Regulated membrane remodeling by Mic60 controls formation of mitochondrial crista junctions

The mitochondrial contact site and cristae organizing system (MICOS) is crucial for the formation of crista junctions and mitochondrial inner membrane architecture. MICOS contains two core components. Mic10 shows membrane-bending activity, whereas Mic60 (mitofilin) forms contact sites between inner and outer membranes. Here we report that Mic60 deforms liposomes into thin membrane tubules and thus displays membrane-shaping activity. We identify a membrane-binding site in the soluble intermembrane space-exposed part of Mic60. This membrane-binding site is formed by a predicted amphipathic helix between the conserved coiled-coil and mitofilin domains. The mitofilin domain negatively regulates the membrane-shaping activity of Mic60. Binding of Mic19 to the mitofilin domain modulates this activity. Membrane binding and shaping by the conserved Mic60-Mic19 complex is crucial for crista junction formation, mitochondrial membrane architecture and efficient respiratory activity. Mic60 thus plays a dual role by shaping inner membrane crista junctions and forming contact sites with the outer membrane

Structural insights into crista junction formation by the Mic60-Mic19 complex

Mitochondrial cristae membranes are the oxidative phosphorylation sites in cells. Crista junctions (CJs) form the highly curved neck regions of cristae and are thought to function as selective entry gates into the cristae space. Little is known about how CJs are generated and maintained. We show that the central coiled-coil (CC) domain of the mitochondrial contact site and cristae organizing system subunit Mic60 forms an elongated, bow tie–shaped tetrameric assembly. Mic19 promotes Mic60 tetramerization via a conserved interface between the Mic60 mitofilin and Mic19 CHCH (CC-helix-CC-helix) domains. Dimerization of mitofilin domains exposes a crescent-shaped membrane-binding site with convex curvature tailored to interact with the curved CJ neck. Our study suggests that the Mic60-Mic19 subcomplex traverses CJs as a molecular strut, thereby controlling CJ architecture and function

Microbial diversity and community composition of caecal microbiota in commercial and indigenous Indian chickens determined using 16s rDNA amplicon sequencing

Different alpha diversity indices for each sample of university farm data estimated using QIIME for primer pair P2 data. OTUs were clustered at > 97% similarity. (XLSX 12 kb

Assessment of probiotics supplementation via feed or water on the growth performance, intestinal morphology and microflora of chickens after experimental infection with Eimeria acervulina, Eimeria maxima and Eimeria tenella

In this study, the effect of probiotic supplementation via drinking water or feed on the performance of broiler chickens experimentally infected with sporulated oocysts of Eimeria acervulina (5 x 10(4)), Eimeria maxima and Eimeria tenella (2 x 10(4) each one) at 14 days of age was evaluated. Two hundred and forty 1-day-old Ross 308 male chicks were separated into eight equal groups with three replicates. Two of the groups, one infected with mixed Eimeria oocysts and the other not, were given a basal diet and served as controls. The remaining groups were also challenged with mixed Eimeria species and received the basal diet and either water supplemented with probiotic (three groups) or probiotic via feed (two groups); the probiotic used consisted of Enterococcus faecium #589, Bifidobacterium animalis #503 and Lactobacillus salivarius #505 at a ratio of 6:3:1. Probiotic supplementation was applied either via drinking water in different inclusion rates (groups W1, W2 and W3) or via feed using uncoated (group FN) or coated strains (group FC). The last group was given the basal diet supplemented with the anticoccidial lasalocid at 75 mg/kg. Each experimental group was given the corresponding diet or drinking water from day 1 to day 42 of age. Throughout the experimental period of 42 days, body weight and feed intake were recorded weekly and feed conversion ratios were calculated. Seven days after infection, the infected control group presented the lowest weight gain values, while probiotics supplied via feed supported growth to a comparable level with that of the lasalocid group. Probiotic groups presented lesion score values and oocyst numbers that were lower than in control infected birds but higher than in the lasalocid group. In the duodenum, jejunum and ileum, the highest villous height values were presented by probiotic groups. In conclusion, a mixture of probiotic substances gave considerable improvement in both growth performance and intestinal health in comparison with infected control birds and fairly similar improvement to an approved anticoccidial during a mixed Eimeria infection

Measuring pressure distribution under the seat cushion and dividing the pressure map in six regions might be beneficial for comfort studies of aircraft seats

Seat pressure maps are often used to evaluate comfort of the users. In this study, we explored the relationships between pressure maps and comfort/discomfort of users in aircraft seats with a focus on a new 6-division method on the pressure maps collected at the bottom of the cushions. An experiment was designed where three cushions with identical shapes but different stiffnesses were prepared. 33 subjects joined the experiment and after sitting on each cushion in 4 postures, they completed comfort questionnaires. Pressure maps on the top as well as the bottom of cushions were collected and analysed. Results indicated that measures on the proposed 6 divisions, especially on the distal posterior thigh regions and regions close to ischial tuberosity of the bottom pressure maps, had larger correlation values to comfort scores compared to other division methods. Practitioner summary: The relations between comfort/discomfort and seat pressure maps collected from the top/bottom of three cushions were studied with 33 subjects in four postures. The distal posterior thigh and ischial tuberosity regions in the proposed 6-division of the bottom pressure maps had larger correlation values to comfort/discomfort compared to other methods.Emerging MaterialsApplied Ergonomics and Desig

