1
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Quintanilla MA, Patel H, Wu H, Sochacki KA, Chandrasekar S, Akamatsu M, Rotty JD, Korobova F, Bear JE, Taraska JW, Oakes PW, Beach JR. Local monomer levels and established filaments potentiate non-muscle myosin 2 assembly. J Cell Biol 2024; 223:e202305023. [PMID: 38353656 PMCID: PMC10866686 DOI: 10.1083/jcb.202305023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 01/02/2024] [Accepted: 01/26/2024] [Indexed: 02/16/2024] Open
Abstract
The ability to dynamically assemble contractile networks is required throughout cell physiology, yet direct biophysical mechanisms regulating non-muscle myosin 2 filament assembly in living cells are lacking. Here, we use a suite of dynamic, quantitative imaging approaches to identify deterministic factors that drive myosin filament appearance and amplification. We find that actin dynamics regulate myosin assembly, but that the static actin architecture plays a less clear role. Instead, remodeling of actin networks modulates the local myosin monomer levels and facilitates assembly through myosin:myosin-driven interactions. Using optogenetically controlled myosin, we demonstrate that locally concentrating myosin is sufficient to both form filaments and jump-start filament amplification and partitioning. By counting myosin monomers within filaments, we demonstrate a myosin-facilitated assembly process that establishes filament stacks prior to partitioning into clusters that feed higher-order networks. Together, these findings establish the biophysical mechanisms regulating the assembly of non-muscle contractile structures that are ubiquitous throughout cell biology.
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Affiliation(s)
- Melissa A. Quintanilla
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Hiral Patel
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Huini Wu
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Kem A. Sochacki
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Shreya Chandrasekar
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Matthew Akamatsu
- Department of Biology, University of Washington, Seattle, WA, USA
| | - Jeremy D. Rotty
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Farida Korobova
- Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - James E. Bear
- Department of Cell Biology and Physiology, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA
| | - Justin W. Taraska
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Patrick W. Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Jordan R. Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
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2
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Stinson MW, Liu S, Laurenson AJ, Rotty JD. Macrophage migration is differentially regulated by fibronectin and laminin through altered adhesion and myosin II localization. Mol Biol Cell 2024; 35:ar22. [PMID: 38088893 PMCID: PMC10881148 DOI: 10.1091/mbc.e23-04-0137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 10/30/2023] [Accepted: 11/28/2023] [Indexed: 12/26/2023] Open
Abstract
Macrophages are indispensable for proper immune surveillance and inflammatory regulation. They also exhibit dramatic phenotypic plasticity and are highly responsive to their local microenvironment, which includes the extracellular matrix (ECM). This work demonstrates that two fibrous ECM glycoproteins, fibronectin (FN) and laminin (LAM), elicit distinct morphological and migratory responses from macrophages in two-dimensional environments. LAM 111 inhibits macrophage cell spreading, but drives them to migrate rapidly and less persistently compared with cells on FN. Differential integrin engagement and ROCK/myosin II organization helps explain why macrophages alter their morphology and migration character on these two ECM components. This study also demonstrates that LAM 111 exerts a suppressive effect toward FN, as macrophages plated on a LAM/FN mixture adopt a morphology and migratory character almost identical to LAM alone. This suggests that distinct responses can be initiated downstream of receptor-ECM engagement, and that one component of the microenvironment may affect the cell's ability to sense another. Overall, macrophages appear intrinsically poised to rapidly switch between distinct migratory characters based on their ECM environments. The role of ECM composition in dictating motile and inflammatory responses in three-dimensional and in vivo contexts warrants further study.
