1
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Matsell E, Andersen JP, Molday RS. Functional and in silico analysis of ATP8A2 and other P4-ATPase variants associated with human genetic diseases. Dis Model Mech 2024; 17:dmm050546. [PMID: 38436085 PMCID: PMC11073571 DOI: 10.1242/dmm.050546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 02/21/2024] [Indexed: 03/05/2024] Open
Abstract
P4-ATPases flip lipids from the exoplasmic to cytoplasmic leaflet of cell membranes, a property crucial for many biological processes. Mutations in P4-ATPases are associated with severe inherited and complex human disorders. We determined the expression, localization and ATPase activity of four variants of ATP8A2, the P4-ATPase associated with the neurodevelopmental disorder known as cerebellar ataxia, impaired intellectual development and disequilibrium syndrome 4 (CAMRQ4). Two variants, G447R and A772P, harboring mutations in catalytic domains, expressed at low levels and mislocalized in cells. In contrast, the E459Q variant in a flexible loop displayed wild-type expression levels, Golgi-endosome localization and ATPase activity. The R1147W variant expressed at 50% of wild-type levels but showed normal localization and activity. These results indicate that the G447R and A772P mutations cause CAMRQ4 through protein misfolding. The E459Q mutation is unlikely to be causative, whereas the R1147W may display a milder disease phenotype. Using various programs that predict protein stability, we show that there is a good correlation between the experimental expression of the variants and in silico stability assessments, suggesting that such analysis is useful in identifying protein misfolding disease-associated variants.
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Affiliation(s)
- Eli Matsell
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | | | - Robert S. Molday
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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2
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Flannery KP, Safwat S, Matsell E, Battula N, Hamed AAA, Mohamed IN, Elseed MA, Koko M, Abubaker R, Abozar F, Elsayed LEO, Bhise V, Molday RS, Salih MA, Yahia A, Manzini MC. A novel missense variant in the ATPase domain of ATP8A2 and review of phenotypic variability of ATP8A2-related disorders caused by missense changes. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.05.15.24306843. [PMID: 38798571 PMCID: PMC11118633 DOI: 10.1101/2024.05.15.24306843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
ATPase, class 1, type 8A, member 2 (ATP8A2) is a P4-ATPase with a critical role in phospholipid translocation across the plasma membrane. Pathogenic variants in ATP8A2 are known to cause cerebellar ataxia, mental retardation, and disequilibrium syndrome 4 (CAMRQ4) which is often associated with encephalopathy, global developmental delay, and severe motor deficits. Here, we present a family with two siblings presenting with global developmental delay, intellectual disability, spasticity, ataxia, nystagmus, and thin corpus callosum. Whole exome sequencing revealed a homozygous missense variant in the nucleotide binding domain of ATP8A2 (p.Leu538Pro) that results in near complete loss of protein expression. This is in line with other missense variants in the same domain leading to protein misfolding and loss of ATPase function. In addition, by performing diffusion-weighted imaging, we identified bilateral hyperintensities in the posterior limbs of the internal capsule suggesting possible microstructural changes in axon tracts that had not been appreciated before and could contribute to the sensorimotor deficits in these individuals.
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Affiliation(s)
- Kyle P. Flannery
- Department of Neuroscience & Cell Biology, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901
| | - Sylvia Safwat
- Department of Neuroscience & Cell Biology, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Eli Matsell
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, B.C., Canada
| | - Namarata Battula
- Department of Neuroscience & Cell Biology, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901
| | | | | | - Maha A. Elseed
- Faculty of Medicine, University of Khartoum, Khartoum, Sudan
| | - Mahmoud Koko
- Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan
| | - Rayan Abubaker
- Sudanese Neurogenetics Research group, Faculty of Medicine, University of Khartoum, Khartoum, Sudan
| | - Fatima Abozar
- Faculty of Medicine, University of Khartoum, Khartoum, Sudan
| | - Liena E. O. Elsayed
- Department of Basic Sciences, College of Medicine, Princess Nourah bint Abdulrahman University, Riyadh, P.O.Box 84428, Riyadh 11671, Saudi Arabia
| | - Vikram Bhise
- Department of Pediatrics and Neurology, Rutgers – Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Robert S. Molday
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, B.C., Canada
| | - Mustafa A. Salih
- Consultant Pediatric Neurologist, Health Sector, King Abdulaziz City for Science and Technology, Riyadh 11442, Saudi Arabia
| | - Ashraf Yahia
- Department of Biochemistry, Faculty of Medicine, University of Khartoum, Khartoum, Sudan
- Center of Neurodevelopmental Disorders (KIND), Centre for Psychiatry Research, Department of Women’s and Children’s Health, Karolinska Institutet and Stockholm Health Care Services, Region Stockholm, Stockholm, Sweden
- Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Solna, Sweden
| | - M. Chiara Manzini
- Department of Neuroscience & Cell Biology, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901
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3
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Skiba NP, Lewis TR, Spencer WJ, Castillo CM, Shevchenko A, Arshavsky VY. Absolute Quantification of Photoreceptor Outer Segment Proteins. J Proteome Res 2023; 22:2703-2713. [PMID: 37493966 PMCID: PMC10513726 DOI: 10.1021/acs.jproteome.3c00267] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Photoreceptor cells generate neuronal signals in response to capturing light. This process, called phototransduction, takes place in a highly specialized outer segment organelle. There are significant discrepancies in the reported amounts of many proteins supporting this process, particularly those of low abundance, which limits our understanding of their molecular organization and function. In this study, we used quantitative mass spectrometry to simultaneously determine the abundances of 20 key structural and functional proteins residing in mouse rod outer segments. We computed the absolute number of molecules of each protein residing within an individual outer segment and the molar ratio among all 20 proteins. The molar ratios of proteins comprising three well-characterized constitutive complexes in outer segments differed from the established subunit stoichiometries of these complexes by less than 7%, highlighting the exceptional precision of our quantification. Overall, this study resolves multiple existing discrepancies regarding the outer segment abundances of these proteins, thereby advancing our understanding of how the phototransduction pathway functions as a single, well-coordinated molecular ensemble.
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Affiliation(s)
- Nikolai P. Skiba
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Tylor R. Lewis
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - William J. Spencer
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Carson M. Castillo
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany 01307
| | - Vadim Y. Arshavsky
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710
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4
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Xing Y, Peng K, Yi Q, Yu D, Shi H, Yang G, Yin S. TMEM30A is essential for hair cell polarity maintenance in postnatal mouse cochlea. Cell Mol Biol Lett 2023; 28:23. [PMID: 36959542 PMCID: PMC10035192 DOI: 10.1186/s11658-023-00437-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 03/08/2023] [Indexed: 03/25/2023] Open
Abstract
BACKGROUND Phosphatidylserine is translocated to the inner leaflet of the phospholipid bilayer membrane by the flippase function of type IV P-tape ATPase (P4-ATPase), which is critical to maintain cellular stability and homeostasis. Transmembrane protein 30A (TMEM30A) is the β-subunit of P4-ATPase. Loss of P4-ATPase function causes sensorineural hearing loss and visual dysfunction in human. However, the function of TMEM30A in the auditory system is unclear. METHODS P4-ATPase subtype expression in the cochlea was detected by immunofluorescence staining and quantitative real-time polymerase chain reaction (qRT-PCR) at different developmental stages. Hair cell specific TMEM30A knockout mice and wild-type littermates were used for the following functional and morphological analysis. Auditory function was evaluated by auditory brainstem response. We investigated hair cell and stereocilia morphological changes by immunofluorescence staining. Scanning electron microscopy was applied to observe the stereocilia ultrastructure. Differentially expressed transcriptomes were analyzed based on RNA-sequencing data from knockout and wild-type mouse cochleae. Differentially expressed genes were verified by qRT-PCR. RESULTS TMEM30A and subtypes of P4-ATPase are expressed in the mouse cochlea in a temporal-dependent pattern. Deletion of TMEM30A in hair cells impaired hearing onset due to progressive hair cell loss. The disrupted kinocilia placement and irregular distribution of spectrin-α in cuticular plate indicated the hair cell planar polarity disruption in TMEM30A deletion hair cells. Hair cell degeneration begins at P7 and finishes around P14. Transcriptional analysis indicates that the focal adhesion pathway and stereocilium tip-related genes changed dramatically. Without the TMEM30A chaperone, excessive ATP8A2 accumulated in the cytoplasm, leading to overwhelming endoplasmic reticulum stress, which eventually contributed to hair cell death. CONCLUSIONS Deletion of TMEM30A led to disrupted planar polarity and stereocilia bundles, and finally led to hair cell loss and auditory dysfunction. TMEM30A is essential for hair cell polarity maintenance and membrane homeostasis. Our study highlights a pivotal role of TMEM30A in the postnatal development of hair cells and reveals the possible mechanisms underlying P4-ATPase-related genetic hearing loss.
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Affiliation(s)
- Yazhi Xing
- Department of Otolaryngology Head & Neck Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1301 Research Bldg, 600 Yishan Rd, Shanghai, China
- Otolaryngology Institute of Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai, 200233, China
| | - Kun Peng
- Health Management Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, 610054, Sichuan, China
| | - Qian Yi
- Health Management Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, 610054, Sichuan, China
| | - Dongzhen Yu
- Department of Otolaryngology Head & Neck Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1301 Research Bldg, 600 Yishan Rd, Shanghai, China
- Otolaryngology Institute of Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai, 200233, China
| | - Haibo Shi
- Department of Otolaryngology Head & Neck Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1301 Research Bldg, 600 Yishan Rd, Shanghai, China
- Otolaryngology Institute of Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai, 200233, China
| | - Guang Yang
- Department of Otolaryngology Head & Neck Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1301 Research Bldg, 600 Yishan Rd, Shanghai, China.
- Otolaryngology Institute of Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai, 200233, China.
| | - Shankai Yin
- Department of Otolaryngology Head & Neck Surgery, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1301 Research Bldg, 600 Yishan Rd, Shanghai, China
- Otolaryngology Institute of Shanghai Jiao Tong University, 600 Yishan Rd, Shanghai, 200233, China
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5
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Skiba NP, Lewis TR, Spencer WJ, Castillo CM, Shevchenko A, Arshavsky VY. Absolute quantification of photoreceptor outer segment proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.19.524794. [PMID: 36711880 PMCID: PMC9882265 DOI: 10.1101/2023.01.19.524794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Photoreceptor cells generate neuronal signals in response to capturing light. This process, called phototransduction, takes place in a highly specialized outer segment organelle. There are significant discrepancies in the reported amounts of many proteins supporting this process, particularly those of low abundance, which limits our understanding of their molecular organization and function. In this study, we used quantitative mass spectrometry to simultaneously measure the outer segment content of twenty key structural and functional proteins. We determined the molar ratio amongst all twenty proteins as well as the number of molecules of each protein residing within an outer segment. To assess the precision of this quantification, we took advantage of the fact that seven of these proteins exist within three constitutive complexes of well-established subunit stoichiometries. Remarkably, our measurements differed from these stoichiometries by less than 7%, highlighting the exceptional precision of our quantification. This allowed us to resolve the existing discrepancies regarding the outer segment abundances of these proteins, thereby advancing our understanding of how the phototransduction pathway functions as a single, well-coordinated molecular ensemble.
