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Martin Carli JF, Dzieciatkowska M, Hernandez TL, Monks J, McManaman JL. Comparative proteomic analysis of human milk fat globules and paired membranes and mouse milk fat globules identifies core cellular systems contributing to mammary lipid trafficking and secretion. Front Mol Biosci 2023; 10:1259047. [PMID: 38169886 PMCID: PMC10759240 DOI: 10.3389/fmolb.2023.1259047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 11/22/2023] [Indexed: 01/05/2024] Open
Abstract
Introduction: Human milk delivers critical nutritional and immunological support to human infants. Milk fat globules (MFGs) and their associated membranes (MFGMs) contain the majority of milk lipids and many bioactive components that contribute to neonatal development and health, yet their compositions have not been fully defined, and the mechanisms responsible for formation of these structures remain incompletely understood. Methods: In this study, we used untargeted mass spectrometry to quantitatively profile the protein compositions of freshly obtained MFGs and their paired, physically separated MFGM fractions from 13 human milk samples. We also quantitatively profiled the MFG protein compositions of 9 pooled milk samples from 18 lactating mouse dams. Results: We identified 2,453 proteins and 2,795 proteins in the majority of human MFG and MFGM samples, respectively, and 1,577 proteins in mouse MFGs. Using paired analyses of protein abundance in MFGMs compared to MFGs (MFGM-MFG; 1% FDR), we identified 699 proteins that were more highly abundant in MFGMs (MFGM-enriched), and 201 proteins that were less abundant in MFGMs (cytoplasmic). MFGM-enriched proteins comprised membrane systems (apical plasma membrane and multiple vesicular membranes) hypothesized to be responsible for lipid and protein secretion and components of membrane transport and signaling systems. Cytoplasmic proteins included ribosomal and proteasomal systems. Comparing abundance between human and mouse MFGs, we found a positive correlation (R 2 = 0.44, p < 0.0001) in the relative abundances of 1,279 proteins that were found in common across species. Discussion: Comparative pathway enrichment analyses between human and mouse samples reveal similarities in membrane trafficking and signaling pathways involved in milk fat secretion and identify potentially novel immunological components of MFGs. Our results advance knowledge of the composition and relative quantities of proteins in human and mouse MFGs in greater detail, provide a quantitative profile of specifically enriched human MFGM proteins, and identify core cellular systems involved in milk lipid secretion.
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Affiliation(s)
- Jayne F. Martin Carli
- Section of Nutrition, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Monika Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Teri L. Hernandez
- College of Nursing, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Division of Endocrinology, Metabolism, and Diabetes, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Jenifer Monks
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - James L. McManaman
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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Singh A, Malla WA, Kumar A, Jain A, Thakur MS, Khare V, Tiwari SP. Review: genetic background of milk fatty acid synthesis in bovines. Trop Anim Health Prod 2023; 55:328. [PMID: 37749432 DOI: 10.1007/s11250-023-03754-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 09/12/2023] [Indexed: 09/27/2023]
Abstract
Milk fat composition is an important trait for the dairy industry as it directly influences the nutritional and technological properties of milk and other dairy products. The synthesis of milk fat is a complex process regulated by a network of genes. Thus, understanding the genetic variation and molecular mechanisms regulating milk fat synthesis will help to improve the nutritional quality of dairy products. In this review, we provide an overview of milk fat synthesis in bovines along with the candidate genes involved in the pathway. We also discuss de novo synthesis of fatty acids (ACSS, ACACA, FASN), uptake of FAs (FATP, FAT, LPL), intracellular activation and channelling of FAs (ACSL, FABP), elongation (EVOLV6), desaturation (SCD, FADS), formation of triglycerides (GPAM, AGPAT, LIPIN, DGAT), and milk lipid secretion (BTN1A1, XDH, PLIN2). The genetic variability of individual fatty acids will help to develop selection strategies for obtaining a healthier milk fat profile in bovines. Thus, this review will offer a potential understanding of the molecular mechanisms that regulate milk fat synthesis in bovines.
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Affiliation(s)
- Akansha Singh
- College of Veterinary Science and Animal Husbandry, NDVSU, Jabalpur, M.P, 482001, India.
| | - Waseem Akram Malla
- ICMR-National Institute of Malaria Research, Field Unit Guwahati, Assam, 781022, India
| | - Amit Kumar
- ICAR- Indian Veterinary Research Institute, Izatnagar, Bareilly, U.P, 243122, India
| | - Asit Jain
- College of Veterinary Science and Animal Husbandry, NDVSU, Jabalpur, M.P, 482001, India
| | - Mohan Singh Thakur
- College of Veterinary Science and Animal Husbandry, NDVSU, Jabalpur, M.P, 482001, India
| | - Vaishali Khare
- College of Veterinary Science and Animal Husbandry, NDVSU, Jabalpur, M.P, 482001, India
| | - Sita Prasad Tiwari
- College of Veterinary Science and Animal Husbandry, NDVSU, Jabalpur, M.P, 482001, India
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3
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Abstract
Mammary lipid secretion is generally held to be unique and remarkably uniform between the many different orders of mammals. It produces a unit membrane-bounded milk fat globule (MFG). The unit membrane is separated from the lipoprotein boundary of what was the cytoplasmic lipid droplet (CLD) boundary by a uniform layer of cytoplasmic proteins. In 3-8% of the MFG in all species examined this cytoplasmic layer widens to include cytoplasmic organelles which are referred to as 'crescents'. This defines the MFG secretion as apocrine indicating a closely regulated process which minimises the loss of mammary epithelial cell (MEC) cytoplasm. The apocrine nature of the secretion might be expected since the evolution of the mammary gland is considered to be from an apocrine secreting skin gland. This short Research Reflection review is designed to investigate the exact cytoplasmic interactions which allow such efficient lipid secretion. There are two main scenarios: one which assumes that the observed close association between CLD and GV results in the CLD being released as a consequence of sequential exocytosis of the content of the associated GV. The second assumes that the CLD and the MEC apical plasmalemma interact in some way which causes the CLD to rise out of the cytoplasm enveloped in the plasmalemma. Here I present the evidence for the two possibilities. The first scenario is favoured, but the second cannot be ruled out.
