The RAC binding domain/IRSp53-MIM homology domain of IRSp53 induces RAC-dependent membrane deformation

The concave surface of the crescent-shaped Bin-amphiphysin-Rvs (BAR) domain is postulated to bind to the cell membrane to induce membrane deformation of a specific curvature. The Rac binding (RCB) domain/IRSp53-MIM homology domain (IMD) has a dimeric structure that is similar to the structure of the BAR domain; however, the RCB domain/IMD has a "zeppelin-shaped" dimer. Interestingly, the RCB domain/IMD of IRSp53 possesses Rac binding, membrane binding, and actin filament binding abilities. Here we report that the RCB domain/IMD of IRSp53 induces membrane deformation independent of the actin filaments in a Rac-dependent manner. In contrast to the BAR domain, the RCB domain/IMD did not cause long tubulation of the artificial liposomes; however, the Rac binding domain caused the formation of small buds on the liposomal surface. When expressed in cells, the Rac binding domain induced outward protrusion of the plasma membrane in a direction opposite to that induced by the BAR domain. Mapping of the amino acids responsible for membrane deformation suggests that the convex surface of the Rac binding domain binds to the membrane in a Rac-dependent manner, which may explain the mechanism of the membrane deformation induced by the RCB domain/IMD.     

MAPKAPK-2-mediated LIM-kinase activation is critical for VEGF-induced actin remodeling and cell migration

Vascular endothelial growth factor-A (VEGF-A) induces actin reorganization and migration of endothelial cells through a p38 mitogen-activated protein kinase (MAPK) pathway. LIM-kinase 1 (LIMK1) induces actin remodeling by phosphorylating and inactivating cofilin, an actin-depolymerizing factor. In this study, we demonstrate that activation of LIMK1 by MAPKAPK-2 (MK2; a downstream kinase of p38 MAPK) represents a novel signaling pathway in VEGF-A-induced cell migration. VEGF-A induced LIMK1 activation and cofilin phosphorylation, and this was inhibited by the p38 MAPK inhibitor SB203580. Although p38 phosphorylated LIMK1 at Ser-310, it failed to activate LIMK1 directly; however, MK2 activated LIMK1 by phosphorylation at Ser-323. Expression of a Ser-323-non-phosphorylatable mutant of LIMK1 suppressed VEGF-A-induced stress fiber formation and cell migration; however, expression of a Ser-323-phosphorylation-mimic mutant enhanced these processes. Knockdown of MK2 by siRNA suppressed VEGF-A-induced LIMK1 activation, stress fiber formation, and cell migration. Expression of kinase-dead LIMK1 suppressed VEGF-A-induced tubule formation. These findings suggest that MK2-mediated LIMK1 phosphorylation/activation plays an essential role in VEGF-A-induced actin reorganization, migration, and tubule formation of endothelial cells.     

Amyloid formation in denatured single-mutant lysozymes where residual structures are modulated

Reduced hen lysozyme has a residual structure involving long-range interaction. It has been demonstrated that a single mutation (A9G, W62G, W111G, or W123G) in the residual structure differently modulates the long-range interactions of reduced lysozyme. To examine whether such variations in the residual structure affect amyloid formation, reduced and alkylated mutant lysozymes were incubated under the amyloid-fibrillation condition. From the analyses of CD spectra and thioflavine T fluorescences, it was suggested that variation in residual structure led to different amyloid formation. Interestingly, the extent of amyloid formation did not always correlate with the extent to which the residual structure was maintained, resulting in the involvement of a hydrophobic cluster normally contained in W111 in the reduced lysozyme.     

The ATR-Chk1 pathway plays a role in the generation of centrosome aberrations induced by Rad51C dysfunction

Rad51C is a central component of two complexes formed by five Rad51 paralogs in vertebrates. These complexes are involved in repairing DNA double-strand breaks through homologous recombination. Despite accumulating evidence suggesting that the paralogs may prevent aneuploidy by controlling centrosome integrity, Rad51C's role in maintaining chromosome stability remains unclear. Here we demonstrate that Rad51C deficiency leads to both centrosome aberrations in an ATR-Chk1-dependent manner and increased aneuploidy in human cells. While it was reported that Rad51C deficiency did not cause centrosome aberrations in interphase in hamster cells, such aberrations were observed in interphase in HCT116 cells with Rad51C dysfunction. Caffeine treatment and down-regulation of ATR, but not that of ATM, reduced the frequency of centrosome aberrations in the mutant cells. Silencing of Rad51C by RNA interference in HT1080 cells resulted in similar aberrations. Treatment with a Chk1 inhibitor and silencing of Chk1 also reduced the frequency in HCT116 mutants. Accumulation of Chk1 at the centrosome and nuclear foci of γH2AX were increased in the mutants. Moreover, the mutant cells had a higher frequency of aneuploidy. These findings indicate that the ATR-Chk1 pathway plays a role in increased centrosome aberrations induced by Rad51C dysfunction.     