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Affiliation(s)
- Matthew W. Stinson
- Uniformed Services University of the Health Sciences, Department of Biochemistry, Bethesda, MD 20814
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817
| | - Sophia Liu
- Uniformed Services University of the Health Sciences, Department of Biochemistry, Bethesda, MD 20814
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817
| | - Alexander J. Laurenson
- Uniformed Services University of the Health Sciences, Department of Biochemistry, Bethesda, MD 20814
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817
| | - Jeremy D. Rotty
- Uniformed Services University of the Health Sciences, Department of Biochemistry, Bethesda, MD 20814
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3
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Stinson MW, Laurenson AJ, Rotty JD. Macrophage migration is differentially regulated by distinct ECM components. bioRxiv 2023:2023.04.27.538597. [PMID: 37162935 PMCID: PMC10168351 DOI: 10.1101/2023.04.27.538597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Macrophages are indispensable for proper immune surveillance and inflammatory regulation. They also exhibit dramatic phenotypic plasticity and are highly responsive to their local microenvironment, which includes the extracellular matrix (ECM). The present work demonstrates that two fibrous ECM glycoproteins, fibronectin (FN) and laminin (LAM), elicit distinct morphological and migratory responses to macrophages in 2D environments. Laminin 111 inhibits macrophage cell spreading, but drives them to migrate rapidly and less persistently compared to cells on fibronectin. Differential integrin engagement and ROCK/myosin II organization helps explain why macrophages alter their morphology and migration character on these two ECM components. The present study also demonstrates that laminin 111 exerts a suppressive effect toward fibronectin, as macrophages plated on a LAM/FN mixture adopt a morphology and migratory character almost identical to LAM alone. This suggests that distinct responses can be initiated downstream of receptor-ECM engagement, and that one component of the microenvironment may affect the cell's ability to sense another. Overall, macrophages appear intrinsically poised to rapidly switch between distinct migratory modes based on their ECM environments. The role of ECM composition in dictating motile and inflammatory responses in 3D and in vivo contexts warrants further study.
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4
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Quintanilla MA, Patel H, Wu H, Sochacki KA, Akamatsu M, Rotty JD, Korobova F, Bear JE, Taraska JW, Oakes PW, Beach JR. Local Monomer Levels and Established Filaments Potentiate Non-Muscle Myosin 2 Assembly. bioRxiv 2023:2023.04.26.538303. [PMID: 37162845 PMCID: PMC10168331 DOI: 10.1101/2023.04.26.538303] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The ability to dynamically assemble contractile networks is required throughout cell physiology, yet the biophysical mechanisms regulating non-muscle myosin 2 filament assembly in living cells are lacking. Here we use a suite of dynamic, quantitative imaging approaches to identify deterministic factors that drive myosin filament appearance and amplification. We find that actin dynamics regulate myosin assembly, but that the actin architecture plays a minimal direct role. Instead, remodeling of actin networks modulates the local myosin monomer levels and facilitates assembly through myosin:myosin driven interactions. Using optogenetically controlled myosin, we demonstrate that locally concentrating myosin is sufficient to both form filaments and jump-start filament amplification and partitioning. By counting myosin monomers within filaments, we demonstrate a myosin-facilitated assembly process that establishes sub-resolution filament stacks prior to partitioning into clusters that feed higher-order networks. Together these findings establish the biophysical mechanisms regulating the assembly of non-muscle contractile structures that are ubiquitous throughout cell biology.
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Affiliation(s)
- Melissa A Quintanilla
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Hiral Patel
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Huini Wu
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Kem A Sochacki
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, USA
| | | | - Jeremy D Rotty
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD
| | - Farida Korobova
- Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - James E Bear
- Department of Cell Biology and Physiology, University of North Carolina-Chapel Hill, Chapel Hill, NC
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, USA
| | - Patrick W Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Jordan R Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
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5
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Qiu R, Zhang J, Rotty JD, Xiang X. Dynein activation in vivo is regulated by the nucleotide states of its AAA3 domain. Curr Biol 2021; 31:4486-4498.e6. [PMID: 34428469 DOI: 10.1016/j.cub.2021.07.081] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 04/29/2021] [Revised: 07/05/2021] [Accepted: 07/29/2021] [Indexed: 01/02/2023]
Abstract
Cytoplasmic dynein is activated by the dynactin complex, cargo adapters and LIS1 (Lissencephaly 1). How this process is regulated in vivo remains unclear. The dynein motor ring contains six AAA+ (ATPases associated with diverse cellular activities) domains. Here, we used the filamentous fungus Aspergillus nidulans to examine whether ATP hydrolysis at AAA3 regulates dynein activation in the context of other regulators. In fungal hyphae, early endosomes undergo dynein-mediated movement away from the microtubule plus ends near the hyphal tip. Dynein normally accumulates at the microtubule plus ends. The early endosomal adaptor Hook protein, together with dynactin, drives dynein activation to cause its relocation to the microtubule minus ends. This activation process depends on LIS1, but LIS1 tends to dissociate from dynein after its activation. In this study, we found that dynein containing a mutation-blocking ATP hydrolysis at AAA3 can undergo LIS1-independent activation, consistent with our genetic data that the same mutation suppresses the growth defect of the A. nidulans LIS1-deletion mutant. Our data also suggest that blocking AAA3 ATP hydrolysis allows dynein activation by dynactin without the early endosomal adaptor. As a consequence, dynein accumulates at microtubule minus ends whereas early endosomes stay near the plus ends. Dynein containing a mutation-blocking ATP binding at AAA3 largely depends on LIS1 for activation, but this mutation abnormally prevents LIS1 dissociation upon dynein activation. Together, our data suggest that the AAA3 ATPase cycle regulates the coordination between dynein activation and cargo binding as well as the dynamic dynein-LIS1 interaction.
