scholarly journals Regulating peroxisome–ER contacts via the ACBD5-VAPB tether by FFAT motif phosphorylation and GSK3β

2022 ◽  
Vol 221 (3) ◽  
Author(s):  
Suzan Kors ◽  
Christian Hacker ◽  
Chloe Bolton ◽  
Renate Maier ◽  
Lena Reimann ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Current Model ◽  
Protein Domain ◽  
Major Sperm Protein ◽  
Peroxisomal Membrane ◽  
Membrane Contact Sites ◽  
Contact Sites

Peroxisomes and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism. They form membrane contacts through interaction of the peroxisomal membrane protein ACBD5 (acyl-coenzyme A–binding domain protein 5) and the ER-resident protein VAPB (vesicle-associated membrane protein–associated protein B). ACBD5 binds to the major sperm protein domain of VAPB via its FFAT-like (two phenylalanines [FF] in an acidic tract) motif. However, molecular mechanisms, which regulate formation of these membrane contact sites, are unknown. Here, we reveal that peroxisome–ER associations via the ACBD5-VAPB tether are regulated by phosphorylation. We show that ACBD5-VAPB binding is phosphatase-sensitive and identify phosphorylation sites in the flanking regions and core of the FFAT-like motif, which alter interaction with VAPB—and thus peroxisome–ER contact sites—differently. Moreover, we demonstrate that GSK3β (glycogen synthase kinase-3 β) regulates this interaction. Our findings reveal for the first time a molecular mechanism for the regulation of peroxisome–ER contacts in mammalian cells and expand the current model of FFAT motifs and VAP interaction.

scholarly journals Regulating peroxisome-ER contacts via the ACBD5-VAPB tether by FFAT motif phosphorylation and GSK3β

2021 ◽  
Author(s):  
Suzan Kors ◽  
Christian Hacker ◽  
Chloe Bolton ◽  
Renate Maier ◽  
Lena Reimann ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Current Model ◽  
Protein Domain ◽  
Major Sperm Protein ◽  
Peroxisomal Membrane ◽  
Membrane Contact Sites ◽  
Contact Sites

Peroxisomes and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism. They form membrane contacts through interaction of the peroxisomal membrane protein ACBD5 [acyl-coenzyme A-binding domain protein 5] and the ER-resident protein VAPB [vesicle-associated membrane protein-associated protein B]. ACBD5 binds to the major sperm protein domain of VAPB via its FFAT-like [two phenylalanines (FF) in an acidic tract] motif. However, molecular mechanisms, which regulate formation of these membrane contact sites, are unknown. Here, we reveal that peroxisome-ER associations via the ACBD5-VAPB tether are regulated by phosphorylation. We show that ACBD5-VAPB binding is phosphatase-sensitive and identify phosphorylation sites in the flanking regions and core of the FFAT-like motif, which alter interaction with VAPB and thus, peroxisome-ER contact sites differently. Moreover, we demonstrate that GSK3β [glycogen synthase kinase-3 beta] regulates this interaction. Our findings reveal for the first time a molecular mechanism for the regulation of peroxisome-ER contacts in mammalian cells and expand the current model of FFAT motifs and VAP interaction.

scholarly journals Interaction Between Phosphoinositide 3-Kinase and the VDAC2 Channel Tethers Endosomes to Mitochondria and Promotes Endosome Maturation

2021 ◽  
Author(s):  
Aya O. Satoh ◽  
Yoichiro Fujioka ◽  
Sayaka Kashiwagi ◽  
Aiko Yoshida ◽  
Mari Fujioka ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Small Gtpase ◽  
Mitochondrial Outer Membrane ◽  
List Type ◽  
Voltage Dependent Anion Channel ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Phosphoinositide 3 Kinase ◽  
Endosome Maturation

SUMMARYIntracellular organelles of mammalian cells communicate with each other during various cellular processes. The functions and molecular mechanisms of such interorganelle association remain largely unclear, however. We here identified voltage-dependent anion channel 2 (VDAC2), a mitochondrial outer membrane protein, as a binding partner of phosphoinositide 3-kinase (PI3K), a regulator of clathrin-independent endocytosis downstream of the small GTPase Ras. VDAC2 was found to tether endosomes positive for the Ras-PI3K complex to mitochondria in response to cell stimulation with epidermal growth factor and to promote clathrin-independent endocytosis as well as endosome maturation at membrane contact sites. With a newly developed optogenetics system to induce mitochondrion-endosome association, we found that, in addition to its structural role in such association, the pore function of VDAC2 is also required for the promotion of endosome maturation. Our findings thus uncover a previously unappreciated role of mitochondrion-endosome association in the regulation of endocytosis and endosome maturation.HighlightsThe mitochondrial protein VDAC2 binds PI3K and tethers endosomes to mitochondriaVDAC2 promotes clathrin-independent endocytosisVDAC2-PI3K interaction induces acidification of endosomes associated with mitochondriaThe pore function of VDAC2 also contributes to endosome maturation at contact sites

scholarly journals Fluorescent Tools to Analyze Peroxisome–Endoplasmic Reticulum Interactions in Mammalian Cells

