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Yusuf IH, MacLaren RE. Choroideremia: Toward Regulatory Approval of Retinal Gene Therapy. Cold Spring Harb Perspect Med 2023; 13:a041279. [PMID: 37277205 PMCID: PMC10691480 DOI: 10.1101/cshperspect.a041279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Choroideremia is an X-linked inherited retinal degeneration characterized by primary centripetal degeneration of the retinal pigment epithelium (RPE), with secondary degeneration of the choroid and retina. Affected individuals experience reduced night vision in early adulthood with blindness in late middle age. The underlying CHM gene encodes REP1, a protein involved in the prenylation of Rab GTPases essential for intracellular vesicle trafficking. Adeno-associated viral gene therapy has demonstrated some benefit in clinical trials for choroideremia. However, challenges remain in gaining regulatory approval. Choroideremia is slowly progressive, which presents difficulties in demonstrating benefit over short pivotal clinical trials that usually run for 1-2 years. Improvements in visual acuity are particularly challenging due to the initial negative effects of surgical detachment of the fovea. Despite these challenges, great progress toward a treatment has been made since choroideremia was first described in 1872.
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Affiliation(s)
- Imran H Yusuf
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, United Kingdom
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, United Kingdom
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AAV2-hCHM Subretinal Delivery to the Macula in Choroideremia: Two Year Interim Results of an Ongoing Phase I/II Gene Therapy Trial. Ophthalmology 2022; 129:1177-1191. [PMID: 35714735 DOI: 10.1016/j.ophtha.2022.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 06/03/2022] [Accepted: 06/07/2022] [Indexed: 11/22/2022] Open
Abstract
PURPOSE To assess the safety of the subretinal delivery of a recombinant adeno-associated virus serotype 2 (AAV2) vector carrying a human CHM-encoding cDNA in choroideremia (CHM). DESIGN Prospective, open-label, non-randomized, dose-escalation, phase 1/2 clinical trial. SUBJECTS, PARTICIPANTS, AND/OR CONTROLS Fifteen CHM patients (ages 20-57 years at dosing). METHODS, INTERVENTION, OR TESTING Patients received uniocular subfoveal injections of low dose (up to 5x1010 vector genome (vg) per eye, n=5) or high dose (up to 1x1011 vg per eye, n=10) AAV2-hCHM. Patients were evaluated pre- and post-operatively for two years with ophthalmic examinations, multimodal retinal imaging and psychophysical testing. MAIN OUTCOME Measures: visual acuity (VA), perimetry (10-2 protocol), spectral-domain optical coherence tomography (SD-OCT) and short-wavelength fundus autofluorescence (SW-FAF). RESULTS We detected no vector-related or systemic toxicities. VA returned to within 15 letters of baseline in all but two patients (one developed acute foveal thinning, another patient, a macular hole); the rest showed no gross changes in foveal structure at two years. There were no significant differences between intervention and control eyes in mean light-adapted sensitivity by perimetry, or in the lateral extent of retinal pigment epithelium (RPE) relative preservation by SD-OCT and SW-FAF. Microperimetry showed non-significant (<3SD of the intervisit variability) gains in sensitivity in some locations and participants in the intervention eye. There were no obvious dose-dependent relationships. CONCLUSIONS VA was within 15 letters of baseline after the subfoveal AAV2-hCHM injections in 13/15 (87%) of the patients. Acute foveal thinning with unchanged perifoveal function in one patient and macular hole in a second suggests foveal vulnerability to the subretinal injections. Longer observation intervals will help establish the significance of the minor differences in sensitivities and rate of disease progression observed between intervention and control eyes.
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3
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MacDonald IM. Lessons learned from research on choroideremia. Ophthalmic Genet 2022; 43:1-8. [PMID: 35080186 DOI: 10.1080/13816810.2022.2025608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 12/04/2021] [Accepted: 12/26/2021] [Indexed: 01/18/2023]
Abstract
Having devoted over 35 years of my professional life to various projects on choroideremia (CHM), I began to reflect on the many lessons that I learned along the way. One of the most important is: we should pay careful attention to possible, unintended psychological harm in clinical research. This lesson was learned early and then reinforced when I engaged CHM patients in an investigator-sponsored Phase IB clinical trial of ocular gene therapy for choroideremia. My second lesson came from the trial itself in that preliminary data may not be sufficient to predict the risks to patients in a clinical trial. In the significant push to begin a gene therapy trial for CHM patients, writing grants, recruiting personnel, interacting with regulatory authorities, acquiring research equipment to test outcome measures, I missed a third lesson. There is significant bias when the principal investigator of an investigator-sponsored clinical trial is also the treating physician in the trial. Ideally, those two roles should be kept separate. Finally, having completed the clinical trial, I learned that gene replacement with an AAV vector may not be the only genetic therapy for CHM; an antisense oligonucleotide therapy may be possible in select cases.
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Affiliation(s)
- Ian M MacDonald
- Departments of Medical Genetics and Ophthalmology & Visual Sciences, University of Alberta, Edmonton, AB, Canada
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4
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Fry LE, Patrício MI, Jolly JK, Xue K, MacLaren RE. Expression of Rab Prenylation Pathway Genes and Relation to Disease Progression in Choroideremia. Transl Vis Sci Technol 2021; 10:12. [PMID: 34254989 PMCID: PMC8287038 DOI: 10.1167/tvst.10.8.12] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Choroideremia results from the deficiency of Rab Escort Protein 1 (REP1), encoded by CHM, involved in the prenylation of Rab GTPases. Here, we investigate whether the transcription and expression of other genes involved in the prenylation of Rab proteins correlates with disease progression in a cohort of patients with choroideremia. Methods Rates of retinal pigment epithelial area loss in 41 patients with choroideremia were measured using fundus autofluorescence imaging for up to 4 years. From lysates of cultured skin fibroblasts donated by patients (n = 15) and controls (n = 14), CHM, CHML, RABGGTB and RAB27A mRNA expression, and REP1 and REP2 protein expression were compared. Results The central autofluorescent island area loss in patients with choroideremia occurred with a mean half-life of 5.89 years (95% confidence interval [CI] = 5.09-6.70), with some patients demonstrating relatively fast or slow rates of progression (range = 3.3-14.1 years). Expression of CHM mRNA and REP1 protein were significantly decreased in all patients. No difference in expression of CHML, RABGGTB, RAB27A, or REP2 was seen between patients and controls. No correlation was seen between expression of the genes analyzed and rates of retinal degeneration. Non-sense induced transcriptional compensation of CHML, a CHM-like retrogene, was not observed in patients with CHM variants predicted to undergo non-sense mediated decay. Conclusions Patients with choroideremia, who are deficient for REP1, show normal levels of expression of other genes involved in Rab prenylation, which do not appear to play any modifying role in the rate of disease progression. Translational Relevance There remains little evidence for selection of patients for choroideremia gene therapy based on genotype.
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Affiliation(s)
- Lewis E Fry
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Maria I Patrício
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Jasleen K Jolly
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Kanmin Xue
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
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Meschede IP, Burgoyne T, Tolmachova T, Seabra MC, Futter CE. Chronically shortened rod outer segments accompany photoreceptor cell death in Choroideremia. PLoS One 2020; 15:e0242284. [PMID: 33201897 PMCID: PMC7671558 DOI: 10.1371/journal.pone.0242284] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 10/29/2020] [Indexed: 01/28/2023] Open
Abstract
X-linked choroideremia (CHM) is a disease characterized by gradual retinal degeneration caused by loss of the Rab Escort Protein, REP1. Despite partial compensation by REP2 the disease is characterized by prenylation defects in multiple members of the Rab protein family that are master regulators of membrane traffic. Remarkably, the eye is the only organ affected in CHM patients, possibly because of the huge membrane traffic burden of the post mitotic photoreceptors, which synthesise outer segments, and the adjacent retinal pigment epithelium that degrades the spent portions each day. In this study, we aimed to identify defects in membrane traffic that might lead to photoreceptor cell death in CHM. In a heterozygous null female mouse model of CHM (Chmnull/WT), degeneration of the photoreceptor layer was clearly evident from increased numbers of TUNEL positive cells compared to age matched controls, small numbers of cells exhibiting signs of mitochondrial stress and greatly increased microglial infiltration. However, most rod photoreceptors exhibited remarkably normal morphology with well-formed outer segments and no discernible accumulation of transport vesicles in the inner segment. The major evidence of membrane trafficking defects was a shortening of rod outer segments that was evident at 2 months of age but remained constant over the period during which the cells die. A decrease in rhodopsin density found in the outer segment may underlie the outer segment shortening but does not lead to rhodopsin accumulation in the inner segment. Our data argue against defects in rhodopsin transport or outer segment renewal as triggers of cell death in CHM.