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Han L, Huang Q, Yang J, Lu W, Hu M, Yang Y, Zhu H, Pang K, Yang G. Proteomic analysis of milk fat globule membranes from small-sized milk fat globules and their function in promoting lipid droplet fusion in bovine mammary epithelial cells. Food Funct 2023; 14:2304-2312. [PMID: 36752527 DOI: 10.1039/d2fo03476j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In mammary epithelial cells, milk fat is synthesized as lipid droplets and secreted in the form of globules. Milk fat globules (MFGs) are covered by a lipid-protein membrane known as the milk fat globule membrane (MFGM). We randomly divided 12 Holstein cows into control and conjugated linoleic acid (CLA) groups. The control group was fed a basal diet, while the CLA group was fed the basal diet + CLA (15 g per kg DM) for 10 days. Cow performance, milk composition, and MFG size were measured daily. On day 10, we extracted MFGM proteins (n = 3) and identified them via quantitative proteomic analysis. We investigated the effects of the MFGM proteins from control and CLA-treated milk on the lipid droplet formation in MAC-T cells. Compared with the control group, the CLA group had reduced milk fat content (3.39 g/100 mL vs. 2.45 g/100 mL) and MFG size parameters (D[4,3] of 3.85 μm vs. 3.37 μm; D[3,2] of 3.24 μm vs. 2.83 μm). The specific surface area (SSA) increased in the CLA group. A total of 361 differentially expressed proteins were identified in the CLA group by iTRAQ quantitative proteomic analysis. Among these proteins, 100 were upregulated and 251 were downregulated (p < 0.05). In MAC-T cells, CLA-MFGM proteins increased the diameter of the lipid droplets to 1.32 μm. CLA-MFGM proteins decreased the proportion of the small lipid droplets (15.33% vs. 47.78%) and increased the proportion of the large lipid droplets (25.04% vs. 11.65%). CLA-MFGM proteins promoted lipid droplet fusion. Therefore, MFGM proteins play an important role in the regulation of the lipid droplet size.
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Affiliation(s)
- Liqiang Han
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Qixue Huang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - JingNa Yang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Wenyan Lu
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Mingyue Hu
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Yanbin Yang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Heshui Zhu
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China.
| | - Kun Pang
- College of Animal Science and Veterinary Medicine, Xinyang Agriculture and Forestry University, Xinyang 464399, P. R. China
| | - Guoyu Yang
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou 450046, P. R. China
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Huang QX, Yang J, Hu M, Lu W, Zhong K, Wang Y, Yang G, Loor JJ, Han L. Milk fat globule membrane proteins are involved in controlling the size of milk fat globules during conjugated linoleic acid-induced milk fat depression. J Dairy Sci 2022; 105:9179-9190. [PMID: 36175227 DOI: 10.3168/jds.2022-22131] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 06/30/2022] [Indexed: 11/19/2022]
Abstract
Milk fat globule membrane (MFGM) proteins surround the triacylglycerol core comprising milk fat globules (MFG). We previously detected a decrease in the size of fat globules during conjugated linoleic acid (CLA)-induced milk fat depression (MFD), and other studies have reported that some MFGM proteins play a central role in regulating mammary cellular lipid droplet size. However, little is known about the relationship between MFD, MFG size, and MFGM proteins in bovine milk. The aim of this study was to investigate the profile of MFGM proteins during MFD induced by CLA. Sixteen mid-lactating Holstein cows (145 ± 24 d in milk) with similar body condition and parity were divided into control and CLA groups over a 10-d period. Cows were fed a basal diet (control, n = 8) or control plus 15 g/kg of dry matter (DM) CLA (n = 8) to induce MFD. Cow performance, milk composition, and MFG size were measured daily. On d 10, MFGM proteins were extracted and identified by quantitative proteomic analysis, and western blotting was used to verify a subset of the identified MFGM proteins. Compared with controls, supplemental CLA did not affect milk production, DM intake, or milk protein and lactose contents. However, CLA reduced milk fat content (3.73 g/100 mL vs. 2.47 g/100 mL) and the size parameters volume-related diameter D[4,3] (3.72 μm vs. 3.35 μm) and surface area-related diameter D[3,2] (3.13 μm vs. 2.80 μm), but increased specific surface area of MFG (1,905 m2/kg vs. 2,188 m2/kg). In total, 177 differentially expressed proteins were detected in milk from cows with CLA-induced MFD, 60 of which were upregulated and 117 downregulated. Correlation analysis showed that MFG size was negatively correlated with various proteins, including XDH and FABP3, and positively correlated with MFG-E8, RAB19, and APOA1. The results provide evidence for an important role of MFGM proteins in regulating MFG diameter, and they facilitate a mechanistic understanding of diet-induced MFD.