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6
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Li J, Zhao Y, Wang N. Physiological and Pathological Functions of TMEM30A: An Essential Subunit of P4-ATPase Phospholipid Flippases. J Lipids 2023; 2023:4625567. [PMID: 37200892 PMCID: PMC10188266 DOI: 10.1155/2023/4625567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/28/2023] [Accepted: 04/15/2023] [Indexed: 05/20/2023] Open
Abstract
Phospholipids are asymmetrically distributed across mammalian plasma membrane. The function of P4-ATPases is to maintain the abundance of phosphatidylserine (PS) and phosphatidylethanolamine (PE) in the inner leaflet as lipid flippases. Transmembrane protein 30A (TMEM30A, also named CDC50A), as an essential β subunit of most P4-ATPases, facilitates their transport and functions. With TMEM30A knockout mice or cell lines, it is found that the loss of TMEM30A has huge influences on the survival of mice and cells because of PS exposure-triggered apoptosis signaling. TMEM30A is a promising target for drug discovery due to its significant roles in various systems and diseases. In this review, we summarize the functions of TMEM30A in different systems, present current understanding of the protein structures and mechanisms of TMEM30A-P4-ATPase complexes, and discuss how these fundamental aspects of TMEM30A may be applied to disease treatment.
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Affiliation(s)
- Jingyi Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education & Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yue Zhao
- Clinical Medical Laboratory, Wenjiang Hospital of Sichuan Provincial People's Hospital, Chengdu, China
| | - Na Wang
- Key Laboratory of Medical Electrophysiology, Ministry of Education & Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
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7
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Pater JA, Penney C, O'Rielly DD, Griffin A, Kamal L, Brownstein Z, Vona B, Vinkler C, Shohat M, Barel O, French CR, Singh S, Werdyani S, Burt T, Abdelfatah N, Houston J, Doucette LP, Squires J, Glaser F, Roslin NM, Vincent D, Marquis P, Woodland G, Benoukraf T, Hawkey-Noble A, Avraham KB, Stanton SG, Young TL. Autosomal dominant non-syndromic hearing loss maps to DFNA33 (13q34) and co-segregates with splice and frameshift variants in ATP11A, a phospholipid flippase gene. Hum Genet 2022; 141:431-444. [PMID: 35278131 PMCID: PMC9035003 DOI: 10.1007/s00439-022-02444-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 02/22/2022] [Indexed: 11/20/2022]
Abstract
Sequencing exomes/genomes have been successful for identifying recessive genes; however, discovery of dominant genes including deafness genes (DFNA) remains challenging. We report a new DFNA gene, ATP11A, in a Newfoundland family with a variable form of bilateral sensorineural hearing loss (SNHL). Genome-wide SNP genotyping linked SNHL to DFNA33 (LOD = 4.77), a locus on 13q34 previously mapped in a German family with variable SNHL. Whole-genome sequencing identified 51 unremarkable positional variants on 13q34. Continuous clinical ascertainment identified several key recombination events and reduced the disease interval to 769 kb, excluding all but one variant. ATP11A (NC_000013.11: chr13:113534963G>A) is a novel variant predicted to be a cryptic donor splice site. RNA studies verified in silico predictions, revealing the retention of 153 bp of intron in the 3' UTR of several ATP11A isoforms. Two unresolved families from Israel were subsequently identified with a similar, variable form of SNHL and a novel duplication (NM_032189.3:c.3322_3327+2dupGTCCAGGT) in exon 28 of ATP11A extended exon 28 by 8 bp, leading to a frameshift and premature stop codon (p.Asn1110Valfs43Ter). ATP11A is a type of P4-ATPase that transports (flip) phospholipids from the outer to inner leaflet of cell membranes to maintain asymmetry. Haploinsufficiency of ATP11A, the phospholipid flippase that specially transports phosphatidylserine (PS) and phosphatidylethanolamine (PE), could leave cells with PS/PE at the extracellular side vulnerable to phagocytic degradation. Given that surface PS can be pharmaceutically targeted, hearing loss due to ATP11A could potentially be treated. It is also likely that ATP11A is the gene underlying DFNA33.
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Affiliation(s)
- Justin A Pater
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Cindy Penney
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
- Centre for Translational Genomics, Memorial University, 300 Prince Phillip Dr., St. John's, NL, Canada
| | - Darren D O'Rielly
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
- Centre for Translational Genomics, Memorial University, 300 Prince Phillip Dr., St. John's, NL, Canada
| | - Anne Griffin
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Lara Kamal
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Zippora Brownstein
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Barbara Vona
- Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Chana Vinkler
- Institute of Medical Genetics, Wolfson Medical Center, 58100, Holon, Israel
| | - Mordechai Shohat
- Bioinformatic Center, Cancer Research Institute, The Wohl Institute for Translational Medicine, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ortal Barel
- Bioinformatic Center, Cancer Research Institute, The Wohl Institute for Translational Medicine, Sheba Medical Center, Tel-Hashomer, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Curtis R French
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Sushma Singh
- Communication Sciences and Disorders, Elborn College, Western University, 1201 Western Road, London, ON, Canada
| | - Salem Werdyani
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Taylor Burt
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Nelly Abdelfatah
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Jim Houston
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Lance P Doucette
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Jessica Squires
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Fabian Glaser
- The Lorry I. Lokey Center for Life Sciences and Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nicole M Roslin
- The Centre for Applied Genomics, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, 686 Bay Street, Toronto, ON, Canada
| | - Daniel Vincent
- Genome Quebec Innovation Centre, McGill University, 740 Dr. Penfield Avenue, Montreal, QC, Canada
| | - Pascale Marquis
- Canadian Centre for Computational Genomics, McGill University and Genome Quebec Innovation Center, 740 Dr. Penfield Avenue, Montreal, QC, Canada
| | - Geoffrey Woodland
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Touati Benoukraf
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Alexia Hawkey-Noble
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada
| | - Karen B Avraham
- Department of Human Molecular Genetics and Biochemistry, Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Susan G Stanton
- Communication Sciences and Disorders, Elborn College, Western University, 1201 Western Road, London, ON, Canada
| | - Terry-Lynn Young
- Faculty of Medicine, Memorial University, 300 Prince Phillip Drive, St. John's, NL, Canada.
- Centre for Translational Genomics, Memorial University, 300 Prince Phillip Dr., St. John's, NL, Canada.
- Communication Sciences and Disorders, Elborn College, Western University, 1201 Western Road, London, ON, Canada.
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8
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Liu W, Peng L, Tian W, Li Y, Zhang P, Sun K, Yang Y, Li X, Li G, Zhu X. Loss of phosphatidylserine flippase β-subunit Tmem30a in podocytes leads to albuminuria and glomerulosclerosis. Dis Model Mech 2021; 14:268980. [PMID: 34080006 PMCID: PMC8246268 DOI: 10.1242/dmm.048777] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 05/25/2021] [Indexed: 12/30/2022] Open
Abstract
The asymmetric distribution of phosphatidylserine (PS) in the cytoplasmic leaflet of eukaryotic cell plasma membranes is regulated by a group of P4-ATPases (named PS flippases) and the β-subunit TMEM30A. Podocytes in the glomerulus form a filtration barrier to prevent the traversing of large cellular elements and macromolecules from the blood into the urinary space. Damage to podocytes can disrupt the filtration barrier and lead to proteinuria and podocytopathy. We observed reduced TMEM30A expression in patients with minimal change disease and membranous nephropathy, indicating potential roles of TMEM30A in podocytopathy. To investigate the role of Tmem30a in the kidney, we generated a podocyte-specific Tmem30a knockout (KO) mouse model using the NPHS2-Cre line. Tmem30a KO mice displayed albuminuria, podocyte degeneration, mesangial cell proliferation with prominent extracellular matrix accumulation and eventual progression to focal segmental glomerulosclerosis. Our data demonstrate a critical role of Tmem30a in maintaining podocyte survival and glomerular filtration barrier integrity. Understanding the dynamic regulation of the PS distribution in the glomerulus provides a unique perspective to pinpointing the mechanism of podocyte damage and potential therapeutic targets.
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Affiliation(s)
- Wenjing Liu
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China.,The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Lei Peng
- Department of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan Clinical Research Center for Kidney Diseases, Sichuan 610072, China
| | - Wanli Tian
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Yi Li
- Department of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan Clinical Research Center for Kidney Diseases, Sichuan 610072, China
| | - Ping Zhang
- Department of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan Clinical Research Center for Kidney Diseases, Sichuan 610072, China
| | - Kuanxiang Sun
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Yeming Yang
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xiao Li
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Guisen Li
- Department of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan Clinical Research Center for Kidney Diseases, Sichuan 610072, China
| | - Xianjun Zhu
- Health Management Center, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China.,The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China.,Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China.,Research Unit for Blindness Prevention of the Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072, China.,Department of Ophthalmology, Shangqiu First People's Hospital, Shangqiu, Henan 476000, China.,Natural Products Research Center, Institute of Chengdu Biology, Sichuan Translational Medicine Hospital, Chinese Academy of Sciences, Chengdu, Sichuan 610072, China
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9
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Raiders S, Black EC, Bae A, MacFarlane S, Klein M, Shaham S, Singhvi A. Glia actively sculpt sensory neurons by controlled phagocytosis to tune animal behavior. eLife 2021; 10:63532. [PMID: 33759761 PMCID: PMC8079151 DOI: 10.7554/elife.63532] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/23/2021] [Indexed: 02/07/2023] Open
Abstract
Glia in the central nervous system engulf neuron fragments to remodel synapses and recycle photoreceptor outer segments. Whether glia passively clear shed neuronal debris or actively prune neuron fragments is unknown. How pruning of single-neuron endings impacts animal behavior is also unclear. Here, we report our discovery of glia-directed neuron pruning in Caenorhabditis elegans. Adult C. elegans AMsh glia engulf sensory endings of the AFD thermosensory neuron by repurposing components of the conserved apoptotic corpse phagocytosis machinery. The phosphatidylserine (PS) flippase TAT-1/ATP8A functions with glial PS-receptor PSR-1/PSR and PAT-2/α-integrin to initiate engulfment. This activates glial CED-10/Rac1 GTPase through the ternary GEF complex of CED-2/CrkII, CED-5/DOCK180, CED-12/ELMO. Execution of phagocytosis uses the actin-remodeler WSP-1/nWASp. This process dynamically tracks AFD activity and is regulated by temperature, the AFD sensory input. Importantly, glial CED-10 levels regulate engulfment rates downstream of neuron activity, and engulfment-defective mutants exhibit altered AFD-ending shape and thermosensory behavior. Our findings reveal a molecular pathway underlying glia-dependent engulfment in a peripheral sense-organ and demonstrate that glia actively engulf neuron fragments, with profound consequences on neuron shape and animal sensory behavior. Neurons are tree-shaped cells that receive information through endings connected to neighbouring cells or the environment. Controlling the size, number and location of these endings is necessary to ensure that circuits of neurons get precisely the right amount of input from their surroundings. Glial cells form a large portion of the nervous system, and they are tasked with supporting, cleaning and protecting neurons. In humans, part of their duties is to ‘eat’ (or prune) unnecessary neuron endings. In fact, this role is so important that defects in glial pruning are associated with conditions such as Alzheimer’s disease. Yet it is still unknown how pruning takes place, and in particular whether it is the neuron or the glial cell that initiates the process. To investigate this question, Raiders et al. enlisted the common laboratory animal Caenorhabditis elegans, a tiny worm with a simple nervous system where each neuron has been meticulously mapped out. First, the experiments showed that glial cells in C. elegans actually prune the endings of sensory neurons. Focusing on a single glia-neuron pair then revealed that the glial cell could trim the endings of a living neuron by redeploying the same molecular machinery it uses to clear dead cell debris. Compared to this debris-clearing activity, however, the glial cell takes a more nuanced approach to pruning: specifically, it can adjust the amount of trimming based on the activity load of the neuron. When Raiders et al. disrupted the glial pruning for a single temperature-sensing neuron, the worm lost its normal temperature preferences; this demonstrated how the pruning activity of a single glial cell can be linked to behavior. Taken together the experiments showcase how C. elegans can be used to study glial pruning. Further work using this model could help to understand how disease emerges when glial cells cannot perform their role, and to spot the genetic factors that put certain individuals at increased risk for neurological and sensory disorders.