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Affiliation(s)
| | | | | | - Miguel C. Seabra
- UCL Institute of Ophthalmology, London, United Kingdom
- Imperial College London, London, United Kingdom
- CEDOC, NOVA Universidade Nova de Lisboa, Lisbon, Portugal
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6
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Patrício MI, Barnard AR, Xue K, MacLaren RE. Choroideremia: molecular mechanisms and development of AAV gene therapy. Expert Opin Biol Ther 2018; 18:807-820. [DOI: 10.1080/14712598.2018.1484448] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Maria I Patrício
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Alun R Barnard
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Kanmin Xue
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
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7
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Fu X, Huu VAN, Duan Y, Kermany DS, Valentim CCS, Zhang R, Zhu J, Zhang CL, Sun X, Zhang K. Clinical applications of retinal gene therapies. PRECISION CLINICAL MEDICINE 2018; 1:5-20. [PMID: 35694125 PMCID: PMC8982485 DOI: 10.1093/pcmedi/pby004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/27/2018] [Accepted: 04/03/2018] [Indexed: 02/05/2023] Open
Abstract
Retinal degenerative diseases are a major cause of blindness. Retinal gene therapy is a
trail-blazer in the human gene therapy field, leading to the first FDA approved gene
therapy product for a human genetic disease. The application of Clustered Regularly
Interspaced Short Palindromic Repeat/Cas9 (CRISPR/Cas9)-mediated gene editing technology
is transforming the delivery of gene therapy. We review the history, present, and future
prospects of retinal gene therapy.
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Affiliation(s)
- Xin Fu
- Guangzhou Women and Children’s Medical Center, Guangzhou Medical University, Guangzhou, China
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Viet Anh Nguyen Huu
- Guangzhou Women and Children’s Medical Center, Guangzhou Medical University, Guangzhou, China
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Yaou Duan
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Daniel S Kermany
- Guangzhou Women and Children’s Medical Center, Guangzhou Medical University, Guangzhou, China
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Carolina C S Valentim
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Runze Zhang
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Jie Zhu
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Charlotte L Zhang
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Xiaodong Sun
- Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai General Hospital, Shanghai Jiaodong University, Shanghai, China
| | - Kang Zhang
- Guangzhou Women and Children’s Medical Center, Guangzhou Medical University, Guangzhou, China
- Shiley Eye Institute, Institute for Engineering in Medicine, Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
- Molecular Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China
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8
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Abstract
Rab proteins are the major regulators of vesicular trafficking in eukaryotic cells. Their activity can be tightly controlled within cells: Regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), they switch between an active GTP-bound state and an inactive GDP-bound state, interacting with downstream effector proteins only in the active state. Additionally, they can bind to membranes via C-terminal prenylated cysteine residues and they can be solubilized and shuttled between membranes by chaperone-like molecules called GDP dissociation inhibitors (GDIs). In this review we give an overview of Rab proteins with a focus on the current understanding of their regulation by GEFs, GAPs and GDI.
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Affiliation(s)
- Matthias P Müller
- a Department of Structural Biochemistry , Max Planck Institute of Molecular Physiology , Dortmund , Germany
| | - Roger S Goody
- a Department of Structural Biochemistry , Max Planck Institute of Molecular Physiology , Dortmund , Germany
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9
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Song KH, Woo SR, Chung JY, Lee HJ, Oh SJ, Hong SO, Shim J, Kim YN, Rho SB, Hong SM, Cho H, Hibi M, Bae DJ, Kim SY, Kim MG, Kim TW, Bae YK. REP1 inhibits FOXO3-mediated apoptosis to promote cancer cell survival. Cell Death Dis 2017; 8:e2536. [PMID: 28055019 PMCID: PMC5386371 DOI: 10.1038/cddis.2016.462] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 11/29/2016] [Accepted: 12/07/2016] [Indexed: 01/15/2023]
Abstract
Rab escort protein 1 (REP1) is a component of Rab geranyl-geranyl transferase 2 complex. Mutations in REP1 cause a disease called choroideremia (CHM), which is an X-linked eye disease. Although it is postulated that REP1 has functions in cell survival or death of various tissues in addition to the eye, how REP1 functions in normal and cancer cells remains to be elucidated. Here, we demonstrated that REP1 is required for the survival of intestinal cells in addition to eyes or a variety of cells in zebrafish, and also has important roles in tumorigenesis. Notably, REP1 is highly expressed in colon cancer tissues and cell lines, and silencing of REP1 sensitizes colon cancer cells to serum starvation- and 5-FU-induced apoptosis. In an effort to elucidate the molecular mechanisms underlying REP1-mediated cell survival under those stress conditions, we identified FOXO3 as a binding partner of REP1 using a yeast two-hybrid (Y2H) assay system, and we demonstrated that REP1 blocked the nuclear trans-localization of FOXO3 through physically interacting with FOXO3, thereby suppressing FOXO3-mediated apoptosis. Importantly, the inhibition of REP1 combined with 5-FU treatment could lead to significant retarded tumor growth in a xenograft tumor model of human cancer cells. Thus, our results suggest that REP1 could be a new therapeutic target in combination treatment for colon cancer patients.
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Affiliation(s)
- Kwon-Ho Song
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, Republic of Korea
| | - Seon Rang Woo
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Translational Research Institute for Incurable Diseases, Korea University College of Medicine, Seoul, Republic of Korea
| | - Joon-Yong Chung
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Hyo-Jung Lee
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, Republic of Korea
| | - Se Jin Oh
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, Republic of Korea
| | - Soon-Oh Hong
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, Republic of Korea
| | - Jaegal Shim
- Comparative Biomedicine Research Branch, Research Institute, National Cancer Center, Goyang, Republic of Korea
| | - Yong Nyun Kim
- Comparative Biomedicine Research Branch, Research Institute, National Cancer Center, Goyang, Republic of Korea
| | - Seung Bae Rho
- Gynecologic Cancer Branch, Research Institute, National Cancer Center, Goyang, Republic of Korea
| | - Seung-Mo Hong
- Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Hanbyoul Cho
- Experimental Pathology Laboratory, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.,Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Masahiko Hibi
- Bioscience and Biotechnology Center, Nagoya University, Nagoya, Japan
| | - Dong-Jun Bae
- ASAN Institute for Life Sciences, ASAN Medical Center, Seoul, Republic of Korea
| | - Sang-Yeob Kim
- ASAN Institute for Life Sciences, ASAN Medical Center, Seoul, Republic of Korea.,Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Min Gyu Kim
- School of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Tae Woo Kim
- Laboratory of Tumor Immunology, Department of Biomedical Sciences, Graduate School of Medicine, Korea University, Seoul, Republic of Korea.,Department of Biochemistry, Korea University College of Medicine, Seoul, Republic of Korea.,Department of Biomedical Sciences, College of Medicine, Korea University, Seoul, Republic of Korea.,Translational Research Institute for Incurable Diseases, Korea University College of Medicine, Seoul, Republic of Korea
| | - Young-Ki Bae
- Comparative Biomedicine Research Branch, Research Institute, National Cancer Center, Goyang, Republic of Korea
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10
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Burgoyne T, O'Connor MN, Seabra MC, Cutler DF, Futter CE. Regulation of melanosome number, shape and movement in the zebrafish retinal pigment epithelium by OA1 and PMEL. J Cell Sci 2015; 128:1400-7. [PMID: 25690007 PMCID: PMC4379728 DOI: 10.1242/jcs.164400] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Analysis of melanosome biogenesis in the retinal pigment epithelium (RPE) is challenging because it occurs predominantly in a short embryonic time window. Here, we show that the zebrafish provides an ideal model system for studying this process because in the RPE the timing of melanosome biogenesis facilitates molecular manipulation using morpholinos. Morpholino-mediated knockdown of OA1 (also known as GPR143), mutations in the human homologue of which cause the most common form of human ocular albinism, induces a major reduction in melanosome number, recapitulating a key feature of the mammalian disease where reduced melanosome numbers precede macromelanosome formation. We further show that PMEL, a key component of mammalian melanosome biogenesis, is required for the generation of cylindrical melanosomes in zebrafish, which in turn is required for melanosome movement into the apical processes and maintenance of photoreceptor integrity. Spherical and cylindrical melanosomes containing similar melanin volumes co-exist in the cell body but only cylindrical melanosomes enter the apical processes. Taken together, our findings indicate that melanosome number and shape are independently regulated and that melanosome shape controls a function in the RPE that depends on localisation in the apical processes.