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Affiliation(s)
- Qi Xue Huang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Jingna Yang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Mingyue Hu
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Wenyan Lu
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Kai Zhong
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Yueying Wang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China
| | - Guoyu Yang
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou 450046, P. R. China
| | - Juan J Loor
- Department of Animal Science and Division of Nutritional Sciences, University of Illinois, Urbana 61801
| | - Liqiang Han
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450046, P. R. China; Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450046, P. R. China.
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Monks J, Orlicky DJ, Libby AE, Dzieciatkowska M, Ladinsky MS, McManaman JL. Perilipin-2 promotes lipid droplet-plasma membrane interactions that facilitate apocrine lipid secretion in secretory epithelial cells of the mouse mammary gland. Front Cell Dev Biol 2022; 10:958566. [PMID: 36158190 PMCID: PMC9500548 DOI: 10.3389/fcell.2022.958566] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 08/16/2022] [Indexed: 11/21/2022] Open
Abstract
Secretory epithelial cells (sMEC) in mammary glands of lactating animals secrete lipids by a novel apocrine mechanism in which cytoplasmic lipid droplets (LD) contact and are enveloped by elements of the apical plasma membrane (APM) before being released into the lumen of the gland as membrane bound structures. The molecular properties of LD-APM contacts and the mechanisms regulating LD membrane envelopment and secretion are not fully understood. Perilipin-2 (Plin2) is a constitutive LD protein that has been proposed to tether LD to the APM through formation of a complex with the transmembrane protein, butyrophilin1a1 (BTN) and the redox enzyme, xanthine oxidoreductase (XOR). Using mice lacking Plin2 and physiological inhibition of apocrine lipid secretion, we demonstrate that LD-APM contact and envelopment are mechanistically distinct steps that they are differentially regulated by Plin2 and independent of LD secretion. We find that Plin2 is not required for formation of LD-APM contacts. However, it increases the percentage of LD that contact the APM and mediates enlargement of the LD-APM contact zone as LD undergo membrane envelopment. The effects of Plin2 LD-APM interactions are associated with increased abundances of BTN, XOR and Cidea, which are implicated as mediators of LD-APM contact formation, on membranes surrounding secreted LD, and with promotion of glycocalyx remodeling at LD-APM contact sites. We propose that Plin2 does not directly mediate contact between LD and the APM but acts by enhancing molecular interactions that stabilize LD-APM contacts and govern membrane envelopment of LD during apocrine lipid secretion. Plin2 does not appear to significantly affect the lipid content of milk in fully lactating animals, but it does increase lipid secretion at the onset of lactation in primaparous dams, which suggest a role in facilitating apocrine lipid secretion in sMEC during their initial transition to a secretory phenotype.
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Affiliation(s)
- Jenifer Monks
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Graduate Program in Integrated Physiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - David J. Orlicky
- Department of Pathology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Andrew E. Libby
- Graduate Program in Integrated Physiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Monica Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Mark S. Ladinsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - James L. McManaman
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Graduate Program in Integrated Physiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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7
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Tai P, Golding M, Singh H, Everett D. The bovine milk fat globule membrane – Liquid ordered domain formation and anticholesteremic effects during digestion. FOOD REVIEWS INTERNATIONAL 2022. [DOI: 10.1080/87559129.2021.2015773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Patrick Tai
- Riddet Institute, Palmerston North, New Zealand
- School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
| | - Matt Golding
- Riddet Institute, Palmerston North, New Zealand
- School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
| | | | - David Everett
- Riddet Institute, Palmerston North, New Zealand
- Grasslands Research Centre, AgResearch, Palmerston North, New Zealand
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8
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Li M, Zheng K, Song W, Yu H, Zhang X, Yue X, Li Q. Quantitative analysis of differentially expressed milk fat globule membrane proteins between donkey and bovine colostrum based on high-performance liquid chromatography with tandem mass spectrometry proteomics. J Dairy Sci 2021; 104:12207-12215. [PMID: 34531055 DOI: 10.3168/jds.2021-20471] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 07/09/2021] [Indexed: 01/20/2023]
Abstract
This study was designed to provide novel insights into milk fat globule membrane (MFGM) proteins in donkey colostrum (DC) and bovine colostrum (BC) using quantitative proteomics. In total, 179 (DC) and 195 (BC) MFGM proteins were characterized, including 71 shared, 108 DC-specific, and 124 BC-specific proteins. Fifty-one shared proteins were selected as differentially expressed MFGM proteins, including 21 upregulated and 30 downregulated proteins in DC. Gene ontology analysis showed that these proteins were mainly enriched in cellular components, including the extracellular exosome, extracellular space, and plasma membrane. Additionally, they were further involved in metabolic pathways, including cholesterol metabolism, the peroxisome proliferator-activated receptor signaling pathway, and purine metabolism. Furthermore, several key protein factors with high connectivity were identified via protein-protein interaction analysis. These results provide more comprehensive knowledge of differences in the biological properties of MFGM proteins in DC and BC as well as pave the way for future studies of the nutritional and functional requirements of these important ingredients toward the development of dairy products based on multiple milk sources.
