scholarly journals Acidocalcisome-Mitochondrion Membrane Contact Sites in Trypanosoma brucei

Pathogens ◽  
2018 ◽  
Vol 7 (2) ◽  
pp. 33 ◽  
Author(s):  
Srinivasan Ramakrishnan ◽  
Beejan Asady ◽  
Roberto Docampo
Keyword(s):  
Trypanosoma Brucei ◽  
Mammalian Cells ◽  
Close Association ◽  
Super Resolution ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Starting Point ◽  
Membrane Contact

Membrane contact sites are regions of close apposition between two organelles, typically less than 30 nanometers apart, that facilitate transfer of biomolecules. The presence of contact sites has been demonstrated in yeast, plants, and mammalian cells. Here, we investigated the presence of such contact sites in Trypanosoma brucei. In mammalian cells, endoplasmic reticulum-mitochondria contact sites facilitate mitochondrial uptake of Ca2+ released by the ER-located inositol 1,4,5-trisphosphate receptor (InsP3R). However, the InsP3R in trypanosomes localizes to acidocalcisomes, which serve as major Ca2+ stores in these parasites. In this work, we have used super-resolution structured illumination microscopy and electron microscopy to identify membrane contact sites that exist between acidocalcisomes and mitochondria. Furthermore, we have confirmed the close association of these organelles using proximity ligation assays. Characterization of these contact sites may be a necessary starting point towards unraveling the role of Ca2+ in regulating trypanosome bioenergetics.

A Platinum(II) Based Correlative Probe for Bacteria

2019 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Kathryn Leslie ◽  
Song Huang ◽  
Stefano Stagni ◽  
Denis Jacquemin ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Super Resolution ◽  
Molecular Probes ◽  
Live Cells ◽  
Structured Illumination ◽  
Luminescent Probe ◽  
Structured Illumination Microscopy ◽  
Cellular Localisation ◽  
Super Resolution Microscopy ◽  
Nanosims Analysis

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. This is especially so for correlative probes, which are proving to be powerful tools for enhancing the imaging of live cells. In this work a platinum(II)-naphthalimide molecule has been developed to extend small molecule correlative probes to bacterial imaging. The probe was designed to exploit the naphthalimide moiety as a luminescent probe for super-resolution microscopy, with the platinum(II) centre enabling visualisation of the complex with ion nanoscopy. Photophysical characterisation and theoretical studies confirmed that the emission properties of the naphthalimide are not altered by the platinum(II) centre. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i>revealed that the platinum(II) centre does not change the sub-cellular localisation of the naphthalimide, and confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis of the sample was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the correlative action of the probe. The successful combination of these two probe moieties with no perturbation of their individual detection introduces a platform for a versatile range of new correlative probes for bacteria.

scholarly journals ORP5 Transfers Phosphatidylserine To Mitochondria And Regulates Mitochondrial Calcium Uptake At Endoplasmic Reticulum - Mitochondria Contact Sites

2019 ◽  
Author(s):  
Leila Rochin ◽  
Cécile Sauvanet ◽  
Eeva Jääskeläinen ◽  
Audrey Houcine ◽  
Amita Arora ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Calcium Uptake ◽  
Vesicular Transport ◽  
Mitochondrial Calcium ◽  
Mitochondrial Membranes ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Mitochondrial Calcium Uptake

SUMMARYMitochondria are dynamic organelles essential for cell survival whose structural and functional integrity rely on selective and regulated transport of lipids from/to the endoplasmic reticulum (ER) and across the two mitochondrial membranes. As they are not connected by vesicular transport, the exchange of lipids between ER and mitochondria occurs at sites of close organelle apposition called membrane contact sites. However, the mechanisms and proteins involved in these processes are only beginning to emerge. Here, we show that ORP5/8 mediate non-vesicular transport of Phosphatidylserine (PS) from the ER to mitochondria in mammalian cells. We also show that ER-mitochondria contacts where ORP5/8 reside are physically and functionally linked to the MIB/MICOS complexes that bridge the mitochondrial membranes, cooperating with them to facilitate PS transfer from the ER to the mitochondria. Finally, we show that ORP5 but not ORP8, additionally regulates import of calcium to mitochondria and consequently cell senescence.

