Cytokinesis is the final step in cell division and is driven by the constriction of the medial actomyosin-based contractile ring (CR) in many eukaryotic cells. In the fission yeast ...Schizosaccharomyces pombe, the IQGAP-like protein Rng2 is required for assembly and constriction of the CR, and specifically interacts with actin filaments (F-actin) in the CR after anaphase. However, the mechanism that timely activates Rng2 has not yet been elucidated. We herein tested the hypothesis that the cytokinetic function of Rng2 is regulated by phosphorylation by examining phenotypes of a series of non-phosphorylatable and phosphomimetic rng2 mutant strains. In phosphomimetic mutant cells, F-actin in the CR was unstable. Genetic analyses indicated that phosphorylated Rng2 was involved in CR assembly in cooperation with myosin-II, whereas the phosphomimetic mutation attenuated the localization of Rng2 to CR F-actin. The present results suggest that Rng2 is phosphorylated during CR assembly and then dephosphorylated, which enhances the interaction between Rng2 and CR F-actin to stabilize the ring, thereby ensuring secure cytokinesis.
•CDK-dependent phosphorylation of IQGAP is involved in cytokinesis in S. pombe.•F-actin in the contractile ring is unstable in a phosphomimetic IQGAP rng2 mutant.•Phosphorylated Rng2 collaborates with myosin-II in assembly of the contractile ring.
Our aim is to compare the efficacy and safety of high-flow nasal cannula (HFNC) against those of nasal continuous positive airway pressure (NCPAP) or nasal intermittent positive-pressure ventilation ...(NIPPV) after extubation in preterm infants.
This prospective, randomized, noninferiority trial was conducted in 6 tertiary NICUs. Infants born at <34 weeks who needed noninvasive ventilation after extubation were enrolled. We randomly assigned infants to an HFNC group when HFNC was used or to an NCPAP/NIPPV group when NCPAP or NIPPV was used. The primary outcome was treatment failure within 7 days after extubation. We then examined clinical aspects of treatment failure with HFNC use.
In total, 176 and 196 infants were assigned to the HFNC and NCPAP/NIPPV groups, respectively. The HFNC group showed a significantly higher rate of treatment failure than that of the NCPAP/NIPPV group, with treatment failure occurring in 54 infants (31%) compared with 31 infants (16%) in the NCPAP/NIPPV group (risk difference, 14.9 percentage points; 95% confidence interval, 6.2-23.2). Histologic chorioamnionitis (
= .02), treated patent ductus arteriosus (
= .001), and corrected gestational age at the start of treatment (
= .007) were factors independently related to treatment failure with HFNC use.
We found HFNC revealed a significantly higher rate of treatment failure than NCPAP or NIPPV after extubation in preterm infants. The independent factors associated with treatment failure with HFNC use were histologic chorioamnionitis, treated patent ductus arteriosus, and a younger corrected gestational age at the start of treatment.
Previously, we reported that polyphenol-rich fraction (named E80) promotes skeletal muscle hypertrophy induced by functional overload in mice. This study indicates that E80 has potential for ...affecting skeletal muscle mass. Then, we evaluate the effect of E80 on atrophic and recovery conditions of skeletal muscle in mice. Hindlimb suspension (unloading) and relanding (reloading) are used extensively to observe disuse muscle atrophy and subsequent muscle mass recovery from atrophy. Eight-week old C57BL/6 mice were fed either a normal diet or a diet containing 0.5% E80 for two weeks under conditions of hindlimb suspension and a subsequent 5 or 10 days of reloading. We found that E80 administration did not prevent atrophy during hindlimb suspension, but promoted recovery of slow-twitch (soleus) muscle mass from atrophy induced by hindlimb suspension. After five days of reloading, we discovered that phosphorylation of the Akt/mammalian target of rapamycin (mTOR) pathway proteins, such as Akt and P70 ribosomal protein S6 kinase (S6K), was activated in the muscle. Therefore, E80 administration accelerated mTOR signal and increased protein synthesis in the reloaded soleus muscle.