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Affiliation(s)
- Mohan Li
- College of Food Science, Shenyang Agricultural University, Shenyang, 110866, China
| | - Kexin Zheng
- College of Food Science, Shenyang Agricultural University, Shenyang, 110866, China
| | - Wanying Song
- College of Food Science, Shenyang Agricultural University, Shenyang, 110866, China
| | - Haikun Yu
- College of Food Science, Shenyang Agricultural University, Shenyang, 110866, China
| | - Xiumin Zhang
- Beijing Academy of Food Sciences, Beijing, 100068, China
| | - Xiqing Yue
- College of Food Science, Shenyang Agricultural University, Shenyang, 110866, China.
| | - Qilong Li
- College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, Shenyang, 110866, China; College of Bioscience and Biotechnology, Shenyang Agricultural University, Shenyang, 110866, China.
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9
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Eichinger A, Neumaier I, Skerra A. The extracellular region of bovine milk butyrophilin exhibits closer structural similarity to human myelin oligodendrocyte glycoprotein than to immunological BTN family receptors. Biol Chem 2021; 402:1187-1202. [PMID: 34342946 DOI: 10.1515/hsz-2021-0122] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 06/17/2021] [Indexed: 11/15/2022]
Abstract
Bovine butyrophilin (BTN1A1) is an abundant type I transmembrane glycoprotein exposed on the surface of milk fat globules. We have solved the crystal structure of its extracellular region via multiple wavelength anomalous dispersion after incorporation of selenomethionine into the bacterially produced protein. The butyrophilin ectodomain exhibits two subdomains with immunoglobulin fold, each comprising a β-sandwich with a central disulfide bridge as well as one N-linked glycosylation. The fifth Cys residue at position 193 is unpaired and prone to forming disulfide crosslinks. The apparent lack of a ligand-binding site or receptor activity suggests a function predominantly as hydrophilic coat protein to prevent coagulation of the milk fat droplets. While there is less structural resemblance to members of the human butyrophilin family such as BTN3A, which play a role as immune receptors, the N-terminal bovine butyrophilin subdomain shows surprising similarity to the human myelin oligodendrocyte glycoprotein, a protein exposed on the surface of myelin sheaths. Thus, our study lends structural support to earlier hypotheses of a correlation between the consumption of cow milk and prevalence of neurological autoimmune diseases and may offer guidance for the breeding of cattle strains that express modified butyrophilin showing less immunological cross-reactivity.
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Affiliation(s)
- Andreas Eichinger
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, D-85354Freising, Germany
| | - Irmgard Neumaier
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, D-85354Freising, Germany
| | - Arne Skerra
- Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, D-85354Freising, Germany
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Lipidomic profiling analysis of the phospholipid molecules in SCAP-induced lipid droplet formation in bovine mammary epithelial cells. Prostaglandins Other Lipid Mediat 2020; 149:106420. [PMID: 31953015 DOI: 10.1016/j.prostaglandins.2020.106420] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 12/15/2019] [Accepted: 01/10/2020] [Indexed: 12/12/2022]
Abstract
The accumulation of lipid droplets (LDs) in the cytoplasm plays an important role in energy balance, membrane synthesis and cell signal transduction. The aim of this study was to investigate the profile of phospholipids after SCAP-induced LD formation in bovine mammary epithelial cells (BMECs). A shRNA-SCAP vector and a SCAP/SREBP vector were used to knock down and overexpress the SCAP gene in BMECs prior to evaluating the effects on LDs using Western blotting, real-time PCR, LD staining and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The average LD diameter was determined following oil red O staining. The overexpression of SCAP increased the abundance of SCD, ACACA and FASN genes and nuclear SREBP1a. In contrast, knocking down SCAP decreased the abundance of the nuclear SREBP1a protein and downregulated the abundance of target genes. Lipid droplet staining revealed that knocking down SCAP reduced LD formation and average LD diameter. In contrast, overexpression of SCAP increased the formation and size of the LDs. The results from an analysis of cellular lipids revealed that phospholipids are the predominant species in the profile of cell lipids. phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are important for determining the size of LDs. The LD formation induced by SCAP gene overexpression and knockdown underscored the role of phospholipids involved in lipid droplet formation and fusion.
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Mather IH, Masedunskas A, Chen Y, Weigert R. Symposium review: Intravital imaging of the lactating mammary gland in live mice reveals novel aspects of milk-lipid secretion. J Dairy Sci 2019; 102:2760-2782. [PMID: 30471915 PMCID: PMC7094374 DOI: 10.3168/jds.2018-15459] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 09/21/2018] [Indexed: 12/22/2022]
Abstract
Milk fat comprises membrane-coated droplets of neutral lipid, which constitute the predominant source of lipids for survival of the suckling neonate. From the perspective of the dairy industry, they are the basis for the manufacture of butter and essential ingredients in the production of cheese, yogurt, and specialty dairy produce. To provide mechanistic insight into the assembly and secretion of lipid droplets during lactation, we developed novel intravital imaging techniques using transgenic mice, which express fluorescently tagged marker proteins. The number 4 mammary glands were surgically prepared under a deep plane of anesthesia and the exposed glands positioned as a skin flap with intact vascular supply on the stage of a laser-scanning confocal microscope. Lipid droplets were stained by prior exposure of the glands to hydrophobic fluorescent BODIPY (boron-dipyrromethene) dyes and their formation and secretion monitored by time-lapse subcellular microscopy over periods of 1 to 2 h. Droplets were transported to the cell apex by directed (superdiffusive) motion at relatively slow and intermittent rates (0-2 µm/min). Regardless of size, droplets grew by numerous fusion events during transport and as they were budding from the cell enveloped by apical membranes. Surprisingly, droplet secretion was not constitutive but required an injection of oxytocin to induce contraction of the myoepithelium with subsequent release of droplets into luminal spaces. These novel results are discussed in the context of the current paradigm for milk fat synthesis and secretion and as a template for future innovations in the dairy industry.
