scholarly journals Lysophosphatidic acid acyltransferase 3 regulates Golgi complex structure and function

2009 ◽  
Vol 186 (2) ◽  
pp. 211-218 ◽  
Author(s):  
John A. Schmidt ◽  
William J. Brown
Keyword(s):  
Lysophosphatidic Acid ◽  
Golgi Complex ◽  
Membrane Trafficking ◽  
Functional Organization ◽  
Complex Structure ◽  
Golgi Membrane ◽  
Direct Role ◽  
Tubule Formation ◽  
In Cells

Recent studies have suggested that the functional organization of the Golgi complex is dependent on phospholipid remodeling enzymes. Here, we report the identification of an integral membrane lysophosphatidic acid–specific acyltransferase, LPAAT3, which regulates Golgi membrane tubule formation, trafficking, and structure by altering phospholipids and lysophospholipids. Overexpression of LPAAT3 significantly inhibited the formation of Golgi membrane tubules in vivo and in vitro. Anterograde and retrograde protein trafficking was slower in cells overexpressing LPAAT3 and accelerated in cells with reduced expression (by siRNA). Golgi morphology was also dependent on LPAAT3 because its knockdown caused the Golgi to become fragmented. These data are the first to show a direct role for a specific phospholipid acyltransferase in regulating membrane trafficking and organelle structure.

scholarly journals The Rate-limiting Enzyme in Phosphatidylcholine Synthesis Regulates Proliferation of the Nucleoplasmic Reticulum

2005 ◽  
Vol 16 (3) ◽  
pp. 1120-1130 ◽  
Author(s):  
Thomas A. Lagace ◽  
Neale D. Ridgway
Keyword(s):  
Membrane Binding ◽  
Chinese Hamster ◽  
Lipid Synthesis ◽  
Temperature Sensitive ◽  
Direct Role ◽  
Tubule Formation ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Nucleoplasmic Reticulum ◽  
Rate Limiting

The nucleus contains a network of tubular invaginations of the nuclear envelope (NE), termed the nucleoplasmic reticulum (NR), implicated in transport, gene expression, and calcium homeostasis. Here, we show that proliferation of the NR, measured by the frequency of NE invaginations and tubules, is regulated by CTP:phosphocholine cytidylyltransferase-α (CCTα), the nuclear and rate-limiting enzyme in the CDP–choline pathway for phosphatidylcholine (PtdCho) synthesis. In Chinese hamster ovary (CHO)-K1 cells, fatty acids triggered activation and translocation of CCTα onto intranuclear tubules characteristic of the NR. This was accompanied by a twofold increase in NR tubules quantified by immunostaining for lamin A/C or the NE. CHO MT58 cells expressing a temperature-sensitive CCTα allele displayed reduced PtdCho synthesis and CCTα expression and minimal proliferation of the NR in response to oleate compared with CHO MT58 cells stably expressing CCTα. Expression of CCTα mutants in CHO58 cells revealed that both enzyme activity and membrane binding promoted NR proliferation. In support of a direct role for membrane binding in NR tubule formation, recombinant CCTα caused the deformation of liposomes into tubules in vitro. This demonstrates that a key nuclear enzyme in PtdCho synthesis coordinates lipid synthesis and membrane deformation to promote formation of a dynamic nuclear-cytoplasmic interface.

scholarly journals The Cirque du Soleil of Golgi membrane dynamics

2009 ◽  
Vol 186 (2) ◽  
pp. 169-171 ◽  
Author(s):  
Vytas A. Bankaitis
Keyword(s):  
Lysophosphatidic Acid ◽  
Metabolic Enzymes ◽  
Membrane Dynamics ◽  
Membrane Remodeling ◽  
Golgi Membrane ◽  
Tubule Formation ◽  
Cirque Du Soleil ◽  
Cell Biol

The role of lipid metabolic enzymes in Golgi membrane remodeling is a subject of intense interest. Now, in this issue, Schmidt and Brown (2009. J. Cell Biol. doi:10.1083/jcb.200904147) report that lysophosphatidic acid–specific acyltransferase, LPAAT3, contributes to Golgi membrane dynamics by suppressing tubule formation.

scholarly journals c-Src-Mediated Phosphorylation of TRIP6 Regulates Its Function in Lysophosphatidic Acid-Induced Cell Migration

2005 ◽  
Vol 25 (14) ◽  
pp. 5859-5868 ◽  
Author(s):  
Yun-Ju Lai ◽  
Chen-Shan Chen ◽  
Weei-Chin Lin ◽  
Fang-Tsyr Lin
Keyword(s):  
Cell Migration ◽  
Lysophosphatidic Acid ◽  
Morphological Changes ◽  
Focal Adhesions ◽  
Dependent Manner ◽  
3T3 Cells ◽  
Erk Activation ◽  
Nih 3T3 ◽  
In Cells

