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Sherman DJ, Liu L, Mamrosh JL, Xie J, Ferbas J, Lomenick B, Ladinsky MS, Verma R, Rulifson IC, Deshaies RJ. The fatty liver disease-causing protein PNPLA3-I148M alters lipid droplet-Golgi dynamics. Proc Natl Acad Sci U S A 2024; 121:e2318619121. [PMID: 38657050 PMCID: PMC11067037 DOI: 10.1073/pnas.2318619121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 03/16/2024] [Indexed: 04/26/2024] Open
Abstract
Nonalcoholic fatty liver disease, recently renamed metabolic dysfunction-associated steatotic liver disease (MASLD), is a progressive metabolic disorder that begins with aberrant triglyceride accumulation in the liver and can lead to cirrhosis and cancer. A common variant in the gene PNPLA3, encoding the protein PNPLA3-I148M, is the strongest known genetic risk factor for MASLD. Despite its discovery 20 y ago, the function of PNPLA3, and now the role of PNPLA3-I148M, remain unclear. In this study, we sought to dissect the biogenesis of PNPLA3 and PNPLA3-I148M and characterize changes induced by endogenous expression of the disease-causing variant. Contrary to bioinformatic predictions and prior studies with overexpressed proteins, we demonstrate here that PNPLA3 and PNPLA3-I148M are not endoplasmic reticulum-resident transmembrane proteins. To identify their intracellular associations, we generated a paired set of isogenic human hepatoma cells expressing PNPLA3 and PNPLA3-I148M at endogenous levels. Both proteins were enriched in lipid droplet, Golgi, and endosomal fractions. Purified PNPLA3 and PNPLA3-I148M proteins associated with phosphoinositides commonly found in these compartments. Despite a similar fractionation pattern as the wild-type variant, PNPLA3-I148M induced morphological changes in the Golgi apparatus, including increased lipid droplet-Golgi contact sites, which were also observed in I148M-expressing primary human patient hepatocytes. In addition to lipid droplet accumulation, PNPLA3-I148M expression caused significant proteomic and transcriptomic changes that resembled all stages of liver disease. Cumulatively, we validate an endogenous human cellular system for investigating PNPLA3-I148M biology and identify the Golgi apparatus as a central hub of PNPLA3-I148M-driven cellular change.
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Affiliation(s)
| | - Lei Liu
- Amgen Research, South San Francisco, CA94080
| | | | | | | | - Brett Lomenick
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA91125
| | - Mark S. Ladinsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA91125
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Sherman DJ, Liu L, Mamrosh JL, Xie J, Ferbas J, Lomenick B, Ladinsky MS, Verma R, Rulifson IC, Deshaies RJ. The fatty liver disease-causing protein PNPLA3-I148M alters lipid droplet-Golgi dynamics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.13.562302. [PMID: 37873239 PMCID: PMC10592801 DOI: 10.1101/2023.10.13.562302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD), recently renamed metabolic dysfunction-associated steatotic liver disease (MASLD), is a progressive metabolic disorder that begins with aberrant triglyceride accumulation in the liver and can lead to cirrhosis and cancer. A common variant in the gene PNPLA3, encoding the protein PNPLA3-I148M, is the strongest known genetic risk factor for MASLD to date. Despite its discovery twenty years ago, the function of PNPLA3, and now the role of PNPLA3-I148M, remain unclear. In this study, we sought to dissect the biogenesis of PNPLA3 and PNPLA3-I148M and characterize changes induced by endogenous expression of the disease-causing variant. Contrary to bioinformatic predictions and prior studies with overexpressed proteins, we demonstrate here that PNPLA3 and PNPLA3-I148M are not endoplasmic reticulum-resident transmembrane proteins. To identify their intracellular associations, we generated a paired set of isogenic human hepatoma cells expressing PNPLA3 and PNPLA3-I148M at endogenous levels. Both proteins were enriched in lipid droplet, Golgi, and endosomal fractions. Purified PNPLA3 and PNPLA3-I148M proteins associated with phosphoinositides commonly found in these compartments. Despite a similar fractionation pattern as the wild-type variant, PNPLA3-I148M induced morphological changes in the Golgi apparatus, including increased lipid droplet-Golgi contact sites, which were also observed in I148M-expressing primary human patient hepatocytes. In addition to lipid droplet accumulation, PNPLA3-I148M expression caused significant proteomic and transcriptomic changes that resembled all stages of liver disease. Cumulatively, we validate an endogenous human cellular system for investigating PNPLA3-I148M biology and identify the Golgi apparatus as a central hub of PNPLA3-I148M-driven cellular change.