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Affiliation(s)
- Rongde Qiu
- Department of Biochemistry and Molecular Biology, the Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Jun Zhang
- Department of Biochemistry and Molecular Biology, the Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Jeremy D Rotty
- Department of Biochemistry and Molecular Biology, the Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA
| | - Xin Xiang
- Department of Biochemistry and Molecular Biology, the Uniformed Services University of the Health Sciences- F. Edward Hébert School of Medicine, Bethesda, MD 20814, USA.
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6
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Tessier S, Doolittle AC, Sao K, Rotty JD, Bear JE, Ulici V, Loeser RF, Shapiro IM, Diekman BO, Risbud MV. Arp2/3 inactivation causes intervertebral disc and cartilage degeneration with dysregulated TonEBP-mediated osmoadaptation. JCI Insight 2020; 5:131382. [PMID: 31961823 DOI: 10.1172/jci.insight.131382] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [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: 06/27/2019] [Accepted: 01/15/2020] [Indexed: 01/01/2023] Open
Abstract
Extracellular matrix and osmolarity influence the development and homeostasis of skeletal tissues through Rho GTPase-mediated alteration of the actin cytoskeleton. This study investigated whether the actin-branching Arp2/3 complex, a downstream effector of the Rho GTPases Cdc42 and Rac1, plays a critical role in maintaining the health of matrix-rich and osmotically loaded intervertebral discs and cartilage. Mice with constitutive intervertebral disc- and cartilage-specific deletion of the critical Arp2/3 subunit Arpc2 (Col2-Cre; Arpc2fl/fl) developed chondrodysplasia and spinal defects. Since these mice did not survive to adulthood, we generated mice with inducible Arpc2 deletion in disc and cartilage (Acan-CreERT2; Arpc2fl/fl). Inactivation of Arp2/3 at skeletal maturity resulted in growth plate closure, loss of proteoglycan content in articular cartilage, and degenerative changes in the intervertebral disc at 1 year of age. Chondrocytes with Arpc2 deletion showed compromised cell spreading on both collagen and fibronectin. Pharmacological inhibition of Cdc42 and Arp2/3 prevented the osmoadaptive transcription factor TonEBP/NFAT5 from recruiting cofactors in response to a hyperosmolarity challenge. Together, these findings suggest that Arp2/3 plays a critical role in cartilaginous tissues through the regulation of cell-extracellular matrix interactions and modulation of TonEBP-mediated osmoadaptation.