ABSTRACT TRIP6 (thyroid receptor-interacting protein 6), also known as ZRP-1 (zyxin-related protein 1), is a member of the zyxin family that has been implicated in cell motility. Previously we have shown that TRIP6 binds to the LPA2 receptor and associates with several components of focal complexes in an agonist-dependent manner and, thus, enhances lysophosphatidic acid (LPA)-induced cell migration. Here we further report that the function of TRIP6 in LPA signaling is regulated by c-Src-mediated phosphorylation of TRIP6 at the Tyr-55 residue. LPA stimulation induces tyrosine phosphorylation of endogenous TRIP6 in NIH 3T3 cells and c-Src-expressing fibroblasts, which is virtually eliminated in Src-null fibroblasts. Strikingly, both phosphotyrosine-55 and proline-58 residues of TRIP6 are required for Crk binding in vitro and in cells. Mutation of Tyr-55 to Phe does not alter the ability of TRIP6 to localize at focal adhesions or associate with actin. However, it abolishes the association of TRIP6 with Crk and p130cas in cells and significantly reduces the function of TRIP6 to promote LPA-induced ERK activation. Ultimately, these signaling events control TRIP6 function in promoting LPA-induced morphological changes and cell migration.

scholarly journals The phospholipase complex PAFAH Ib regulates the functional organization of the Golgi complex

2010 ◽  
Vol 190 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Marie E. Bechler ◽  
Anne M. Doody ◽  
Esther Racoosin ◽  
Lin Lin ◽  
Kelvin H. Lee ◽  
...  
Keyword(s):  
Golgi Complex ◽  
Functional Organization ◽  
Platelet Activating Factor ◽  
Pla2 Activity ◽  
Tubule Formation ◽  
Platelet Activating Factor Acetylhydrolase ◽  
Catalytically Active ◽  
Membrane Tubulation ◽  
Dependent Transport ◽  
And Function

We report that platelet-activating factor acetylhydrolase (PAFAH) Ib, comprised of two phospholipase A2 (PLA2) subunits, α1 and α2, and a third subunit, the dynein regulator lissencephaly 1 (LIS1), mediates the structure and function of the Golgi complex. Both α1 and α2 partially localize on Golgi membranes, and purified catalytically active, but not inactive α1 and α2 induce Golgi membrane tubule formation in a reconstitution system. Overexpression of wild-type or mutant α1 or α2 revealed that both PLA2 activity and LIS1 are important for maintaining Golgi structure. Knockdown of PAFAH Ib subunits fragments the Golgi complex, inhibits tubule-mediated reassembly of intact Golgi ribbons, and slows secretion of cargo. Our results demonstrate a cooperative interplay between the PLA2 activity of α1 and α2 with LIS1 to facilitate the functional organization of the Golgi complex, thereby suggesting a model that links phospholipid remodeling and membrane tubulation to dynein-dependent transport.

scholarly journals Inhibition of a Golgi Complex Lysophospholipid Acyltransferase Induces Membrane Tubule Formation and Retrograde Trafficking

2003 ◽  
Vol 14 (8) ◽  
pp. 3459-3469 ◽  
Author(s):  
Daniel Drecktrah ◽  
Kimberly Chambers ◽  
Esther L. Racoosin ◽  
Edward B. Cluett ◽  
Amy Gucwa ◽  
...  
Keyword(s):  
Cholesterol Acyltransferase ◽  
Brefeldin A ◽  
Golgi Membrane ◽  
Tubule Formation ◽  
Golgi Membranes ◽  
Lysophospholipid Acyltransferase ◽  
Membrane Tubules ◽  
Additional Support ◽  
Membrane Shape

Recent studies have suggested that formation of Golgi membrane tubules involves the generation of membrane-associated lysophospholipids by a cytoplasmic Ca2+-independent phospholipase A2 (PLA2). Herein, we provide additional support for this idea by showing that inhibition of lysophospholipid reacylation by a novel Golgi-associated lysophosphatidylcholine acyltransferase (LPAT) induces the rapid tubulation of Golgi membranes, leading in their retrograde movement to the endoplasmic reticulum. Inhibition of the Golgi LPAT was achieved by 2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide (CI-976), a previously characterized antagonist of acyl-CoA cholesterol acyltransferase. The effect of CI-976 was similar to that of brefeldin A, except that the coatomer subunit β-COP remained on Golgi-derived membrane tubules. CI-976 also enhanced the cytosol-dependent formation of tubules from Golgi complexes in vitro and increased the levels of lysophosphatidylcholine in Golgi membranes. Moreover, preincubation of cells with PLA2 antagonists inhibited the ability of CI-976 to induce tubules. These results suggest that Golgi membrane tubule formation can result from increasing the content of lysophospholipids in membranes, either by stimulation of a PLA2 or by inhibition of an LPAT. These two opposing enzyme activities may help to coordinately regulate Golgi membrane shape and tubule formation.

scholarly journals Regulation of Golgi turnover by CALCOCO1-mediated selective autophagy

2021 ◽  
Vol 220 (6) ◽  
Author(s):  
Thaddaeus Mutugi Nthiga ◽  
Birendra Kumar Shrestha ◽  
Jack-Ansgar Bruun ◽  
Kenneth Bowitz Larsen ◽  
Trond Lamark ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Golgi Complex ◽  
Eukaryotic Cells ◽  
Golgi Membrane ◽  
Selective Autophagy ◽  
Physiological Demands ◽  
Size And Morphology ◽  
In Cells