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Affiliation(s)
| | - Lei Liu
- Amgen Research, South San Francisco, CA 94080, USA
| | | | | | - John Ferbas
- Amgen Research, Thousand Oaks, CA 91320, USA
| | - Brett Lomenick
- Proteome Exploration Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
| | - Mark S. Ladinsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Rati Verma
- Amgen Research, Thousand Oaks, CA 91320, USA
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Kinderman F, Yerby B, Jawa V, Joubert MK, Joh NH, Malella J, Herskovitz J, Xie J, Ferbas J, McBride HJ. Impact of Precipitation of Antibody Therapeutics After Subcutaneous Injection on Pharmacokinetics and Immunogenicity. J Pharm Sci 2019; 108:1953-1963. [DOI: 10.1016/j.xphs.2019.01.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/07/2019] [Accepted: 01/11/2019] [Indexed: 11/26/2022]
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Farquhar RE, Rodrigues E, Hamilton KL. The Role of the Cytoskeleton and Myosin-Vc in the Targeting of KCa3.1 to the Basolateral Membrane of Polarized Epithelial Cells. Front Physiol 2017; 7:639. [PMID: 28101059 PMCID: PMC5209343 DOI: 10.3389/fphys.2016.00639] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 12/06/2016] [Indexed: 12/27/2022] Open
Abstract
Understanding the targeting of KCa3.1 to the basolateral membrane (BLM) of polarized epithelial cells is still emerging. Here, we examined the role of the cytoskeleton (microtubules and microfilaments) and Myosin-Vc (Myo-Vc) in the targeting of KCa3.1 in Fischer rat thyroid epithelial cells. We used a pharmacological approach with immunoblot (for the BLM expression of KCa3.1), Ussing chamber (functional BLM expression of KCa3.1) and siRNA experiments. The actin cytoskeleton inhibitors cytochalasin D (10 μM, 5 h) and latrunculin A (10 μM, 5 h) reduced the targeting of KCa3.1 to the BLM by 88 ± 4 and 70 ± 5%, respectively. Colchicine (10 μM, 5 h) a microtubule inhibitor reduced targeting of KCa3.1 to the BLM by 63 ± 7% and decreased 1-EBIO-stimulated KCa3.1 K+ current by 46 ± 18%, compared with control cells. ML9 (10 μM, 5 h), an inhibitor of myosin light chain kinase, decreased targeting of the channel by 83 ± 2% and reduced K+ current by 54 ± 8% compared to control cells. Inhibiting Myo-V with 2,3-butanedione monoxime (10 mM, 5 h) reduced targeting of the channel to the BLM by 58 ± 5% and decreased the stimulated current of KCa3.1 by 48 ± 12% compared with control cells. Finally, using siRNA for Myo-Vc, we demonstrated that knockdown of Myo-Vc reduced the BLM expression of KCa3.1 by 44 ± 7% and KCa3.1 K+ current by 1.04 ± 0.14 μA compared with control cells. These data suggest that the microtubule and microfilament cytoskeleton and Myo-Vc are critical for the targeting of KCa3.1.
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Affiliation(s)
- Rachel E Farquhar
- Department of Physiology, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand
| | - Ely Rodrigues
- Department of Medicine, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand
| | - Kirk L Hamilton
- Department of Physiology, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand
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Schwingshackl A, Roan E, Teng B, Waters CM. TREK-1 Regulates Cytokine Secretion from Cultured Human Alveolar Epithelial Cells Independently of Cytoskeletal Rearrangements. PLoS One 2015; 10:e0126781. [PMID: 26001192 PMCID: PMC4441361 DOI: 10.1371/journal.pone.0126781] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 03/28/2015] [Indexed: 01/15/2023] Open
Abstract
Background TREK-1 deficient alveolar epithelial cells (AECs) secrete less IL-6, more MCP-1, and contain less F-actin. Whether these alterations in cytokine secretion and F-actin content are related remains unknown. We now hypothesized that cytokine secretion from TREK-1-deficient AECs was regulated by cytoskeletal rearrangements. Methods We determined F-actin and α-tubulin contents of control, TREK-1-deficient and TREK-1-overexpressing human A549 cells by confocal microscopy and western blotting, and measured IL-6 and MCP-1 levels using real-time PCR and ELISA. Results Cytochalasin D decreased the F-actin content of control cells. Jasplakinolide increased the F-actin content of TREK-1 deficient cells, similar to the effect of TREK-1 overexpression in control cells. Treatment of control and TREK-1 deficient cells with TNF-α, a strong stimulus for IL-6 and MCP-1 secretion, had no effect on F-actin structures. The combination of TNF-α+cytochalasin D or TNF-α+jasplakinolide had no additional effect on the F-actin content or architecture when compared to cytochalasin D or jasplakinolide alone. Although TREK-1 deficient AECs contained less F-actin at baseline, quantified biochemically, they contained more α-tubulin. Exposure to nocodazole disrupted α-tubulin filaments in control and TREK-1 deficient cells, but left the overall amount of α-tubulin unchanged. Although TNF-α had no effect on the F-actin or α-tubulin contents, it increased IL-6 and MCP-1 production and secretion from control and TREK-1 deficient cells. IL-6 and MCP-1 secretions from control and TREK-1 deficient cells after TNF-α+jasplakinolide or TNF-α+nocodazole treatment was similar to the effect of TNF-α alone. Interestingly, cytochalasin D decreased TNF-α-induced IL-6 but not MCP-1 secretion from control but not TREK-1 deficient cells. Conclusion Although cytochalasin D, jasplakinolide and nocodazole altered the F-actin and α-tubulin structures of control and TREK-1 deficient AEC, the changes in cytokine secretion from TREK-1 deficient cells cannot be explained by cytoskeletal rearrangements in these cells.
