Journal: Nucleic Acids Research
Article Title: Mitochondrial DNA replication is regulated by endoplasmic reticulum-mitochondrial contact sites, the mitochondrial calcium uniporter, and manganese
doi: 10.1093/nar/gkag233
Figure Lengend Snippet: Gene-silencing Reticulon 4 or ERLIN2 inhibits mtDNA replication in primary human fibroblasts. Cells were transfected with and without silencer RNA Tm targeting RTN4 or ERLIN2 (Thermo Fisher). Isolated protein from fibroblasts was immunoblotted for Reticulon 4 ( A ) or ERLIN2 ( D ) after fractionation by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and quantified relative to stained total protein (No-stain™) ( n = 3–4 independent experiments). Representative images of cells treated without and with silencer RNAs targeting RTN4 ( B ) or ERLIN2 ( E ) pulse-labelled with bromo-deoxyuridine (BrdU) for 8 h and stained with the anti-BrdU antibody (green), and anti-TOMM20 antibody (red), the latter to highlight the mitochondrial network. Scale bar = 30 µm. Quantification of the cytoplasmic BrdU foci (C, F). Data represent the pooled results of three independent experiments (Figs and , and ). Data in panel (C) are derived from an analysis of 316 non-target transfected cells (NT) versus 247 RTN4 silenced cells ( n = 10 independent experiments, P < .001). Data in panel ( F ) are derived from an analysis of 308 NT cells versus 229 ERLIN2 silenced cells ( n = 10 independent experiments, P < .001). ( G ) Interpretation of the relationship between ERMCS and mtDNA replication. The mtDNA forms nucleoprotein complexes, or nucleoids, which are tightly associated with the IMM (inner mitochondrial membrane). MtDNA replicates (detected as BrdU incorporation in newly synthesized DNA—green circles) where the tubular ER (TER) forms connections with the mitochondria that include lipid rafts associated with the outer mitochondrial membrane (OMM). Without Reticulon 4 TER cannot form, while the absence ERLIN2 compromises the lipid microdomains; hence, the absence of RTN4 and ERLIN2 inhibit mtDNA synthesis (pink nucleoids containing non-replicating mtDNA).
Article Snippet: Anti-DNA (Progen, #690014S, 1:250), BrdU (Abcam, #Ab6326, 1:250), TOMM20 (Proteintech, #11802-1-AP, 1:250), TOMM20 (Santa Cruz, #Sc-17764, 1:250), GRP75 (Santa Cruz, #Sc-133137, 1:200), IP3R1 (Novus, #NB120-5908, 1:200), ERLIN2 (Sigma–Aldrich, #HPA002025, 1:200), RTN4 (Atlas, #HPA023977, only ICC, 1:250), KDEL (Novus, #NBP1-97469, 1:700), GRP78/BiP (Abcam, #ab21685, 1:1000).
Techniques: Transfection, Isolation, Fractionation, Polyacrylamide Gel Electrophoresis, SDS Page, Staining, Derivative Assay, Membrane, BrdU Incorporation Assay, Synthesized