-
Science (New York, N.Y.) Sep 2012Cells have developed ways to sense and control the size of their organelles. Size-sensing mechanisms range from direct measurements provided by dedicated reporters to... (Review)
Review
Cells have developed ways to sense and control the size of their organelles. Size-sensing mechanisms range from direct measurements provided by dedicated reporters to indirect functional readouts, and they are used to modify organelle size under both normal and stress conditions. Organelle size can also be controlled in the absence of an identifiable size sensor. Studies on flagella have dissected principles of size sensing and control, and it will be exciting to see how these principles apply to other organelles.
Topics: Animals; Biological Transport; Cell Physiological Phenomena; Flagella; Humans; Models, Biological; Organelle Size; Organelles
PubMed: 22955827
DOI: 10.1126/science.1223539 -
IUBMB Life Aug 2013Organelles within a eukaryotic cell respond to age-related intracellular stresses and environmental factors by altering their functional states to generate, direct and... (Review)
Review
Organelles within a eukaryotic cell respond to age-related intracellular stresses and environmental factors by altering their functional states to generate, direct and process the flow of interorganellar information that is essential for establishing a pro- or antiaging cellular pattern. The scope of this review is to critically analyze recent progress in understanding how various intercompartmental (i.e., organelle-organelle and organelle-cytosol) communications regulate cellular aging in evolutionarily distant eukaryotes. Our analysis suggests a model for an intricate network of intercompartmental communications that underly cellular aging in eukaryotic organisms across phyla. This proposed model posits that the numerous directed, coordinated and regulated organelle-organelle and organelle-cytosol communications integrated into this network define the long-term viability of a eukaryotic cell and, thus, are critical for regulating cellular aging.
Topics: Animals; Cell Compartmentation; Cellular Senescence; Cytosol; Humans; Lysosomes; Mechanistic Target of Rapamycin Complex 1; Mitochondria; Models, Biological; Multiprotein Complexes; Organelles; Peroxisomes; Signal Transduction; TOR Serine-Threonine Kinases; Vacuoles
PubMed: 23818261
DOI: 10.1002/iub.1183 -
Philosophical Transactions of the Royal... May 2018Compartmentalization is a characterizing feature of complexity in cells, used to organize their biochemistry. Membrane-bound organelles are most widely known, but... (Review)
Review
Compartmentalization is a characterizing feature of complexity in cells, used to organize their biochemistry. Membrane-bound organelles are most widely known, but non-membrane-bound liquid organelles also exist. These have recently been shown to form by phase separation of specific types of proteins known as scaffolds. This forms two phases: a condensate that is enriched in scaffold protein separated by a phase boundary from the cytoplasm or nucleoplasm with a low concentration of the scaffold protein. Phase separation is well known for synthetic polymers, but also appears important in cells. Here, we review the properties of proteins important for forming these non-membrane-bound organelles, focusing on the energetically favourable interactions that drive condensation. On this basis we make qualitative predictions about how cells may control compartmentalization by condensates; the partition of specific molecules to a condensate; the control of condensation and dissolution of condensates; and the regulation of condensate nucleation. There are emerging data supporting many of these predictions, although future results may prove incorrect. It appears that many molecules may have the ability to modulate condensate formation, making condensates a potential target for future therapeutics. The emerging properties of condensates are fundamentally unlike the properties of membrane-bound organelles. They have the capacity to rapidly integrate cellular events and act as a new class of sensors for internal and external environments.This article is part of the theme issue 'Self-organization in cell biology'.