Contact ◽  
2019 ◽  
Vol 2 ◽  
pp. 251525641984864 ◽  
Author(s):  
Alexa Bishop ◽  
Maki Kamoshita ◽  
Josiah B. Passmore ◽  
Christian Hacker ◽  
Tina A. Schrader ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Proximity Ligation Assay ◽  
Reporter System ◽  
Peroxisomal Membrane ◽  
Proximity Ligation ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

Peroxisomes (POs) and the endoplasmic reticulum (ER) cooperate extensively in lipid-related metabolic pathways, and the ER also provides phospholipids to enable the peroxisomal membrane to expand prior to division. Recently, we identified peroxisomal proteins, ACBD5 and ACBD4, and the ER protein vesicle-associated membrane protein-associated protein-B (VAPB) as tethering components, which physically interact to foster PO–ER associations at membrane contact sites. Overexpression or loss of these tether proteins alters the extent of PO–ER interactions, impacting on lipid exchange between these two compartments. To facilitate further studies into PO–ER associations at the level of membrane contact sites, their role, composition, and regulation, we have developed two fluorescence-based systems to monitor PO–ER interactions. We modified a proximity ligation assay and a split-fluorescence reporter system using split superfolder green fluorescent protein. Using the proximity ligation assay, we were able to measure the changes in PO–ER interactions while the split-fluorescence reporter was more limited and only allowed us to label PO–ER contacts. We show that both techniques can be useful additions to the toolkit of methods to study PO–ER associations and explore the relative merits of each.

scholarly journals Pex24 and Pex32 are required to tether peroxisomes to the ER for organelle biogenesis, positioning and segregation in yeast

2020 ◽  
Vol 133 (16) ◽  
pp. jcs246983 ◽  
Author(s):  
Fei Wu ◽  
Rinse de Boer ◽  
Arjen M. Krikken ◽  
Arman Akşit ◽  
Nicola Bordin ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Matrix Protein ◽  
Protein Import ◽  
Hansenula Polymorpha ◽  
Major Effect ◽  
Organelle Biogenesis ◽  
Peroxisomal Membrane ◽  
Contact Sites ◽  
Membrane Growth

ABSTRACTThe yeast Hansenula polymorpha contains four members of the Pex23 family of peroxins, which characteristically contain a DysF domain. Here we show that all four H. polymorpha Pex23 family proteins localize to the endoplasmic reticulum (ER). Pex24 and Pex32, but not Pex23 and Pex29, predominantly accumulate at peroxisome–ER contacts. Upon deletion of PEX24 or PEX32 – and to a much lesser extent, of PEX23 or PEX29 – peroxisome–ER contacts are lost, concomitant with defects in peroxisomal matrix protein import, membrane growth, and organelle proliferation, positioning and segregation. These defects are suppressed by the introduction of an artificial peroxisome–ER tether, indicating that Pex24 and Pex32 contribute to tethering of peroxisomes to the ER. Accumulation of Pex32 at these contact sites is lost in cells lacking the peroxisomal membrane protein Pex11, in conjunction with disruption of the contacts. This indicates that Pex11 contributes to Pex32-dependent peroxisome–ER contact formation. The absence of Pex32 has no major effect on pre-peroxisomal vesicles that occur in pex3 atg1 deletion cells.

scholarly journals Systematic Prediction of FFAT Motifs Across Eukaryote Proteomes Identifies Nucleolar and Eisosome Proteins With the Predicted Capacity to Form Bridges to the Endoplasmic Reticulum

Contact ◽  
2019 ◽  
Vol 2 ◽  
pp. 251525641988313 ◽  
Author(s):  
John A. Slee ◽  
Timothy P. Levine
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Common Mechanism ◽  
Linear Motif ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Cytoplasmic Proteins ◽  
Eukaryotic Proteins ◽  
Minimum Number ◽  
Membrane Contact