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Affiliation(s)
| | - Marie N O'Connor
- UCL Institute of Ophthalmology, London EC1V 9EL, UK MRC Laboratory for Molecular Cell Biology, University College, London WC1E 6BT, UK
| | | | - Daniel F Cutler
- MRC Laboratory for Molecular Cell Biology, University College, London WC1E 6BT, UK
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11
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Rab proteins: the key regulators of intracellular vesicle transport. Exp Cell Res 2014; 328:1-19. [PMID: 25088255 DOI: 10.1016/j.yexcr.2014.07.027] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 07/06/2014] [Accepted: 07/23/2014] [Indexed: 01/01/2023]
Abstract
Vesicular/membrane trafficking essentially regulates the compartmentalization and abundance of proteins within the cells and contributes in many signalling pathways. This membrane transport in eukaryotic cells is a complex process regulated by a large and diverse array of proteins. A large group of monomeric small GTPases; the Rabs are essential components of this membrane trafficking route. Most of the Rabs are ubiquitously expressed proteins and have been implicated in vesicle formation, vesicle motility/delivery along cytoskeleton elements and docking/fusion at target membranes through the recruitment of effectors. Functional impairments of Rabs affecting transport pathways manifest different diseases. Rab functions are accompanied by cyclical activation and inactivation of GTP-bound and GDP-bound forms between the cytosol and membranes which is regulated by upstream regulators. Rab proteins are characterized by their distinct sub-cellular localization and regulate a wide variety of endocytic, transcytic and exocytic transport pathways. Mutations of Rabs affect cell growth, motility and other biological processes.
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12
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Vasireddy V, Mills JA, Gaddameedi R, Basner-Tschakarjan E, Kohnke M, Black AD, Alexandrov K, Zhou S, Maguire AM, Chung DC, Mac H, Sullivan L, Gadue P, Bennicelli JL, French DL, Bennett J. AAV-mediated gene therapy for choroideremia: preclinical studies in personalized models. PLoS One 2013; 8:e61396. [PMID: 23667438 PMCID: PMC3646845 DOI: 10.1371/journal.pone.0061396] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/08/2013] [Indexed: 11/19/2022] Open
Abstract
Choroideremia (CHM) is an X- linked retinal degeneration that is symptomatic in the 1st or 2nd decade of life causing nyctalopia and loss of peripheral vision. The disease progresses through mid-life, when most patients become blind. CHM is a favorable target for gene augmentation therapy, as the disease is due to loss of function of a protein necessary for retinal cell health, Rab Escort Protein 1 (REP1).The CHM cDNA can be packaged in recombinant adeno-associated virus (rAAV), which has an established track record in human gene therapy studies, and, in addition, there are sensitive and quantitative assays to document REP1 activity. An animal model that accurately reflects the human condition is not available. In this study, we tested the ability to restore REP1 function in personalized in vitro models of CHM: lymphoblasts and induced pluripotent stems cells (iPSCs) from human patients. The initial step of evaluating safety of the treatment was carried out by evaluating for acute retinal histopathologic effects in normal-sighted mice and no obvious toxicity was identified. Delivery of the CHM cDNA to affected cells restores REP1 enzymatic activity and also restores proper protein trafficking. The gene transfer is efficient and the preliminary safety data are encouraging. These studies pave the way for a human clinical trial of gene therapy for CHM.
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Affiliation(s)
- Vidyullatha Vasireddy
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Jason A. Mills
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Rajashekhar Gaddameedi
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Etiena Basner-Tschakarjan
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Monika Kohnke
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia
| | - Aaron D. Black
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Krill Alexandrov
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia
| | - Shangzhen Zhou
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Albert M. Maguire
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Daniel C. Chung
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Helen Mac
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Lisa Sullivan
- Department of Anatomic Pathology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Paul Gadue
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Jeannette L. Bennicelli
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Deborah L. French
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- Department of Pathology and Laboratory Medicine, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Jean Bennett
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Seixas E, Barros M, Seabra MC, Barral DC. Rab and Arf proteins in genetic diseases. Traffic 2013; 14:871-85. [PMID: 23565987 DOI: 10.1111/tra.12072] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 04/03/2013] [Accepted: 04/08/2013] [Indexed: 01/29/2023]
Abstract
Rab and ADP-ribosylation factor (Arf) family proteins are master regulators of membrane trafficking and are involved in all steps of vesicular transport. These families of small guanine-nucleotide-binding (G) proteins are well suited to regulate membrane trafficking processes since their nucleotide state determines their conformation and the capacity to bind to a multitude of effectors, which mediate their functions. In recent years, several inherited diseases have been associated with mutations in genes encoding proteins belonging to these two families or in proteins that regulate their GTP-binding cycle. The genetic diseases that are caused by defects in Rabs, Arfs or their regulatory proteins are heterogeneous and display diverse symptoms. However, these diseases mainly affect two types of subcellular compartments, namely lysosome-related organelles and cilia. Also, several of these diseases affect the nervous system. Thus, the study of these diseases represents an opportunity to understand their etiology and the molecular mechanisms involved, as well as to develop novel therapeutic strategies.
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Affiliation(s)
- Elsa Seixas
- CEDOC, Faculdade de Ciências Médicas, FCM, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
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14
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Boye SE, Boye SL, Lewin AS, Hauswirth WW. A comprehensive review of retinal gene therapy. Mol Ther 2013; 21:509-19. [PMID: 23358189 DOI: 10.1038/mt.2012.280] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Blindness, although not life threatening, is a debilitating disorder for which few, if any treatments exist. Ocular gene therapies have the potential to profoundly improve the quality of life in patients with inherited retinal disease. As such, tremendous focus has been given to develop such therapies. Several factors make the eye an ideal organ for gene-replacement therapy including its accessibility, immune privilege, small size, compartmentalization, and the existence of a contralateral control. This review will provide a comprehensive summary of (i) existing gene therapy clinical trials for several genetic forms of blindness and (ii) preclinical efficacy and safety studies in a variety of animal models of retinal disease which demonstrate strong potential for clinical application. To be as comprehensive as possible, we include additional proof of concept studies using gene replacement, neurotrophic/neuroprotective, optogenetic, antiangiogenic, or antioxidative stress strategies as well as a description of the current challenges and future directions in the ocular gene therapy field to this review as a supplement.
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Affiliation(s)
- Shannon E Boye
- Department of Ophthalmology, University of Florida, Gainesville, FL, USA.
