Roles for Mitochondrial Complex I subunits in regulating synaptic transmission and growth

To identify conserved components of synapse function that are also associated with human diseases, we conducted a genetic screen. We used the Drosophila melanogaster neuromuscular junction (NMJ) as a model. We employed RNA interference (RNAi) on selected targets and assayed synapse function by electrophysiology. We focused our screen on genetic factors known to be conserved from human neurological or muscle functions (321 total RNAi lines screened). Knockdown of a particular Mitochondrial Complex I (MCI) subunit gene (ND-20L) lowered levels of NMJ neurotransmission. Due to the severity of the phenotype, we studied MCI function further. Knockdown of core MCI subunits concurrently in neurons and muscle led to impaired neurotransmission. Further, pharmacology targeting MCI phenocopied the impaired neurotransmission phenotype. Finally, MCI subunit knockdowns led to profound cytological defects, including reduced NMJ growth and altered NMJ morphology. Mitochondria are essential for cellular bioenergetics and produce ATP through oxidative phosphorylation. Five multi-protein complexes achieve this task, and MCI is the largest. Impaired Mitochondrial Complex I subunits in humans are associated with disorders such as Parkinsons disease, Leigh syndrome, and cardiomyopathy. Together, our data present an analysis of Complex I in the context of synapse function and plasticity. We speculate that in the context of human MCI dysfunction, similar neuronal and synaptic defects could contribute to pathogenesis.

Database of glutamate gated chloride (GluCl) subunits across 125 nematode species: patterns of gene accretion and sequence diversification

Glutamate Gated Chloride (GluCl) channels belong to the Cys-loop receptor superfamily. GluCl channels are activated by glutamate (Glu) and form substrates for the anti-parasitic drugs from the avermectin family. GluCl channels are pentameric, and each subunit contains an N-terminal extracellular domain that binds Glu and four helical transmembrane domains (TMs), which contain binding sites for avermectin drugs. In order to provide more insight into phylum-wide patterns of GluCl subunit gene expansion and sequence diversity across nematodes, we have developed a database of predicted GluCl subunit genes from 125 nematode species. Our analysis into this dataset described assorted patterns of species-specific GluCl gene counts across different nematodes as well as sequence diversity in key residues thought to be involved in avermectin binding.

Heterozygous missense variant of the proteasome subunit β-type 9 causes neonatal-onset autoinflammation and immunodeficiency

Impaired proteasome activity due to genetic variants of certain subunits might lead to proteasome-associated autoinflammatory syndromes (PRAAS). Here we report a de novo heterozygous missense variant of the PSMB9 proteasome subunit gene in two unrelated Japanese infants resulting in amino acid substitution of the glycine (G) by aspartic acid (D) at position 156 of the encoded protein β1i. In addition to PRAAS-like manifestations, these individuals suffer from pulmonary hypertension and immunodeficiency, which are distinct from typical PRAAS symptoms. The missense variant results in impaired immunoproteasome maturation and activity, yet ubiquitin accumulation is hardly detectable in the patients. A mouse model of the heterozygous human genetic variant (Psmb9G156D/+) recapitulates the proteasome defects and the immunodeficiency phenotype of patients. Structurally, PSMB9 G156D interferes with the β-ring-βring interaction of the wild type protein that is necessary for 20S proteasome formation. We propose the term, proteasome-associated autoinflammatory syndrome with immunodeficiency (PRAAS-ID), to indicate a separate category of autoinflammatory diseases, similar to, but distinct from PRAAS, that describes the patients in this study.

Genome-wide survey of Gγ subunit gene family in eight Rosaceae and expression analysis of PbrGGs in pear (Pyrus bretschneideri)

Background Heterotrimeric G-proteins, composed of Gα, Gβ and Gγ subunits, are important signal transmitters, mediating the cellular response to multiple stimuli in animals and plants. The Gγ subunit is an essential component of the G-protein, providing appropriate functional specificity to the heterotrimer complex and has been well studied in many species. However, the evolutionary history, expression pattern and functional characteristics of Gγ subunits has not been explored in the Rosaceae, representing many important fruit crops. Results In this study, 35 Gγ subunit genes were identified from the eight species belonging to the Rosaceae family. Based on the structural gene characteristics, conserved protein motifs and phylogenetic analysis of the Gγ subunit genes, the genes were classified into three clades. Purifying selection was shown to play an important role in the evolution of Gγ subunit genes, while a recent whole-genome duplication event was the principal force determining the expansion of the Gγ subunit gene family in the subfamily Maloideae. Gγ subunit genes exhibited diverse spatiotemporal expression patterns in Chinese white pear, including fruit, root, ovary and bud, and under abiotic stress conditions, the relative expression of Gγ subunit genes were up-regulated or down-regulated. In addition, seven of the Gγ subunit proteins in pear were located on the plasma membrane, in the cytoplasm or nucleus. Conclusion Overall, this study of the Gγ subunit gene family in eight Rosaceae species provided useful information to better understand the evolution and expression of these genes and facilitated further exploration of their functions in these important crop plants.

Modifications in Gamma-aminobutyric Acid type A Receptor Subunit Gene Expression During Macrophage Differentiation and Propofol Administration in THP-1 Cells

Background: Gamma-aminobutyric acid type A (GABAA) receptors are thought to play a role in the functioning of the immune system. GABAA receptors have 19 types of subunits, the components of which determine their physiological functions. However, the subunits that are expressed in immune cells during inflammation have not been fully investigated. Recent reports have shown that anesthetic agents may affect the gene expression of GABAA receptors subunits in immune cells. Therefore, we aimed to investigate the changes in GABAA receptor subunit gene expression during macrophage differentiation and propofol administration in order to clarify the relationship between the expression of GABAA receptors and the immunomodulatory effect of propofol.Methods: Human acute monocytic leukemia (THP-1) cells were differentiated into macrophage-like cells (M0 THP-1); subsequently, M0 THP-1 cells were differentiated into inflammatory M1 macrophage-like cells (M1 THP-1). Propofol was administered during the differentiation into M1 THP-1 cells. Using reverse transcriptase polymerase chain reaction, we examined which GABAA receptor subunit genes were expressed and whether there were changes in the gene expression during macrophage differentiation and propofol administration in THP-1 cells.Results: The expression of the α1, α4, β1, β2, γ1, and γ2 subunits increased during differentiation into M0 THP-1 cells. The expression of the α1, α4, β1, β2, γ2, and δ subunits decreased and that of the γ1 subunit increased during differentiation into M1 THP-1 cells. The gene expression of the α1, α4, and β2 subunits increased upon administering propofol during differentiation into M1 THP-1 cells.Conclusions: The gene expression of GABAA receptor subunits changed during macrophage differentiation in THP-1 cells. The expressions of α1 and α4 increased following propofol administration during the differentiation into M1 THP-1 cells, which may indicate that the GABAA receptor is involved in the immunosuppressive effects of propofol. This study can help in the choice of anesthetic agents for proinflammatory conditions such as highly-invasive surgery.