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Affiliation(s)
- Stephan Raiders
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.,Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, United States
| | - Erik Calvin Black
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Andrea Bae
- Laboratory of Developmental Genetics, The Rockefeller University, New York, United States.,Cellular Imaging Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Stephen MacFarlane
- Department of Physics and Department of Biology, University of Miami, Coral Gables, United States
| | - Mason Klein
- Department of Physics and Department of Biology, University of Miami, Coral Gables, United States
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, New York, United States
| | - Aakanksha Singhvi
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.,Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, United States.,Department of Biological Structure, University of Washington School of Medicine, Seattle, United States.,Brotman Baty Institute for Precision Medicine, Seattle, United States
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10
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The transport mechanism of P4 ATPase lipid flippases. Biochem J 2021; 477:3769-3790. [PMID: 33045059 DOI: 10.1042/bcj20200249] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/02/2020] [Accepted: 09/16/2020] [Indexed: 12/18/2022]
Abstract
P4 ATPase lipid flippases are ATP-driven transporters that translocate specific lipids from the exoplasmic to the cytosolic leaflet of biological membranes, thus establishing a lipid gradient between the two leaflets that is essential for many cellular processes. While substrate specificity, subcellular and tissue-specific expression, and physiological functions have been assigned to a number of these transporters in several organisms, the mechanism of lipid transport has been a topic of intense debate in the field. The recent publication of a series of structural models based on X-ray crystallography and cryo-EM studies has provided the first glimpse into how P4 ATPases have adapted the transport mechanism used by the cation-pumping family members to accommodate a substrate that is at least an order of magnitude larger than cations.
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11
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George SS, Steele CR, Ricci AJ. Rat Auditory Inner Hair Cell Mechanotransduction and Stereociliary Membrane Diffusivity Are Similarly Modulated by Calcium. iScience 2020; 23:101773. [PMID: 33294782 PMCID: PMC7689183 DOI: 10.1016/j.isci.2020.101773] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/03/2020] [Accepted: 11/03/2020] [Indexed: 11/16/2022] Open
Abstract
The lipid bilayer plays a pivotal role in force transmission to many mechanically-gated channels. We developed the technology to monitor membrane diffusivity in order to test the hypothesis positing that Ca2+ regulates open probability (P o) of cochlear hair cell mechanotransduction (MET) channels via the plasma membrane. The stereociliary membrane was more diffusive (9x) than the basolateral membrane. Elevating intracellular Ca2+ buffering or lowering extracellular Ca2+ reduced stereociliary diffusivity and increased MET P o. In contrast, prolonged depolarization increased stereociliary diffusivity and reduced MET P o. No comparable effects were noted for soma measurements. Although MET channels are located in the shorter stereocilia rows, both rows had similar baseline diffusivity and showed similar responses to Ca2+ manipulations and MET channel blocks, suggesting that diffusivity is independent of MET. Together, these data suggest that the stereociliary membrane is a component of a calcium-modulated viscoelastic-like element regulating hair cell mechanotransduction.
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Affiliation(s)
- Shefin S George
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, 240 Pasteur Drive, Stanford, CA 94305, USA
| | - Charles R Steele
- Department of Mechanical Engineering, Building 520, 440 Escondido Mall, Stanford University, CA 94305, USA
| | - Anthony J Ricci
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, 240 Pasteur Drive, Stanford, CA 94305, USA.,Department of Molecular and Cellular Physiology, School of Medicine, Stanford University, 291 Campus Drive, Stanford, CA 94305, USA
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12
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Disease Mutation Study Identifies Critical Residues for Phosphatidylserine Flippase ATP11A. BIOMED RESEARCH INTERNATIONAL 2020; 2020:7342817. [PMID: 32596364 PMCID: PMC7288202 DOI: 10.1155/2020/7342817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 04/21/2020] [Indexed: 11/17/2022]
Abstract
Phosphatidylserine flippase (P4-ATPase) transports PS from the outer to the inner leaflet of the lipid bilayer in the membrane to maintain PS asymmetry, which is important for biological activities of the cell. ATP11A is expressed in multiple tissues and plays a role in myotube formation. However, the detailed cellular function of ATP11A remains elusive. Mutation analysis revealed that I91, L308, and E897 residues in ATP8A2 are important for flippase activity. In order to investigate the roles of these corresponding amino acid residues in ATP11A protein, we assessed the expression and cellular localization of the respective ATP11A mutant proteins. ATP11A mainly localizes to the Golgi and plasma membrane when coexpressed with the β-subunit of the complex TMEM30A. Y300F mutation causes reduced ATP11A expression, and Y300F and D913K mutations affect correct localization of the Golgi and plasma membrane. In addition, Y300F and D913K mutations also affect PS flippase activity. Our data provides insight into important residues of ATP11A.
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13
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Affiliation(s)
- Hye-Won Shin
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hiroyuki Takatsu
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
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14
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Collin GB, Gogna N, Chang B, Damkham N, Pinkney J, Hyde LF, Stone L, Naggert JK, Nishina PM, Krebs MP. Mouse Models of Inherited Retinal Degeneration with Photoreceptor Cell Loss. Cells 2020; 9:cells9040931. [PMID: 32290105 PMCID: PMC7227028 DOI: 10.3390/cells9040931] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/05/2020] [Accepted: 04/07/2020] [Indexed: 12/12/2022] Open
Abstract
Inherited retinal degeneration (RD) leads to the impairment or loss of vision in millions of individuals worldwide, most frequently due to the loss of photoreceptor (PR) cells. Animal models, particularly the laboratory mouse, have been used to understand the pathogenic mechanisms that underlie PR cell loss and to explore therapies that may prevent, delay, or reverse RD. Here, we reviewed entries in the Mouse Genome Informatics and PubMed databases to compile a comprehensive list of monogenic mouse models in which PR cell loss is demonstrated. The progression of PR cell loss with postnatal age was documented in mutant alleles of genes grouped by biological function. As anticipated, a wide range in the onset and rate of cell loss was observed among the reported models. The analysis underscored relationships between RD genes and ciliary function, transcription-coupled DNA damage repair, and cellular chloride homeostasis. Comparing the mouse gene list to human RD genes identified in the RetNet database revealed that mouse models are available for 40% of the known human diseases, suggesting opportunities for future research. This work may provide insight into the molecular players and pathways through which PR degenerative disease occurs and may be useful for planning translational studies.
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Affiliation(s)
- Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Navdeep Gogna
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Nattaya Damkham
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
- Siriraj Center of Excellence for Stem Cell Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Jai Pinkney
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lillian F. Hyde
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lisa Stone
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Jürgen K. Naggert
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
| | - Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
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15
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Choi H, Andersen JP, Molday RS. Expression and functional characterization of missense mutations in ATP8A2 linked to severe neurological disorders. Hum Mutat 2019; 40:2353-2364. [PMID: 31397519 DOI: 10.1002/humu.23889] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 07/30/2019] [Accepted: 08/04/2019] [Indexed: 11/09/2022]
Abstract
ATP8A2 is a P4-ATPase (adenosine triphosphate) that actively flips phosphatidylserine and phosphatidylethanolamine from the exoplasmic to the cytoplasmic leaflet of cell membranes to generate and maintain phospholipid asymmetry. Mutations in the ATP8A2 gene have been reported to cause severe autosomal recessive neurological diseases in humans characterized by intellectual disability, hypotonia, chorea, and hyperkinetic movement disorders with or without optic and cerebellar atrophy. To determine the effect of disease-associated missense mutations on ATP8A2, we expressed six variants with the accessory subunit CDC50A in HEK293T cells. The level of expression, cellular localization, and functional activity were analyzed by western blot analysis, immunofluorescence microscopy, and ATPase activity assays. Two variants (p.Ile376Met and p.Lys429Met) expressed at normal ATP8A2 levels and preferentially localized to the Golgi-recycling endosomes, but were devoid of ATPase activity. Four variants (p.Lys429Asn, pAla544Pro, p.Arg625Trp, and p.Trp702Arg) expressed poorly, localized to the endoplasmic reticulum, and lacked ATPase activity. The expression of these variants was increased twofold by the addition of the proteasome inhibitor MG132. We conclude that the p.Ile376Met and p.Lys429Met variants fold in a native-like conformation, but lack key amino acid residues required for ATP-dependent lipid transport. In contrast, the p.Lys429Asn, pAla544Pro, p.Arg625Trp, and p.Trp702Arg variants are highly misfolded and undergo rapid proteosomal degradation.
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Affiliation(s)
- Hanbin Choi
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jens P Andersen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
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16
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Xiong L, Zhang L, Yang Y, Li N, Lai W, Wang F, Zhu X, Wang T. ER complex proteins are required for rhodopsin biosynthesis and photoreceptor survival in Drosophila and mice. Cell Death Differ 2019; 27:646-661. [PMID: 31263175 PMCID: PMC7206144 DOI: 10.1038/s41418-019-0378-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 06/11/2019] [Accepted: 06/13/2019] [Indexed: 12/17/2022] Open
Abstract
Defective rhodopsin homeostasis is one of the major causes of retinal degeneration, including the disease Retinitis pigmentosa. To identify cellular factors required for the biosynthesis of rhodopsin, we performed a genome-wide genetic screen in Drosophila for mutants with reduced levels of rhodopsin. We isolated loss-of-function alleles in endoplasmic reticulum membrane protein complex 3 (emc3), emc5, and emc6, each of which exhibited defective phototransduction and photoreceptor cell degeneration. EMC3, EMC5, and EMC6 were essential for rhodopsin synthesis independent of the ER associated degradation (ERAD) pathway, which eliminates misfolded proteins. We generated null mutations for all EMC subunits, and further demonstrated that different EMC subunits play roles in different cellular functions. Conditional knockout of the Emc3 gene in mice led to mislocalization of rhodopsin protein and death of cone and rod photoreceptor cells. These data indicate conserved roles for EMC subunits in maintaining rhodopsin homeostasis and photoreceptor function, and suggest that retinal degeneration may also be caused by defects in early biosynthesis of rhodopsin.