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15
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Khan AR. Oligomerization of rab/effector complexes in the regulation of vesicle trafficking. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 117:579-614. [PMID: 23663983 DOI: 10.1016/b978-0-12-386931-9.00021-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rabs comprise the largest member of the Ras superfamily of small GTPases with over 60 proteins in mammals and 11 proteins in yeast. Like all small GTPases, Rabs oscillate between an inactive GDP-bound conformation and an active GTP-bound state that is tethered to lipid membranes via a C-terminal prenylation site on conserved cysteine residues. In their active state, Rabs regulate various aspects of membrane trafficking, including vesicle formation, transport, docking, and fusion. The critical element of biological activity is the recruitment of cytosolic effector proteins to specific endomembranes by active Rabs. The importance of Rabs in cellular processes is apparent from their links to genetic disorders, immunodeficiency, cancer, and pathogen invasion. During the last decade, numerous structures of complexes have shed light on the molecular basis for Rab/effector specificity and their topological organization on subcellular membranes. Here, I review the known structures of Rab/effector complexes and their modes of oligomerization. This is followed by a brief discussion on the thermodynamics of effector recruitment, which has not been documented sufficiently in previous reviews. A summary of diseases associated with Rab/effector trafficking pathways concludes this chapter.
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Affiliation(s)
- Amir R Khan
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
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16
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Gogolin L, Schroeder H, Itzen A, Goody RS, Niemeyer CM, Becker CFW. Protein-DNA arrays as tools for detection of protein-protein interactions by mass spectrometry. Chembiochem 2012. [PMID: 23208955 DOI: 10.1002/cbic.201200597] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Analysis of multiple protein-protein interactions using microarray technology remains challenging, and site-specific immobilization of functional proteins is a key step in these approaches. Here we establish the efficient synthesis of protein-DNA conjugates for several members of a small family of GTPases. The family of Rab/Ypt GTPases is intimately involved in vesicular trafficking in yeast and serves as a model for the much larger group of analogous human proteins, the Rab protein family, with more than 60 members. The Ypt-DNA hybrid molecules described here are used for DNA-directed immobilization on glass- and silica-based microarrays. Methods for the detection of protein-DNA conjugates, as well as approaches for nucleotide exchange and distinguishing between GDP- and GTP-bound Ypts on microarrays, are reported. The high specificity of different Rab/Ypt-effector interactions, which also depends on the bound nucleotide, is shown by fluorescence readout of microarrays. Furthermore, initial experiments demonstrate that direct readout by mass spectrometry can be achieved with commercially available instruments. These developments will significantly contribute to the elucidation of complex transport networks in eukaryotic cells.
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Affiliation(s)
- Lars Gogolin
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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17
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Gutkowska M, Swiezewska E. Structure, regulation and cellular functions of Rab geranylgeranyl transferase and its cellular partner Rab Escort Protein. Mol Membr Biol 2012; 29:243-56. [DOI: 10.3109/09687688.2012.693211] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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18
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Abstract
PURPOSE : To determine the value of a topical carbonic anhydrase inhibitor on the macular thickness and function in choroideremia patients with cystoid macular edema. METHODS : Two choroideremia patients with cystoid macular edema, observed by spectral-domain optical coherence tomography, were treated with a topical form of carbonic anhydrase inhibitor. Examinations performed before and during treatment included best-corrected visual acuity by using the Early Treatment Diabetic Retinopathy Study charts and contrast sensitivity measured with briefly presented grating targets and the Pelli-Robson letter contrast sensitivity chart, microperimetry, and spectral-domain optical coherence tomography. RESULTS : The 2 choroideremia patients treated with dorzolamide 2% formulation had a noticeable reduction in macular thickness by spectral-domain optical coherence tomography. This reduction was found in both eyes after 2 months of treatment. After an additional 3 months of the same treatment regimen, a more noticeable reduction in macular thickness was observed. The two study patients had improvement of their visual acuity, in at least one eye, on Early Treatment Diabetic Retinopathy Study charts, but no clinically significant changes for the other measures of visual function. CONCLUSION : The present study shows the potential efficacy of topical dorzolamide for treating choroideremia patients with cystoid macular edema.
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Aguilar B, Amissah F, Duverna R, Lamango NS. Polyisoprenylation potentiates the inhibition of polyisoprenylated methylated protein methyl esterase and the cell degenerative effects of sulfonyl fluorides. Curr Cancer Drug Targets 2011; 11:752-62. [PMID: 21599633 DOI: 10.2174/156800911796191015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 04/15/2011] [Indexed: 11/22/2022]
Abstract
The polyisoprenylation pathway incorporates a reversible step that metabolizes polyisoprenylated methylated proteins from the ester to the carboxylate form. Polyisoprenylated protein methyl transferase (PPMTase) catalyses the esterification whereas polyisoprenylated methylated protein methyl esterase (PMPMEase) hydrolyzes them. Significant changes in the balance between the two enzymes may alter polyisoprenylated protein function possibly resulting in disease. Previous studies show that PMPMEase is the serine hydrolase, Sus scrofa carboxylesterase. Its susceptibility to the nonspecific serine hydrolase inhibitor, phenylmethylsulfonyl fluoride (PMSF) paved the way for its use as a prototypical compound to design and synthesize a series of putative high affinity specific inhibitors of PMPMEase. Pseudo first-order kinetics revealed an over 680-fold increase in k(obs)/[I] values from PMSF (6 M(-1)-1s(-1)), S-phenyl (L-50, 180 M(-1)s(-1)), S-benzyl (L-51, 350 M(-1)s(-1)), S-trans, trans-farnesyl (L-28, 2000 M(-1)s(-1)), to S-trans-geranylated (L-23, 4100 M(-1)s(-1)) 2-thioethanesulfonyl fluorides. C10 S-alkyl substitution revealed a k(obs)/[I] value (1800 M(-1)s(-1)) that was 298 times greater than that for PMSF. The compounds induced the degeneration of human neuroblastoma SH-SY5Y cells with EC(50) values of 49, 130 and >1000 µM for L-28, L-23 and PMSF, respectively. The increased affinity with the polyisoprenyl derivatization is consistent with the observed substrate specificity and the reported hydrophobic nature of the active site. These results suggest that (1) PMPMEase is a key enzyme for polyisoprenylated protein metabolism, (2) regulation of its activity is essential for maintaining normal cell viability, (3) abnormal activities may be involved in degenerative diseases and cancers and (4) its specific inhibitors may be useful in combating cancers.
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Affiliation(s)
- Byron Aguilar
- College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida 32307, USA
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20
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Agola JO, Jim PA, Ward HH, Basuray S, Wandinger-Ness A. Rab GTPases as regulators of endocytosis, targets of disease and therapeutic opportunities. Clin Genet 2011; 80:305-18. [PMID: 21651512 PMCID: PMC3187864 DOI: 10.1111/j.1399-0004.2011.01724.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Rab GTPases are well-recognized targets in human disease, although are underexplored therapeutically. Elucidation of how mutant or dysregulated Rab GTPases and accessory proteins contribute to organ specific and systemic disease remains an area of intensive study and an essential foundation for effective drug targeting. Mutation of Rab GTPases or associated regulatory proteins causes numerous human genetic diseases. Cancer, neurodegeneration and diabetes represent examples of acquired human diseases resulting from the up- or downregulation or aberrant function of Rab GTPases. The broad range of physiologic processes and organ systems affected by altered Rab GTPase activity is based on pivotal roles in responding to cell signaling and metabolic demand through the coordinated regulation of membrane trafficking. The Rab-regulated processes of cargo sorting, cytoskeletal translocation of vesicles and appropriate fusion with the target membranes control cell metabolism, viability, growth and differentiation. In this review, we focus on Rab GTPase roles in endocytosis to illustrate normal function and the consequences of dysregulation resulting in human disease. Selected examples are designed to illustrate how defects in Rab GTPase cascades alter endocytic trafficking that underlie neurologic, lipid storage, and metabolic bone disorders as well as cancer. Perspectives on potential therapeutic modulation of GTPase activity through small molecule interventions are provided.
