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English Journal

Novel intracellular functions of apolipoproteins: the ApoO protein family as constituents of the Mitofilin/MINOS complex determines cristae morphology in mitochondria.

Koob S, Reichert AS.AbstractAbstract Mitochondria exist in a highly dynamic network that is constantly altered by fusion and fission events depending on various factors such as cellular bioenergetic state and cell cycle. Next to this dynamic nature of the organelle, its cristae membrane also undergoes drastic morphological changes upon physiological or pathological alterations. The Mitofilin/mitochondrial inner membrane organizing system (MINOS) complex was recently reported to ensure mitochondrial architecture and crista junction integrity. Several subunits of this complex are linked to a diverse set of neurological human disorders. Recently, two apolipoproteins, ApoO (APOO) and ApoO-like (APOOL) were suggested to represent constituents of the mammalian Mitofilin/MINOS complex. APOOL was shown to bind the mitochondrial phospholipid cardiolipin (CL) and to interact physically with this complex. In this review we highlight the current view on the mammalian Mitofilin/MINOS complex and focus on APOOL and the role of CL in determining cristae morphology. We will discuss possible functions of the Mitofilin/MINOS complex on lipid transport, on assembly of respiratory supercomplexes, on F1FO-ATP synthase organization, on contact site formation, and on trapping CL within the cristae subcompartment.
Biological chemistry.Biol Chem.2014 Mar 1;395(3):285-96. doi: 10.1515/hsz-2013-0274.
Abstract Mitochondria exist in a highly dynamic network that is constantly altered by fusion and fission events depending on various factors such as cellular bioenergetic state and cell cycle. Next to this dynamic nature of the organelle, its cristae membrane also undergoes drastic morphological cha
PMID 24391192

Insulin receptor substrate-1 associates with small nucleolar RNA which contributes to ribosome biogenesis.

Ozoe A1, Sone M1, Fukushima T2, Kataoka N3, Chida K1, Asano T4, Hakuno F1, Takahashi S1.Author information 1Graduate School of Agriculture and Life Sciences, The University of Tokyo , Tokyo , Japan.2Graduate School of Agriculture and Life Sciences, The University of Tokyo , Tokyo , Japan ; Institute of Biomedical and Health Sciences, Hiroshima University , Hiroshima , Japan.3Laboratory for Malignancy Control Research, Medical Innovation Center, Graduate School of Medicine, Kyoto University , Kyoto , Japan.4Institute of Biomedical and Health Sciences, Hiroshima University , Hiroshima , Japan.AbstractInsulin receptor substrates (IRSs) are well known to play crucial roles in mediating intracellular signals of insulin-like growth factors (IGFs)/insulin. Previously, we showed that IRS-1 forms high molecular mass complexes containing RNAs. To identify RNAs in IRS-1 complexes, we performed ultraviolet (UV) cross-linking and immunoprecipitation analysis using HEK293 cells expressing FLAG-IRS-1 and FLAG-IRS-2. We detected the radioactive signals in the immunoprecipitates of FLAG-IRS-1 proportional to the UV irradiation, but not in the immunoprecipitates of FLAG-IRS-2, suggesting the direct contact of RNAs with IRS-1. RNAs cross-linked to IRS-1 were then amplified by RT-PCR, followed by sequence analysis. We isolated sequence tags attributed to 25 messenger RNAs and 8 non-coding RNAs, including small nucleolar RNAs (snoRNAs). We focused on the interaction of IRS-1 with U96A snoRNA (U96A) and its host Rack1 (receptor for activated C kinase 1) pre-mRNA. We confirmed the interaction of IRS-1 with U96A, and with RACK1 pre-mRNA by immunoprecipitation with IRS-1 followed by Northern blotting or RT-PCR analyses. Mature U96A in IRS-1(-/-) mouse embryonic fibroblasts was quantitatively less than WT. We also found that a part of nuclear IRS-1 is localized in the Cajal body, a nuclear subcompartment where snoRNA mature. The unanticipated function of IRS-1 in snoRNA biogenesis highlights the potential of RNA-associated IRS-1 complex to open a new line of investigation to dissect the novel mechanisms regulating IGFs/insulin-mediated biological events.
Frontiers in endocrinology.Front Endocrinol (Lausanne).2014 Mar 4;5:24. doi: 10.3389/fendo.2014.00024. eCollection 2014.
Insulin receptor substrates (IRSs) are well known to play crucial roles in mediating intracellular signals of insulin-like growth factors (IGFs)/insulin. Previously, we showed that IRS-1 forms high molecular mass complexes containing RNAs. To identify RNAs in IRS-1 complexes, we performed ultraviole
PMID 24624118

Dynamics of Polycomb chromatin domains under conditions of increased molecular crowding.

Smigová J1, Juda P, Bártová E, Raška I.Author information 1Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic.AbstractBACKGROUND INFORMATION: A Polycomb (PcG) body is an orphan nuclear subcompartment characterised by accumulations of Polycomb repressive complex 1 (PRC1) proteins. However, seemingly contradictory reports have appeared that describe the PcG bodies either as protein-based bodies in the interchromatin compartment or chromatin domains. In this respect, molecular crowding is an important factor for the assembly and stability of nuclear subcompartments. In order to settle this contradiction, crowding experiments, that represent a convenient model distinguishing between interchromatin and chromatin compartments, were carried out.
Biology of the cell / under the auspices of the European Cell Biology Organization.Biol Cell.2013 Nov;105(11):519-34. doi: 10.1111/boc.201300022. Epub 2013 Sep 16.
BACKGROUND INFORMATION: A Polycomb (PcG) body is an orphan nuclear subcompartment characterised by accumulations of Polycomb repressive complex 1 (PRC1) proteins. However, seemingly contradictory reports have appeared that describe the PcG bodies either as protein-based bodies in the interchromatin
PMID 23937274