Residual Structures in the Acid-Unfolded States of Vλ6 Proteins Affect Amyloid Fibrillation

Many proteins form amyloid-like fibrils in vitro under partially or highly unfolding conditions. Recently, we showed that the residual structure in highly unfolded state is closely related to amyloid fibril formation in hen lysozyme. Thus, to better understand the role of the residual structure on amyloid fibril formation, we focused on AL amyloidosis, which results from the extracellular deposition of monoclonal immunoglobulin light-chain variable domains (V_Ls) as insoluble fibrils. We examined the relationship between the residual structure and amyloid fibril formation on three λ6 recombinant V_L (rVλ6) proteins, wild type, Jto, and Wil. Although rVλ6 proteins are highly unfolded in pH 2, ¹⁵N NMR transverse relaxation experiments revealed nonrandom structures in regions, which include some hydrophobic residues and a single disulfide bond, indicating the existence of residual structure in rVλ6 proteins. However, the residual structure of Wil was markedly disrupted compared with those of the other proteins, despite there being no significant differences in amino acid sequences. Fibrillation experiments revealed that Wil had a longer lag time for fibril formation than the others. When the single disulfide bond was reduced and alkylated, the residual structure was largely disrupted and fibril formation was delayed in all three rVλ6 proteins. It was suggested that the residual structure in highly unfolded state has a crucial role in amyloid fibril formation in many proteins, even pathogenic ones.     

Isolation and characterization of microsatellite markers from Robinia pseudoacacia L

Microsatellite markers were isolated from Robinia pseudoacacia L. using an enrichment method. Eleven of the 23 primer pairs designed successfully amplified unambiguous and polymorphic single loci among 39 individual R. pseudoacacia L. from northeastern Japan. The observed and expected heterozygosities of the 11 microsatellite markers ranged from 0.333 to 0.821 and from 0.489 to 0.867, respectively. The polymorphisms observed at the 11 microsatellite loci are useful genetic data for forest ecological studies involving R. pseudoacacia L.     

Estimation of surface soil properties in peatland using ALOS/PALSAR

By examining the area of the Sarobetsu Mire in northern Japan using ALOS/PALSAR data, we have clarified the backscattering behavior and characteristics of the L-band microwaves when used in the study of peatlands. We classified the vegetation into six categories and noted the differences in scattering intensity and incident-angle dependencies among these. The scattering intensity for HH and HV polarizations was greatest with sasa (dwarf bamboo) and reeds, and least with sphagnum. The incident-angle dependency with the HH polarization was higher for sasa and reed than for other vegetation types. Analysis of the polarization revealed that such differences among vegetation classes were reflected most clearly in the volume scattering characteristic. Applying simple and multiple regression analysis for the environmental factors of soil, hydrology, vegetation, and roughness against the backscatter coefficient, we also found stronger interrelations with soil factors such as bulk density, nitrogen and carbon content, and C/N ratio, and against the backscatter coefficient, than with either the roughness or vegetation. Based on such results, we clarified the unique scattering characteristics of peatlands in which scattering from the surface soil is more marked than that from other elements. We consequently estimated the spatial distribution of surface soil characteristics in peatland using the combined data available from L-band satellite SAR, aircraft laser (airborne LiDAR), and optical sensors.     

Parallel reinforcement learning for weighted multi-criteria model with adaptive margin

Reinforcement learning (RL) for a linear family of tasks is described in this paper. The key of our discussion is nonlinearity of the optimal solution even if the task family is linear; we cannot obtain the optimal policy using a naive approach. Although an algorithm exists for calculating the equivalent result to Q-learning for each task simultaneously, it presents the problem of explosion of set sizes. We therefore introduce adaptive margins to overcome this difficulty.     

Oxidation of myosin heavy chain and reduction in force production in hyperthyroid rat soleus.

We tested the hypothesis that a force reduction in hyperthyroid rat soleus muscle would be associated with oxidative modification in myosin heavy chain (MHC). Daily injection of thyroid hormone [3,5,3'-triiodo-L-thyronine (T3)] for 21 days depressed isometric forces of whole soleus muscle across a range of stimulus frequencies (P < 0.01). In fiber bundles, hyperthyroidism also led to pronounced reductions (P < 0.01) in both K+ - and 4-chloro-m-cresol-induced contracture forces. The degrees of the reductions were similar between these two contractures that were induced by distinct reagents. Treatment with T3 elicited a significant decrease ( approximately 14%; P < 0.05) in the relative content of MHC contained in myofibrillar proteins. The content of carbonyl groups in myofibrillar protein extracts was elevated (P < 0.05) by approximately 50% in T3-treated muscles. Immunoblot analyses on T3-treated muscles showed a greater increase (106%; P < 0.05) of the carbonyl content in MHC than in myofibrillar protein extracts. These data suggest that in hyperthyroidism the decrease in force production of skeletal muscles may stem primarily from failure in myofibrillar protein function resulting from oxidative modification of MHC.     

Sleep Deprivation Influences Diurnal Variation of Human Time Perception with Prefrontal Activity Change: A Functional Near-Infrared Spectroscopy Study

Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well as cortical areas involving the prefrontal cortex (PFC). It has also been reported that the PFC is vulnerable to sleep deprivation, which has an influence on various cognitive functions. The present study is aimed at elucidating the influence of PFC vulnerability to sleep deprivation on short-time perception, using the optical imaging technique of functional near-infrared spectroscopy. Eighteen participants performed 10-s time production tasks before (at 21:00) and after (at 09:00) experimental nights both in sleep-controlled and sleep-deprived conditions in a 4-day laboratory-based crossover study. Compared to the sleep-controlled condition, one-night sleep deprivation induced a significant reduction in the produced time simultaneous with an increased hemodynamic response in the left PFC at 09:00. These results suggest that activation of the left PFC, which possibly reflects functional compensation under a sleep-deprived condition, is associated with alteration of short-time perception.