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Affiliation(s)
- Liangyao Xiong
- Peking University-Tsinghua University-National Institute of Biological Sciences Joint Graduate Program, School of Life Sciences, Peking University, Beijing, 100871, China.,National Institute of Biological Sciences, Beijing, 102206, China
| | - Lin Zhang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610072, China
| | - Yeming Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610072, China
| | - Na Li
- Southwest Jiaotong University, Chengdu, Sichuan, China
| | - Wenjia Lai
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Fengchao Wang
- National Institute of Biological Sciences, Beijing, 102206, China.,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, 100871, China
| | - Xianjun Zhu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610072, China. .,Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China. .,Chinese Academy of Sciences Sichuan Translational Medicine Hospital, Chengdu, China. .,Department of Ophthalmology, First People's Hospital of Shangqiu, Shangqiu, Henan, China.
| | - Tao Wang
- National Institute of Biological Sciences, Beijing, 102206, China. .,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, 100871, China.
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17
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Liou AY, Molday LL, Wang J, Andersen JP, Molday RS. Identification and functional analyses of disease-associated P4-ATPase phospholipid flippase variants in red blood cells. J Biol Chem 2019; 294:6809-6821. [PMID: 30850395 DOI: 10.1074/jbc.ra118.007270] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 03/06/2019] [Indexed: 02/04/2023] Open
Abstract
ATP-dependent phospholipid flippase activity crucial for generating lipid asymmetry was first detected in red blood cell (RBC) membranes, but the P4-ATPases responsible have not been directly determined. Using affinity-based MS, we show that ATP11C is the only abundant P4-ATPase phospholipid flippase in human RBCs, whereas ATP11C and ATP8A1 are the major P4-ATPases in mouse RBCs. We also found that ATP11A and ATP11B are present at low levels. Mutations in the gene encoding ATP11C are responsible for blood and liver disorders, but the disease mechanisms are not known. Using heterologous expression, we show that the T415N substitution in the phosphorylation motif of ATP11C, responsible for congenital hemolytic anemia, reduces ATP11C expression, increases retention in the endoplasmic reticulum, and decreases ATPase activity by 61% relative to WT ATP11C. The I355K substitution in the transmembrane domain associated with cholestasis and anemia in mice was expressed at WT levels and trafficked to the plasma membrane but was devoid of activity. We conclude that the T415N variant causes significant protein misfolding, resulting in low protein expression, cellular mislocalization, and reduced functional activity. In contrast, the I355K variant folds and traffics normally but lacks key contacts required for activity. We propose that the loss in ATP11C phospholipid flippase activity coupled with phospholipid scramblase activity results in the exposure of phosphatidylserine on the surface of RBCs, decreasing RBC survival and resulting in anemia.
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Affiliation(s)
- Angela Y Liou
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | - Laurie L Molday
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | - Jiao Wang
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | - Jens Peter Andersen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, Building 1160, DK-8000 Aarhus C, Denmark
| | - Robert S Molday
- From the Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
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18
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Ying G, Frederick JM, Baehr W. Deletion of both centrin 2 (CETN2) and CETN3 destabilizes the distal connecting cilium of mouse photoreceptors. J Biol Chem 2019; 294:3957-3973. [PMID: 30647131 DOI: 10.1074/jbc.ra118.006371] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/09/2019] [Indexed: 02/03/2023] Open
Abstract
Centrins (CETN1-4) are ubiquitous and conserved EF-hand-family Ca2+-binding proteins associated with the centrosome, basal body, and transition zone. Deletion of CETN1 or CETN2 in mice causes male infertility or dysosmia, respectively, without affecting photoreceptor function. However, it remains unclear to what extent centrins are redundant with each other in photoreceptors. Here, to explore centrin redundancy, we generated Cetn3 GT/GT single-knockout and Cetn2 -/-;Cetn3 GT/GT double-knockout mice. Whereas the Cetn3 deletion alone did not affect photoreceptor function, simultaneous ablation of Cetn2 and Cetn3 resulted in attenuated scotopic and photopic electroretinography (ERG) responses in mice at 3 months of age, with nearly complete retina degeneration at 1 year. Removal of CETN2 and CETN3 activity from the lumen of the connecting cilium (CC) destabilized the photoreceptor axoneme and reduced the CC length as early as postnatal day 22 (P22). In Cetn2 -/-;Cetn3 GT/GT double-knockout mice, spermatogenesis-associated 7 (SPATA7), a key organizer of the photoreceptor-specific distal CC, was depleted gradually, and CETN1 was condensed to the mid-segment of the CC. Ultrastructural analysis revealed that in this double knockout, the axoneme of the CC expanded radially at the distal end, with vertically misaligned outer segment discs and membrane whorls. These observations suggest that CETN2 and CETN3 cooperate in stabilizing the CC/axoneme structure.
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Affiliation(s)
- Guoxin Ying
- From the Department of Ophthalmology, University of Utah Health Science Center, Salt Lake City, Utah 84132,
| | - Jeanne M Frederick
- From the Department of Ophthalmology, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Wolfgang Baehr
- From the Department of Ophthalmology, University of Utah Health Science Center, Salt Lake City, Utah 84132, .,the Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah 84112, and.,the Department of Biology, University of Utah, Salt Lake City, Utah 84132
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19
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Roland BP, Naito T, Best JT, Arnaiz-Yépez C, Takatsu H, Yu RJ, Shin HW, Graham TR. Yeast and human P4-ATPases transport glycosphingolipids using conserved structural motifs. J Biol Chem 2018; 294:1794-1806. [PMID: 30530492 DOI: 10.1074/jbc.ra118.005876] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 11/29/2018] [Indexed: 12/21/2022] Open
Abstract
Lipid transport is an essential process with manifest importance to human health and disease. Phospholipid flippases (P4-ATPases) transport lipids across the membrane bilayer and are involved in signal transduction, cell division, and vesicular transport. Mutations in flippase genes cause or contribute to a host of diseases, such as cholestasis, neurological deficits, immunological dysfunction, and metabolic disorders. Genome-wide association studies have shown that ATP10A and ATP10D variants are associated with an increased risk of diabetes, obesity, myocardial infarction, and atherosclerosis. Moreover, ATP10D SNPs are associated with elevated levels of glucosylceramide (GlcCer) in plasma from diverse European populations. Although sphingolipids strongly contribute to metabolic disease, little is known about how GlcCer is transported across cell membranes. Here, we identify a conserved clade of P4-ATPases from Saccharomyces cerevisiae (Dnf1, Dnf2), Schizosaccharomyces pombe (Dnf2), and Homo sapiens (ATP10A, ATP10D) that transport GlcCer bearing an sn2 acyl-linked fluorescent tag. Further, we establish structural determinants necessary for recognition of this sphingolipid substrate. Using enzyme chimeras and site-directed mutagenesis, we observed that residues in transmembrane (TM) segments 1, 4, and 6 contribute to GlcCer selection, with a conserved glutamine in the center of TM4 playing an essential role. Our molecular observations help refine models for substrate translocation by P4-ATPases, clarify the relationship between these flippases and human disease, and have fundamental implications for membrane organization and sphingolipid homeostasis.
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Affiliation(s)
- Bartholomew P Roland
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Tomoki Naito
- the Graduate School of Pharmaceutical Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jordan T Best
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Cayetana Arnaiz-Yépez
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Hiroyuki Takatsu
- the Graduate School of Pharmaceutical Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Roger J Yu
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Hye-Won Shin
- the Graduate School of Pharmaceutical Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Todd R Graham
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
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20
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Shin HW, Takatsu H. Substrates of P4‐ATPases: beyond aminophospholipids (phosphatidylserine and phosphatidylethanolamine). FASEB J 2018; 33:3087-3096. [DOI: 10.1096/fj.201801873r] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hye-Won Shin
- Graduate School of Pharmaceutical SciencesKyoto University Kyoto Japan
| | - Hiroyuki Takatsu
- Graduate School of Pharmaceutical SciencesKyoto University Kyoto Japan
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21
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Ying G, Boldt K, Ueffing M, Gerstner CD, Frederick JM, Baehr W. The small GTPase RAB28 is required for phagocytosis of cone outer segments by the murine retinal pigmented epithelium. J Biol Chem 2018; 293:17546-17558. [PMID: 30228185 PMCID: PMC6231133 DOI: 10.1074/jbc.ra118.005484] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/12/2018] [Indexed: 12/19/2022] Open
Abstract
RAB28, a member of the RAS oncogene family, is a ubiquitous, farnesylated, small GTPase of unknown function present in photoreceptors and the retinal pigmented epithelium (RPE). Nonsense mutations of the human RAB28 gene cause recessive cone-rod dystrophy 18 (CRD18), characterized by macular hyperpigmentation, progressive loss of visual acuity, RPE atrophy, and severely attenuated cone and rod electroretinography (ERG) responses. In an attempt to elucidate the disease-causing mechanism, we generated Rab28-/- mice by deleting exon 3 and truncating RAB28 after exon 2. We found that Rab28-/- mice recapitulate features of the human dystrophy (i.e. they exhibited reduced cone and rod ERG responses and progressive retina degeneration). Cones of Rab28-/- mice extended their outer segments (OSs) to the RPE apical processes and formed enlarged, balloon-like distal tips before undergoing degeneration. The visual pigment content of WT and Rab28-/- cones was comparable before the onset of degeneration. Cone phagosomes were almost absent in Rab28-/- mice, whereas rod phagosomes displayed normal levels. A protein-protein interaction screen identified several RAB28-interacting proteins, including the prenyl-binding protein phosphodiesterase 6 δ-subunit (PDE6D) and voltage-gated potassium channel subfamily J member 13 (KCNJ13) present in the RPE apical processes. Of note, the loss of PDE6D prevented delivery of RAB28 to OSs. Taken together, these findings reveal that RAB28 is required for shedding and phagocytosis of cone OS discs.
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Affiliation(s)
- Guoxin Ying
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
| | - Karsten Boldt
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Marius Ueffing
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Cecilia D Gerstner
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Jeanne M Frederick
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Wolfgang Baehr
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
- the Departments of Neurobiology and Anatomy and
- Biology, University of Utah, Salt Lake City, Utah 84112
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22
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Phosphatidylserine is a marker for axonal debris engulfment but its exposure can be decoupled from degeneration. Cell Death Dis 2018; 9:1116. [PMID: 30389906 PMCID: PMC6214901 DOI: 10.1038/s41419-018-1155-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/25/2018] [Accepted: 10/08/2018] [Indexed: 02/08/2023]
Abstract
Apoptotic cells expose Phosphatidylserine (PS), that serves as an “eat me” signal for engulfing cells. Previous studies have shown that PS also marks degenerating axonsduring developmental pruning or in response to insults (Wallerian degeneration), but the pathways that control PS exposure on degenerating axons are largely unknown. Here, we used a series of in vitro assays to systematically explore the regulation of PS exposure during axonal degeneration. Our results show that PS exposure is regulated by the upstream activators of axonal pruning and Wallerian degeneration. However, our investigation of signaling further downstream revealed divergence between axon degeneration and PS exposure. Importantly, elevation of the axonal energetic status hindered PS exposure, while inhibition of mitochondrial activity caused PS exposure, without degeneration. Overall, our results suggest that the levels of PS on the outer axonal membrane can be dissociated from the degeneration process and that the axonal energetic status plays a key role in the regulation of PS exposure.