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Affiliation(s)
- Steven Tessier
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College
| | - Alexandra C Doolittle
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College.,Graduate Program in Cell Biology and Regenerative Medicine, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Kimheak Sao
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College.,Graduate Program in Cell Biology and Regenerative Medicine, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Jeremy D Rotty
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.,Department of Cell Biology and Physiology.,UNC Lineberger Comprehensive Cancer Center
| | - James E Bear
- Department of Cell Biology and Physiology.,UNC Lineberger Comprehensive Cancer Center
| | - Veronica Ulici
- Thurston Arthritis Research Center, and.,Division of Rheumatology, Allergy, and Immunology, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Richard F Loeser
- Thurston Arthritis Research Center, and.,Division of Rheumatology, Allergy, and Immunology, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Irving M Shapiro
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College.,Graduate Program in Cell Biology and Regenerative Medicine, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Brian O Diekman
- Division of Rheumatology, Allergy, and Immunology, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill and Raleigh, North Carolina, USA
| | - Makarand V Risbud
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College.,Graduate Program in Cell Biology and Regenerative Medicine, Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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7
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Freemerman AJ, Zhao L, Pingili AK, Teng B, Cozzo AJ, Fuller AM, Johnson AR, Milner JJ, Lim MF, Galanko JA, Beck MA, Bear JE, Rotty JD, Bezavada L, Smallwood HS, Puchowicz MA, Liu J, Locasale JW, Lee DP, Bennett BJ, Abel ED, Rathmell JC, Makowski L. Myeloid Slc2a1-Deficient Murine Model Revealed Macrophage Activation and Metabolic Phenotype Are Fueled by GLUT1. J Immunol 2019; 202:1265-1286. [PMID: 30659108 PMCID: PMC6360258 DOI: 10.4049/jimmunol.1800002] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 12/03/2018] [Indexed: 12/15/2022]
Abstract
Macrophages (MΦs) are heterogeneous and metabolically flexible, with metabolism strongly affecting immune activation. A classic response to proinflammatory activation is increased flux through glycolysis with a downregulation of oxidative metabolism, whereas alternative activation is primarily oxidative, which begs the question of whether targeting glucose metabolism is a viable approach to control MΦ activation. We created a murine model of myeloid-specific glucose transporter GLUT1 (Slc2a1) deletion. Bone marrow-derived MΦs (BMDM) from Slc2a1M-/- mice failed to uptake glucose and demonstrated reduced glycolysis and pentose phosphate pathway activity. Activated BMDMs displayed elevated metabolism of oleate and glutamine, yet maximal respiratory capacity was blunted in MΦ lacking GLUT1, demonstrating an incomplete metabolic reprogramming. Slc2a1M-/- BMDMs displayed a mixed inflammatory phenotype with reductions of the classically activated pro- and anti-inflammatory markers, yet less oxidative stress. Slc2a1M-/- BMDMs had reduced proinflammatory metabolites, whereas metabolites indicative of alternative activation-such as ornithine and polyamines-were greatly elevated in the absence of GLUT1. Adipose tissue MΦs of lean Slc2a1M-/- mice had increased alternative M2-like activation marker mannose receptor CD206, yet lack of GLUT1 was not a critical mediator in the development of obesity-associated metabolic dysregulation. However, Ldlr-/- mice lacking myeloid GLUT1 developed unstable atherosclerotic lesions. Defective phagocytic capacity in Slc2a1M-/- BMDMs may have contributed to unstable atheroma formation. Together, our findings suggest that although lack of GLUT1 blunted glycolysis and the pentose phosphate pathway, MΦ were metabolically flexible enough that inflammatory cytokine release was not dramatically regulated, yet phagocytic defects hindered MΦ function in chronic diseases.
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Affiliation(s)
- Alex J. Freemerman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - Liyang Zhao
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - Ajeeth K. Pingili
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Bin Teng
- Department of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Alyssa J. Cozzo
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - Ashley M. Fuller
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Amy R. Johnson
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - J. Justin Milner
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - Maili F. Lim
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - Joseph A. Galanko
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Melinda A. Beck
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799
| | - James E. Bear
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jeremy D. Rotty
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Lavanya Bezavada
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Heather S. Smallwood
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Michelle A. Puchowicz
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Juan Liu
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Duke University, Durham, NC 27710
| | - Jason W. Locasale
