scholarly journals Sphingolipids mediate polar sorting of PIN2 through phosphoinositide consumption at the trans-Golgi network

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yoko Ito ◽  
Nicolas Esnay ◽  
Matthieu Pierre Platre ◽  
Valérie Wattelet-Boyer ◽  
Lise C. Noack ◽  
...  
Keyword(s):  
Protein Sorting ◽  
Acyl Chain ◽  
Plant Cells ◽  
Animal Cells ◽  
Contact Sites ◽  
Acyl Chain Length ◽  
Lipid Exchange ◽  
Anionic Lipids ◽  
Phosphatidylinositol 4 ◽  
Golgi Network

AbstractThe lipid composition of organelles acts as a landmark to define membrane identity and specify subcellular function. Phosphoinositides are anionic lipids acting in protein sorting and trafficking at the trans-Golgi network (TGN). In animal cells, sphingolipids control the turnover of phosphoinositides through lipid exchange mechanisms at endoplasmic reticulum/TGN contact sites. In this study, we discover a mechanism for how sphingolipids mediate phosphoinositide homeostasis at the TGN in plant cells. Using multiple approaches, we show that a reduction of the acyl-chain length of sphingolipids results in an increased level of phosphatidylinositol-4-phosphate (PtdIns(4)P or PI4P) at the TGN but not of other lipids usually coupled to PI4P during exchange mechanisms. We show that sphingolipids mediate Phospholipase C (PLC)-driven consumption of PI4P at the TGN rather than local PI4P synthesis and that this mechanism is involved in the polar sorting of the auxin efflux carrier PIN2 at the TGN. Together, our data identify a mode of action of sphingolipids in lipid interplay at the TGN during protein sorting.

scholarly journals Sphingolipids mediate polar sorting of PIN2 through phosphoinositide consumption at the trans-Golgi Network

2020 ◽  
Author(s):  
Yoko Ito ◽  
Nicolas Esnay ◽  
Matthieu Pierre Platre ◽  
Lise C. Noack ◽  
Wilhelm Menzel ◽  
...  
Keyword(s):  
Protein Sorting ◽  
Acyl Chain ◽  
Plant Cells ◽  
Animal Cells ◽  
Contact Sites ◽  
Acyl Chain Length ◽  
Lipid Exchange ◽  
Anionic Lipids ◽  
Phosphatidylinositol 4 ◽  
Golgi Network

AbstractThe lipid composition of organelles acts as a landmark to define membrane identity and specify subcellular function. Phosphoinositides are anionic lipids acting in protein sorting and trafficking at the trans-Golgi network (TGN). In animal cells, sphingolipids are known to control the turnover of phosphoinositides through lipid exchange mechanisms at endoplasmic reticulum/TGN contact sites. In this study, we discovered a completely new mechanism acting on sphingolipid-mediated phosphoinositides homeostasis at the TGN in plant cells. We used multi-approaches to show that a reduction of the acyl-chain length of sphingolipid results in increased level of phosphatidylinositol-4-phosphate (PI4P) at the TGN, independently from either lipid exchange induced by sphingolipid synthetic flux, or local PI4P synthesis. Instead, we found that sphingolipids mediate the consumption of PI4P through phosphoinositide-specific phospholipase C (PI-PLC) and this process impacts the sorting of the auxin efflux carrier PIN2 at the TGN. Together, our data identify a new mode of action of sphingolipids in lipid interplay at the TGN during protein sorting.