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Affiliation(s)
- J O Agola
- Department of Pathology Cancer Center, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
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21
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Vázquez-Martínez R, Malagón MM. Rab proteins and the secretory pathway: the case of rab18 in neuroendocrine cells. Front Endocrinol (Lausanne) 2011; 2:1. [PMID: 22649356 PMCID: PMC3355916 DOI: 10.3389/fendo.2011.00001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 01/03/2011] [Indexed: 11/21/2022] Open
Abstract
The secretory pathway is a process characteristic of cells specialized in secretion such as endocrine cells and neurons. It consists of different stages that are dependent on specific transport of proteins in vesicular-tubular carriers. Biochemical analyses have unveiled a number of protein families that confer identity to carrier vesicles and specificity to their transport. Among them is the family of Rab proteins, Ras-like small GTPases that anchor to the surface of transport vesicles and participate in vesicle formation from the donor compartment, transport along cytoskeletal tracks, and docking and fusion with the acceptor compartment. All of these functions are accomplished through the recruitment of effector proteins, such as sorting adaptors, tethering factors, kinases, phosphatases, and motors. The numerous Rab proteins have distinct subcellular distributions throughout the endomembrane system, which ensures efficient cargo transfer. Rab proteins act as molecular switches that alternate between a cytosolic GDP-bound, inactive form and a membrane-associated GTP-bound, active conformation. Cycling between inactive and active states is a highly regulated process that enables Rabs to confer spatio-temporal precision to the different stages through which a vesicle passes during its lifespan. This review focuses on our current knowledge on Rab functioning, from their structural features to the multiple regulatory proteins and effectors that control Rab activity and translate Rab function. Furthermore, we also summarize the information available on a particular Rab protein, Rab18, which has been linked to the control of secretory granule traffic in neuroendocrine cells.
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Affiliation(s)
- Rafael Vázquez-Martínez
- Department of Cell Biology, Physiology and Immunology, University of CordobaCordoba, Spain
- Instituto Maimónides de Investigación Biomédica, Biomedical Research Center in Red Physiopathology of Obesity and NutritionCordoba, Spain
| | - Maria M. Malagón
- Department of Cell Biology, Physiology and Immunology, University of CordobaCordoba, Spain
- Instituto Maimónides de Investigación Biomédica, Biomedical Research Center in Red Physiopathology of Obesity and NutritionCordoba, Spain
- *Correspondence: Maria M. Malagón, Department of Cell Biology, Physiology and Immunology, Universidad de Córdoba, Campus de Rabanales, Edificio Severo-Ochoa, Planta 3, E-14014 Córdoba, Spain. e-mail:
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22
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Heal WP, Tate EW. Getting a chemical handle on proteinpost-translational modification. Org Biomol Chem 2010; 8:731-8. [DOI: 10.1039/b917894e] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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23
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Rudolph G, Preising M, Kalpadakis P, Haritoglou C, Lang GE, Lorenz B. Phenotypic variability in three carriers from a family with choroideremia and a frameshift mutation 1388delCCinsG in the REP-1 gene. Ophthalmic Genet 2009; 24:203-14. [PMID: 14566650 DOI: 10.1076/opge.24.4.203.17232] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
PURPOSE To perform genotype-phenotype correlations in a family with choroideremia. METHODS A three-generation family with two affected males and five carriers was the subject of the study. Molecular genetic analysis using single-strand conformation polymorphism analysis (SSCP) was conducted in all subjects, while electroretinography (ERG), multifocal ERG (mfERG), scanning laser ophthalmoscope microperimetry (SLO perimetry), fluorescein angiography, and Arden contrast color testing were performed in one male and three carriers. RESULTS The findings in the affected male were typical for advanced choroideremia. The three carriers demonstrated a variable clinical phenotype including reduction of visual acuity and ERG and angiographic changes in one. Molecular genetic analysis revealed a functional null mutation (1388delCCinsG) in the REP-1 gene. CONCLUSIONS A severe retinal pathology was found in the affected male, indicating that the 1388delCCinsG is a severe mutation. Varying phenotypes were present in the three carriers examined. The phenotype in carriers has been explained by random X-inactivation with varying expression of the inactivated and activated gene copy inside the same cell of both the retinal pigment epithelium and the rods. This thesis is in agreement with the clinical data obtained here.
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Affiliation(s)
- Günther Rudolph
- Kooperationsgruppe Ophthalmogenetik der LMU und GSF University Eye Hospital, LMU, München, Germany.
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24
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Preising MN, Wegscheider E, Friedburg C, Poloschek CM, Wabbels BK, Lorenz B. Fundus Autofluorescence in Carriers of Choroideremia and Correlation with Electrophysiologic and Psychophysical Data. Ophthalmology 2009; 116:1201-9.e1-2. [DOI: 10.1016/j.ophtha.2009.01.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 12/12/2008] [Accepted: 01/15/2009] [Indexed: 10/20/2022] Open
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Tanaka D, Kameyama K, Okamoto H, Doi M. Caenorhabditis elegans Rab escort protein (REP-1) differently regulates each Rab protein function and localization in a tissue-dependent manner. Genes Cells 2009; 13:1141-57. [PMID: 19090809 DOI: 10.1111/j.1365-2443.2008.01232.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rab proteins play a critical role in intracellular vesicle trafficking and require post-translational modification by adding lipids at the C-terminus for proper functions. This modification is preceded by the formation of a trimeric protein complex with the Rab escort protein (REP) and the Rab geranylgeranyltransferase (RabGGTase). However, the genetic hierarchy among these proteins and the tissue-specificity of each protein function are not yet clearly understood. Here we identified the Caenorhabditis elegans rep-1 gene and found that a rep-1 mutant showed a mild defect in synaptic transmission and defecation behaviors. Genetic analyses using the exocytic Rab mutants rab-3 or rab-27 suggested that rep-1 functions only in the RAB-27 pathway, and not in the RAB-3 pathway, for synaptic transmission at neuromuscular junctions. However, the disruption of REP-1 did not cause defecation defects compared to severe defects in either RAB-27 or RabGGTase disruption, suggesting that REP-1 is not essential for RAB-27 signaling in defection. Some Rab proteins did not physically interact with REP-1, and localization of these Rab proteins was not severely affected by REP-1 disruption. These findings suggest that REP-1 functions are required in specific Rab pathways and in specific tissues, and that some Rab proteins are functionally prenylated without REP-1.
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Affiliation(s)
- Daisuke Tanaka
- Neuroscience Research Institute, AIST, Tsukuba, Ibaraki 305-8566, Japan
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26
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Grover S, Fishman GA. Choroidal Dystrophies. Ophthalmology 2009. [DOI: 10.1016/b978-0-323-04332-8.00085-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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27
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Krock BL, Bilotta J, Perkins BD. Noncell-autonomous photoreceptor degeneration in a zebrafish model of choroideremia. Proc Natl Acad Sci U S A 2007; 104:4600-5. [PMID: 17360570 PMCID: PMC1810335 DOI: 10.1073/pnas.0605818104] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Choroideremia is an X-linked hereditary retinal degeneration resulting from mutations in the Rab escort protein-1 (REP1). The Rep1 protein facilitates posttranslational modification of Rab proteins, which regulate intracellular trafficking in the retinal pigment epithelium (RPE) and photoreceptors and are likely involved in the removal of outer segment disk membranes by the RPE. A critical question for potential treatment of choroideremia is whether photoreceptor degeneration results from autonomous defects in opsin transport within the photoreceptor or as a nonautonomous and secondary consequence of RPE degeneration. To address this question, we have characterized the retinal pathology in zebrafish rep1 mutants, which carry a recessive nonsense mutation in the REP1 gene. Zebrafish rep1 mutants exhibit degeneration of the RPE and photoreceptors and complete loss of visual function as measured by electroretinograms. In the mutant RPE, photoreceptor outer segment material was not effectively eliminated, and large vacuoles were observed. However, opsin trafficking in photoreceptors occurred normally. Mosaic analysis revealed that photoreceptor degeneration was nonautonomous and required contact with the mutant RPE as mutant photoreceptors were rescued in wild-type hosts and wild-type photoreceptors degenerated in mutant hosts. We conclude that mutations in REP1 disrupt cellular processes in the RPE, which causes photoreceptor death as a secondary consequence. These results suggest that therapies that correct the RPE may successfully rescue photoreceptor loss in choroideremia.
