1
|
Wang Y, Nguyen HP, Xue P, Xie Y, Yi D, Lin F, Dinh J, Viscarra JA, Ibe NU, Duncan RE, Sul HS. ApoL6 associates with lipid droplets and disrupts Perilipin1-HSL interaction to inhibit lipolysis. Nat Commun 2024; 15:186. [PMID: 38167864 PMCID: PMC10762002 DOI: 10.1038/s41467-023-44559-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/18/2023] [Indexed: 01/05/2024] Open
Abstract
Adipose tissue stores triacylglycerol (TAG) in lipid droplets (LD) and release fatty acids upon lipolysis during energy shortage. We identify ApoL6 as a LD-associated protein mainly found in adipose tissue, specifically in adipocytes. ApoL6 expression is low during fasting but induced upon feeding. ApoL6 knockdown results in smaller LD with lower TAG content in adipocytes, while ApoL6 overexpression causes larger LD with higher TAG content. We show that the ApoL6 affects adipocytes through inhibition of lipolysis. While ApoL6, Perilipin 1 (Plin1), and HSL can form a complex on LD, C-terminal ApoL6 directly interacts with N-terminal Plin1 to prevent Plin1 binding to HSL, to inhibit lipolysis. Thus, ApoL6 ablation decreases white adipose tissue mass, protecting mice from diet-induced obesity, while ApoL6 overexpression in adipose brings obesity and insulin resistance, making ApoL6 a potential future target against obesity and diabetes.
Collapse
Affiliation(s)
- Yuhui Wang
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Hai P Nguyen
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Pengya Xue
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Ying Xie
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Danielle Yi
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Frances Lin
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Jennie Dinh
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Jose A Viscarra
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Nnejiuwa U Ibe
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Robin E Duncan
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, N2T 2N4, Canada
| | - Hei S Sul
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA.
| |
Collapse
|
2
|
Ibe NU, Subramanian A, Mukherjee S. Non-canonical activation of the ER stress sensor ATF6 by Legionella pneumophila effectors. Life Sci Alliance 2021; 4:4/12/e202101247. [PMID: 34635501 PMCID: PMC8507491 DOI: 10.26508/lsa.202101247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 09/29/2021] [Accepted: 10/01/2021] [Indexed: 12/16/2022] Open
Abstract
Legionella pneumophila secretes toxins into the host cell that induce the non-canonical processing and activation of the ER stress sensor and transcription factor ATF6 via a mechanism that is distinct from the canonical pathway activated by unfolded protein buildup. The intracellular bacterial pathogen Legionella pneumophila (L.p.) secretes ∼330 effector proteins into the host cell to sculpt an ER-derived replicative niche. We previously reported five L.p. effectors that inhibit IRE1, a key sensor of the homeostatic unfolded protein response (UPR) pathway. In this study, we discovered a subset of L.p. toxins that selectively activate the UPR sensor ATF6, resulting in its cleavage, nuclear translocation, and target gene transcription. In a deviation from the conventional model, this L.p.–dependent activation of ATF6 does not require its transport to the Golgi or its cleavage by the S1P/S2P proteases. We believe that our findings highlight the unique regulatory control that L.p. exerts upon the three UPR sensors and expand the repertoire of bacterial proteins that selectively perturb host homeostatic pathways.
Collapse
Affiliation(s)
- Nnejiuwa U Ibe
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA
| | - Advait Subramanian
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA.,Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Shaeri Mukherjee
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA .,George Williams Hooper Foundation, University of California, San Francisco, San Francisco, CA, USA
| |
Collapse
|
3
|
Jeng EE, Bhadkamkar V, Ibe NU, Gause H, Jiang L, Chan J, Jian R, Jimenez-Morales D, Stevenson E, Krogan NJ, Swaney DL, Snyder MP, Mukherjee S, Bassik MC. Systematic Identification of Host Cell Regulators of Legionella pneumophila Pathogenesis Using a Genome-wide CRISPR Screen. Cell Host Microbe 2019; 26:551-563.e6. [PMID: 31540829 DOI: 10.1016/j.chom.2019.08.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/26/2019] [Accepted: 08/27/2019] [Indexed: 12/12/2022]
Abstract
During infection, Legionella pneumophila translocates over 300 effector proteins into the host cytosol, allowing the pathogen to establish an endoplasmic reticulum (ER)-like Legionella-containing vacuole (LCV) that supports bacterial replication. Here, we perform a genome-wide CRISPR-Cas9 screen and secondary targeted screens in U937 human monocyte/macrophage-like cells to systematically identify host factors that regulate killing by L. pneumophila. The screens reveal known host factors hijacked by L. pneumophila, as well as genes spanning diverse trafficking and signaling pathways previously not linked to L. pneumophila pathogenesis. We further characterize C1orf43 and KIAA1109 as regulators of phagocytosis and show that RAB10 and its chaperone RABIF are required for optimal L. pneumophila replication and ER recruitment to the LCV. Finally, we show that Rab10 protein is recruited to the LCV and ubiquitinated by the effectors SidC/SdcA. Collectively, our results provide a wealth of previously undescribed insights into L. pneumophila pathogenesis and mammalian cell function.