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Affiliation(s)
- Andreas Schwingshackl
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN, United States of America
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, United States of America
- * E-mail:
| | - Esra Roan
- Department of Biomedical Engineering, University of Memphis, Memphis, TN, United States of America
| | - Bin Teng
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, United States of America
| | - Christopher M. Waters
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, United States of America
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, United States of America
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Stanley AC, Lieu ZZ, Wall AA, Venturato J, Khromykh T, Hamilton NA, Gleeson PA, Stow JL. Recycling endosome-dependent and -independent mechanisms for IL-10 secretion in LPS-activated macrophages. J Leukoc Biol 2012; 92:1227-39. [PMID: 23012430 DOI: 10.1189/jlb.0412191] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
IL-10 is a key anti-inflammatory cytokine secreted by activated macrophages as a feedback control mechanism to prevent excessive inflammatory responses. Here, we define multiple intracellular trafficking pathways involved in the secretion of newly synthesized IL-10 from macrophages following TLR4 activation with LPS, and show how this relates to the previously defined trafficking pathways for IL-6 and TNF in macrophages simultaneously producing these proinflammatory cytokines. IL-10 exits the Golgi in multiple tubular carriers, including those dependent on p230GRIP. Some of the IL-10 is then delivered to recycling endosomes, where cytokine sorting may occur prior to its release. Another portion of the IL-10 is delivered to the cell surface in distinct vesicles colabeled for apoE. Thus, we show at least two post-Golgi pathways via which IL-10 is trafficked, ensuring its secretion from activated macrophages under different physiological conditions.
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Affiliation(s)
- A C Stanley
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
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Schechter JE, Warren DW, Mircheff AK. A Lacrimal Gland is a Lacrimal Gland, But Rodent's and Rabbit's Are Not Human. Ocul Surf 2010; 8:111-34. [DOI: 10.1016/s1542-0124(12)70222-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Carlsson SK, Edman MC, Delbro D, Gierow JP. Adenosine A2 receptor presence and synergy with cholinergic stimulation in rabbit lacrimal gland. Curr Eye Res 2010; 35:466-74. [PMID: 20465439 DOI: 10.3109/02713681003602667] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Secretion from the lacrimal gland is an important part of the well-being of the eye, and a central part in the search for treatment of dry eye syndrome. Adenosine has stimulatory effects on the lacrimal gland, and can potentiate the effect of the cholinergic agonist carbachol (Cch). The aim of the present study is to investigate the presence of the adenosine A(2) receptor subtypes A(2A) and A(2B) in the rabbit lacrimal gland, and to characterize their role in regulated acinar cell secretion. METHODS Expression of the receptors was investigated using reverse transcriptase-PCR (RT-PCR) and immunofluorescence, and secretion effects were studied using a secretion assay in isolated lacrimal gland acinar cells. RESULTS Presence of both receptors was detected by RT-PCR and immunofluorescence. The secretion assay revealed a minor effect of stimulation of the A(2) receptors, and a strong synergistic effect with the cholinergic agonist Cch. The synergistic effect was significantly reduced by the A(2B) antagonist PSB 1115, but not by the A(2A) antagonist SCH 58261, indicating that A(2B) is the receptor responsible for this potentiation. CONCLUSIONS The study reveals the presence of the adenosine A(2) receptor subtypes as well as a role for them in lacrimal gland secretion, and especially in the synergy with purinergic and cholinergic stimulation.
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