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Affiliation(s)
- Ian H Mather
- Department of Animal and Avian Sciences, University of Maryland, College Park 20742; National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892.
| | - Andrius Masedunskas
- National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Yun Chen
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21205
| | - Roberto Weigert
- National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
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12
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Abstract
Milk is a unique and complete nutritive source for the mammal neonate, also providing immune protection and developmental signals. Lactation is a complex process, proper to the mother and child dyad, and including numerous variables ranging from psychological aspects to the secretory functioning of the mammary epithelial cells, all contributing to a successful breastfeeding. This review gives an integrated overview of the physiology of lactation with a particular focus on cellular and molecular mechanisms involved in milk product secretion and their regulations.
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Affiliation(s)
- Sandrine Truchet
- VIM, UR 892 INRA, Université Paris-Saclay, Jouy-en-Josas, France.
| | - Edith Honvo-Houéto
- GABI, INRA/AgroParisTech/Université Paris-Saclay, Domaine de Vilvert, 78352 Jouy-en-Josas, France.
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13
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Masedunskas A, Chen Y, Stussman R, Weigert R, Mather IH. Kinetics of milk lipid droplet transport, growth, and secretion revealed by intravital imaging: lipid droplet release is intermittently stimulated by oxytocin. Mol Biol Cell 2017; 28:935-946. [PMID: 28179456 PMCID: PMC5385942 DOI: 10.1091/mbc.e16-11-0776] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/13/2017] [Accepted: 02/01/2017] [Indexed: 12/21/2022] Open
Abstract
The lipid droplet (LD) fraction of milk has attracted special attention because it supplies preformed lipids for neonatal development, and the assembled LDs are secreted by a unique apocrine mechanism. Because many aspects of this key process remain uncharacterized, we developed a facile method for the intravital imaging of mammary cells in transgenic mice that express fluorescently tagged marker proteins. Using these techniques, we describe the first kinetic analysis of LD growth and secretion at peak lactation in real time. LD transit from basal to apical regions was slow (0-2 μm/min) and frequently intermittent. Droplets grew by the fusion of preexisting droplets, with no restriction on the size of fusogenic partners. Most droplet expansion took several hours and occurred in apical nucleation centers, either close to or in association with the apical surface. Droplets even continued to expand as they were emerging from the cell. Contrary to expectations, LDs attached to the apical plasma membrane but still associated with the cytoplasm were released after oxytocin-mediated contraction of the myoepithelium. Thus milk LD secretion is an intermittently regulated process. This novel procedure will have broad application for investigating trafficking events within the mammary epithelium in real time.
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Affiliation(s)
- Andrius Masedunskas
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Yun Chen
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Rebecca Stussman
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Roberto Weigert
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Ian H Mather
- Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892 .,Intracellular Membrane Trafficking Section, National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892.,Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742
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14
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Wooding FBP, Mather IH. Ultrastructural and immunocytochemical evidence for the reorganisation of the milk fat globule membrane after secretion. Cell Tissue Res 2017; 367:283-295. [PMID: 27677271 PMCID: PMC5269472 DOI: 10.1007/s00441-016-2505-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 09/07/2016] [Indexed: 11/29/2022]
Abstract
This paper reports a detailed ultrastructural and immunocytochemical investigation of the structure of the milk fat globule membrane (MFGM) in a variety of species. The process follows the same pattern in all mammals so far investigated. The initial (or primary) MFGM immediately on release from the mammary cell is a continuous unit membrane with a thin underlying layer of cytoplasmic origin and a monolayer of phospholipid separating it from the core lipid. This structure changes rapidly as the milk fat globule (MFG) moves into the alveolar lumen. The unit membrane plus the underlying layer of cytoplasm modifies drastically into discontinuous patches and networks. These are superimposed upon a continuous apparently structureless sheet of electron dense material stabilising the MFG and similar to that which bounded the lipid in the cell. The underlying layer of the patches increases in electron density and immunocytochemistry demonstrates localisation of MFGM proteins in this layer. In four species, the dense material shows ordered paracrystalline molecular arrays in section and en face views. All the arrays show the same basic pattern and unit size as determined by optical diffraction. Similar patches, networks and arrays are present on the surface of expressed MFG. Negative staining of lipid-extracted expressed MFGs shows similar patches and networks of membrane. These also occasionally show the crystalline arrays and label with MFGM protein antibodies. Similar networks and strands of plasma membrane on the MFG surface are shown by our CLSM examination of unfixed expressed MFG from mice genetically modified to express a fluorescent molecule as a normal plasma membrane constituent.
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Affiliation(s)
- F B Peter Wooding
- Physiology Neuroscience and Development Department, Cambridge University, Cambridge, CB2 3EG, UK.
| | - Ian H Mather
- Department of Animal and Avian Sciences, University of Maryland, College Park, MD20742, USA
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15
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Relationships between milks differentiated on native milk fat globule characteristics and fat, protein and calcium compositions. Animal 2017; 11:507-518. [DOI: 10.1017/s1751731116001646] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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16
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Affiliation(s)
- F B Peter Wooding
- Department of Physiology, Development and Neuroscience, Cambridge University, Downing St, Cambridge, CB2 3EG, UK.