The endoplasmic reticulum (ER), the most pervasive organelle, exchanges information and material with many other organelles, but the extent of its interorganelle connections and the proteins that form bridges are not well known. The integral ER membrane protein vesicle-associated membrane protein-associated protein (VAP) is found in multiple bridges, interacting with many proteins that contain a short linear motif consisting of “two phenylalanines in an acidic tract” (FFAT). The VAP-FFAT interaction is the most common mechanism by which cytoplasmic proteins, particularly interorganelle bridges, target the ER. Therefore, predicting new FFAT motifs may both find new individual peripheral ER proteins and identify new routes of communication involving the ER. Here, we searched for FFAT motifs across whole proteomes. The excess of eukaryotic proteins with FFAT motifs over background was ≥0.8%, suggesting that this is the minimum number of peripheral ER proteins. In yeast, where VAP was previously known to bind 4 proteins with FFAT motifs, a detailed analysis of a subset of proteins predicted 20 FFAT motifs. Extrapolating these findings to the whole proteome estimated the number of FFAT motifs in yeast at approximately 50 to 55 (0.9% of proteome). Among these previously unstudied FFAT motifs, most have known functions outside the ER, so could be involved in interorganelle communication. Many of these can target well-characterized membrane contact sites; however, some are in nucleoli and eisosomes, organelles previously unknown to have molecular bridges to the ER. We speculate that the nucleolar and eisosomal proteins with predicted motifs may function while bridging to the ER, indicating novel ER–nucleolus and ER–eisosome routes of interorganelle communication.

scholarly journals Peroxisomal Peripheral Membrane Protein YlInp1p Is Required for Peroxisome Inheritance and Influences the Dimorphic Transition in the Yeast Yarrowia lipolytica

2007 ◽  
Vol 6 (9) ◽  
pp. 1528-1537 ◽  
Author(s):  
Jinlan Chang ◽  
Andrei Fagarasanu ◽  
Richard A. Rachubinski
Keyword(s):  
Membrane Protein ◽  
Yarrowia Lipolytica ◽  
Mother Cell ◽  
Molecular Mechanisms ◽  
Peroxisomal Membrane ◽  
Mycelial Form ◽  
Dimorphic Transition ◽  
Dimorphic Yeast ◽  
In Cells

ABSTRACT Eukaryotic cells have evolved molecular mechanisms to ensure the faithful inheritance of organelles by daughter cells in order to maintain the benefits afforded by the compartmentalization of biochemical functions. Little is known about the inheritance of peroxisomes, organelles of lipid metabolism. We have analyzed peroxisome dynamics and inheritance in the dimorphic yeast Yarrowia lipolytica. Most peroxisomes are anchored at the periphery of cells of Y. lipolytica. In vivo video microscopy showed that at cell division, approximately half of the anchored peroxisomes in the mother cell are dislodged individually from their static positions and transported to the bud. Peroxisome motility is dependent on the actin cytoskeleton. YlInp1p is a peripheral peroxisomal membrane protein that affects the partitioning of peroxisomes between mother cell and bud in Y. lipolytica. In cells lacking YlInp1p, most peroxisomes were transferred to the bud, with only a few remaining in the mother cell, while in cells overexpressing YlInp1p, peroxisomes were preferentially retained in the mother cell, resulting in buds nearly devoid of peroxisomes. Our results are consistent with a role for YlInp1p in anchoring peroxisomes in cells. YlInp1p has a role in the dimorphic transition in Y. lipolytica, as cells lacking the YlINP1 gene more readily convert from the yeast to the mycelial form in oleic acid-containing medium, the metabolism of which requires peroxisomal activity, than does the wild-type strain. This study reports the first analysis of organelle inheritance in a true dimorphic yeast and identifies the first protein required for peroxisome inheritance in Y. lipolytica.

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 Peroxisomal Membrane Contact Sites in Yeasts

2021 ◽  
Vol 9 ◽  
Author(s):  
Amit S. Joshi
Keyword(s):  
Lipid Droplets ◽  
Peroxisome Biogenesis ◽  
Functional Importance ◽  
Peroxisomal Membrane ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Recent Developments ◽  
Membrane Contacts ◽  
Membrane Bound ◽  
Membrane Contact

Peroxisomes are ubiquitous, single membrane-bound organelles that play a crucial role in lipid metabolism and human health. While peroxisome number is maintained by the division of existing peroxisomes, nascent peroxisomes can be generated from the endoplasmic reticulum (ER) membrane in yeasts. During formation and proliferation, peroxisomes maintain membrane contacts with the ER. In addition to the ER, contacts between peroxisomes and other organelles such as lipid droplets, mitochondria, vacuole, and plasma membrane have been reported. These membrane contact sites (MCS) are dynamic and important for cellular function. This review focuses on the recent developments in peroxisome biogenesis and the functional importance of peroxisomal MCS in yeasts.

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