PI4P/PS countertransport by ORP10 at ER–endosome membrane contact sites regulates endosome fission

2021 ◽  
Vol 221 (1) ◽  
Author(s):  
Asami Kawasaki ◽  
Akiko Sakai ◽  
Hiroki Nakanishi ◽  
Junya Hasegawa ◽  
Tomohiko Taguchi ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Binding Protein ◽  
Dependent Manner ◽  
Oxysterol Binding Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Lipid Exchange ◽  
Membrane Contact ◽  
Phosphatidylinositol 4

Membrane contact sites (MCSs) serve as a zone for nonvesicular lipid transport by oxysterol-binding protein (OSBP)-related proteins (ORPs). ORPs mediate lipid countertransport, in which two distinct lipids are transported counterdirectionally. How such lipid countertransport controls specific biological functions, however, remains elusive. We report that lipid countertransport by ORP10 at ER–endosome MCSs regulates retrograde membrane trafficking. ORP10, together with ORP9 and VAP, formed ER–endosome MCSs in a phosphatidylinositol 4-phosphate (PI4P)-dependent manner. ORP10 exhibited a lipid exchange activity toward its ligands, PI4P and phosphatidylserine (PS), between liposomes in vitro, and between the ER and endosomes in situ. Cell biological analysis demonstrated that ORP10 supplies a pool of PS from the ER, in exchange for PI4P, to endosomes where the PS-binding protein EHD1 is recruited to facilitate endosome fission. Our study highlights a novel lipid exchange at ER–endosome MCSs as a nonenzymatic PI4P-to-PS conversion mechanism that organizes membrane remodeling during retrograde membrane trafficking.

scholarly journals The ER cholesterol sensor SCAP promotes CARTS biogenesis at ER–Golgi membrane contact sites

2020 ◽  
Vol 220 (1) ◽  
Author(s):  
Yuichi Wakana ◽  
Kaito Hayashi ◽  
Takumi Nemoto ◽  
Chiaki Watanabe ◽  
Masato Taoka ◽  
...  
Keyword(s):  
Lipid Transfer ◽  
Golgi Membrane ◽  
Proteolytic Activation ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Defective Mutant ◽  
Transport Defect ◽  
Membrane Contact ◽  
Phosphatidylinositol 4 ◽  
Golgi Network

In response to cholesterol deprivation, SCAP escorts SREBP transcription factors from the endoplasmic reticulum to the Golgi complex for their proteolytic activation, leading to gene expression for cholesterol synthesis and uptake. Here, we show that in cholesterol-fed cells, ER-localized SCAP interacts through Sac1 phosphatidylinositol 4-phosphate (PI4P) phosphatase with a VAP–OSBP complex, which mediates counter-transport of ER cholesterol and Golgi PI4P at ER–Golgi membrane contact sites (MCSs). SCAP knockdown inhibited the turnover of PI4P, perhaps due to a cholesterol transport defect, and altered the subcellular distribution of the VAP–OSBP complex. As in the case of perturbation of lipid transfer complexes at ER–Golgi MCSs, SCAP knockdown inhibited the biogenesis of the trans-Golgi network–derived transport carriers CARTS, which was reversed by expression of wild-type SCAP or a Golgi transport–defective mutant, but not of cholesterol sensing–defective mutants. Altogether, our findings reveal a new role for SCAP under cholesterol-fed conditions in the facilitation of CARTS biogenesis via ER–Golgi MCSs, depending on the ER cholesterol.

scholarly journals Phospholipid exchange shows insulin receptor activity is supported by both the propensity to form wide bilayers and ordered domains (rafts)

2021 ◽  
Author(s):  
Pavana Suresh ◽  
W. Todd Miller ◽  
Erwin London
Keyword(s):  
Insulin Receptor ◽  
Chain Length ◽  
Mammalian Cells ◽  
Plasma Membranes ◽  
Acyl Chain ◽  
Phospholipid Composition ◽  
Domain Formation ◽  
Lipid Structure ◽  
Acyl Chain Length ◽  
Lipid Exchange