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17
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Honvo-Houéto E, Henry C, Chat S, Layani S, Truchet S. The endoplasmic reticulum and casein-containing vesicles contribute to milk fat globule membrane. Mol Biol Cell 2016; 27:2946-64. [PMID: 27535430 PMCID: PMC5042581 DOI: 10.1091/mbc.e16-06-0364] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/03/2016] [Indexed: 12/28/2022] Open
Abstract
The endoplasmic reticulum and the secretory vesicles contribute to the formation of the milk fat globule membrane. In addition, lipid raft microdomains may play a role in the transport and/or secretion of the milk fat globule, and SNARE proteins appear to coordinate membrane exchanges during milk product secretion. During lactation, mammary epithelial cells secrete huge amounts of milk from their apical side. The current view is that caseins are secreted by exocytosis, whereas milk fat globules are released by budding, enwrapped by the plasma membrane. Owing to the number and large size of milk fat globules, the membrane surface needed for their release might exceed that of the apical plasma membrane. A large-scale proteomics analysis of both cytoplasmic lipid droplets and secreted milk fat globule membranes was used to decipher the cellular origins of the milk fat globule membrane. Surprisingly, differential analysis of protein profiles of these two organelles strongly suggest that, in addition to the plasma membrane, the endoplasmic reticulum and the secretory vesicles contribute to the milk fat globule membrane. Analysis of membrane-associated and raft microdomain proteins reinforces this possibility and also points to a role for lipid rafts in milk product secretion. Our results provide evidence for a significant contribution of the endoplasmic reticulum to the milk fat globule membrane and a role for SNAREs in membrane dynamics during milk secretion. These novel aspects point to a more complex model for milk secretion than currently envisioned.
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Affiliation(s)
- Edith Honvo-Houéto
- INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France
| | - Céline Henry
- INRA, UMR1319, MICALIS, PAPPSO, F-78352 Jouy-en-Josas Cedex, France
| | - Sophie Chat
- INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France
| | - Sarah Layani
- INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France
| | - Sandrine Truchet
- INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France
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18
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Monks J, Dzieciatkowska M, Bales ES, Orlicky DJ, Wright RM, McManaman JL. Xanthine oxidoreductase mediates membrane docking of milk-fat droplets but is not essential for apocrine lipid secretion. J Physiol 2016; 594:5899-5921. [PMID: 27357166 PMCID: PMC5063925 DOI: 10.1113/jp272390] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 06/14/2016] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Xanthine oxidoreductase (XOR) modulates milk lipid secretion and lactation initiation. XOR is required for butyrophilin1a1 clustering in the membrane during milk lipid secretion. XOR mediates apical membrane reorganization during milk lipid secretion. Loss of XOR delays milk fat globule secretion. XOR loss alters the proteome of milk fat globules. ABSTRACT Apocrine secretion is utilized by epithelial cells of exocrine glands. These cells bud off membrane-bound particles into the lumen of the gland, losing a portion of the cytoplasm in the secretion product. The lactating mammary gland secretes milk lipid by this mechanism, and xanthine oxidoreductase (XOR) has long been thought to be functionally important. We generated mammary-specific XOR knockout (MGKO) mice, expecting lactation to fail. Histology of the knockout glands showed very large lipid droplets enclosed in the mammary alveolar cells, but milk analysis showed that these large globules were secreted. Butyrophilin, a membrane protein known to bind to XOR, was clustered at the point of contact of the cytoplasmic lipid droplet with the apical plasma membrane, in the wild-type gland but not in the knockout, suggesting that XOR mediates 'docking' to this membrane. Secreted milk fat globules were isolated from mouse milk of wild-type and XOR MGKO dams, and subjected to LC-MS/MS for analysis of protein component. Proteomic results showed that loss of XOR leads to an increase in cytoplasmic, cytoskeletal, Golgi apparatus and lipid metabolism proteins associated with the secreted milk fat globule. Association of XOR with the lipid droplet results in membrane docking and more efficient retention of cytoplasmic components by the secretory cell. Loss of XOR then results in a reversion to a more rudimentary, less efficient, apocrine secretion mechanism, but does not prevent milk fat globule secretion.
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Affiliation(s)
- Jenifer Monks
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, School of Medicine, University of Colorado Anschutz Medical Center, Aurora, CO, 80045, USA.