scholarly journals Di-arginine and FFAT-like motifs retain a subpopulation of PRA1 at ER-mitochondria membrane contact sites

2020 ◽  
Author(s):  
Ameair Abu Irqeba ◽  
Judith Mosinger Ogilvie
Keyword(s):  
Mammalian Cells ◽  
Protein Localization ◽  
Transmembrane Protein ◽  
Amino Acid Sequences ◽  
Terminal Region ◽  
Rab Gtpases ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Er Retention ◽  
Membrane Contact

ABSTRACTPrenylated Rab Acceptor 1 (PRA1/Rabac1) is a four-pass transmembrane protein that has been found to localize to the Golgi and promiscuously associate with a diverse array of Rab GTPases. We have previously identified PRA1 to be among the earliest significantly down-regulated genes in the rd1 mouse model of retinitis pigmentosa, a retinal degenerative disease. Here, we show that an endogenous subpopulation of PRA1 resides within the endoplasmic reticulum (ER) at ER-mitochondria membrane contact sites in cultured mammalian cells. We also demonstrate that PRA1 contains two previously unidentified ER retention/retrieval amino acid sequences on its cytosolic N-terminal region: a membrane distal di-arginine motif and a novel membrane proximal FFAT-like motif. Using a truncation construct that lacks complete Golgi targeting information, we show that mutation of either motif leads to an increase in cell surface localization, while mutation of both motifs exhibits an additive effect. We also present evidence that illustrates that N- or C- terminal addition of a tag to full-length PRA1 leads to differential localization to either the Golgi or reticular ER, phenotypes that do not completely mirror endogenous protein localization. The presence of multiple ER retention motifs on the PRA1 N-terminal region further suggests that it has a functional role within the ER.

scholarly journals OSBP-Related Protein Family in Lipid Transport over Membrane Contact Sites

2015 ◽  
Vol 8s1 ◽  
pp. LPI.S31726 ◽  
Author(s):  
Vesa M. Olkkonen
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Binding Protein ◽  
High Capacity ◽  
Retrograde Transport ◽  
Protein Family ◽  
Oxysterol Binding Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

Increasing evidence suggests that oxysterol-binding protein-related proteins (ORPs) localize at membrane contact sites, which are high-capacity platforms for inter-organelle exchange of small molecules and information. ORPs can simultaneously associate with the two apposed membranes and transfer lipids across the interbilayer gap. Oxysterol-binding protein moves cholesterol from the endoplasmic reticulum to trans-Golgi, driven by the retrograde transport of phosphatidylinositol-4-phosphate (PI4P). Analogously, yeast Osh6p mediates the transport of phosphatidylserine from the endoplasmic reticulum to the plasma membrane in exchange for PI4P, and ORP5 and -8 are suggested to execute similar functions in mammalian cells. ORPs may share the capacity to bind PI4P within their ligand-binding domain, prompting the hypothesis that bidirectional transport of a phosphoinositide and another lipid may be a common theme among the protein family. This model, however, needs more experimental support and does not exclude a function of ORPs in lipid signaling.

scholarly journals Structure illumination microscopy imaging of lipid vesicles in live bacteria with naphthalimide-appended organometallic complexes

2021 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Matteo Vezzelli ◽  
Kathryn Leslie ◽  
Song Huang ◽  
Stefano Stagni ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Super Resolution ◽  
Lipid Vesicles ◽  
Molecular Probes ◽  
Organometallic Complexes ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Microscopy Imaging ◽  
Multiple Imaging ◽  
Super Resolution Microscopy

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. Here, organometallic molecular probes have been developed and assessed for bacterial imaging, designed to have the potential to support multiple imaging modalities. The chemical structure of the probes is designed around a metal-naphthalimide structure. The 4-amino-1,8-naphthalimide moiety, covalently appended through a pyridine ancillary ligand, acts as a luminescent probe for super-resolution microscopy. On the other hand, the metal centre, rhenium(I) or platinum(II) in the current study, enables techniques such as nanoSIMS. While the rhenium(I) complex was not sufficiently stable to be used as probe, the platinum(II) analogue showed good chemical and biological stability. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i> confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and demonstrate the potential of this chemical architecture to enable multimodal imaging. The successful combination of these two moieties introduces a platform that could lead to a versatile range of multi-functional probes for bacteria.<br>

scholarly journals The Unfolded Protein Response and Membrane Contact Sites: Tethering as a Matter of Life and Death?