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23
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Disruption of Tmem30a results in cerebellar ataxia and degeneration of Purkinje cells. Cell Death Dis 2018; 9:899. [PMID: 30185775 PMCID: PMC6125289 DOI: 10.1038/s41419-018-0938-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 07/30/2018] [Accepted: 08/02/2018] [Indexed: 12/11/2022]
Abstract
Phospholipids are asymmetrically distributed across mammalian plasma membrane with phosphatidylserine (PS) and phosphatidylethanolamine concentrated in the cytoplasmic leaflet of the membrane bilayer. This asymmetric distribution is dependent on a group of P4-ATPases named PS flippases. The proper transport and function of PS flippases require a β-subunit transmembrane protein 30 A (TMEM30A). Disruption of PS flippases led to several human diseases. However, the roles of TMEM30A in the central nervous system remain elusive. To investigate the role of Tmem30a in the cerebellum, we developed a Tmem30a Purkinje cell (PC)-specific knockout (KO) mouse model. The Tmem30a KO mice displayed early-onset ataxia and progressive PC death. Deficiency in Tmem30a led to an increased expression of Glial fibrillary acidic protein and astrogliosis in regions with PC loss. Elevated C/EBP homologous protein and BiP expression levels indicated the presence of endoplasmic reticulum stress in the PCs prior to visible cell loss. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis suggested that apoptotic cell death occurred in the cerebellum. Our data demonstrate that loss of Tmem30a in PCs results in protein folding and transport defects, a substantial decrease in dendritic spine density, increased astrogliosis and PC death. Taken together, our data demonstrate an essential role of Tmem30a in the cerebellum PCs.
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24
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Wang J, Molday LL, Hii T, Coleman JA, Wen T, Andersen JP, Molday RS. Proteomic Analysis and Functional Characterization of P4-ATPase Phospholipid Flippases from Murine Tissues. Sci Rep 2018; 8:10795. [PMID: 30018401 PMCID: PMC6050252 DOI: 10.1038/s41598-018-29108-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 07/05/2018] [Indexed: 01/31/2023] Open
Abstract
P4-ATPases are a subfamily of P-type ATPases that flip phospholipids across membranes to generate lipid asymmetry, a property vital to many cellular processes. Mutations in several P4-ATPases have been linked to severe neurodegenerative and metabolic disorders. Most P4-ATPases associate with one of three accessory subunit isoforms known as CDC50A (TMEM30A), CDC50B (TMEM30B), and CDC50C (TMEM30C). To identify P4-ATPases that associate with CDC50A, in vivo, and determine their tissue distribution, we isolated P4-ATPases-CDC50A complexes from retina, brain, liver, testes, and kidney on a CDC50A immunoaffinity column and identified and quantified P4-ATPases from their tryptic peptides by mass spectrometry. Of the 12 P4-ATPase that associate with CDC50 subunits, 10 P4-ATPases were detected. Four P4-ATPases (ATP8A1, ATP11A, ATP11B, ATP11C) were present in all five tissues. ATP10D was found in low amounts in liver, brain, testes, and kidney, and ATP8A2 was present in significant amounts in retina, brain, and testes. ATP8B1 was detected only in liver, ATP8B3 and ATP10A only in testes, and ATP8B2 primarily in brain. We also show that ATP11A, ATP11B and ATP11C, like ATP8A1 and ATP8A2, selectively flip phosphatidylserine and phosphatidylethanolamine across membranes. These studies provide new insight into the tissue distribution, relative abundance, subunit interactions and substrate specificity of P4-ATPase-CDC50A complexes.
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Affiliation(s)
- Jiao Wang
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
- Laboratory of Molecular Neural Biology, Institute of Systems Biology, School of Life Sciences, Shanghai University, Shanghai, 200444, China
| | - Laurie L Molday
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Theresa Hii
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Jonathan A Coleman
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Tieqiao Wen
- Laboratory of Molecular Neural Biology, Institute of Systems Biology, School of Life Sciences, Shanghai University, Shanghai, 200444, China
| | - Jens P Andersen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, Bldg. 1160, DK-8000, Aarhus C, Denmark
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
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25
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McMillan HJ, Telegrafi A, Singleton A, Cho MT, Lelli D, Lynn FC, Griffin J, Asamoah A, Rinne T, Erasmus CE, Koolen DA, Haaxma CA, Keren B, Doummar D, Mignot C, Thompson I, Velsher L, Dehghani M, Vahidi Mehrjardi MY, Maroofian R, Tchan M, Simons C, Christodoulou J, Martín-Hernández E, Guillen Sacoto MJ, Henderson LB, McLaughlin H, Molday LL, Molday RS, Yoon G. Recessive mutations in ATP8A2 cause severe hypotonia, cognitive impairment, hyperkinetic movement disorders and progressive optic atrophy. Orphanet J Rare Dis 2018; 13:86. [PMID: 30012219 PMCID: PMC6048855 DOI: 10.1186/s13023-018-0825-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 05/15/2018] [Indexed: 12/30/2022] Open
Abstract
Background ATP8A2 mutations have recently been described in several patients with severe, early-onset hypotonia and cognitive impairment. The aim of our study was to characterize the clinical phenotype of patients with ATP8A2 mutations. Methods An observational study was conducted at multiple diagnostic centres. Clinical data is presented from 9 unreported and 2 previously reported patients with ATP8A2 mutations. We compare their features with 3 additional patients that have been previously reported in the medical literature. Results Eleven patients with biallelic ATP8A2 mutations were identified, with a mean age of 9.4 years (range 2.5–28 years). All patients with ATP8A2 mutations (100%) demonstrated developmental delay, severe hypotonia and movement disorders, specifically chorea or choreoathetosis (100%), dystonia (27%) and facial dyskinesia (18%). Optic atrophy was observed in 78% of patients for whom funduscopic examination was performed. Symptom onset in all (100%) was noted before 6 months of age, with 70% having symptoms noted at birth. Feeding difficulties were common (91%) although most patients were able to tolerate pureed or thickened feeds, and 3 patients required gastrostomy tube insertion. MRI of the brain was normal in 50% of the patients. A smaller proportion was noted to have mild cortical atrophy (30%), delayed myelination (20%) and/or hypoplastic optic nerves (20%). Functional studies were performed on differentiated induced pluripotent cells from one child, which confirmed a decrease in ATP8A2 expression compared to control cells. Conclusions ATP8A2 gene mutations have emerged as the cause of a novel neurological phenotype characterized by global developmental delays, severe hypotonia and hyperkinetic movement disorders, the latter being an important distinguishing feature. Optic atrophy is common and may only become apparent in the first few years of life, necessitating repeat ophthalmologic evaluation in older children. Early recognition of the cardinal features of this condition will facilitate diagnosis of this complex neurologic disorder. Electronic supplementary material The online version of this article (10.1186/s13023-018-0825-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hugh J McMillan
- Division of Neurology, Department of Pediatrics, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON, Canada
| | | | | | | | - Daniel Lelli
- Division of Neurology, Department of Medicine, The Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada
| | - Francis C Lynn
- Diabetes Research Program, Child and Family Research Institute, Vancouver, BC, Canada.,Department of Surgery and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Julie Griffin
- Weisskopf Child Evaluation Center, Department of Pediatrics, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Alexander Asamoah
- Weisskopf Child Evaluation Center, Department of Pediatrics, School of Medicine, University of Louisville, Louisville, KY, USA
| | - Tuula Rinne
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Corrie E Erasmus
- Department of Neurology, Donders Center of Neuroscience, Radboud University Medical Center, Nijmegen, The Netherlands
| | - David A Koolen
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Charlotte A Haaxma
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Boris Keren
- Assistance Publique Hôpitaux de Paris, Département de Génétique, Groupe Hospitalier, Pitié-Salpêtrière, Paris, France
| | - Diane Doummar
- Service de Neuropédiatrie, Hôpital Armand-Trousseau, Paris, France
| | - Cyril Mignot
- Assistance Publique Hôpitaux de Paris, Département de Génétique, Groupe Hospitalier, Pitié-Salpêtrière, Paris, France.,Centre de Référence Déficiences Intellectuelles de Causes Rares, GH Pitié Salpêtrière, Paris, France.,Groupe de Recherche Clinique UPMC Déficience Intellectuelle de Causes Rares et Autisme GH Pitié-Salpêtrière, Paris, France
| | - Islay Thompson
- Genetics Program, North York General Hospital, Toronto, ON, Canada
| | - Lea Velsher
- Genetics Program, North York General Hospital, Toronto, ON, Canada
| | - Mohammadreza Dehghani
- Medical Genetics Research Centre, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.,Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Mohammad Yahya Vahidi Mehrjardi
- Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.,Diabetes Research Centre, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Reza Maroofian
- Human Genetics Research Centre, Molecular and Clinical Sciences Institute, St George's University of London, London, UK
| | - Michel Tchan
- Department of Genetic Medicine, Westmead Hospital, Westmead, NSW, Australia.,Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Cas Simons
- Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, Australia
| | - John Christodoulou
- Neurodevelopmental Genomics Research Group, Murdoch Childrens Research Institute and Department of Paediatrics, Melbourne Medical School, University of Melbourne, Melbourne, VIC, Australia
| | - Elena Martín-Hernández
- Unidad de Enfermedades Mitocondriales-Metabólicas Hereditarias, Servicio de Pediatría Hospital Universitario 12 de Octubre, Universidad Complutense de Madrid, Madrid, Spain
| | | | | | | | - Laurie L Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.,Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, BC, Canada
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.,Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, BC, Canada
| | - Grace Yoon
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada. .,Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
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26
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Vuckovic D, Mezzavilla M, Cocca M, Morgan A, Brumat M, Catamo E, Concas MP, Biino G, Franzè A, Ambrosetti U, Pirastu M, Gasparini P, Girotto G. Whole-genome sequencing reveals new insights into age-related hearing loss: cumulative effects, pleiotropy and the role of selection. Eur J Hum Genet 2018; 26:1167-1179. [PMID: 29725052 PMCID: PMC6057993 DOI: 10.1038/s41431-018-0126-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 02/05/2018] [Accepted: 02/13/2018] [Indexed: 01/17/2023] Open
Abstract
Age-related hearing loss (ARHL) is the most common sensory disorder in the elderly. Although not directly life threatening, it contributes to loss of autonomy and is associated with anxiety, depression and cognitive decline. To search for genetic risk factors underlying ARHL, a large whole-genome sequencing (WGS) approach has been carried out in a cohort of 212 cases and controls, both older than 50 years to select genes characterized by a burden of variants specific to cases or controls. Accordingly, the total variation load per gene was compared and two groups were detected: 375 genes more variable in cases and 371 more variable in controls. In both cases, Gene Ontology analysis showed that the largest enrichment for biological processes (fold > 5, p-value = 0.042) was the “sensory perception of sound”, suggesting cumulative genetic effects were involved. Replication confirmed 141 genes, while additional analysis based on natural selection led to a prioritization of 21 genes. The majority of them (20 out of 21) showed positive expression in mouse cochlea cDNA and were associated with two functional pathways. Among them, two genes were previously associated with hearing (CSMD1 and PTRPD) and re-sequenced in a large Italian cohort of ARHL patients (N = 389). Results led to the identification of six coding variants not detected in cases so far, suggesting a possible protective role, which requires investigation. In conclusion, we show that this multistep strategy (WGS, selection, expression, pathway analysis and targeted re-sequencing) can provide major insights into the molecular characterization of complex diseases such as ARHL.