| | - Monika Dzieciatkowska
- Biochemistry Department, School of Medicine, University of Colorado Anschutz Medical Center, Aurora, CO, 80045, USA
| | - Elise S Bales
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, School of Medicine, University of Colorado Anschutz Medical Center, Aurora, CO, 80045, USA
| | - David J Orlicky
- Department of Pathology, School of Medicine, University of Colorado Anschutz Medical Center, Aurora, CO, 80045, USA
| | | | - James L McManaman
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, School of Medicine, University of Colorado Anschutz Medical Center, Aurora, CO, 80045, USA
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19
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Affiliation(s)
- David A. Rhodes
- Department of Pathology, Immunology Division, University of Cambridge, Cambridge Institute for Medical Research, Cambridge CB2 0XY, United Kingdom; ,
| | - Walter Reith
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, CH-1211 Geneva 4, Switzerland;
| | - John Trowsdale
- Department of Pathology, Immunology Division, University of Cambridge, Cambridge Institute for Medical Research, Cambridge CB2 0XY, United Kingdom; ,
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20
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Ma X, Wang W, Bittner F, Schmidt N, Berkey R, Zhang L, King H, Zhang Y, Feng J, Wen Y, Tan L, Li Y, Zhang Q, Deng Z, Xiong X, Xiao S. Dual and Opposing Roles of Xanthine Dehydrogenase in Defense-Associated Reactive Oxygen Species Metabolism in Arabidopsis. THE PLANT CELL 2016; 28:1108-26. [PMID: 27152019 PMCID: PMC4904670 DOI: 10.1105/tpc.15.00880] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 04/20/2016] [Accepted: 05/03/2016] [Indexed: 05/18/2023]
Abstract
While plants produce reactive oxygen species (ROS) for stress signaling and pathogen defense, they need to remove excessive ROS induced during stress responses in order to minimize oxidative damage. How can plants fine-tune this balance and meet such conflicting needs? Here, we show that XANTHINE DEHYDROGENASE1 (XDH1) in Arabidopsis thaliana appears to play spatially opposite roles to serve this purpose. Through a large-scale genetic screen, we identified three missense mutations in XDH1 that impair XDH1's enzymatic functions and consequently affect the powdery mildew resistance mediated by RESISTANCE TO POWDERY MILDEW8 (RPW8) in epidermal cells and formation of xanthine-enriched autofluorescent objects in mesophyll cells. Further analyses revealed that in leaf epidermal cells, XDH1 likely functions as an oxidase, along with the NADPH oxidases RbohD and RbohF, to generate superoxide, which is dismutated into H2O2 The resulting enrichment of H2O2 in the fungal haustorial complex within infected epidermal cells helps to constrain the haustorium, thereby contributing to RPW8-dependent and RPW8-independent powdery mildew resistance. By contrast, in leaf mesophyll cells, XDH1 carries out xanthine dehydrogenase activity to produce uric acid in local and systemic tissues to scavenge H2O2 from stressed chloroplasts, thereby protecting plants from stress-induced oxidative damage. Thus, XDH1 plays spatially specified dual and opposing roles in modulation of ROS metabolism during defense responses in Arabidopsis.
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Affiliation(s)
- Xianfeng Ma
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850 Hunan Provincial Key Laboratory for Germplasm Innovation and Utilization of Crop, Hunan Agricultural University, Changsha 410128, China Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China
| | - Wenming Wang
- Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China
| | - Florian Bittner
- Department of Plant Biology, Braunschweig University of Technology, 38106 Braunschweig, Germany
| | - Nadine Schmidt
- Department of Plant Biology, Braunschweig University of Technology, 38106 Braunschweig, Germany
| | - Robert Berkey
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
| | - Lingli Zhang
- Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China
| | - Harlan King
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
| | - Yi Zhang
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
| | - Jiayue Feng
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850 College of Horticulture, Northwest A&F University, Yangling 712100, China
| | - Yinqiang Wen
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850 College of Horticulture, Northwest A&F University, Yangling 712100, China
| | - Liqiang Tan
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
| | - Yue Li
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
| | - Qiong Zhang
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
| | - Ziniu Deng
- Hunan Provincial Key Laboratory for Germplasm Innovation and Utilization of Crop, Hunan Agricultural University, Changsha 410128, China
| | - Xingyao Xiong
- Hunan Provincial Key Laboratory for Germplasm Innovation and Utilization of Crop, Hunan Agricultural University, Changsha 410128, China The Institute of Vegetables and Flowers Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Shunyuan Xiao
- Institute of Biosciences and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20850
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21
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Wooding FBP, Sargeant TJ. Immunocytochemical Evidence for Golgi Vesicle Involvement in Milk Fat Globule Secretion. J Histochem Cytochem 2015; 63:943-51. [PMID: 26374828 DOI: 10.1369/0022155415608918] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/03/2015] [Indexed: 12/23/2022] Open
Abstract
The exact mechanism of secretion of the milk fat globule (MFG) from the mammary secretory cell is still controversial. We have previously suggested close involvement of Golgi vesicles in this process. This paper provides direct immunocytochemical evidence that butyrophilin is present in the Golgi stack and vesicles in ovine and caprine mammary glands. We suggest that it is the butyrophilin in the Golgi vesicle membrane that forms the specific association with the adipophilin on the lipid surface in the cytoplasm. Exocytosis of the associated Golgi vesicle will then initiate the process of MFG secretion. Further exocytosis of associated Golgi vesicles will continue and complete the process. Areas of the plasmalemma that have butyrophilin delivered by previous non-lipid associated Golgi exocytoses may also contribute to the process of forming the milk fat globule membrane (MFGM).