Collapse
Affiliation(s)
- Edwin E Jeng
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA; Program in Cancer Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Varun Bhadkamkar
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Nnejiuwa U Ibe
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Haley Gause
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Lihua Jiang
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Joanne Chan
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ruiqi Jian
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - David Jimenez-Morales
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA; Quantitative Biosciences Institute (QBI), University of California, San Francisco, San Francisco, CA, USA; The J. David Gladstone Institutes, San Francisco, CA, USA
| | - Erica Stevenson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA; Quantitative Biosciences Institute (QBI), University of California, San Francisco, San Francisco, CA, USA; The J. David Gladstone Institutes, San Francisco, CA, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA; Quantitative Biosciences Institute (QBI), University of California, San Francisco, San Francisco, CA, USA; The J. David Gladstone Institutes, San Francisco, CA, USA
| | - Danielle L Swaney
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA; Quantitative Biosciences Institute (QBI), University of California, San Francisco, San Francisco, CA, USA; The J. David Gladstone Institutes, San Francisco, CA, USA
| | - Michael P Snyder
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Shaeri Mukherjee
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA.
| | - Michael C Bassik
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
| |
Collapse
|
4
|
Lek MT, Cruz S, Ibe NU, Beck WHJ, Bielicki JK, Weers PMM, Narayanaswami V. Swapping the N- and C-terminal domains of human apolipoprotein E3 and AI reveals insights into their structure/activity relationship. PLoS One 2017. [PMID: 28644829 PMCID: PMC5482431 DOI: 10.1371/journal.pone.0178346] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Apolipoprotein (apo) E3 and apoAI are exchangeable apolipoproteins that play a dominant role in regulating plasma lipoprotein metabolism. ApoE3 (299 residues) is composed of an N-terminal (NT) domain bearing a 4-helix bundle and a C-terminal (CT) domain bearing a series of amphipathic α-helices. ApoAI (243 residues) also comprises a highly helical NT domain and a less structured CT tail. The objective of this study was to understand their structural and functional role by generating domain swapped chimeras: apoE3-NT/apoAI-CT and apoAI-NT/apoE-CT. The bacterially overexpressed chimeras were purified by affinity chromatography and their identity confirmed by immunoblotting and mass spectrometry. Their α-helical content was comparable to that of the parent proteins. ApoE3-NT/apoAI-CT retained the denaturation profile of apoE3 NT domain, with apoAI CT tail eliciting a relatively unstructured state; its lipid binding ability improved dramatically compared to apoE3 indicative of a significant role of apoAI CT tail in lipid binding interaction. The LDL receptor interaction and ability to promote ABCA1-mediated cholesterol efflux of apoE3-NT/apoAI-CT was comparable to that of apoE3. In contrast, apoAI-NT/apoE-CT elicited an unfolding pattern and lipid binding ability that were similar to that of apoAI. As expected, DMPC/apoAI-NT/apoE-CT discoidal particles did not elicit LDLr binding ability, and promoted SR-B1 mediated cellular uptake of lipids to a limited extent. However, apoAI-NT/apoE-CT displayed an enhanced ability to promote cholesterol efflux compared to apoAI, indicative of a significant role for apoE CT domain in mediating this function. Together, these results indicate that the functional attributes of apoAI and apoE3 can be conferred on each other and that NT-CT domain interactions significantly modulate their structure and function.
Collapse
Affiliation(s)
- Mark T. Lek
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Siobanth Cruz
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Nnejiuwa U. Ibe
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Wendy H. J. Beck
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - John K. Bielicki
- Donner Laboratory, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Paul M. M. Weers
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Vasanthy Narayanaswami
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
- * E-mail:
| |
Collapse
|
5
|
Dwivedi P, Rodriguez J, Ibe NU, Weers PMM. Deletion of the N- or C-Terminal Helix of Apolipophorin III To Create a Four-Helix Bundle Protein. Biochemistry 2016; 55:3607-15. [PMID: 27280697 DOI: 10.1021/acs.biochem.6b00381] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Apolipophorin III (apoLp-III) is an exchangeable apolipoprotein found in insects and plays an important function in lipid transport. The protein has an unusual five-helix bundle architecture, deviating from the common four-helix bundle motif. To understand the role of the additional helix in apoLp-III, the N-terminal or C-terminal helix was deleted to create a putative four-helix bundle protein. While the protein lacking helix-1 could be expressed in bacteria albeit at reduced yields, apoLp-III lacking helix-5 could not be produced. Mutational analysis by truncating helix-5 showed that a minimum segment of approximately one-third of the C-terminal helix is required for protein expression. The variant lacking helix-5 was produced by inserting a methionine residue between helix-4 and -5; subsequent cyanogenbromide cleavage generated the four-helix variant. Both N- and C-terminal helix deletion variants displayed significantly reduced helical content, protein stability, and tertiary structure. Despite the significantly altered structure, the variants were still fully functional. The rate of dimyristoylphosphatidylcholine vesicle solubilization was enhanced 4-5-fold compared to the wild-type protein, and the deletion variants were effective in binding to lipolyzed low density lipoprotein thereby preventing lipoprotein aggregation. These results show that the additional helix of apoLp-III is not essential for lipid binding but is required for proper folding to keep the protein into a stable conformation.
Collapse
Affiliation(s)
- Pankaj Dwivedi
- Department of Chemistry and Biochemistry, California State University , Long Beach, California 90840, United States
| | - Johana Rodriguez
- Department of Chemistry and Biochemistry, California State University , Long Beach, California 90840, United States
| | - Nnejiuwa U Ibe
- Department of Chemistry and Biochemistry, California State University , Long Beach, California 90840, United States
| | - Paul M M Weers
- Department of Chemistry and Biochemistry, California State University , Long Beach, California 90840, United States
| |
Collapse
|