Topics: Biophysical Phenomena; Cytoplasm; Organelles; Proteins
PubMed: 29632271
DOI: 10.1098/rstb.2017.0193 -
BioEssays : News and Reviews in... Jan 2015Why the DNA-containing organelles, chloroplasts, and mitochondria, are inherited maternally is a long standing and unsolved question. However, recent years have seen a... (Review)
Review
Why the DNA-containing organelles, chloroplasts, and mitochondria, are inherited maternally is a long standing and unsolved question. However, recent years have seen a paradigm shift, in that the absoluteness of uniparental inheritance is increasingly questioned. Here, we review the field and propose a unifying model for organelle inheritance. We argue that the predominance of the maternal mode is a result of higher mutational load in the paternal gamete. Uniparental inheritance evolved from relaxed organelle inheritance patterns because it avoids the spread of selfish cytoplasmic elements. However, on evolutionary timescales, uniparentally inherited organelles are susceptible to mutational meltdown (Muller's ratchet). To prevent this, fall-back to relaxed inheritance patterns occurs, allowing low levels of sexual organelle recombination. Since sexual organelle recombination is insufficient to mitigate the effects of selfish cytoplasmic elements, various mechanisms for uniparental inheritance then evolve again independently. Organelle inheritance must therefore be seen as an evolutionary unstable trait, with a strong general bias to the uniparental, maternal, mode.
Topics: Animals; Female; Genome; Humans; Inheritance Patterns; Models, Genetic; Organelles; Phylogeny; Selection, Genetic
PubMed: 25302405
DOI: 10.1002/bies.201400110 -
Molecular Biology of the Cell Mar 2018
Topics: Animals; Cilia; Congresses as Topic; Endoplasmic Reticulum; Humans; Mitochondria; Models, Biological; Organelle Biogenesis; Organelles; Schizosaccharomyces; Shigella
PubMed: 29535176
DOI: 10.1091/mbc.E17-11-0681 -
Translational Stroke Research Dec 2013The highly evolutionarily conserved 70 kDa heat shock protein (HSP70) family was first understood for its role in protein folding and response to stress. Subsequently,... (Review)
Review
The highly evolutionarily conserved 70 kDa heat shock protein (HSP70) family was first understood for its role in protein folding and response to stress. Subsequently, additional functions have been identified for it in regulation of organelle interaction, of the inflammatory response, and of cell death and survival. Overexpression of HSP70 family members is associated with increased resistance to and improved recovery from cerebral ischemia. MicroRNAs (miRNAs) are important posttranscriptional regulators that interact with multiple target messenger RNAs (mRNA) coordinately regulating target genes, including chaperones. The members of the HSP70 family are now appreciated to work together as networks to facilitate organelle communication and regulate inflammatory signaling and cell survival after cerebral ischemia. This review will focus on the new concept of the role of the chaperone network in the organelle network and its novel regulation by miRNA.
Topics: Brain Ischemia; HSP70 Heat-Shock Proteins; Humans; MicroRNAs; Mitochondria; Molecular Chaperones; Organelles; Protein Folding; RNA, Messenger
PubMed: 24323423
DOI: 10.1007/s12975-013-0280-3 -
Molecular Plant Jun 2019Mitochondria and plastids form dynamic, evolving populations physically embedded in the fluctuating environment of the plant cell. Their evolutionary heritage has shaped... (Review)
Review
Mitochondria and plastids form dynamic, evolving populations physically embedded in the fluctuating environment of the plant cell. Their evolutionary heritage has shaped how the cell controls the genetic structure and the physical behavior of its organelle populations. While the specific genes involved in these processes are gradually being revealed, the governing principles underlying this controlled behavior remain poorly understood. As the genetic and physical dynamics of these organelles are central to bioenergetic performance and plant physiology, this challenges both fundamental biology and strategies to engineer better-performing plants. This article reviews current knowledge of the physical and genetic behavior of mitochondria and chloroplasts in plant cells. An overarching hypothesis is proposed whereby organelles face a tension between genetic robustness and individual control and responsiveness, and different species resolve this tension in different ways. As plants are immobile and thus subject to fluctuating environments, their organelles are proposed to favor individual responsiveness, sacrificing genetic robustness. Several notable features of plant organelles, including large genomes, mtDNA recombination, fragmented organelles, and plastid/mitochondrial differences may potentially be explained by this hypothesis. Finally, the ways that quantitative and systems biology can help shed light on the plethora of open questions in this field are highlighted.