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Affiliation(s)
- Bryan L. Krock
- *Department of Biology, Texas A & M University, College Station, TX 77843; and
| | - Joseph Bilotta
- Department of Psychology and Biotechnology Center, Western Kentucky University, Bowling Green, KY 42101
| | - Brian D. Perkins
- *Department of Biology, Texas A & M University, College Station, TX 77843; and
- To whom correspondence should be addressed. E-mail:
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Futter CE. The molecular regulation of organelle transport in mammalian retinal pigment epithelial cells. ACTA ACUST UNITED AC 2006; 19:104-11. [PMID: 16524426 DOI: 10.1111/j.1600-0749.2006.00303.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Retinal pigment epithelial cells contain large numbers of melanosomes that can enter the apical processes extending between the outer segments of the overlying photoreceptors. Every day the distal portion of the photoreceptor outer segment is shed and phagocytosed by the retinal pigment epithelial cell. The phagosome is then transported into the cell body and the contents degraded by lysosomal enzymes. This review focuses on recent progress made in the identification of molecules that regulate the transport of melanosomes into the apical processes and the transport of phagosomes into the cell body. Myosin VIIa is a key player in both processes and, at least in the case of melanosome movement, myosin VIIa is recruited to the melanosome via the GTPase, Rab27a. The possible role played by defects in the transport of melanosomes and phagosomes in the development of retinal degenerative diseases is discussed.
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Affiliation(s)
- Clare E Futter
- Division of Cell Biology, Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK.
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Leung KF, Baron R, Seabra MC. Thematic review series: Lipid Posttranslational Modifications. Geranylgeranylation of Rab GTPases. J Lipid Res 2006; 47:467-75. [PMID: 16401880 DOI: 10.1194/jlr.r500017-jlr200] [Citation(s) in RCA: 188] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Rab GTPases require special machinery for protein prenylation, which include Rab escort protein (REP) and Rab geranylgeranyl transferase (RGGT). The current model of Rab geranylgeranylation proposes that REP binds Rab and presents it to RGGT. After geranylgeranylation of Rab C-terminal cysteines, REP delivers the prenylated protein to membranes. The REP-like protein Rab GDP dissociation inhibitor (RabGDI) then recycles the prenylated Rab between the membrane and the cytosol. The recent solution of crystal structures of the Rab prenylation machinery has helped to refine this model and provided further insights. The hydrophobic prenyl binding pocket of RGGT and geranylgeranyl transferase type-I (GGT-I) differs from that of farnesyl transferase (FT). A bulky tryptophan residue in FT restricts the size of the pocket, whereas in RGGT and GGT-I, this position is occupied by smaller residues. A highly conserved phenylalanine in REP, which is absent in RabGDI, is critical for the formation of the REP:RGGT complex. Finally, a geranylgeranyl binding site conserved in REP and RabGDI has been identified within helical domain II. The postprenylation events, including the specific targeting of Rabs to target membranes and the requirement for single versus double geranylgeranylation by different Rabs, remain obscure and should be the subject of future studies.
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Affiliation(s)
- Ka Fai Leung
- Molecular and Cellular Medicine, Division of Biomedical Sciences, Imperial College London, London SW7 2AZ, UK
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30
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Tolmachova T, Anders R, Abrink M, Bugeon L, Dallman MJ, Futter CE, Ramalho JS, Tonagel F, Tanimoto N, Seeliger MW, Huxley C, Seabra MC. Independent degeneration of photoreceptors and retinal pigment epithelium in conditional knockout mouse models of choroideremia. J Clin Invest 2006; 116:386-94. [PMID: 16410831 PMCID: PMC1326146 DOI: 10.1172/jci26617] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Accepted: 11/01/2005] [Indexed: 01/09/2023] Open
Abstract
Choroideremia (CHM) is an X-linked degeneration of the retinal pigment epithelium (RPE), photoreceptors, and choroid, caused by loss of function of the CHM/REP1 gene. REP1 is involved in lipid modification (prenylation) of Rab GTPases, key regulators of intracellular vesicular transport and organelle dynamics. To study the pathogenesis of CHM and to develop a model for assessing gene therapy, we have created a conditional mouse knockout of the Chm gene. Heterozygous-null females exhibit characteristic hallmarks of CHM: progressive degeneration of the photoreceptors, patchy depigmentation of the RPE, and Rab prenylation defects. Using tamoxifen-inducible and tissue-specific Cre expression in combination with floxed Chm alleles, we show that CHM pathogenesis involves independently triggered degeneration of photoreceptors and the RPE, associated with different subsets of defective Rabs.
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Affiliation(s)
- Tanya Tolmachova
- Molecular and Cellular Medicine Section, Division of Biomedical Sciences, Imperial College London, London, United Kingdom
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31
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Rak A, Pylypenko O, Niculae A, Pyatkov K, Goody RS, Alexandrov K. Structure of the Rab7:REP-1 Complex. Cell 2004; 117:749-60. [PMID: 15186776 DOI: 10.1016/j.cell.2004.05.017] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Revised: 04/12/2004] [Accepted: 04/13/2004] [Indexed: 11/22/2022]
Abstract
Members of the RabGDI/REP family serve as multifunctional regulators of the Rab family of GTP binding proteins. Mutations in members of this family, such as REP-1, lead to abnormalities, including progressive retinal degradation (choroideremia) in humans. The crystal structures of the REP-1 protein in complex with monoprenylated or C-terminally truncated Rab7 proteins revealed that Rab7 interacts with the Rab binding platform of REP-1 via an extended interface involving the Switch 1 and 2 regions. The C terminus of the REP-1 molecule functions as a mobile lid covering a conserved hydrophobic patch on the surface of REP-1 that in the complex coordinates the C terminus of Rab proteins. Using semisynthetic fluorescent Rab27A, we demonstrate that although Rab27A can be prenylated by REP-2, this reaction can be effectively inhibited by other Rab proteins, providing a possible explanation for the accumulation of unprenylated Rab27A in choroideremia.
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Affiliation(s)
- Alexey Rak
- Max-Planck-Institute for Molecular Physiology, Otto-Hahn-Str. 11, 44227 Dortmund, Germany
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Futter CE, Ramalho JS, Jaissle GB, Seeliger MW, Seabra MC. The role of Rab27a in the regulation of melanosome distribution within retinal pigment epithelial cells. Mol Biol Cell 2004; 15:2264-75. [PMID: 14978221 PMCID: PMC404021 DOI: 10.1091/mbc.e03-10-0772] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Melanosomes within the retinal pigment epithelium (RPE) of mammals have long been thought to exhibit no movement in response to light, unlike fish and amphibian RPE. Here we show that the distribution of melanosomes within the mouse RPE undergoes modest but significant changes with the light cycle. Two hours after light onset, there is a threefold increase in the number of melanosomes in the apical processes that surround adjacent photoreceptors. In skin melanocytes, melanosomes are motile and evenly distributed throughout the cell periphery. This distribution is due to the interaction with the cortical actin cytoskeleton mediated by a tripartite complex of Rab27a, melanophilin, and myosin Va. In ashen (Rab27a null) mice RPE, melanosomes are unable to move beyond the adherens junction axis and do not enter apical processes, suggesting that Rab27a regulates melanosome distribution in the RPE. Unlike skin melanocytes, the effects of Rab27a are mediated through myosin VIIa in the RPE, as evidenced by the similar melanosome distribution phenotype observed in shaker-1 mice, defective in myosin VIIa. Rab27a and myosin VIIa are likely to be required for association with and movement through the apical actin cytoskeleton, which is a prerequisite for entry into the apical processes.
