The membrane attack complex, perforin and cholesterol-dependent cytolysin superfamily of pore-forming proteins

The membrane attack complex and perforin proteins (MACPFs) and bacterial cholesterol-dependent cytolysins (CDCs) are two branches of a large and diverse superfamily of pore-forming proteins that function in immunity and pathogenesis. During pore formation, soluble monomers assemble into large transmembrane pores through conformational transitions that involve extrusion and refolding of two α-helical regions into transmembrane β-hairpins. These transitions entail a dramatic refolding of the protein structure, and the resulting assemblies create large holes in cellular membranes, but they do not use any external source of energy. Structures of the membrane-bound assemblies are required to mechanistically understand and modulate these processes. In this Commentary, we discuss recent advances in the understanding of assembly mechanisms and molecular details of the conformational changes that occur during MACPF and CDC pore formation

Investigating the role of brinp1 in zebrafish development

The Membrane Attack Complex - PerForin (MACPF) superfamily is known to have a diverse array of roles in immunity, embryonic development and neural function. BRINPs (Bone Morphogenetic Protein – Retinoic Acid Inducible Neural specific Proteins) are a family of three MACPF domain-containing proteins that are highly expressed during rodent neural development. Each contains a MACPF domain, but the remainder of the molecule has no significant sequence similarity to any other structurally or functionally characterised protein. BRINP orthologues are highly conserved across vertebrates, suggesting they perform essential functions. In rodents, all three Brinps are ubiquitously expressed in the brain at early embryonic stages, with Brinp1 most highly expressed. In postnatal to adult stages Brinp1 expression is restricted to the hippocampus, olfactory bulb, cerebellum and cerebral cortex. Only low expression of Brinp2 and Brinp3 is observed at these stages. In this study, the zebrafish animal model was used to study the function of brinps in the developing brain, and to determine the effect of disrupting their function. A bioinformatic approach was applied to explore the evolutionary relationships between BRINP family members. The locus arrangement of BRINP genes is conserved in mammals and teleosts. Full-length zebrafish orthologues were identified and cloned, and two additional brinp3 paralogues were discovered. Brinp gene expression in zebrafish was reminiscent of the expression in rodents. Expression was unrestricted in the brain at early stages (24 hpf) and localised to specific brain structures in older embryos (48-72 hpf). Expression was also observed in the primordial fin buds. In addition to the broad and overlapping expression pattern of all brinps, brinp1 was exclusively detected in the lateral line primordium. Through morpholino oligonucleotide gene silencing, loss of function of the brinp1 gene was examined and determined to result in pleiotropic defects in the developing embryo. At 48 hpf, embryos exhibited a curved body axis, aberrant neuromast formation and defects in axonal projections in the head and tail. Finally, this study has led to the identification of a pathway in which brinp1 may function. It was possible to reverse the effect of the curved tail and loss of neuromasts by 72 hpf using a Tyrosine kinase B (TrkB) receptor agonist, providing preliminary evidence that brinp1 functions in the BDNF/ TrkB receptor pathway

A transgenic zebrafish model of hepatocyte function in human Z α1-antitrypsin deficiency

Abstract In human α1-antitrypsin deficiency, homozygous carriers of the Z (E324K) mutation in the gene SERPINA1 have insufficient circulating α1-antitrypsin and are predisposed to emphysema. Misfolding and accumulation of the mutant protein in hepatocytes also causes endoplasmic reticulum stress and underpins long-term liver damage. Here, we describe transgenic zebrafish (Danio rerio) expressing the wildtype or the Z mutant form of human α1-antitrypsin in hepatocytes. As observed in afflicted humans, and in rodent models, about 80% less α1-antitrypsin is evident in the circulation of zebrafish expressing the Z mutant. Although these zebrafish also show signs of liver stress, they do not accumulate α1-antitrypsin in hepatocytes. This new zebrafish model will provide useful insights into understanding and treatment of α1-antitrypsin deficiency.</jats:p

P. Baehni, professeur en médecine dentaire

P. Baehni, professeur en médecine dentair

Additional file 3: Figure S3. of Brinp1 −/− mice exhibit autism-like behaviour, altered memory, hyperactivity and increased parvalbumin-positive cortical interneuron density

Pyramidal neuron distribution in the adult Brinp1 −/− somatosensory neocortex. a Normal density of NeuN+ cells in the Brinp1 −/− somatosensory neocortex. b No significant change in distribution of NeuN+ cells through somatosensory cortical layers, F(1,6) = 1.423, p = 0.278, repeat measures two-way ANOVA. Sections counterstained with DAPI. c No significant changes in Cux1 cell number or distribution were detected in the Brinp1 −/− somatosensory neocortex, F(1,6) = 2.027, p = 0.204, repeat measures two-way ANOVA. N = 4 WT, 4 Brinp1 −/− mice. *p < 0.05, **p < 0.01. All data represented as the mean ± SD. (PNG 2569 kb

Additional file 4: Figure S4. of Brinp1 −/− mice exhibit autism-like behaviour, altered memory, hyperactivity and increased parvalbumin-positive cortical interneuron density

Up-regulation of Astrotactin 1 and Astrotactin 2 mRNA in the embryonic brain and adult hippocampus of Brinp1 knock-out mice (normalised with actin). a qPCR showing a significant increase in Astn2 mRNA, t(9) = 2.829, p = 0.0222, in the developing (E18.5) mouse brain. Levels of exon 3-deleted Brinp1 mRNA (Brinp1Δe3) also increase t(9) = 2.733, p = 0.0231, unpaired Student’s t tests. No significant changes overserved for Brinp2 mRNA levels or Brinp3 mRNA levels. b An increase in Astn1 and Astn2 expression was also detectable in the hippocampus at 6 weeks of the Brinp1 −/− mice: Astn1: t(9) = 3.384, p = 0.0081, Astn2: t(9) = 2.821, p = 0.0200, unpaired Student’s t tests. No significant changes were detected in levels of Brinp1Δe3 mRNA, Brinp2 mRNA or Brinp3 mRNA. c No significant change in expression of Brinps or Astrotactins in the 6-week-old Brinp1 −/− cortex. N = 3 WT, 4 Brinp1 −/−, *p < 0.05, **p < 0.01. Normalisation against actin expression levels. All data represented as the mean ± SE. (PNG 70 kb