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Affiliation(s)
- F B Peter Wooding
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (FBPW)
| | - Timothy J Sargeant
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom (TJS)
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22
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Nishino T, Okamoto K, Kawaguchi Y, Matsumura T, Eger BT, Pai EF, Nishino T. The C-terminal peptide plays a role in the formation of an intermediate form during the transition between xanthine dehydrogenase and xanthine oxidase. FEBS J 2015; 282:3075-90. [PMID: 25817260 PMCID: PMC4832347 DOI: 10.1111/febs.13277] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 03/09/2015] [Accepted: 03/21/2015] [Indexed: 01/24/2023]
Abstract
UNLABELLED Mammalian xanthine oxidoreductase can exist in both dehydrogenase and oxidase forms. Conversion between the two is implicated in such diverse processes as lactation, anti-bacterial activity, reperfusion injury and a growing number of diseases. We have constructed a variant of the rat liver enzyme that lacks the carboxy-terminal amino acids 1316-1331; it appears to assume an intermediate form, exhibiting a mixture of dehydrogenase and oxidase activities. The purified variant protein retained ~ 50-70% of oxidase activity even after prolonged dithiothreitol treatment, supporting a previous prediction that the C-terminal region plays a role in the dehydrogenase to oxidase conversion. In the crystal structure of the protein variant, most of the enzyme stays in an oxidase conformation. After 15 min of incubation with a high concentration of NADH, however, the corresponding X-ray structures showed a dehydrogenase-type conformation. On the other hand, disulfide formation between Cys535 and Cys992, which can clearly be seen in the electron density map of the crystal structure of the variant after removal of dithiothreitol, goes in parallel with the complete conversion to oxidase, resulting in structural changes identical to those observed upon proteolytic cleavage of the linker peptide. These results indicate that the dehydrogenase-oxidase transformation occurs rather readily and the insertion of the C-terminal peptide into the active site cavity of its subunit stabilizes the dehydrogenase form. We propose that the intermediate form can be generated (e.g. in endothelial cells) upon interaction of the C-terminal peptide portion of the enzyme with other proteins or the cell membrane. DATABASE Coordinate sets and structure factors for the four crystal structures reported in the present study have been deposited in the Protein Data Bank under the identification numbers 4YRW, 4YTZ, 4YSW, and 4YTY.
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Affiliation(s)
- Tomoko Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
| | - Ken Okamoto
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
| | - Yuko Kawaguchi
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
| | - Tomohiro Matsumura
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
| | - Bryan T Eger
- Department of Biochemistry, University of Toronto, ON, Canada
| | - Emil F Pai
- Department of Biochemistry, University of Toronto, ON, Canada
- Departments of Medical Biophysics and Molecular Genetics, University of Toronto, ON, Canada
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/University Health Network, Toronto, ON, Canada
| | - Takeshi Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
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23
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Henry C, Saadaoui B, Bouvier F, Cebo C. Phosphoproteomics of the goat milk fat globule membrane: New insights into lipid droplet secretion from the mammary epithelial cell. Proteomics 2015; 15:2307-17. [PMID: 25737190 DOI: 10.1002/pmic.201400245] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 01/26/2015] [Accepted: 02/26/2015] [Indexed: 12/24/2022]
Abstract
Mechanisms of milk lipid secretion are highly controversial. Analyzing the fine protein composition of the "milk fat globule membrane" (MFGM), the triple-layered membrane surrounding milk lipid droplets (LDs) can provide mechanistic clues to better understand LD biosynthesis and secretion pathways in mammary epithelial cells (MECs). We therefore combined a high-sensitive Q-Exactive LC-MS/MS analysis of MFGM-derived peptides to the use of an in-house database intended to improve protein identification in the goat species. Using this approach, we performed the identification of 442 functional groups of proteins in the MFGM from goat milk. To get a more dynamic view of intracellular mechanisms driving LD dynamics in the MECs, we decided to investigate for the first time whether MFGM proteins were phosphorylated. MFGM proteins were sequentially digested by lysine-C and trypsin proteases and the resulting peptides were fractionated by a strong cation exchange chromatography. Titanium beads were used to enrich phosphopeptides from strong cation exchange chromatography eluted fractions. This approach lets us pinpoint 271 sites of phosphorylation on 124 unique goat MFGM proteins. Enriched GO terms associated with phosphorylated MFGM proteins were protein transport and actin cytoskeleton organization. Gained data are discussed with regard to lipid secretory mechanisms in the MECs. All MS data have been deposited in the ProteomeXchange with identifier PXD001039 (http://proteomecentral.proteomexchange.org/dataset/PXD001039).
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Affiliation(s)
- Céline Henry
- INRA, UMR1319, MICALIS, Plateforme PAPSSO (Plateforme d'Analyse Protéomique Paris Sud Ouest), Jouy-en-Josas, France
| | - Besma Saadaoui
- Faculté des Sciences de Gabès, Université de Gabès, cité Erriadh Zrig, Tunisia
| | | | - Christelle Cebo
- INRA, UMR1313 Unité Génétique Animale et Biologie Intégrative, Equipe Génomique Fonctionnelle et Physiologie de la Glande Mammaire (GFP-GM), Jouy-en-Josas, France
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24
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Stat3 controls cell death during mammary gland involution by regulating uptake of milk fat globules and lysosomal membrane permeabilization. Nat Cell Biol 2014; 16:1057-1068. [PMID: 25283994 PMCID: PMC4216597 DOI: 10.1038/ncb3043] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 08/26/2014] [Indexed: 12/14/2022]
Abstract
We have previously demonstrated that Stat3 regulates lysosomal-mediated programmed cell death (LM-PCD) during mouse mammary gland involution in vivo. However, the mechanism that controls the release of lysosomal cathepsins to initiate cell death in this context has not been elucidated. We show here that Stat3 regulates the formation of large lysosomal vacuoles that contain triglyceride. Furthermore, we demonstrate that milk fat globules (MFGs) are toxic to epithelial cells and that, when applied to purified lysosomes, the MFG hydrolysate oleic acid potently induces lysosomal leakiness. Additionally, uptake of secreted MFGs coated in butyrophilin 1A1 is diminished in Stat3-ablated mammary glands and loss of the phagocytosis bridging molecule MFG-E8 results in reduced leakage of cathepsins in vivo. We propose that Stat3 regulates LM-PCD in mouse mammary gland by switching cellular function from secretion to uptake of MFGs. Thereafter, perturbation of lysosomal vesicle membranes by high levels of free fatty acids results in controlled leakage of cathepsins culminating in cell death.
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