Two novel proteins in the mitochondrial outer membrane mediate β-barrel protein assembly

Mitochondrial outer and inner membranes contain translocators that achieve protein translocation across and/or insertion into the membranes. Recent evidence has shown that mitochondrial β-barrel protein assembly in the outer membrane requires specific translocator proteins in addition to the components of the general translocator complex in the outer membrane, the TOM40 complex. Here we report two novel mitochondrial outer membrane proteins in yeast, Tom13 and Tom38/Sam35, that mediate assembly of mitochondrial β-barrel proteins, Tom40, and/or porin in the outer membrane. Depletion of Tom13 or Tom38/Sam35 affects assembly pathways of the β-barrel proteins differently, suggesting that they mediate different steps of the complex assembly processes of β-barrel proteins in the outer membrane

Involvement of both protein kinase C and G proteins in superoxide production after IgE triggering in guinea pig eosinophils

ABSTRACTTo study the function and mechanism of eosinophils via the low affinity IgE receptor (FceRII), we examined the production of 02 metabolites by measuring the luminol-dependent chemiluminescence (LDCL) response and the generation of cysteinyl leukotrienes. Eosinophils obtained from guinea pig peritoneal fluid sensitized with horse serum were purified. Luminol-dependent chemiluminescence was induced by stimulation with monoclonal anti-CD23 antibody, but not by mouse serum (controls). The mean (±SEM) value of LDCL was 20.6±1.3X103 c.p.m. This reaction consisted of an initial rapid phase and a propagation phase and ended within lOmin. Guinea pig eosinophils were histochemically stained with monoclonal anti-CD23 antibody. The major product generated in the LDCL response was superoxide, as determined by the measurement of superoxide by cytochrome c reduction and the complete inhibitory effect of superoxide dismutase on the LDCL response. Pretreatment with either pertussis toxin or cholera toxin inhibited the LDCL reaction. Depletion of bivalent ions by EDTA inhibited this response and the protein kinase C inhibitor D-sphingosin inhibited both 1-oleoyl-2-acetyl-glycerol-induced and FcϵRII-mediated LDCL. These findings suggest that the NADPH-protein kinase C pathway may be involved in the FceRII-mediated LDCL response in guinea pig eosinophils

Increased Cholera Toxin-, and Forskolin-induced Cyclic AMP Accumulations in Psoriatic Involved Versus Uninvolved or Normal Human Epidermis

Psoriatic involved epidermis reveals variously altered receptor-adenylate cyclase responses; among them the most prominent is defective beta-adrenergic adenylate cyclase response, which is normally the major receptor-adenylate cyclase system of human epidermis. It is known that activation of hormone-stimulated adenylate cyclase, a membrane-bound enzyme complex, requires functional coupling of at least 3 distinct subunits: 1) receptor subunit (R), 2) guanine nucleotide binding protein (G), and 3) catalytic subunit (C). The precise nature of the beta-adrenergic defect in the psoriatic epidermis, however, remains to be determined, especially in terms of G and C function. Using the involved and uninvolved skin from psoriatic patients, we investigated effects of cholera toxin (which monitors G-C interaction) and forskolin (which monitors C function) on the adenylate cyclase system of epidermis, which were compared with those of normal human epidermis. Both agents increased cyclic AMP levels of involved, uninvolved, and normal human epidermis. Marked accumulations were observed in the presence of cyclic nucleotide phosphodiesterase inhibitor, isobutyl- methyixanthine (IBMX); without the phosphodiesterase inhibitor, the effect of each agent was minimal. Comparison of the effects of cholera toxin revealed that the psoriatic involved epidermis accumulates much more cyclic AMP than the uninvolved epidermis (involved: 193 ± 65; uninvolved: 117 ± 54 pmoles/mg protein/5 h). Similarly forskolin-induced cyclic AMP accumulations of the involved epidermis were much more than those of uninvolved epidermis (involved: 374 ± 152; uninvolved: 101 ± 41 pmoles/mg protein/2 h). Those of normal human epidermis were not significantly different from those of uninvolved epidermis (cholera toxin: 99 ± 36 pmoles/mg protein/5 h; forskolin: 84 ± 22 pmoles/mg protein/2 h). Our results indicate that G and C function and their interaction is not defective (but rather increased) in the posoriatic involved epidermis. This suggests that the defective beta-adrenergic response of psoriatic involved epidermis reflects defective R or R-G interaction of the epidermal adenylate cyclase system

Tim23–Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import

Mitochondrial protein traffic requires coordinated operation of protein translocator complexes in the mitochondrial membrane. The TIM23 complex translocates and inserts proteins into the mitochondrial inner membrane. Here we analyze the intermembrane space (IMS) domains of Tim23 and Tim50, which are essential subunits of the TIM23 complex, in these functions. We find that interactions of Tim23 and Tim50 in the IMS facilitate transfer of precursor proteins from the TOM40 complex, a general protein translocator in the outer membrane, to the TIM23 complex. Tim23–Tim50 interactions also facilitate a late step of protein translocation across the inner membrane by promoting motor functions of mitochondrial Hsp70 in the matrix. Therefore, the Tim23–Tim50 pair coordinates the actions of the TOM40 and TIM23 complexes together with motor proteins for mitochondrial protein import

