin reductases (TrxRs) contain selenium as selenocysteine (Sec) in the C-terminal redox center -Gly-Cys-Sec-Gly-OH to reduce Trx and other substrates; a Sec-to-Cys substitution in mammalian TrxR yields an almost inactive enzyme. The corresponding tetrapeptide sequence in Drosophila melanogaster TrxR (Dm-TrxR), -Ser-Cys-Cys-Ser-OH, endows the orthologous enzyme with a catalytic competence similar to mammalian selenoenzymes, but implementation of the Ser-containing tetrapeptide sequence SCCS into the mammalian enzyme does not restore the activity of the Sec-to-Cys mutant form (turnover number <2/min). MOPAC calculation suggested that the C-terminal hexapeptide Pro-Ala-Ser-Cys-Cys-Ser-OH functions as a redox center that alleviates the necessity for selenium in Dm-TrxR, and a mutant form of human lung TrxR that mimics this hexapeptide sequence showed improved catalytic turnover (17.4/min for DTNB and 13.2/min for E. coli trx) compared to the Sec-to-Cys mutant. MOPAC calculation also suggested that the dominant form of the Pro-containing hexapeptide is a C+ conformation, which perhaps has a catalytic advantage in facile reduction of the intramolecular disulfide bond between Cys497 and Cys498 by the N-terminal redox center in the neighboring subunit.     

Combined eradication strategy for CAE in a dairy goat farm in Japan

We conducted an eradication program from 2002 to 2006 against caprine arthritis-encephalitis (CAE) virus (CAEV) in an important farm that maintained goat breeds and had a high prevalence of CAEV infection. The program did not involve the slaughter and replacement of entire flocks, but rather the prevention of both vertical and horizontal transmission. The program consisted of (1) removal of kids immediately after birth, (2) segregation of each generation, and (3) culling of positive goats in periodical tests. All goats born before 2002 were regarded as infected and grouped into herd A. Kids born during the program were divided into several herds on the basis of CAEV infection risk, raised with calf milk replacer, and periodically tested by polymerase chain reaction (PCR) and the agar gel immunodiffusion (AGID) test. A total of 205 kids were produced from 137 parents in herd A, 92 of which were distinctly infected. Only 11 of the 205 kids were infected with CAEV and were culled. The remaining 194 kids and all other kids born from other herds were negative by PCR and AGID testing throughout the program. The milk yield of primiparous does was significantly increased after the eradication program. These findings indicate that the combine use of isolated and milk-deprived rearing and periodical detection testing are effective in establishing a CAEV-free flock from an infected flock.     

A Coiled-coil Clamp Controls Both Conformation and Clustering of Stromal Interaction Molecule 1 (STIM1)

Store-operated Ca²⁺ entry, essential for the adaptive immunity, is initiated by the endoplasmic reticulum (ER) Ca²⁺ sensor STIM1. Ca²⁺ entry occurs through the plasma membrane resident Ca²⁺ channel Orai1 that directly interacts with the C-terminal STIM1 domain, named SOAR/CAD. Depletion of the ER Ca²⁺ store controls this STIM1/Orai1 interaction via transition to an extended STIM1 C-terminal conformation, exposure of the SOAR/CAD domain, and STIM1/Orai1 co-clustering. Here we developed a novel approach termed FRET-derived Interaction in a Restricted Environment (FIRE) in an attempt to dissect the interplay of coiled-coil (CC) interactions in controlling STIM1 quiescent as well as active conformation and cluster formation. We present evidence of a sequential activation mechanism in the STIM1 cytosolic domains where the interaction between CC1 and CC3 segment regulates both SOAR/CAD exposure and CC3-mediated higher-order oligomerization as well as cluster formation. These dual levels of STIM1 auto-inhibition provide efficient control over the coupling to and activation of Orai1 channels.     

Delivery of Full-Length Factor VIII Using a piggyBac Transposon Vector to Correct a Mouse Model of Hemophilia A

Viral vectors have been used for hemophilia A gene therapy. However, due to its large size, full-length Factor VIII (FVIII) cDNA has not been successfully delivered using conventional viral vectors. Moreover, viral vectors may pose safety risks, e.g., adverse immunological reactions or virus-mediated cytotoxicity. Here, we took advantages of the non-viral vector gene delivery system based on piggyBac DNA transposon to transfer the full-length FVIII cDNA, for the purpose of treating hemophilia A. We tested the efficiency of this new vector system in human 293T cells and iPS cells, and confirmed the expression of the full-length FVIII in culture media using activity-sensitive coagulation assays. Hydrodynamic injection of the piggyBac vectors into hemophilia A mice temporally treated with an immunosuppressant resulted in stable production of circulating FVIII for over 300 days without development of anti-FVIII antibodies. Furthermore, tail-clip assay revealed significant improvement of blood coagulation time in the treated mice.piggyBac transposon vectors can facilitate the long-term expression of therapeutic transgenes in vitro and in vivo. This novel gene transfer strategy should provide safe and efficient delivery of FVIII.     