Topics: Cell Nucleus; Chloroplasts; Mitochondria; Organelles; Plant Cells; Plastids
PubMed: 30445187
DOI: 10.1016/j.molp.2018.11.002 -
The FEBS Journal May 2020Cellular organelles that lack a surrounding lipid bilayer, such as the nucleolus and stress granule, represent a newly recognized, general paradigm of cellular... (Review)
Review
Cellular organelles that lack a surrounding lipid bilayer, such as the nucleolus and stress granule, represent a newly recognized, general paradigm of cellular organization. The formation of such biomolecular condensates that include 'membraneless organelles' (MLOs) by liquid-liquid phase separation (LLPS) has been in the focus of a surge of recent studies. Through a combination of in vitro and in vivo approaches, thousands of potential phase-separating proteins have been identified, and it was found that different cellular MLOs share many common components. These perplexing observations raise the question of how cells regulate the timing and specificity of LLPS, and ensure that different MLOs form and disperse at the right moment and cellular location and can preserve their identity and physical separation. This guide gives an overview of basic regulatory mechanisms, which manifest through the action of intrinsic regulatory elements, alternative splicing, post-translational modifications, and a broad range of phase-separating partners. We also elaborate on the cellular integration of these different mechanisms and highlight how complex regulation can orchestrate the parallel functioning of a dozen or so different MLOs in the cell.
Topics: Cytoplasm; Humans; Lipid Bilayers; Organelles; Protein Processing, Post-Translational; Proteins
PubMed: 32080961
DOI: 10.1111/febs.15254 -
Biochimica Et Biophysica Acta Feb 2013Cells have complex membranous organelles for the compartmentalization and the regulation of most intracellular processes. Organelle biogenesis and maintenance requires... (Review)
Review
Cells have complex membranous organelles for the compartmentalization and the regulation of most intracellular processes. Organelle biogenesis and maintenance requires newly synthesized proteins, each of which needs to go from the ribosome translating its mRNA to the correct membrane for insertion or transclocation to an a organellar subcompartment. Decades of research have revealed how proteins are targeted to the correct organelle and translocated across one or more organelle membranes ro the compartment where they function. The paradigm examples involve interactions between a peptide sequence in the protein, localization factors, and various membrane embedded translocation machineries. Membrane translocation is either cotranslational or posttranslational depending on the protein and target organelle. Meanwhile research in embryos, neurons and yeast revealed an alternative targeting mechanism in which the mRNA is localized and only then translated to synthesize the protein in the correct location. In these cases, the targeting information is coded by the cis-acting sequences in the mRNA ("Zipcodes") that interact with localization factors and, in many cases, are transported by the molecular motors on the cytoskeletal filaments. Recently, evidence has been found for this "mRNA based" mechanism in organelle protein targeting to endoplasmic reticulum, mitochondria, and the photosynthetic membranes within chloroplasts. Here we review known and potential roles of mRNA localization in protein targeting to and within organelles. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
Topics: Amino Acid Sequence; Animals; Chloroplasts; Endoplasmic Reticulum; Mitochondria; Organelles; Protein Transport; Proteins; RNA, Messenger
PubMed: 23457718
DOI: 10.1016/j.bbamcr.2012.04.004 -
Current Opinion in Microbiology Oct 2013Genetic drift and mutational pressure have shaped the evolution of mitochondrial and chloroplast genomes, giving rise to mechanisms that regulate their gene expression,... (Review)
Review
Genetic drift and mutational pressure have shaped the evolution of mitochondrial and chloroplast genomes, giving rise to mechanisms that regulate their gene expression, which often differ from those in their prokaryotic ancestors. Advances in next generation sequencing technologies have enabled highly detailed characterization of organelle transcriptomes and the discovery of new transcripts and mechanisms for controlling gene expression. Here we discuss the common features of organelle transcriptomes that stem from their prokaryotic origin and some of the new innovations that are unique to organelles of multicellular organisms.
Topics: Animals; Chloroplasts; Mitochondria; Plant Cells; Plants; Transcriptome
PubMed: 23932204
DOI: 10.1016/j.mib.2013.07.011