During cytokinesis in many eukaryotic cells, myosin‐II concentrates at the equatorial cortex with actin filaments (F‐actin) and is supposed to generate forces to divide the cell into two, which is ...called the contractile ring (CR) hypothesis. Several lines of evidence indicate that the myosin‐II is recruited independently of F‐actin and interacts specifically with the equatorial F‐actin. Molecular details of these mechanisms are still unknown. We used the fission yeast Schizosaccharomyces pombe to investigate the regulation of myosin‐II localization. We demonstrate that the CR myosin‐II was composed of F‐actin‐dependent and ‐independent fractions by simultaneously observing F‐actin and myosin. The F‐actin‐independent fraction was visualized as cortical dots in the absence of F‐actin. IQGAP Rng2, an indispensable element of CR, was implicated in maintenance of the F‐actin‐independent fraction of myosin‐II, whereas anillin Mid1 was required for assembly but not for maintenance of the fraction. In the CR of the rng2 mutant, myosin‐II was less concentrated, unstable, and nonhomogeneous, which often resulted in cytokinesis failure. These results suggest that Rng2 tethers myosin‐II to the cortex along the CR independently of F‐actin to provide a sufficient concentration. The robust localization of myosin‐II would ensure successful cytokinesis.
In the fission yeast Schizosaccharomyces pombe (Sp), Mid1/Dmf1 plays an important role in positioning the division site by inducing formation of the contractile ring (CR). Mid1, emanating from the ...nucleus located in the cell center, forms a dozen of nodes in the middle cell cortex ahead of mitosis, and actin filaments and myosin II accumulated at each node interact and assemble the CR in metaphase. Curiously, in another fission yeast S. japonicus (Sj), CR formation begins after nuclear segregation in late anaphase. Here, we investigated the role of S. japonicus Mid1 during mitosis to compare the molecular mechanisms that determine the cell division site in Schizosaccharomyces. Similar to Sp Mid1, Sj Mid1 often accumulated in the nucleus of interphase cells. Moreover, Sj Mid1 localized to cortical dots with myosin II in the future division site and formed a medial ring in mitotic cells. However, S. japonicus cells without Mid1 function still carried out symmetrical binary division. Therefore, the Mid1 dependency for positional control of the cell division site is possibly different between the two species. Meanwhile, we found that Sj Mid1 enhanced CR formation, in a manner possibly similar to that by Sp Mid1.
We investigated the role of S. japonicus Mid1 during mitosis to compare the molecular mechanisms that determine the cell division site in Schizosaccharomyces. Although the Mid1 dependency for positional control of the cell division site is possibly different between the fission yeast species, we found that Sj Mid1 enhanced CR formation, in a manner possibly similar to that by S. pombe Mid1.
Mitochondria activation factor (MAF) is a high-molecular-weight polyphenol extracted from black tea that stimulates training-induced 5' adenosine monophosphate-activated protein kinase (AMPK) ...activation and improves endurance capacity. Originally, MAF was purified from black tea using butanol and acetone, making it unsuitable for food preparation. Hence, we extracted a MAF-rich sample "E80" from black tea, using ethanol and water only. Here, we examined the effects of E80 on resistance training. Eight-week old C57BL/6 mice were fed with a normal diet or a diet containing 0.5% E80 for 4, 7 and 14 days under conditions of functional overload. It was found that E80 administration promoted overload-induced hypertrophy and induced phosphorylation of the Akt/mammalian target of rapamycin (mTOR) pathway proteins, such as Akt, P70 ribosomal protein S6 kinase (p70S6K), and S6 in the plantaris muscle. Therefore, functional overload and E80 administration accelerated mTOR signaling and increased protein synthesis in the muscle, thereby inducing hypertrophy.