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Affiliation(s)
- Dragana Vuckovic
- Medical Sciences, Chirurgical and Health Department, University of Trieste, Trieste, Italy. .,Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy.
| | - Massimo Mezzavilla
- Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Massimiliano Cocca
- Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Anna Morgan
- Medical Sciences, Chirurgical and Health Department, University of Trieste, Trieste, Italy.,Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Marco Brumat
- Medical Sciences, Chirurgical and Health Department, University of Trieste, Trieste, Italy
| | - Eulalia Catamo
- Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Maria Pina Concas
- Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Ginevra Biino
- Institute of Molecular Genetics, National Research Council of Italy, Pavia, Italy
| | - Annamaria Franzè
- Ceinge Advanced Biotechnology, Naples, Italy.,Neuroscience, Reproductive and Odontology Sciences Department, University of Naples "Federico II", Naples, Italy
| | - Umberto Ambrosetti
- UO Audiology, Fondazione IRCCS Ca Granda, Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milan, Italy.,Audiology Unit, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Mario Pirastu
- Institute of Population Genetics, National Research Council of Italy, Sassari, Italy
| | - Paolo Gasparini
- Medical Sciences, Chirurgical and Health Department, University of Trieste, Trieste, Italy.,Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
| | - Giorgia Girotto
- Medical Sciences, Chirurgical and Health Department, University of Trieste, Trieste, Italy.,Medical Genetics, Institute for Maternal and Child Health - IRCCS "Burlo Garofolo", Trieste, Italy
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27
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Mioka T, Fujimura-Kamada K, Mizugaki N, Kishimoto T, Sano T, Nunome H, Williams DE, Andersen RJ, Tanaka K. Phospholipid flippases and Sfk1p, a novel regulator of phospholipid asymmetry, contribute to low permeability of the plasma membrane. Mol Biol Cell 2018. [PMID: 29540528 PMCID: PMC5935070 DOI: 10.1091/mbc.e17-04-0217] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Phospholipid flippase (type 4 P-type ATPase) plays a major role in the generation of phospholipid asymmetry in eukaryotic cell membranes. Loss of Lem3p-Dnf1/2p flippases leads to the exposure of phosphatidylserine (PS) and phosphatidylethanolamine (PE) on the cell surface in yeast, resulting in sensitivity to PS- or PE-binding peptides. We isolated Sfk1p, a conserved membrane protein in the TMEM150/FRAG1/DRAM family, as a multicopy suppressor of this sensitivity. Overexpression of SFK1 decreased PS/PE exposure in lem3Δ mutant cells. Consistent with this, lem3Δ sfk1Δ double mutant cells exposed more PS/PE than the lem3Δ mutant. Sfk1p was previously implicated in the regulation of the phosphatidylinositol-4 kinase Stt4p, but the effect of Sfk1p on PS/PE exposure in lem3Δ was independent of Stt4p. Surprisingly, Sfk1p did not facilitate phospholipid flipping but instead repressed it, even under ATP-depleted conditions. We propose that Sfk1p negatively regulates transbilayer movement of phospholipids irrespective of directions. In addition, we showed that the permeability of the plasma membrane was dramatically elevated in the lem3Δ sfk1Δ double mutant in comparison with the corresponding single mutants. Interestingly, total ergosterol was decreased in the lem3Δ sfk1Δ mutant. Our results suggest that phospholipid asymmetry is required for the maintenance of low plasma membrane permeability.
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Affiliation(s)
- Tetsuo Mioka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Konomi Fujimura-Kamada
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Nahiro Mizugaki
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Takuma Kishimoto
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Takamitsu Sano
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - Hitoshi Nunome
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
| | - David E Williams
- Departments of Chemistry and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Raymond J Andersen
- Departments of Chemistry and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Kazuma Tanaka
- Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Life Science, Kita-ku, Sapporo 060-0815, Japan
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28
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Nowotny M, Kiefer L, Andre D, Fabrizius A, Hankeln T, Reuss S. Hearing Without Neuroglobin. Neuroscience 2017; 366:138-148. [DOI: 10.1016/j.neuroscience.2017.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 10/05/2017] [Accepted: 10/06/2017] [Indexed: 12/11/2022]
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29
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Zhang L, Yang Y, Li S, Zhang S, Zhu X, Tai Z, Yang M, Liu Y, Guo X, Chen B, Jiang Z, Lu F, Zhu X. Loss of Tmem30a leads to photoreceptor degeneration. Sci Rep 2017; 7:9296. [PMID: 28839191 PMCID: PMC5571223 DOI: 10.1038/s41598-017-09506-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/26/2017] [Indexed: 12/16/2022] Open
Abstract
Phosphatidylserine (PS) is asymmetrically distributed between the outer and inner leaflets of the plasma membrane in eukaryotic cells. PS asymmetry on the plasma membrane depends on the activities of P4-ATPases, and disruption of PS distribution can lead to various disease conditions. Folding and transporting of P4-ATPases to their cellular destination requires the β subunit TMEM30A proteins. However, the in vivo functions of Tmem30a remain unknown. To this end, we generated retinal-specific Tmem30a-knockout mice to investigate its roles in vivo for the first time. Our data demonstrated that loss of Tmem30a in mouse cone cells leads to mislocalization of cone opsin, loss of photopic electroretinogram (ERG) responses and loss of cone cells. Mechanistically, Tmem30a-mutant mouse embryonic fibroblasts (MEFs) exhibited diminished PS flippase activity and increased exposure of PS on the cell surface. The broad loss of Tmem30a in adult mice led to a reduced scotopic photoresponse, mislocalization of ATP8A2 to the inner segment and cell body, and increased apoptosis in the retina. Our data demonstrated novel essential roles of Tmem30a in the retina.
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Affiliation(s)
- Lin Zhang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Department of Laboratory Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Yeming Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Department of Laboratory Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Shujin Li
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Chengdu Institute of Biology, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, Sichuan, China
| | - Shanshan Zhang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Xiong Zhu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Zhengfu Tai
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Chengdu Institute of Biology, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, Sichuan, China
| | - Mu Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Chengdu Institute of Biology, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, Sichuan, China
| | - Yuqing Liu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.,Department of Laboratory Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Xinzheng Guo
- Department of Ophthalmology, Yale University School of Medicine, New Haven, CT, USA
| | - Bo Chen
- Department of Ophthalmology, Yale University School of Medicine, New Haven, CT, USA
| | - Zhilin Jiang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China
| | - Fang Lu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China. .,Department of Laboratory Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China.
| | - Xianjun Zhu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study and School of Medicine, Hospital of the University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China. .,Department of Laboratory Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, 610072, China. .,Institute of Laboratory Animal Sciences, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China. .,Chengdu Institute of Biology, Chinese Academy of Sciences Sichuan Translational Medicine Research Hospital, Chengdu, Sichuan, China.
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Zhou T, Souzeau E, Sharma S, Landers J, Mills R, Goldberg I, Healey PR, Graham S, Hewitt AW, Mackey DA, Galanopoulos A, Casson RJ, Ruddle JB, Ellis J, Leo P, Brown MA, MacGregor S, Lynn DJ, Burdon KP, Craig JE. Whole exome sequencing implicates eye development, the unfolded protein response and plasma membrane homeostasis in primary open-angle glaucoma. PLoS One 2017; 12:e0172427. [PMID: 28264060 PMCID: PMC5338784 DOI: 10.1371/journal.pone.0172427] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 02/03/2017] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To identify biological processes associated with POAG and its subtypes, high-tension (HTG) and normal-tension glaucoma (NTG), by analyzing rare potentially damaging genetic variants. METHODS A total of 122 and 65 unrelated HTG and NTG participants, respectively, with early onset advanced POAG, 103 non-glaucoma controls and 993 unscreened ethnicity-matched controls were included in this study. Study participants without myocilin disease-causing variants and non-glaucoma controls were subjected to whole exome sequencing on an Illumina HiSeq2000. Exomes of participants were sequenced on an Illumina HiSeq2000. Qualifying variants were rare in the general population (MAF < 0.001) and potentially functionally damaging (nonsense, frameshift, splice or predicted pathogenic using SIFT or Polyphen2 software). Genes showing enrichment of qualifying variants in cases were selected for pathway and network analysis using InnateDB. RESULTS POAG cases showed enrichment of rare variants in camera-type eye development genes (p = 1.40×10-7, corrected p = 3.28×10-4). Implicated eye development genes were related to neuronal or retinal development. HTG cases were significantly enriched for key regulators in the unfolded protein response (UPR) (p = 7.72×10-5, corrected p = 0.013). The UPR is known to be involved in myocilin-related glaucoma; our results suggest the UPR has a role in non-myocilin causes of HTG. NTG cases showed enrichment in ion channel transport processes (p = 1.05×10-4, corrected p = 0.027) including calcium, chloride and phospholipid transporters involved in plasma membrane homeostasis. Network analysis also revealed enrichment of the MHC Class I antigen presentation pathway in HTG, and the EGFR1 and cell-cycle pathways in both HTG and NTG. CONCLUSION This study suggests that mutations in eye development genes are enriched in POAG. HTG can result from aberrant responses to protein misfolding which may be amenable to molecular chaperone therapy. NTG is associated with impaired plasma membrane homeostasis increasing susceptibility to apoptosis.
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Affiliation(s)
- Tiger Zhou
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
- * E-mail:
| | - Emmanuelle Souzeau
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
| | - Shiwani Sharma
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
| | - John Landers
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
| | - Richard Mills
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
| | - Ivan Goldberg
- University of Sydney Discipline of Ophthalmology, Sydney, Australia
- Glaucoma Unit, Sydney Eye Hospital, Sydney, Australia
| | - Paul R. Healey
- University of Sydney Discipline of Ophthalmology, Sydney, Australia
- Centre for Vision Research, Westmead Institute for Medical Research, University of Sydney, Sydney, Australia
| | - Stuart Graham
- University of Sydney Discipline of Ophthalmology, Sydney, Australia
| | - Alex W. Hewitt
- University of Tasmania Menzies Institute for Medical Research, Hobart, Australia
| | - David A. Mackey
- University of Western Australia Centre for Ophthalmology and Visual Science, Lions Eye Institute, Perth, Australia
| | - Anna Galanopoulos
- University of Adelaide, Discipline of Ophthalmology & Visual Sciences, Adelaide, Australia
| | - Robert J. Casson
- University of Adelaide, Discipline of Ophthalmology & Visual Sciences, Adelaide, Australia
| | - Jonathan B. Ruddle
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Australia
| | - Jonathan Ellis
- University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Australia
| | - Paul Leo
- University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Australia
| | - Matthew A. Brown
- University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Australia
| | - Stuart MacGregor
- Statistical Genetics, QIMR Berghofer Medical Research Institute, Royal Brisbane Hospital, Brisbane, Australia
| | - David J. Lynn
- EMBL Australia Group, Infection & Immunity Theme, South Australian Medical and Health Research Institute, Adelaide, Australia
- Flinders University, School of Medicine, Adelaide, Australia
| | - Kathryn P. Burdon
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
- University of Tasmania Menzies Institute for Medical Research, Hobart, Australia
| | - Jamie E. Craig
- Flinders University, Department of Ophthalmology, Bedford Park, South Australia, Australia
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Chalat M, Moleschi K, Molday RS. C-terminus of the P4-ATPase ATP8A2 functions in protein folding and regulation of phospholipid flippase activity. Mol Biol Cell 2016; 28:452-462. [PMID: 27932490 PMCID: PMC5341728 DOI: 10.1091/mbc.e16-06-0453] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 10/28/2016] [Accepted: 12/01/2016] [Indexed: 12/18/2022] Open
Abstract
ATP8A2 is a P4-ATPase that flips phosphatidylserine and phosphatidylethanolamine across cell membranes. This generates membrane phospholipid asymmetry, a property important in many cellular processes, including vesicle trafficking. ATP8A2 deficiency causes severe neurodegenerative diseases. We investigated the role of the C-terminus of ATP8A2 in its expression, subcellular localization, interaction with its subunit CDC50A, and function as a phosphatidylserine flippase. C-terminal deletion mutants exhibited a reduced tendency to solubilize in mild detergent and exit the endoplasmic reticulum. The solubilized protein, however, assembled with CDC50A and displayed phosphatidylserine flippase activity. Deletion of the C-terminal 33 residues resulted in reduced phosphatidylserine-dependent ATPase activity, phosphatidylserine flippase activity, and neurite extension in PC12 cells. These reduced activities were reversed with 60- and 80-residue C-terminal deletions. Unlike the yeast P4-ATPase Drs2, ATP8A2 is not regulated by phosphoinositides but undergoes phosphorylation on the serine residue within a CaMKII target motif. We propose a model in which the C-terminus of ATP8A2 consists of an autoinhibitor domain upstream of the C-terminal 33 residues and an anti-autoinhibitor domain at the extreme C-terminus. The latter blocks the inhibitory activity of the autoinhibitor domain. We conclude that the C-terminus plays an important role in the efficient folding and regulation of ATP8A2.