Contact ◽  
2018 ◽  
Vol 1 ◽  
pp. 251525641877051 ◽  
Author(s):  
Alexander R. van Vliet ◽  
Maria Livia Sassano ◽  
Patrizia Agostinis
Keyword(s):  
Unfolded Protein Response ◽  
Cell Fate ◽  
Mammalian Cells ◽  
Cell Fate Decisions ◽  
Unfolded Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
The Unfolded Protein Response ◽  
Protein Response

The endoplasmic reticulum (ER) is the most extensive organelle of the eukaryotic cell and constitutes the major site of protein and lipid synthesis and regulation of intracellular Ca2+ levels. To exert these functions properly, the ER network is shaped in structurally and functionally distinct domains that dynamically remodel in response to intrinsic and extrinsic cues. Moreover, the ER establishes a tight communication with virtually all organelles of the cell through specific subdomains called membrane contact sites. These contact sites allow preferential, nonvesicular channeling of key biological mediators including lipids and Ca2+ between organelles and are harnessed by the ER to interface with and coregulate a variety of organellar functions that are vital to maintain homeostasis. When ER homeostasis is lost, a condition that triggers the activation of an evolutionarily conserved pathway called the unfolded protein response (UPR), the ER undergoes rapid remodeling. These dynamic changes in ER morphology are functionally coupled to the modulation or formation of contact sites with key organelles, such as mitochondria and the plasma membrane, which critically regulate cell fate decisions of the ER-stressed cells. Certain components of the UPR have been shown to facilitate the formation of contact sites through various mechanisms including remodeling of the actin cytoskeleton. In this review, we discuss old and emerging evidence linking the UPR machinery to contact site formation in mammalian cells and discuss their important role in cellular homeostasis.

scholarly journals Roles for ER:endosome membrane contact sites in ligand-stimulated intraluminal vesicle formation

2018 ◽  
Vol 46 (5) ◽  
pp. 1055-1062 ◽  
Author(s):  
Louise H. Wong ◽  
Emily R. Eden ◽  
Clare E. Futter
Keyword(s):  
Membrane Proteins ◽  
Mammalian Cells ◽  
Tyrosine Phosphatase ◽  
Endosomal Sorting ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contacts ◽  
Epidermal Growth ◽  
Membrane Contact ◽  
Multivesicular Endosomes

Multivesicular endosomes/bodies (MVBs) sort membrane proteins between recycling and degradative pathways. Segregation of membrane proteins onto intraluminal vesicles (ILVs) of MVBs removes them from the recycling pathway and facilitates their degradation following fusion of MVBs with lysosomes. Sorting of many cargos onto ILVs depends on the ESCRT (Endosomal Sorting Complex Required for Transport) machinery, although ESCRT-independent mechanisms also exist. In mammalian cells, efficient sorting of ligand-stimulated epidermal growth factor receptors onto ILVs also depends on the tyrosine phosphatase, PTP1B, an ER-localised enzyme that interacts with endosomal targets at membrane contacts between MVBs and the ER. This review focuses on the potential roles played by ER:MVB membrane contact sites in regulating ESCRT-dependent ILV formation.

scholarly journals A platinum(II)-napthalimide probe for sub-cellular imaging of bacteria

2020 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Kathryn Leslie ◽  
Song Huang ◽  
Stefano Stagni ◽  
Denis Jacquemin ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Super Resolution ◽  
Molecular Probes ◽  
Structured Illumination ◽  
Luminescent Probe ◽  
Structured Illumination Microscopy ◽  
Correlative Imaging ◽  
Super Resolution Microscopy ◽  
Nanosims Analysis ◽  
Small Molecule Probe

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. A platinum(II)-naphthalimide molecule has been developed as a small molecule probe for bacterial imaging, designed to have the potential for correlative imaging. The naphthalimide moiety acts as a luminescent probe for super-resolution microscopy, functioning independently of the platinum(II) centre which enabled visualisation of the complex with ion nanoscopy. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i> confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the multimodal action of the probe. The successful combination of these two probe moieties introduces a platform that could lead to a versatile range of correlative probes for bacteria.<br>

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