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Duke University, Durham, NC 27710
| | | | - Brian J. Bennett
- U.S. Department of Agriculture Western Human Nutrition Research Center, Davis, CA 95616
| | - E. Dale Abel
- Division of Endocrinology and Metabolism, University of Iowa Carver College of Medicine, Iowa City, IA 52242;,Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242; and
| | - Jeff C. Rathmell
- Department of Pathology, Microbiology, and Immunology, Vanderbilt Center for Immunobiology, Vanderbilt University, Nashville, TN 37232
| | - Liza Makowski
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 25799; .,Department of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163
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8
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Zhao L, Cozzo AJ, Johnson AR, Christensen T, Freemerman AJ, Bear JE, Rotty JD, Bennett BJ, Makowski L. Lack of myeloid Fatp1 increases atherosclerotic lesion size in Ldlr -/- mice. Atherosclerosis 2017; 266:182-189. [PMID: 29035781 DOI: 10.1016/j.atherosclerosis.2017.10.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 09/07/2017] [Accepted: 10/06/2017] [Indexed: 12/14/2022]
Abstract
BACKGROUND AND AIMS Altered metabolism is an important regulator of macrophage (MΦ) phenotype, which contributes to inflammatory diseases such as atherosclerosis. Broadly, pro-inflammatory, classically-activated MΦs (CAM) are glycolytic while alternatively-activated MΦs (AAM) oxidize fatty acids, although overlap exists. We previously demonstrated that MΦ fatty acid transport protein 1 (FATP1, Slc27a1) was necessary to maintain the oxidative and anti-inflammatory AAM phenotype in vivo in a model of diet-induced obesity. The aim of this study was to examine how MΦ metabolic reprogramming through FATP1 ablation affects the process of atherogenesis. We hypothesized that FATP1 limits MΦ-mediated inflammation during atherogenesis. Thus, mice lacking MΦ Fatp1 would display elevated formation of atherosclerotic lesions in a mouse model lacking the low-density lipoprotein (LDL) receptor (Ldlr-/-). METHODS We transplanted bone marrow collected from Fatp1+/+ or Fatp1-/- mice into Ldlr-/- mice and fed chimeric mice a Western diet for 12 weeks. Body weight, blood glucose, and plasma lipids were measured. Aortic sinus and aorta lesions were quantified. Atherosclerotic plaque composition, oxidative stress, and inflammation were analyzed histologically. RESULTS Compared to Fatp1+/+Ldlr-/- mice, Fatp1-/-Ldlr-/- mice exhibited significantly larger lesion area and elevated oxidative stress and inflammation in the atherosclerotic plaque. Macrophage and smooth muscle cell content did not differ by Fatp1 genotype. There were no significant systemic alterations in LDL, high-density lipoprotein (HDL), total cholesterol, or triacylglyceride, suggesting that the effect was local to the cells of the vessel microenvironment in a Fatp1-dependent manner. CONCLUSIONS MΦ Fatp1 limits atherogenesis and may be a viable target to metabolically reprogram MΦs.
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Affiliation(s)
- Liyang Zhao
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Alyssa J Cozzo
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Amy R Johnson
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Taylor Christensen
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Alex J Freemerman
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - James E Bear
- Lineberger Cancer Center, Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jeremy D Rotty
- Lineberger Cancer Center, Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Brian J Bennett
- USDA Western Human Nutrition Research Center, Davis, CA 95616, USA
| | - Liza Makowski
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA; University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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9
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Rotty JD, Brighton HE, Craig SL, Asokan SB, Cheng N, Ting JP, Bear JE. Arp2/3 Complex Is Required for Macrophage Integrin Functions but Is Dispensable for FcR Phagocytosis and In Vivo Motility. Dev Cell 2017; 42:498-513.e6. [PMID: 28867487 DOI: 10.1016/j.devcel.2017.08.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [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: 01/06/2017] [Revised: 06/19/2017] [Accepted: 08/02/2017] [Indexed: 11/18/2022]
Abstract
The Arp2/3 complex nucleates branched actin, forming networks involved in lamellipodial protrusion, phagocytosis, and cell adhesion. We derived primary bone marrow macrophages lacking Arp2/3 complex (Arpc2-/-) and directly tested its role in macrophage functions. Despite protrusion and actin assembly defects, Arpc2-/- macrophages competently phagocytose via FcR and chemotax toward CSF and CX3CL1. However, CR3 phagocytosis and fibronectin haptotaxis, both integrin-dependent processes, are disrupted. Integrin-responsive actin assembly and αM/β2 integrin localization are compromised in Arpc2-/- cells. Using an in vivo system to observe endogenous monocytes migrating toward full-thickness ear wounds we found that Arpc2-/- monocytes maintain cell speeds and directionality similar to control. Our work reveals that the Arp2/3 complex is not a general requirement for phagocytosis or chemotaxis but is a critical driver of integrin-dependent processes. We demonstrate further that cells lacking Arp2/3 complex function in vivo remain capable of executing important physiological responses that require rapid directional motility.