The Golgi complex is essential for the processing, sorting, and trafficking of newly synthesized proteins and lipids. Golgi turnover is regulated to meet different cellular physiological demands. The role of autophagy in the turnover of Golgi, however, has not been clarified. Here we show that CALCOCO1 binds the Golgi-resident palmitoyltransferase ZDHHC17 to facilitate Golgi degradation by autophagy during starvation. Depletion of CALCOCO1 in cells causes expansion of the Golgi and accumulation of its structural and membrane proteins. ZDHHC17 itself is degraded by autophagy together with other Golgi membrane proteins such as TMEM165. Taken together, our data suggest a model in which CALCOCO1 mediates selective Golgiphagy to control Golgi size and morphology in eukaryotic cells via its interaction with ZDHHC17.

scholarly journals Membrane Tubule-mediated Reassembly and Maintenance of the Golgi Complex Is Disrupted by Phospholipase A2Antagonists

1999 ◽  
Vol 10 (6) ◽  
pp. 1763-1782 ◽  
Author(s):  
Paul de Figueiredo ◽  
Renée S. Polizotto ◽  
Daniel Drecktrah ◽  
William J. Brown
Keyword(s):  
Steady State ◽  
Golgi Complex ◽  
Membrane Trafficking ◽  
Biological Significance ◽  
Vitro Assay ◽  
In Vitro Reconstitution ◽  
Dynamic Maintenance ◽  
Membrane Tubules ◽  
Insight Into

Although membrane tubules can be found extending from, and associated with, the Golgi complex of eukaryotic cells, their physiological function has remained unclear. To gain insight into the biological significance of membrane tubules, we have developed methods for selectively preventing their formation. We show here that a broad range of phospholipase A2(PLA2) antagonists not only arrest membrane tubule–mediated events that occur late in the assembly of the Golgi complex but also perturb its normal steady-state tubulovesicular architecture by inducing a reversible fragmentation into separate “mini-stacks.” In addition, we show that these same compounds prevent the formation of membrane tubules from Golgi stacks in an in vitro reconstitution system. This in vitro assay was further used to demonstrate that the relevant PLA2activity originates from the cytoplasm. Taken together, these results demonstrate that Golgi membrane tubules, sensitive to potent and selective PLA2antagonists, mediate both late events in the reassembly of the Golgi complex and the dynamic maintenance of its steady-state architecture. In addition, they implicate a role for cytoplasmic PLA2enzymes in mediating these membrane trafficking events.

scholarly journals De novo macrocyclic peptides for inhibiting, stabilising and probing the function of the Retromer endosomal trafficking complex

2020 ◽  
Author(s):  
Kai-En Chen ◽  
Qian Guo ◽  
Yi Cui ◽  
Amy K. Kendall ◽  
Timothy A. Hill ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Cyclic Peptides ◽  
De Novo ◽  
Late Onset ◽  
Endosomal Trafficking ◽  
Endosomal Membrane ◽  
Cellular Localisation ◽  
Macrocyclic Peptides ◽  
In Cells

ABSTRACTThe Retromer complex (Vps35-Vps26-Vps29) is essential for endosomal membrane trafficking and signalling. Mutations in Retromer cause late-onset Parkinson’s disease, while viral and bacterial pathogens can hijack the complex during cellular infection. To modulate and probe its function we have created a novel series of macrocyclic peptides that bind Retromer with high affinity and specificity. Crystal structures show the majority of cyclic peptides bind to Vps29 via a Pro-Leu-containing sequence, structurally mimicking known interactors such as TBC1D5, and blocking their interaction with Retromer in vitro and in cells. By contrast, macrocyclic peptide RT-L4 binds Retromer at the Vps35-Vps26 interface and is a more effective molecular chaperone than reported small molecules, suggesting a new therapeutic avenue for targeting Retromer. Finally, tagged peptides can be used to probe the cellular localisation of Retromer and its functional interactions in cells, providing novel tools for studying Retromer function.

scholarly journals The Golgi-Associated Hook3 Protein Is a Member of a Novel Family of Microtubule-Binding Proteins

2001 ◽  
Vol 152 (5) ◽  
pp. 923-934 ◽  
Author(s):  
Jason H. Walenta ◽  
Aaron J. Didier ◽  
Xinran Liu ◽  
Helmut Krämer
Keyword(s):  
Golgi Complex ◽  
Membrane Trafficking ◽  
Spatial Organization ◽  
Large Fraction ◽  
Coiled Coil ◽  
Brefeldin A ◽  
Associated Proteins ◽  
Terminal Domains

Microtubules are central to the spatial organization of diverse membrane-trafficking systems. Here, we report that Hook proteins constitute a novel family of cytosolic coiled coil proteins that bind to organelles and to microtubules. The conserved NH2-terminal domains of Hook proteins mediate attachment to microtubules, whereas the more divergent COOH-terminal domains mediate the binding to organelles. Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo. Unlike other cis-Golgi–associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization. Because overexpression of Hook3 caused fragmentation of the Golgi complex, we propose that Hook3 participates in defining the architecture and localization of the mammalian Golgi complex.

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