Vast diversity and high specificity of antigen recognition by antibodies are hallmarks of the acquired immune system. Although the molecular mechanisms that yield the extremely large antibody ...repertoires are precisely understood, comprehensive description of the global antibody repertoire generated in individual bodies has been hindered by the lack of powerful measures. To obtain holistic understanding of the antibody-repertoire space, we used next-generation sequencing (NGS) to analyze the deep profiles of naive and antigen-responding repertoires of the IgM, IgG1, and IgG2c classes formed in individual mice. The overall landscapes of naive IgM repertoires were almost the same for each mouse, whereas those of IgG1 and IgG2c differed considerably among naive individuals. Next, we immunized mice with a model antigen, nitrophenol (NP)-hapten linked to chicken γ-globulin (CGG) carrier, and compared the antigen-responding repertoires in individual mice. To extract the complete antigen response, we developed an intelligible method for detecting common components of antigen-responding repertoires. The major responding antibodies were IGHV1-72/IGHD1-1/IGHJ2 for NP-hapten and IGHV9-3/IGHD3-1/IGHJ2 for CGG-carrier protein. The antigen-binding specificities of the identified antibodies were confirmed through ELISA after antibody-gene synthesis and expression of the corresponding NGS reads. Thus, we deciphered antigen-responding antibody repertoires by inclusively analyzing the antibody-repertoire space generated in individual bodies by using NGS, which avoided inadvertent omission of key antibody repertoires.
•Global antigen-responding antibody repertoires in individuals remain undescribed.•An NGS-based method to decipher antibody repertoires in mice was established.•Naive and antigen-responding IgM, IgG1, and IgG2c repertoires were revealed.•NGS-output sequences were used for synthesizing and expressing antibody genes.•Antigen-binding specificity of the identified antibodies was confirmed using ELISA.
Sporulation, gametogenesis in yeast, consists of meiotic nuclear division and spore morphogenesis. In the fission yeast Schizosaccharomyces pombe, the four haploid nuclei produced after meiosis II ...are encapsulated by the forespore membrane (FSM), which is newly synthesized from spindle pole bodies (SPBs) in the cytoplasm of the mother cell as spore precursors. Although the coordination between meiosis and FSM assembly is vital for proper sporulation, the underlying mechanism remains unclear. In the present study, we identified a new meiosis-specific protein Npg1, and found that it was involved in the efficient formation of spores and spore viability. The accumulation and organization of the FSM was compromised in npg1-null cells, leading to the error-prone envelopment of nuclei. Npg1 was first seen as internuclear dots and translocated to the SPBs before the FSM assembled. Genetic analysis revealed that Npg1 worked in conjunction with the FSM proteins Spo3 and Meu14. These results suggest a possible signaling link from the nucleus to the meiotic SPBs in order to associate the onset of FSM assembly with meiosis II, which ensures the successful partitioning of gametic nuclei.
A contractile ring (CR) is involved in cytokinesis in animal and yeast cells. Although several types of actin-bundling proteins associate with F-actin in the CR, their individual roles in the CR have ...not yet been elucidated in detail. Ain1 is the sole α-actinin homologue in the fission yeast Schizosaccharomyces pombe and specifically localizes to the CR with a high turnover rate. S. pombe cells lacking the ain1+ gene show defects in cytokinesis under stress conditions. We herein investigated the biochemical activity and cellular localization mechanisms of Ain1. Ain1 showed weaker affinity to F-actin in vitro than other actin-bundling proteins in S. pombe. We identified a mutation that presumably loosened the interaction between two calponin-homology domains constituting the single actin-binding domain (ABD) of Ain1, which strengthened the actin-binding activity of Ain1. This mutant protein induced a deformation in the ring shape of the CR. Neither a truncated protein consisting only of an N-terminal ABD nor a truncated protein lacking a C-terminal region containing an EF-hand motif localized to the CR, whereas the latter was involved in the bundling of F-actin in vitro. We herein propose detailed mechanisms for how each part of the molecule is involved in the proper cellular localization and function of Ain1.
Aerobic exercise can promote "fast-to-slow transition" in skeletal muscles, i.e. an increase in oxidative fibers, mitochondria, and myoglobin and improvement in glucose and lipid metabolism. Here, we ...found that mice administered Mitochondria Activation Factor (MAF) combined with exercise training could run longer distances and for a longer time compared with the exercise only group; MAF is a high-molecular-weight polyphenol purified from black tea. Furthermore, MAF intake combined with exercise training increased phosphorylation of AMPK and mRNA level of glucose transporter 4 (GLUT4). Thus, our data demonstrate for the first time that MAF activates exercise training-induced intracellular signaling pathways that involve AMPK, and improves endurance capacity.
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