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Affiliation(s)
- Jeremy D Rotty
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hailey E Brighton
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stephanie L Craig
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Sreeja B Asokan
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ning Cheng
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Oral Biology Curriculum, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jenny P Ting
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Oral Biology Curriculum, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - James E Bear
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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King SJ, Asokan SB, Haynes EM, Zimmerman SP, Rotty JD, Alb JG, Tagliatela A, Blake DR, Lebedeva IP, Marston D, Johnson HE, Parsons M, Sharpless NE, Kuhlman B, Haugh JM, Bear JE. Lamellipodia are crucial for haptotactic sensing and response. J Cell Sci 2016; 129:2329-42. [PMID: 27173494 DOI: 10.1242/jcs.184507] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [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: 12/08/2015] [Accepted: 05/05/2016] [Indexed: 12/11/2022] Open
Abstract
Haptotaxis is the process by which cells respond to gradients of substrate-bound cues, such as extracellular matrix proteins (ECM); however, the cellular mechanism of this response remains poorly understood and has mainly been studied by comparing cell behavior on uniform ECMs with different concentrations of components. To study haptotaxis in response to gradients, we utilized microfluidic chambers to generate gradients of the ECM protein fibronectin, and imaged the cell migration response. Lamellipodia are fan-shaped protrusions that are common in migrating cells. Here, we define a new function for lamellipodia and the cellular mechanism required for haptotaxis - differential actin and lamellipodial protrusion dynamics lead to biased cell migration. Modest differences in lamellipodial dynamics occurring over time periods of seconds to minutes are summed over hours to produce differential whole cell movement towards higher concentrations of fibronectin. We identify a specific subset of lamellipodia regulators as being crucial for haptotaxis. Numerous studies have linked components of this pathway to cancer metastasis and, consistent with this, we find that expression of the oncogenic Rac1 P29S mutation abrogates haptotaxis. Finally, we show that haptotaxis also operates through this pathway in 3D environments.
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Affiliation(s)
- Samantha J King
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Sreeja B Asokan
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Elizabeth M Haynes
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Seth P Zimmerman
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jeremy D Rotty
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - James G Alb
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alicia Tagliatela
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Devon R Blake
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Pharmacology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599, USA
| | - Irina P Lebedeva
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Howard Hughes Medical Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Daniel Marston
- Department of Pharmacology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599, USA
| | - Heath E Johnson
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Maddy Parsons
- King's College London, Randall Institute, London SE1 8RT, UK
| | - Norman E Sharpless
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Brian Kuhlman
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jason M Haugh
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - James E Bear
- UNC Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA Howard Hughes Medical Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Rotty JD, Bear JE. Competition and collaboration between different actin assembly pathways allows for homeostatic control of the actin cytoskeleton. Bioarchitecture 2015; 5:27-34. [PMID: 26430713 DOI: 10.1080/19490992.2015.1090670] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Tremendous insight into actin-associated proteins has come from careful biochemical and cell biological characterization of their activities and regulation. However, many studies of their cellular behavior have only considered each in isolation. Recent efforts reveal that assembly factors compete for polymerization-competent actin monomers, suggesting that actin is homeostatically regulated. It seems that a major regulatory component is competition between Arp2/3-activating nucleation promoting factors and profilin for actin monomers. The result is differential delivery of actin to different pathways, allowing for simultaneous assembly of competing F-actin structures and collaborative building of higher order cellular structures. Although there are likely to be additional factors that regulate actin homeostasis, especially in a cell type-dependent fashion, we advance the notion that competition between actin assembly factors results in a tunable system that can be adjusted according to extracellular and intracellular cues.
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Affiliation(s)
- Jeremy D Rotty
- a UNC Lineberger Comprehensive Cancer Center; University of North Carolina at Chapel Hill ; Chapel Hill , NC USA.,b Department of Cell Biology and Physiology; University of North Carolina at Chapel Hill ; Chapel Hill , NC USA
| | - James E Bear
- a UNC Lineberger Comprehensive Cancer Center; University of North Carolina at Chapel Hill ; Chapel Hill , NC USA.,b Department of Cell Biology and Physiology; University of North Carolina at Chapel Hill ; Chapel Hill , NC USA
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Johnson HE, King SJ, Asokan SB, Rotty JD, Bear JE, Haugh JM. F-actin bundles direct the initiation and orientation of lamellipodia through adhesion-based signaling. ACTA ACUST UNITED AC 2015; 208:443-55. [PMID: 25666809 PMCID: PMC4332254 DOI: 10.1083/jcb.201406102] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [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] [Indexed: 01/03/2023]
Abstract
Mesenchymal cells such as fibroblasts are weakly polarized and reorient directionality by a lamellipodial branching mechanism that is stabilized by phosphoinositide 3-kinase (PI3K) signaling. However, the mechanisms by which new lamellipodia are initiated and directed are unknown. Using total internal reflection fluorescence microscopy to monitor cytoskeletal and signaling dynamics in migrating cells, we show that peripheral F-actin bundles/filopodia containing fascin-1 serve as templates for formation and orientation of lamellipodia. Accordingly, modulation of fascin-1 expression tunes cell shape, quantified as the number of morphological extensions. Ratiometric imaging reveals that F-actin bundles/filopodia play both structural and signaling roles, as they prime the activation of PI3K signaling mediated by integrins and focal adhesion kinase. Depletion of fascin-1 ablated fibroblast haptotaxis on fibronectin but not platelet-derived growth factor chemotaxis. Based on these findings, we conceptualize haptotactic sensing as an exploration, with F-actin bundles directing and lamellipodia propagating the process and with signaling mediated by adhesions playing the role of integrator.
