Organelles bring order to eukaryotic cells, as the membrane-bound compartments that ensure the localized control of specific cellular activities. Their formation must therefore be tightly regulated but also sufficiently dynamic to allow adaptation to a changing cellular environment and to guarantee that they are correctly inherited during cell division.
Although early microscopy studies at the turn of the last century led to an appreciation of the variety of such entities in cells, their dynamic nature and functional remits became clear only with the advent of modern cell biological techniques. Furthermore, it has taken us longer still to get to grips with the mechanisms by which such organelles are formed and maintained. In this Focus issue, we home in on a selected set of organelles: the autophagosome, lipid droplets, peroxisomes and chloroplasts. Although some have received less attention over the years than the major organelles of the secretory pathway, the fundamental importance of each is now understood.
As these articles highlight, the biogenesis of different organelles involves common regulatory themes, such as the use of dedicated machineries for organelle-specific protein import and the outsourcing of membranes, as well as defining features that are tightly entwined with their unique morphology, physical properties and biological function. In this Focus, we hope to emphasize the progress that is being made in characterizing organelle formation and homeostasis, and the wonder of these biological centres of excellence.
Research Highlights
Cell division: Ciliary membrane inheritance directs ciliogenesis
doi:10.1038/nrm3697
Nature Reviews Molecular Cell Biology 14, 750 (2013)
Nuclear organization: Microtubule shaping of the nucleus
doi:10.1038/nrm3698
Nature Reviews Molecular Cell Biology 14, 752 (2013)
IN BRIEF
Development: Multiciliogenesis from scratch | PDF (81 KB)
p751 | doi:10.1038/nrm3709
Nature Reviews Molecular Cell Biology 14, 751 (2013)
Autophagy: Selective degradation of P granule components | PDF (81 KB)
p751 | doi:10.1038/nrm3710
Nature Reviews Molecular Cell Biology 14, 751 (2013)
Exocytosis: A sortilin for secretory granules | PDF (81 KB)
p751 | doi:10.1038/nrm3711
Nature Reviews Molecular Cell Biology 14, 751 (2013)
Foreword
Size and position matter
Graham Warren
doi:10.1038/nrm3705
Nature Reviews Molecular Cell Biology 14, 755 (2013)
Reviews
The autophagosome: origins unknown, biogenesis complex
Christopher A. Lamb, Tamotsu Yoshimori & Sharon A. Tooze
doi:10.1038/nrm3696
Nature Reviews Molecular Cell Biology 14, 759 (2013)
Autophagosome biogenesis starts at the isolation membrane (also called the phagophore). Our understanding of the molecular processes that initiate the isolation membrane, the membrane sources from which this membrane originates and how it is expanded to the autophagosome membrane by autophagy-related (ATG) proteins and the vesicular trafficking machinery, is increasing.
The biophysics and cell biology of lipid droplets
Abdou Rachid Thiam, Robert V. Farese Jr & Tobias C. Walther
doi:10.1038/nrm3699
Nature Reviews Molecular Cell Biology 14, 775 (2013)
Lipid droplets are intracellular organelles that store oil-based reserves of metabolic energy and components of membrane lipids. Basic biophysical principles of emulsions are important for lipid droplet biology, their formation, growth and shrinkage. Such mechanisms enable cells to use emulsified oil when required. The surfactant composition at the lipid droplet surface is crucial for homeostasis and protein targeting to their surfaces.
Biogenesis and homeostasis of chloroplasts and other plastids
Paul Jarvis & Enrique López-Juez
doi:10.1038/nrm3702
Nature Reviews Molecular Cell Biology 14, 787 (2013)
Chloroplasts are the ancestral members of the plastid organelle family. Their identity, division and biogenesis require the import of nucleus-encoded proteins and tight coordination between the organellar genetic system and the nucleocytosolic system. The ubiquitin–proteasome system also links plastid homeostasis and biogenesis to organismal development.
Peroxisomes take shape
Jennifer J. Smith & John D. Aitchison
doi:10.1038/nrm3700
Nature Reviews Molecular Cell Biology 14, 803 (2013)
The control of peroxisome biogenesis by different mechanisms, including de novo generation or growth and fisson of existing peroxisomes, may be coordinated to control peroxisome size and number. Dissecting this process should aid our understanding of how peroxisome dynamics are regulated, with implications for peroxisome-related diseases.
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