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Affiliation(s)
- Madhavan Chalat
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Kody Moleschi
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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32
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Esposito EA, Jones MJ, Doom JR, MacIsaac JL, Gunnar MR, Kobor MS. Differential DNA methylation in peripheral blood mononuclear cells in adolescents exposed to significant early but not later childhood adversity. Dev Psychopathol 2016; 28:1385-1399. [PMID: 26847422 PMCID: PMC5903568 DOI: 10.1017/s0954579416000055] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Internationally adopted adolescents who are adopted as young children from conditions of poverty and deprivation have poorer physical and mental health outcomes than do adolescents conceived, born, and raised in the United States by families similar to those who adopt internationally. Using a sample of Russian and Eastern European adoptees to control for Caucasian race and US birth, and nonadopted offspring of well-educated and well-resourced parents to control for postadoption conditions, we hypothesized that the important differences in environments, conception to adoption, might be reflected in epigenetic patterns between groups, specifically in DNA methylation. Thus, we conducted an epigenome-wide association study to compare DNA methylation profiles at approximately 416,000 individual CpG loci from peripheral blood mononuclear cells of 50 adopted youth and 33 nonadopted youth. Adopted youth averaged 22 months at adoption, and both groups averaged 15 years at testing; thus, roughly 80% of their lives were lived in similar circumstances. Although concurrent physical health did not differ, cell-type composition predicted using the DNA methylation data revealed a striking difference in the white blood cell-type composition of the adopted and nonadopted youth. After correcting for cell type and removing invariant probes, 30 CpG sites in 19 genes were more methylated in the adopted group. We also used an exploratory functional analysis that revealed that 223 gene ontology terms, clustered in neural and developmental categories, were significantly enriched between groups.
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Affiliation(s)
- Elisa A. Esposito
- Institute of Child Development, University of Minnesota, 51 East River Parkway, Minneapolis, MN 55455
- Widener University, One University Place, Chester, PA 19013
| | - Meaghan J. Jones
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, 950 West 28 Avenue, Vancouver, V5Z 4H4, Canada
| | - Jenalee R. Doom
- Institute of Child Development, University of Minnesota, 51 East River Parkway, Minneapolis, MN 55455
| | - Julia L MacIsaac
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, 950 West 28 Avenue, Vancouver, V5Z 4H4, Canada
| | - Megan R. Gunnar
- Institute of Child Development, University of Minnesota, 51 East River Parkway, Minneapolis, MN 55455
- Child and Brain Development Program, Canadian Institute for Advanced Research, Canada
| | - Michael S. Kobor
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, 950 West 28 Avenue, Vancouver, V5Z 4H4, Canada
- Child and Brain Development Program, Canadian Institute for Advanced Research, Canada
- Human Early Learning Partnership, School of Population and Public Health, University of British Columbia
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New ATP8A2 gene mutations associated with a novel syndrome: encephalopathy, intellectual disability, severe hypotonia, chorea and optic atrophy. Neurogenetics 2016; 17:259-263. [PMID: 27679995 DOI: 10.1007/s10048-016-0496-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 09/14/2016] [Accepted: 09/16/2016] [Indexed: 01/14/2023]
Abstract
We report the clinical and biochemical findings from two unrelated patients who presented with a novel syndrome: encephalopathy, intellectual disability, severe hypotonia, chorea and optic atrophy. Whole exome sequencing (WES) uncovered a homozygous mutation in the ATP8A2 gene (NM_016529:c.1287G > T, p.K429N) in one patient and compound heterozygous mutations (c.1630G > C, p.A544P and c.1873C > T, p.R625W) in the other. Only one haploinsufficiency case and a family with a homozygous mutation in ATP8A2 gene (c.1128C > G, p.I376M) have been described so far, with phenotypes that differed slightly from the patients described herein. In conclusion, our data expand both the genetic and phenotypic spectrum associated with ATP8A2 gene mutations.
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Pomorski TG, Menon AK. Lipid somersaults: Uncovering the mechanisms of protein-mediated lipid flipping. Prog Lipid Res 2016; 64:69-84. [PMID: 27528189 DOI: 10.1016/j.plipres.2016.08.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 08/10/2016] [Indexed: 12/22/2022]
Abstract
Membrane lipids diffuse rapidly in the plane of the membrane but their ability to flip spontaneously across a membrane bilayer is hampered by a significant energy barrier. Thus spontaneous flip-flop of polar lipids across membranes is very slow, even though it must occur rapidly to support diverse aspects of cellular life. Here we discuss the mechanisms by which rapid flip-flop occurs, and what role lipid flipping plays in membrane homeostasis and cell growth. We focus on conceptual aspects, highlighting mechanistic insights from biochemical and in silico experiments, and the recent, ground-breaking identification of a number of lipid scramblases.
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Affiliation(s)
- Thomas Günther Pomorski
- Faculty of Chemistry and Biochemistry, Molecular Biochemistry, Ruhr University Bochum, Universitätstrasse 150, D-44780 Bochum, Germany; Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA.
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Goldberg AFX, Moritz OL, Williams DS. Molecular basis for photoreceptor outer segment architecture. Prog Retin Eye Res 2016; 55:52-81. [PMID: 27260426 DOI: 10.1016/j.preteyeres.2016.05.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/27/2016] [Accepted: 05/29/2016] [Indexed: 01/11/2023]
Abstract
To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ∼10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained.
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Affiliation(s)
- Andrew F X Goldberg
- Eye Research Institute, Oakland University, 417 Dodge Hall, Rochester, MI, 48309, USA.
| | - Orson L Moritz
- Department of Ophthalmology & Visual Sciences, University of British Columbia, Vancouver, BC, Canada
| | - David S Williams
- Department of Ophthalmology and Jules Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, USA
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36
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Abstract
Rhodopsin has been intensively characterized in its role as a visual pigment and G protein-coupled receptor responsible for dim-light vision. We recently discovered that it also functions as an ATP-independent phospholipid scramblase: when reconstituted into large unilamellar vesicles, rhodopsin accelerates the normally sluggish transbilayer translocation of common phospholipids by more than 1000-fold, to rates in excess of 10 000 phospholipids transported per rhodopsin per second. Here we summarize the work leading to this discovery and speculate on the mechanism by which rhodopsin scrambles phospholipids. We also present a hypothesis that rhodopsin's scramblase activity is necessary for the function of the ABC transporter ABCA4 that is responsible for mitigating the toxic accumulation of 11-cis-retinal and bis-retinoids in the retina.
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Affiliation(s)
- Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8 and Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8.
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
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37
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Andersen JP, Vestergaard AL, Mikkelsen SA, Mogensen LS, Chalat M, Molday RS. P4-ATPases as Phospholipid Flippases-Structure, Function, and Enigmas. Front Physiol 2016; 7:275. [PMID: 27458383 PMCID: PMC4937031 DOI: 10.3389/fphys.2016.00275] [Citation(s) in RCA: 205] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 06/20/2016] [Indexed: 01/26/2023] Open
Abstract
P4-ATPases comprise a family of P-type ATPases that actively transport or flip phospholipids across cell membranes. This generates and maintains membrane lipid asymmetry, a property essential for a wide variety of cellular processes such as vesicle budding and trafficking, cell signaling, blood coagulation, apoptosis, bile and cholesterol homeostasis, and neuronal cell survival. Some P4-ATPases transport phosphatidylserine and phosphatidylethanolamine across the plasma membrane or intracellular membranes whereas other P4-ATPases are specific for phosphatidylcholine. The importance of P4-ATPases is highlighted by the finding that genetic defects in two P4-ATPases ATP8A2 and ATP8B1 are associated with severe human disorders. Recent studies have provided insight into how P4-ATPases translocate phospholipids across membranes. P4-ATPases form a phosphorylated intermediate at the aspartate of the P-type ATPase signature sequence, and dephosphorylation is activated by the lipid substrate being flipped from the exoplasmic to the cytoplasmic leaflet similar to the activation of dephosphorylation of Na(+)/K(+)-ATPase by exoplasmic K(+). How the phospholipid is translocated can be understood in terms of a peripheral hydrophobic gate pathway between transmembrane helices M1, M3, M4, and M6. This pathway, which partially overlaps with the suggested pathway for migration of Ca(2+) in the opposite direction in the Ca(2+)-ATPase, is wider than the latter, thereby accommodating the phospholipid head group. The head group is propelled along against its concentration gradient with the hydrocarbon chains projecting out into the lipid phase by movement of an isoleucine located at the position corresponding to an ion binding glutamate in the Ca(2+)- and Na(+)/K(+)-ATPases. Hence, the P4-ATPase mechanism is quite similar to the mechanism of these ion pumps, where the glutamate translocates the ions by moving like a pump rod. The accessory subunit CDC50 may be located in close association with the exoplasmic entrance of the suggested pathway, and possibly promotes the binding of the lipid substrate. This review focuses on properties of mammalian and yeast P4-ATPases for which most mechanistic insight is available. However, the structure, function and enigmas associated with mammalian and yeast P4-ATPases most likely extend to P4-ATPases of plants and other organisms.