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Affiliation(s)
- Heath E Johnson
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Samantha J King
- UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599
| | - Sreeja B Asokan
- UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599
| | - Jeremy D Rotty
- UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599
| | - James E Bear
- UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599
| | - Jason M Haugh
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
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Rotty JD, Wu C, Haynes EM, Suarez C, Winkelman JD, Johnson HE, Haugh JM, Kovar DR, Bear JE. Profilin-1 serves as a gatekeeper for actin assembly by Arp2/3-dependent and -independent pathways. Dev Cell 2014; 32:54-67. [PMID: 25543281 DOI: 10.1016/j.devcel.2014.10.026] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 09/12/2014] [Accepted: 10/30/2014] [Indexed: 12/31/2022]
Abstract
Cells contain multiple F-actin assembly pathways, including the Arp2/3 complex, formins, and Ena/VASP, which have largely been analyzed separately. They collectively generate the bulk of F-actin from a common pool of G-actin; however, the interplay and/or competition between these pathways remains poorly understood. Using fibroblast lines derived from an Arpc2 conditional knockout mouse, we established matched-pair cells with and without the Arp2/3 complex. Arpc2(-/-) cells lack lamellipodia and migrate more slowly than WT cells but have F-actin levels indistinguishable from controls. Actin assembly in Arpc2(-/-) cells was resistant to cytochalasin-D and was highly dependent on profilin-1 and Ena/VASP but not formins. Profilin-1 depletion in WT cells increased F-actin and Arp2/3 complex in lamellipodia. Conversely, addition of exogenous profilin-1 inhibited Arp2/3 complex actin nucleation in vitro and in vivo. Antagonism of the Arp2/3 complex by profilin-1 in cells appears to maintain actin homeostasis by balancing Arp2/3 complex-dependent and -independent actin assembly pathways.
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Affiliation(s)
- Jeremy D Rotty
- University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Congying Wu
- University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Elizabeth M Haynes
- University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Jonathan D Winkelman
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Heath E Johnson
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Jason M Haugh
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - James E Bear
- University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Rotty JD, Coulombe PA. A wound-induced keratin inhibits Src activity during keratinocyte migration and tissue repair. J Exp Med 2012. [DOI: 10.1084/jem2095oia8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Abstract
Keratin 6 negatively regulates Src kinase activity and the migratory potential of skin keratinocytes during wound repair. Injury to the epidermis triggers an elaborate homeostatic response resulting in tissue repair and recovery of the vital barrier function. The type II keratins 6a and 6b (K6a and K6b) are among the genes induced early on in wound-proximal keratinocytes and maintained during reepithelialization. Paradoxically, genetic ablation of K6a and K6b results in enhanced keratinocyte migration. In this paper, we show that this trait results from activation of Src kinase and key Src substrates that promote cell migration. Endogenous Src physically associated with keratin proteins in keratinocytes in a K6-dependent fashion. Purified Src bound K6-containing filaments via its SH2 domain in a novel phosphorylation-independent manner, resulting in kinase inhibition. K6 protein was enriched in the detergent-resistant membrane (DRM), a key site of Src inhibition, and DRMs from K6-null keratinocytes were depleted of both keratin and Src. We conclude that K6 negatively regulates Src kinase activity and the migratory potential of skin keratinocytes during wound repair. Our findings may also be important in related contexts such as cancer.
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Affiliation(s)
- Jeremy D Rotty
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21202, USA
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Abstract
Mounting evidence suggests that keratin post-translational modifications are crucial for many cellular processes. Now, keratin 18 modified by the addition of an O-linked N-acetylglucosamine residue is shown to be as a critical effector of stress-responsive Akt signalling, providing an important link between keratin glycosylation and cell survival.
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