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Affiliation(s)
- Clare E Futter
- Division of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
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Larijani B, Hume AN, Tarafder AK, Seabra MC. Multiple factors contribute to inefficient prenylation of Rab27a in Rab prenylation diseases. J Biol Chem 2003; 278:46798-804. [PMID: 12941939 DOI: 10.1074/jbc.m307799200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Post-translational geranylgeranylation of Rab GT-Pases is essential for their membrane association and function as regulators of intracellular vesicular transport. The reaction is catalyzed by Rab geranylgeranyltransferase (RGGT) and is assisted by the Rab escort proteins (REP), which form stable complexes with newly synthesized GDP-bound Rabs. Two genetic diseases involve the Rab geranylgeranylation machinery: choroideremia, an X-linked retinal degeneration resulting from loss-of-function mutations in REP1, and gunmetal, a mouse model of Hermansky-Pudlak syndrome resulting from mutations in the alpha-subunit of RGGT. A small subset of Rab proteins is selectively under-prenylated in both diseases, most notably Rab27a. Here we analyze why Rab27a is selectively affected in diseases of Rab geranylgeranylation. Semi-quantitative immunoblotting suggests that mass action, i.e. the amount of Rab27a relative to other Rabs, is unlikely to be a factor as the expression level of Rab27a is similar to other Rabs not affected in these diseases. In vitro binding assays and fluorescence resonance energy transfer detected by fluorescence lifetime imaging microscopy in intact cells demonstrate that Rab27a binds equally well to both REP1 and REP2, suggesting differential affinity of Rab27a for REP isoforms is not an important factor. However, steady-state kinetic analysis of the geranylgeranylation reaction indicates that REP2-Rab27a has lower affinity for RGGT compared with REP1-Rab27a. Furthermore, we show that Rab27a has relatively low GTPase activity, presumably decreasing the affinity of the REP interaction in vivo. We suggest that the restricted phenotypes observed in these diseases result from multiple contributing factors.
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Affiliation(s)
- Banafshé Larijani
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College London, London SW7 2AZ, U.K
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Anand V, Barral DC, Zeng Y, Brunsmann F, Maguire AM, Seabra MC, Bennett J. Gene therapy for choroideremia: in vitro rescue mediated by recombinant adenovirus. Vision Res 2003; 43:919-26. [PMID: 12668061 DOI: 10.1016/s0042-6989(02)00389-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Choroideremia (CHM) is an X-linked retinal degenerative disease resulting from a lack of functional Rab Escort Protein-1 (REP-1). As a first step in developing gene-based therapies for this disease, we evaluated the feasibility of delivering functional REP-1 to defective lymphocytes and fibroblasts isolated from individuals with CHM. A recombinant adenovirus delivering the full-length human cDNA encoding REP-1 under the control of a cytomegalovirus promoter was generated. Adenovirus-mediated delivery of REP-1 rescued the defective cells as assessed through protein and enzymatic assays. Ultimately, it may be possible to use virus-mediated delivery of REP-1 to evaluate disease intervention in vivo.
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Affiliation(s)
- Vibha Anand
- Department of Ophthalmology, F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6069, USA.
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35
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Pereira-Leal JB, Strom M, Godfrey RF, Seabra MC. Structural determinants of Rab and Rab Escort Protein interaction: Rab family motifs define a conserved binding surface. Biochem Biophys Res Commun 2003; 301:92-7. [PMID: 12535645 DOI: 10.1016/s0006-291x(02)02963-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Rab proteins are a large family of monomeric GTPases with 60 members identified in the human genome. Rab GTPases require an isoprenyl modification to their C-terminus for membrane association and function in the regulation of vesicular trafficking pathways. This reaction is catalysed by Rab geranylgeranyl transferase, which recognises as protein substrate any given Rab in a 1:1 complex with Rab Escort Protein (REP). REP is therefore able to bind many distinct Rab proteins but the molecular basis for this activity is still unclear. We recently identified conserved motifs in Rabs termed RabF motifs, which we proposed to mediate a conserved mode of interaction between Rabs and REPs. Here, we tested this hypothesis. We first used REP1 as a bait in the yeast two-hybrid system and isolated strictly full-length Rabs, suggesting that REP recognises multiple regions within and properly folded Rabs. We introduced point mutations in Rab3a as a model Rab and assessed the ability of the mutants to interact with REP using the yeast two-hybrid system and an in vitro prenylation assay. We identified several residues that affect REP:Rab binding in the RabF1, RabF3, and RabF4 regions (which include parts of the switch I and II regions), but not other RabF regions. These results support the hypothesis that Rabs bind REP via conserved RabF motifs and provide a molecular explanation for the preferential recognition of the GDP-bound conformation of Rab by REP.
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Affiliation(s)
- José B Pereira-Leal
- Cell and Molecular Biology Section, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, UK
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36
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Abstract
SUMMARY Three different protein prenyltransferases (farnesyltransferase and geranylgeranyltransferases I and II) catalyze the attachment of prenyl lipid anchors 15 or 20 carbons long to the carboxyl termini of a variety of eukaryotic proteins. Farnesyltransferase and geranylgeranyltransferase I both recognize a 'Ca1a2X' motif on their protein substrates; geranylgeranyltransferase II recognizes a different, non-CaaX motif. Each enzyme has two subunits. The genes encoding CaaX protein prenyltransferases are considerably longer than those encoding non-CaaX subunits, as a result of longer introns. Alternative splice forms are predicted to occur, but the extent to which each splice form is translated and the functions of the different resulting isoforms remain to be established. Farnesyltransferase-inhibitor drugs have been developed as anti-cancer agents and may also be able to treat several other diseases. The effects of these inhibitors are complicated, however, by the overlapping substrate specificities of geranylgeranyltransferase I and farnesyltransferase.
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37
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Ramalho JS, Anders R, Jaissle GB, Seeliger MW, Huxley C, Seabra MC. Rapid degradation of dominant-negative Rab27 proteins in vivo precludes their use in transgenic mouse models. BMC Cell Biol 2002; 3:26. [PMID: 12401133 PMCID: PMC137576 DOI: 10.1186/1471-2121-3-26] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2002] [Accepted: 10/28/2002] [Indexed: 02/27/2023] Open
Abstract
BACKGROUND Transgenic mice have proven to be a powerful system to study normal and pathological gene functions. Here we describe an attempt to generate a transgenic mouse model for choroideremia (CHM), a slow-onset X-linked retinal degeneration caused by mutations in the Rab Escort Protein-1 (REP1) gene. REP1 is part of the Rab geranylgeranylation machinery, a modification that is essential for Rab function in membrane traffic. The loss of REP1 in CHM patients may trigger retinal degeneration through its effects on Rab proteins. We have previously reported that Rab27a is the Rab most affected in CHM lymphoblasts and hypothesised that the selective dysfunction of Rab27a (and possibly a few other Rab GTPases) plays an essential role in the retinal degenerative process. RESULTS To investigate this hypothesis, we generated several lines of dominant-negative, constitutively-active and wild-type Rab27a (and Rab27b) transgenic mice whose expression was driven either by the pigment cell-specific tyrosinase promoter or the ubiquitous beta-actin promoter. High levels of mRNA and protein were observed in transgenic lines expressing wild-type or constitutively active Rab27a and Rab27b. However, only modest levels of transgenic protein were expressed. Pulse-chase experiments suggest that the dominant-negative proteins, but not the constitutively-active or wild type proteins, are rapidly degraded. Consistently, no significant phenotype was observed in our transgenic lines. Coat-colour was normal, indicating normal Rab27a activity. Retinal function as determined by fundoscopy, angiography, electroretinography and histology was also normal. CONCLUSIONS We suggest that the instability of the dominant-negative mutant Rab27 proteins in vivo precludes the use of this approach to generate mouse models of disease caused by Rab27 GTPases.