Structural and functional analysis of the NLRP4 pyrin domain

NLRP4 is a member of the nucleotide-binding and leucine-rich repeat receptor (NLR) family of cytosolic receptors and a member of an inflammation signaling cascade. Here, we present the crystal structure of the NLRP4 pyrin domain (PYD) at 2.3 Å resolution. The NLRP4 PYD is a member of the death domain (DD) superfamily and adopts a DD fold consisting of six α-helices tightly packed around a hydrophobic core, with a highly charged surface that is typical of PYDs. Importantly, however, we identified several differences between the NLRP4 PYD crystal structure and other PYD structures that are significant enough to affect NLRP4 function and its interactions with binding partners. Notably, the length of helix α3 and the α2−α3 connecting loop in the NLRP4 PYD are unique among PYDs. The apoptosis-associated speck-like protein containing a CARD (ASC) is an adaptor protein whose interactions with a number of distinct PYDs are believed to be critical for activation of the inflammatory response. Here, we use co-immunoprecipitation, yeast two-hybrid, and nuclear magnetic resonance chemical shift perturbation analysis to demonstrate that, despite being important for activation of the inflammatory response and sharing several similarities with other known ASC-interacting PYDs (i.e., ASC2), NLRP4 does not interact with the adaptor protein ASC. Thus, we propose that the factors governing homotypic PYD interactions are more complex than the currently accepted model, which states that complementary charged surfaces are the main determinants of PYD–PYD interaction specificity

Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1

Balanced fusion and fission are key for the proper function and physiology of mitochondria. Remodelling of the mitochondrial inner membrane is mediated by the dynamin-like protein mitochondrial genome maintenance 1 (Mgm1) in fungi or the related protein optic atrophy 1 (OPA1) in animals. Mgm1 is required for the preservation of mitochondrial DNA in yeast, whereas mutations in the OPA1 gene in humans are a common cause of autosomal dominant optic atrophy-a genetic disorder that affects the optic nerve. Mgm1 and OPA1 are present in mitochondria as a membrane-integral long form and a short form that is soluble in the intermembrane space. Yeast strains that express temperature-sensitive mutants of Mgm1 or mammalian cells that lack OPA1 display fragmented mitochondria, which suggests that Mgm1 and OPA1 have an important role in inner-membrane fusion. Consistently, only the mitochondrial outer membrane-not the inner membrane-fuses in the absence of functional Mgm1. Mgm1 and OPA1 have also been shown to maintain proper cristae architecture; for example, OPA1 prevents the release of pro-apoptotic factors by tightening crista junctions. Finally, the short form of OPA1 localizes to mitochondrial constriction sites, where it presumably promotes mitochondrial fission. How Mgm1 and OPA1 perform their diverse functions in membrane fusion, scission and cristae organization is at present unknown. Here we present crystal and electron cryo-tomography structures of Mgm1 from Chaetomium thermophilum. Mgm1 consists of a GTPase (G) domain, a bundle signalling element domain, a stalk, and a paddle domain that contains a membrane-binding site. Biochemical and cell-based experiments demonstrate that the Mgm1 stalk mediates the assembly of bent tetramers into helical filaments. Electron cryo-tomography studies of Mgm1-decorated lipid tubes and fluorescence microscopy experiments on reconstituted membrane tubes indicate how the tetramers assemble on positively or negatively curved membranes. Our findings convey how Mgm1 and OPA1 filaments dynamically remodel the mitochondrial inner membrane

Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1

Balanced fusion and fission are key for the proper function and physiology of mitochondria. Remodelling of the mitochondrial inner membrane is mediated by the dynamin like protein mitochondrial genome maintenance 1 Mgm1 in fungi or the related protein optic atrophy 1 OPA1 in animals. Mgm1 is required for the preservation of mitochondrial DNA in yeast6, whereas mutations in the OPA1 gene in humans are a common cause of autosomal dominant optic atrophy a genetic disorder that affects the optic nerve. Mgm1 and OPA1 are present in mitochondria as a membrane integral long form and a short form that is soluble in the intermembrane space. Yeast strains that express temperature sensitive mutants of Mgm or mammalian cells that lack OPA1 display fragmented mitochondria, which suggests that Mgm1 and OPA1 have an important role in inner membrane fusion. Consistently, only the mitochondrial outer membrane not the inner membrane fuses in the absence of functional Mgm113. Mgm1 and OPA1 have also been shown to maintain proper cristae architecture; for example, OPA1 prevents the release of pro apoptotic factors by tightening crista junctions. Finally, the short form of OPA1 localizes to mitochondrial constriction sites, where it presumably promotes mitochondrial fission. How Mgm1 and OPA1 perform their diverse functions in membrane fusion, scission and cristae organization is at present unknown. Here we present crystal and electron cryo tomography structures of Mgm1 from Chaetomium thermophilum. Mgm1 consists of a GTPase G domain, a bundle signalling element domain, a stalk, and a paddle domain that contains a membrane binding site. Biochemical and cell based experiments demonstrate that the Mgm1 stalk mediates the assembly of bent tetramers into helical filaments. Electron cryo tomography studies of Mgm1 decorated lipid tubes and fluorescence microscopy experiments on reconstituted membrane tubes indicate how the tetramers assemble on positively or negatively curved membranes. Our findings convey how Mgm1 and OPA1 filaments dynamically remodel the mitochondrial inner membran