Identification of Tam41 maintaining integrity of the TIM23 protein translocator complex in mitochondria

Newly synthesized mitochondrial proteins are imported into mitochondria with the aid of protein translocator complexes in the outer and inner mitochondrial membranes. We report the identification of yeast Tam41, a new member of mitochondrial protein translocator systems. Tam41 is a peripheral inner mitochondrial membrane protein facing the matrix. Disruption of the TAM41 gene led to temperature-sensitive growth of yeast cells and resulted in defects in protein import via the TIM23 translocator complex at elevated temperature both in vivo and in vitro. Although Tam41 is not a constituent of the TIM23 complex, depletion of Tam41 led to a decreased molecular size of the TIM23 complex and partial aggregation of Pam18 and -16. Import of Pam16 into mitochondria without Tam41 was retarded, and the imported Pam16 formed aggregates in vitro. These results suggest that Tam41 facilitates mitochondrial protein import by maintaining the functional integrity of the TIM23 protein translocator complex from the matrix side of the inner membrane

生後早期の心理的ストレスが雌雄ラットの性成熟、性行動に与える影響

Purpose: We studied the influence of psychological stress during the early neonatal period on sexual maturation and sexual behavior in rats. Methods: Neonatal male and female rats were divided into control (C) and maternal separation (MS) groups (n = 20‐24 per group). The pups in the MS groups were placed in isolation cages for 240 minutes/d from postnatal days 2‐11. Vaginal opening (VO) in females and preputial separation (PS) in males (indicators of sexual maturation) were monitored, as was the estrous cycle in females. Thereafter, sexual behavior was monitored twice at 13 and 15 weeks of age. Results: As for sexual maturation, the onset of PS occurred significantly earlier in the MS group than in the C group, whereas the onset of VO did not differ between the groups. The length of the estrous cycle did not differ between the groups. The frequencies of sexual behaviors did not differ between the groups in either sex. Conclusions: In conclusion, early‐life psychological stress induced by MS advanced sexual maturation in male rats, whereas it did not affect sexual maturation in female rats. On the other hand, early‐life psychological stress might not affect sexual behavior in adulthood in either sex

Advent of Continents: A New Hypothesis

The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10-20 km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian arc are underlain by crust ~35 km thick. Interestingly, andesite magmas dominate eruptive products from the former volcanoes and mostly basaltic lavas erupt from the latter. According to the hypothesis presented here, rising mantle diapirs stall near the base of the oceanic crust at depths controlled by the thickness of the overlying crust. Where the crust is thin, melting occurs at relatively low pressures in the mantle wedge producing andesitic magmas. Where the crust is thick, melting pressures are higher and only basaltic magmas tend to be produced. The implications of this hypothesis are: (1) the rate of continental crust accumulation, which is andesitic in composition, would have been greatest soon after subduction initiated on Earth, when most crust was thin; and (2) most andesite magmas erupted on continental crust could be recycled from “primary” andesite originally produced in oceanic arcs

The Molecular Outflows in the rho Ophiuchi Main Cloud: Implications For Turbulence Generation

We present the results of CO (J=3-2) and CO (J=1-0) mapping observations toward the active cluster forming clump, L1688, in the rho Ophiuchi molecular cloud. From the CO (J=3-2) and CO (J=1-0) data cubes, we identify five outflows, whose driving sources are VLA 1623, EL 32, LFAM 26, EL 29, and IRS 44. Among the identified outflows, the most luminous outflow is the one from the prototypical Class 0 source, VLA 1623. We also discover that the EL 32 outflow located in the Oph B2 region has very extended blueshifted and redshifted lobes with wide opening angles. This outflow is most massive and have the largest momentum among the identified outflows in the CO (J=1-0) map. We estimate the total energy injection rate due to the molecular outflows identified by the present and previous studies to be about 0.2 L_solar, larger than or at least comparable to the turbulence dissipation rate [~(0.03 - 0.1) L_solar]. Therefore, we conclude that the protostellar outflows are likely to play a significant role in replenishing the supersonic turbulence in this clump.Comment: 37 pages, 9 figures, accepted for publication in The Astrophysical Journa

Weight reduction by using a formula diet recovers menstruation in obese patients with an ovulatory disorder

Aim: To determine the effectiveness of a formula diet in weight reduction and the recovery of menstruation in obese patients with ovulatory disorders. Methods: After the enrollment of 39 obese women with ovulatory disorders, they replaced one or two of their three normal meals with a microdiet (MD) (240 kcal/meal) for 24 weeks. Physical, endocrinological, and biochemical tests were conducted before and at 12 and 24 weeks of the study. Of the 39 women enrolled, 26 were not taking clomiphene. They were divided into three groups according to their body weight outcomes and then analyzed for menstruation recovery. Results: A weight reduction of ≥5% was observed in 31 (81.5%) of the 39 women. There were significant decreases in the body weight and Body Mass Index during the study. Menstruation returned in 18 (69%) of the 26 patients without clomiphene treatment, with the recovery being significantly more prevalent in the groups (totally 81.0%) that exhibited a 5%‐10% weight reduction and ≥10% weight reduction, compared to the group with a <5% weight reduction. Conclusion: The use of a formula diet effectively reduced the patients’ body weight and led to the recovery of menstruation in these obese patients with ovulatory disorders