ABSTRACTUsing efficient methyl-alpha-cyclodextrin mediated lipid exchange, we studied the effect of altering plasma membrane outer leaflet phospholipid composition upon the activity of insulin receptor (IR) in mammalian cells. After substitution of endogenous lipids with lipids having an ability to form liquid ordered (Lo) domains (sphingomyelins) or liquid disordered (Ld) domains (unsaturated phosphatidylcholines (PCs)), we found that the propensity of lipids to form ordered domains is required for high IR activity. Additional substitution experiments using a series of saturated PCs showed that IR activity increased substantially with increasing acyl chain length. Increasing acyl chain length increases both bilayer width and the propensity to form ordered domains. To distinguish the effects of membrane width and domain formation, we incorporated purified IR into alkyl maltoside micelles with increasing hydrocarbon lengths. IR activity increases with increased chain length, but more modestly than by increasing lipid acyl chain length in cells. This suggests that the ability to form Lo domains as well as wide bilayer width contributes to increased IR activity. Inhibition of phosphatases with sodium orthovanadate showed that some of the lipid dependence of IR activity upon lipid structure reflected protection from phosphatases by lipids that support Lo domain formation. The results are consistent with a model in which a combination of bilayer width and ordered domain formation modulate IR activity via effects upon IR conformation and accessibility to phosphatases.SignificanceThis study shows how methyl-α-cyclodextrin mediated lipid exchange can be used to probe the influence of lipid structure upon the functioning of a transmembrane receptor. Plasma membranes having a propensity to form Lo domains are required to support a high level of IR activity. The studies indicate this may reflect an effect of lipid environment upon IR domain localization, which in turn alters its conformation and vulnerability to phosphatases. Alterations in lipid composition could conceivably regulate IR activity in vivo.

scholarly journals Staying in touch: Taking a closer look at ER–Golgi contact sites

2019 ◽  
Vol 218 (3) ◽  
pp. 729-731 ◽  
Author(s):  
Maria Livia Sassano ◽  
Patrizia Agostinis
Keyword(s):  
Lipid Homeostasis ◽  
Trans Golgi Network ◽  
Contact Sites ◽  
Lipid Exchange ◽  
Cell Biol ◽  
Molecular Determinants ◽  
Golgi Network ◽  
Molecular Nature

ER–Golgi contact sites regulate lipid homeostasis and trafficking across the trans-Golgi network. However, their molecular nature is elusive. In this issue, Venditti et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201812020 and https://doi.org/10.1083/jcb.201812021) shine new light on the molecular determinants coupling lipid exchange and cargo exit with maintenance of ER–Golgi contacts.

Golgi-derived PI(4)P-containing vesicles drive late steps of mitochondrial division

Science ◽  
2020 ◽  
Vol 367 (6484) ◽  
pp. 1366-1371 ◽  
Author(s):  
Shun Nagashima ◽  
Luis-Carlos Tábara ◽  
Lisa Tilokani ◽  
Vincent Paupe ◽  
Hanish Anand ◽  
...  
Keyword(s):  
Cell Fate ◽  
Mitochondrial Network ◽  
Mitochondrial Division ◽  
Cell Fate Decisions ◽  
Contact Sites ◽  
Mammalian Cell Lines ◽  
Guanosine Triphosphatase ◽  
Phosphatidylinositol 4 ◽  
Golgi Network ◽  
Adp Ribosylation Factor

Mitochondrial plasticity is a key regulator of cell fate decisions. Mitochondrial division involves Dynamin-related protein-1 (Drp1) oligomerization, which constricts membranes at endoplasmic reticulum (ER) contact sites. The mechanisms driving the final steps of mitochondrial division are still unclear. Here, we found that microdomains of phosphatidylinositol 4-phosphate [PI(4)P] on trans-Golgi network (TGN) vesicles were recruited to mitochondria–ER contact sites and could drive mitochondrial division downstream of Drp1. The loss of the small guanosine triphosphatase ADP-ribosylation factor 1 (Arf1) or its effector, phosphatidylinositol 4-kinase IIIβ [PI(4)KIIIβ], in different mammalian cell lines prevented PI(4)P generation and led to a hyperfused and branched mitochondrial network marked with extended mitochondrial constriction sites. Thus, recruitment of TGN-PI(4)P–containing vesicles at mitochondria–ER contact sites may trigger final events leading to mitochondrial scission.

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