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Affiliation(s)
| | | | | | | | - Madhavan Chalat
- Department of Biochemistry and Molecular Biology, University of British ColumbiaVancouver, BC, Canada
| | - Robert S. Molday
- Department of Biochemistry and Molecular Biology, University of British ColumbiaVancouver, BC, Canada
- *Correspondence: Robert S. Molday
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Panatala R, Hennrich H, Holthuis JCM. Inner workings and biological impact of phospholipid flippases. J Cell Sci 2015; 128:2021-32. [PMID: 25918123 DOI: 10.1242/jcs.102715] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The plasma membrane, trans-Golgi network and endosomal system of eukaryotic cells are populated with flippases that hydrolyze ATP to help establish asymmetric phospholipid distributions across the bilayer. Upholding phospholipid asymmetry is vital to a host of cellular processes, including membrane homeostasis, vesicle biogenesis, cell signaling, morphogenesis and migration. Consequently, defining the identity of flippases and their biological impact has been the subject of intense investigations. Recent work has revealed a remarkable degree of kinship between flippases and cation pumps. In this Commentary, we review emerging insights into how flippases work, how their activity is controlled according to cellular demands, and how disrupting flippase activity causes system failure of membrane function, culminating in membrane trafficking defects, aberrant signaling and disease.
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Affiliation(s)
- Radhakrishnan Panatala
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands Molecular Cell Biology Division, University of Osnabrück, 49076 Osnabrück, Germany
| | - Hanka Hennrich
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands
| | - Joost C M Holthuis
- Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 Utrecht, The Netherlands Molecular Cell Biology Division, University of Osnabrück, 49076 Osnabrück, Germany
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Lee S, Uchida Y, Wang J, Matsudaira T, Nakagawa T, Kishimoto T, Mukai K, Inaba T, Kobayashi T, Molday RS, Taguchi T, Arai H. Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase. EMBO J 2015; 34:669-88. [PMID: 25595798 PMCID: PMC4365035 DOI: 10.15252/embj.201489703] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
P4-ATPases translocate aminophospholipids, such as phosphatidylserine (PS), to the cytosolic leaflet of membranes. PS is highly enriched in recycling endosomes (REs) and is essential for endosomal membrane traffic. Here, we show that PS flipping by an RE-localized P4-ATPase is required for the recruitment of the membrane fission protein EHD1. Depletion of ATP8A1 impaired the asymmetric transbilayer distribution of PS in REs, dissociated EHD1 from REs, and generated aberrant endosomal tubules that appear resistant to fission. EHD1 did not show membrane localization in cells defective in PS synthesis. ATP8A2, a tissue-specific ATP8A1 paralogue, is associated with a neurodegenerative disease (CAMRQ). ATP8A2, but not the disease-causative ATP8A2 mutant, rescued the endosomal defects in ATP8A1-depleted cells. Primary neurons from Atp8a2-/- mice showed a reduced level of transferrin receptors at the cell surface compared to Atp8a2+/+ mice. These findings demonstrate the role of P4-ATPase in membrane fission and give insight into the molecular basis of CAMRQ.
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Affiliation(s)
- Shoken Lee
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Yasunori Uchida
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Jiao Wang
- Departments of Biochemistry and Molecular Biology and Ophthalmology and Visual Sciences, Centre for Macular Research University of British Columbia, Vancouver, BC, Canada
| | - Tatsuyuki Matsudaira
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Takatoshi Nakagawa
- Department of Pharmacology, Osaka Medical College, Takatsuki-city Osaka, Japan
| | | | - Kojiro Mukai
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan Lipid Biology Laboratory, RIKEN, Wako-shi Saitama, Japan
| | - Takehiko Inaba
- Lipid Biology Laboratory, RIKEN, Wako-shi Saitama, Japan
| | | | - Robert S Molday
- Departments of Biochemistry and Molecular Biology and Ophthalmology and Visual Sciences, Centre for Macular Research University of British Columbia, Vancouver, BC, Canada
| | - Tomohiko Taguchi
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan Pathological Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Hiroyuki Arai
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan Pathological Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
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Sotoca JV, Alvarado JC, Fuentes-Santamaría V, Martinez-Galan JR, Caminos E. Hearing impairment in the P23H-1 retinal degeneration rat model. Front Neurosci 2014; 8:297. [PMID: 25278831 PMCID: PMC4166116 DOI: 10.3389/fnins.2014.00297] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 08/31/2014] [Indexed: 12/17/2022] Open
Abstract
The transgenic P23H line 1 (P23H-1) rat expresses a variant of rhodopsin with a mutation that leads to loss of visual function. This rat strain is an experimental model usually employed to study photoreceptor degeneration. Although the mutated protein should not interfere with other sensory functions, observing severe loss of auditory reflexes in response to natural sounds led us to study auditory brain response (ABR) recording. Animals were separated into different hearing levels following the response to natural stimuli (hand clapping and kissing sounds). Of all the analyzed animals, 25.9% presented auditory loss before 50 days of age (P50) and 45% were totally deaf by P200. ABR recordings showed that all the rats had a higher hearing threshold than the control Sprague-Dawley (SD) rats, which was also higher than any other rat strains. The integrity of the central and peripheral auditory pathway was analyzed by histology and immunocytochemistry. In the cochlear nucleus (CN), statistical differences were found between SD and P23H-1 rats in VGluT1 distribution, but none were found when labeling all the CN synapses with anti-Syntaxin. This finding suggests anatomical and/or molecular abnormalities in the auditory downstream pathway. The inner ear of the hypoacusic P23H-1 rats showed several anatomical defects, including loss and disruption of hair cells and spiral ganglion neurons. All these results can explain, at least in part, how hearing impairment can occur in a high percentage of P23H-1 rats. P23H-1 rats may be considered an experimental model with visual and auditory dysfunctions in future research.
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Affiliation(s)
- Jorge V Sotoca
- Deparment of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities (IDINE), University of Castilla-La Mancha Albacete, Spain ; Barn och Ungdomsmedicin Eskilstuna, Sweden
| | - Juan C Alvarado
- Deparment of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities (IDINE), University of Castilla-La Mancha Albacete, Spain
| | - Verónica Fuentes-Santamaría
- Deparment of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities (IDINE), University of Castilla-La Mancha Albacete, Spain
| | - Juan R Martinez-Galan
- Deparment of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities (IDINE), University of Castilla-La Mancha Albacete, Spain
| | - Elena Caminos
- Deparment of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities (IDINE), University of Castilla-La Mancha Albacete, Spain
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Ilmjärv S, Reimets R, Hundahl CA, Luuk H. Effect of light on global gene expression in the neuroglobin-deficient mouse retina. Biomed Rep 2014; 2:780-786. [PMID: 25279145 DOI: 10.3892/br.2014.364] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 09/03/2014] [Indexed: 01/18/2023] Open
Abstract
Several previous studies have raised controversy over the functional role of neuroglobin (Ngb) in the retina. Certain studies indicate a significant impact of Ngb on retinal physiology, whereas others are conflicting. The present is an observational study that tested the effect of Ngb deficiency on gene expression in dark- and light-adapted mouse retinas. Large-scale gene expression profiling was performed using GeneChip® Mouse Exon 1.0 ST arrays and the results were compared to publicly available data sets. The lack of Ngb was found to have a minor effect on the light-induced retinal gene expression response. In addition, there was no increase in the expression of marker genes associated with hypoxia, endoplasmic reticulum-stress and oxidative stress in the Ngb-deficient retina. By contrast, several genes were identified that appeared to be differentially expressed between the genotypes when the effect of light was ignored. The present study indicates that Ngb deficiency does not lead to major alternations in light-dependent gene expression response, but leads to subtle systemic differences of a currently unknown functional significance.
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Affiliation(s)
- Sten Ilmjärv
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia ; Quretec Ltd, University of Tartu, Tartu 50411, Estonia
| | - Riin Reimets
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia ; The Centre for Disease Models and Biomedical Imaging, University of Tartu, Tartu 50411, Estonia
| | - Christian Ansgar Hundahl
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia ; The Centre for Disease Models and Biomedical Imaging, University of Tartu, Tartu 50411, Estonia ; Department of Clinical Biochemistry, Bispebjerg Hospital, Copenhagen 2400, Denmark
| | - Hendrik Luuk
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia ; The Centre for Disease Models and Biomedical Imaging, University of Tartu, Tartu 50411, Estonia
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Kim HY, Huang BX, Spector AA. Phosphatidylserine in the brain: metabolism and function. Prog Lipid Res 2014; 56:1-18. [PMID: 24992464 DOI: 10.1016/j.plipres.2014.06.002] [Citation(s) in RCA: 210] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/18/2014] [Accepted: 06/21/2014] [Indexed: 01/08/2023]
Abstract
Phosphatidylserine (PS) is the major anionic phospholipid class particularly enriched in the inner leaflet of the plasma membrane in neural tissues. PS is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by phosphatidylserine synthase 1 and phosphatidylserine synthase 2 located in the endoplasmic reticulum. Activation of Akt, Raf-1 and protein kinase C signaling, which supports neuronal survival and differentiation, requires interaction of these proteins with PS localized in the cytoplasmic leaflet of the plasma membrane. Furthermore, neurotransmitter release by exocytosis and a number of synaptic receptors and proteins are modulated by PS present in the neuronal membranes. Brain is highly enriched with docosahexaenoic acid (DHA), and brain PS has a high DHA content. By promoting PS synthesis, DHA can uniquely expand the PS pool in neuronal membranes and thereby influence PS-dependent signaling and protein function. Ethanol decreases DHA-promoted PS synthesis and accumulation in neurons, which may contribute to the deleterious effects of ethanol intake. Improvement of some memory functions has been observed in cognitively impaired subjects as a result of PS supplementation, but the mechanism is unclear.
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Affiliation(s)
- Hee-Yong Kim
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States.
| | - Bill X Huang
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States
| | - Arthur A Spector
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States
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Lipid flippase modulates olfactory receptor expression and odorant sensitivity in Drosophila. Proc Natl Acad Sci U S A 2014; 111:7831-6. [PMID: 24821794 DOI: 10.1073/pnas.1401938111] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In Drosophila melanogaster, the male-specific pheromone cVA (11-cis-vaccenyl acetate) functions as a sex-specific social cue. However, our understanding of the molecular mechanisms underlying cVA pheromone transduction and its regulation are incomplete. Using a genetic screen combined with an electrophysiological assay to monitor pheromone-evoked activity in the cVA-sensing Or67d neurons, we identified an olfactory sensitivity factor encoded by the dATP8B gene, the Drosophila homolog of mammalian ATP8B. dATP8B is expressed in all olfactory neurons that express Orco, the odorant receptor coreceptor, and the odorant responses in most Orco-expressing neurons are reduced. Or67d neurons are severely affected, with strongly impaired cVA-induced responses and lacking spontaneous spiking in the mutants. The dATP8B locus encodes a member of the P4-type ATPase family thought to flip aminophospholipids such as phosphatidylserine and phosphatidylethanolamine from one membrane leaflet to the other. dATP8B protein is concentrated in the cilia of olfactory neuron dendrites, the site of odorant transduction. Focusing on Or67d neuron function, we show that Or67d receptors are mislocalized in dATP8B mutants and that cVA responses can be restored to dATP8B mutants by misexpressing a wild-type dATP8B rescuing transgene, by expressing a vertebrate P4-type ATPase member in the pheromone-sensing neurons or by overexpressing Or67d receptor subunits. These findings reveal an unexpected role for lipid translocation in olfactory receptor expression and sensitivity to volatile odorants.
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