The signaling adaptor gab1 regulates cell polarity by acting as a par protein scaffold

Cell polarity plays a key role in development and is disrupted in tumors, yet the molecules and mechanisms that regulate polarity remain poorly defined. We found that the scaffolding adaptor GAB1 interacts with two polarity proteins, PAR1 and PAR3. GAB1 binds PAR1 and enhances its kinase activity. GAB1 brings PAR1 and PAR3 into a transient complex, stimulating PAR3 phosphorylation by PAR1. GAB1 and PAR6 bind the PAR3 PDZ1 domain and thereby compete for PAR3 binding. Consequently, GAB1 depletion causes PAR3 hypophosphorylation and increases PAR3/PAR6 complex formation, resulting in accelerated and enhanced tight junction formation, increased transepithelial resistance, and lateral domain shortening. Conversely, GAB1 overexpression, in a PAR1/PAR3-dependent manner, disrupts epithelial apical-basal polarity, promotes multilumen cyst formation, and enhances growth factor-induced epithelial cell scattering. Our results identify GAB1 as a negative regulator of epithelial?cell polarity that functions as a scaffold for modulating PAR protein complexes on the lateral membrane.     

Developmental changes in expression, subcellular distribution, and function of Drosophila N-cadherin, guided by a cell-intrinsic program during neuronal differentiation

Cell adhesion molecules (CAMs) perform numerous functions during neural development. An individual CAM can play different roles during each stage of neuronal differentiation; however, little is known about how such functional switching is accomplished. Here we show that Drosophila N-cadherin (CadN) is required at multiple developmental stages within the same neuronal population and that its sub-cellular expression pattern changes between the different stages. During development of mushroom body neurons and motoneurons, CadN is expressed at high levels on growing axons, whereas expression becomes downregulated and restricted to synaptic sites in mature neurons. Phenotypic analysis of CadN mutants reveals that developing axons require CadN for axon guidance and fasciculation, whereas mature neurons for terminal growth and receptor clustering. Furthermore, we demonstrate that CadN downregulation can be achieved in cultured neurons without synaptic contact with other cells. Neuronal silencing experiments using Kir(2.1) indicate that neuronal excitability is also dispensable for CadN downregulation in vivo. Interestingly, downregulation of CadN can be prematurely induced by ectopic expression of a nonselective cation channel, dTRPA1, in developing neurons. Together, we suggest that switching of CadN expression during neuronal differentiation involves regulated cation influx within neurons.     

Macrophages play a unique role in the plaque calcification by enhancing the osteogenic signals exerted by vascular smooth muscle cells

Vascular calcification is a major risk factor for the cardiovascular disease, yet its underlying molecular mechanisms remain to be elucidated. Recently, we identified that osteogenic signals via bone morphogenetic protein (BMP)-2 exerted by vascular smooth muscle cells (VSMCs) play a crucial role in the formation of atherosclerotic plaque calcification. Here we report a synergistic interaction between macrophages and VSMCs with respect to plaque calcification. Treatment with conditioned medium (CM) of macrophages dramatically enhanced BMP-2 expression in VSMCs, while it substantially reduced the expression of matrix Gla-protein (MGP) that inhibits the BMP-2 osteogenic signaling. As a result, macrophages significantly accelerated the osteoblastic differentiation of C2C12 cells induced by VSMC-CM. In contrast, macrophage-CM did not enhance the osteoblastic gene expressions in VSMCs, indicating that macrophages unlikely induced the osteoblastic trans-differentiation of VSMCs. We then examined the effect of recombinant TNF-α and IL-1β on the VSMC-derived osteogenic signals. Similar to the macrophage-CM, both cytokines enhanced BMP-2 expression and reduced MGP expression in VSMCs. Nevertheless, only the neutralization of TNF-α but not IL-1β attenuated the effect of macrophage-CM on the expression of these genes in VSMCs, due to the very low concentration of IL-1β in the macrophage-CM. On the other hand, VSMCs significantly enhanced IL-1β expression in macrophages, which might in turn accelerate the VSMC-mediated osteogenic signals. Together, we identified a unique role of macrophages in the formation of plaque calcification in coordination with VSMCs. This interaction between macrophages and VSMCs is a potential therapeutic target to treat and prevent the atherosclerotic plaque calcification.