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MESH Headings
- Animals
- COS Cells
- Cell Line
- Chlorocebus aethiops
- Choroideremia/genetics
- Choroideremia/metabolism
- Crosses, Genetic
- Disease Models, Animal
- Female
- Gene Expression Regulation/genetics
- Genes, Dominant/genetics
- Genetic Vectors/biosynthesis
- Genetic Vectors/genetics
- Hair Color/genetics
- Hair Color/physiology
- Immunoblotting
- Mice
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Mice, Transgenic
- Mutation/genetics
- Phenotype
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Retina/physiopathology
- Vision, Ocular/genetics
- Vision, Ocular/physiology
- rab GTP-Binding Proteins/biosynthesis
- rab GTP-Binding Proteins/genetics
- rab GTP-Binding Proteins/immunology
- rab GTP-Binding Proteins/metabolism
- rab27 GTP-Binding Proteins
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Affiliation(s)
- José S Ramalho
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Sir Alexander Fleming Building, Exhibition Road, London, SW7 2AZ, UK
| | - Ross Anders
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Sir Alexander Fleming Building, Exhibition Road, London, SW7 2AZ, UK
| | - Gesine B Jaissle
- Department of Pathophysiology of Vision and Neuropthalmology, University Eye Hospital, Tübingen, Germany
| | - Mathias W Seeliger
- Department of Pathophysiology of Vision and Neuropthalmology, University Eye Hospital, Tübingen, Germany
| | - Clare Huxley
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Sir Alexander Fleming Building, Exhibition Road, London, SW7 2AZ, UK
| | - Miguel C Seabra
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Sir Alexander Fleming Building, Exhibition Road, London, SW7 2AZ, UK
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38
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Abstract
The cliché 'a picture is worth a thousand words' is a testament to the power of the visual system in helping us deal with our physical environment. Rarely do perturbations to the visual system, even minor ones, go unnoticed. Major defects in eye development may occur in the absence of systemic problems which threaten health. Ocular anomalies offer a window into many developmental events which would otherwise be difficult to study.
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Affiliation(s)
- R A Saleem
- Department of Medical Genetics, University of Alberta, Edmonton, Canada
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39
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Abstract
Membrane and protein traffic in the secretory and endocytic pathways is mediated by vesicular transport. Recent studies of certain key regulators of vesicular transport, the Rab GTPases, have linked Rab dysfunction to human disease. Mutations in Rab27a result in Griscelli syndrome, caused by defects in melanosome transport in melanocytes and loss of cytotoxic killing activity in Tcells. Other genetic diseases are caused by partial dysfunction of multiple Rab proteins resulting from mutations in general regulators of Rab activity; Rab escort protein-1 (choroideremia), Rab geranylgeranyl transferase (Hermansky-Pudlak syndrome) and Rab GDP dissociation inhibitor-alpha (X-linked mental retardation). In infectious diseases caused by intracellular microorganisms, the function of endocytic Rabs is altered either as part of host defences or as part of survival strategy of the pathogen. The human genome is predicted to contain 60 RAB genes, suggesting that future work could reveal further links between Rab dysfunction and disease.
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Affiliation(s)
- Miguel C Seabra
- Cell and Molecular Biology, Division of Biomedical Sciences, Faculty of Medicine, Imperial College, Exhibition Road, London, UK SW7 2AZ.
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40
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Coxon FP, Helfrich MH, Larijani B, Muzylak M, Dunford JE, Marshall D, McKinnon AD, Nesbitt SA, Horton MA, Seabra MC, Ebetino FH, Rogers MJ. Identification of a novel phosphonocarboxylate inhibitor of Rab geranylgeranyl transferase that specifically prevents Rab prenylation in osteoclasts and macrophages. J Biol Chem 2001; 276:48213-22. [PMID: 11581260 DOI: 10.1074/jbc.m106473200] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitrogen-containing bisphosphonate drugs inhibit bone resorption by inhibiting FPP synthase and thereby preventing the synthesis of isoprenoid lipids required for protein prenylation in bone-resorbing osteoclasts. NE10790 is a phosphonocarboxylate analogue of the potent bisphosphonate risedronate and is a weak anti-resorptive agent. Although NE10790 was a poor inhibitor of FPP synthase, it did inhibit prenylation in J774 macrophages and osteoclasts, but only of proteins of molecular mass approximately 22-26 kDa, the prenylation of which was not affected by peptidomimetic inhibitors of either farnesyl transferase (FTI-277) or geranylgeranyl transferase I (GGTI-298). These 22-26-kDa proteins were shown to be geranylgeranylated by labelling J774 cells with [(3)H]geranylgeraniol. Furthermore, NE10790 inhibited incorporation of [(14)C]mevalonic acid into Rab6, but not into H-Ras or Rap1, proteins that are modified by FTase and GGTase I, respectively. These data demonstrate that NE10790 selectively prevents Rab prenylation in intact cells. In accord, NE10790 inhibited the activity of recombinant Rab GGTase in vitro, but did not affect the activity of recombinant FTase or GGTase I. NE10790 therefore appears to be the first specific inhibitor of Rab GGTase to be identified. In contrast to risedronate, NE10790 inhibited bone resorption in vitro without markedly affecting osteoclast number or the F-actin "ring" structure in polarized osteoclasts. However, NE10790 did alter osteoclast morphology, causing the formation of large intracellular vacuoles and protrusion of the basolateral membrane into large, "domed" structures that lacked microvilli. The anti-resorptive activity of NE10790 is thus likely due to disruption of Rab-dependent intracellular membrane trafficking in osteoclasts.
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Affiliation(s)
- F P Coxon
- Department of Medicine and Therapeutics, Medical Microbiology, and Pathology, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom.
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41
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Pereira-Leal JB, Hume AN, Seabra MC. Prenylation of Rab GTPases: molecular mechanisms and involvement in genetic disease. FEBS Lett 2001; 498:197-200. [PMID: 11412856 DOI: 10.1016/s0014-5793(01)02483-8] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Small GTPases of the Rab family regulate membrane transport pathways. More than 50 mammalian Rab proteins are known, many with transport step-specific localisation. Rabs must associate with cellular membranes for activity and membrane attachment is mediated by prenyl (geranylgeranyl) post-translational modification. Mutations in genes encoding proteins essential for the geranylgeranylation reaction, Rab escort protein and Rab geranylgeranyl transferase, underlie genetic diseases. Choroideremia patients have loss of function mutations in REP1 and the murine Hermansky-Pudlak syndrome model gunmetal possesses a splice-site mutation in the alpha-subunit of RGGT. Here we discuss recent insights into Rab prenylation and advances towards our understanding of both diseases.
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Affiliation(s)
- J B Pereira-Leal
- Cell and Molecular Biology Section, Division of Biomedical Sciences, Imperial College School of Medicine, Sir Alexander Fleming Building, Exhibition Road, SW7 2AZ, London, UK
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42
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Syed N, Smith JE, John SK, Seabra MC, Aguirre GD, Milam AH. Evaluation of retinal photoreceptors and pigment epithelium in a female carrier of choroideremia. Ophthalmology 2001; 108:711-20. [PMID: 11297488 DOI: 10.1016/s0161-6420(00)00643-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
PURPOSE To clarify the pathogenesis of choroideremia. STUDY DESIGN Human tissue study. TISSUES: Eyes of an 88-year-old symptomatic female carrier of choroideremia (CHM) and six normal, age-matched donors. METHODS The eyes were processed for histopathologic examination, including immunocytochemistry with an antibody against the CHM gene product, REP-1, and retinal cell-specific markers. RESULTS The CHM carrier retina showed patchy degeneration, but the photoreceptor and retinal pigment epithelium (RPE) loss appeared to be independent. The choriocapillaris was normal except where retinal areas were severely degenerate. The CHM gene product, REP-1, was localized to the cytoplasm of rods but not cones. CONCLUSIONS It has generally been considered that photoreceptor degeneration in CHM is secondary to loss of the choriocapillaris or RPE. This study suggests that the rod photoreceptors are a primary site of disease in CHM.
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Affiliation(s)
- N Syed
- Scheie Eye Institute, University of Pennsylvania, 51 North 39th Street, Philadelphia, PA 19104, USA
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Caillol N, Pasqualini E, Lloubes R, Lombardo D. Impairment of bile salt-dependent lipase secretion in human pancreatic tumoral SOJ-6 cells. J Cell Biochem 2000; 79:628-47. [PMID: 10996854 DOI: 10.1002/1097-4644(20001215)79:4<628::aid-jcb120>3.0.co;2-t] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bile salt-dependent lipase (BSDL) was detected in human SOJ-6 and rat AR4-2J pancreatic cells. Whereas AR4-2J cells actively secreted the enzyme, BSDL was retained within the Golgi compartment of SOJ-6 cells. Because Rab6 is involved in vesicle transport in the Golgi apparatus and the trans-Golgi network, we confirmed the presence of Rab6 in these cells. In rat AR4-2J cells, Rab6 as well as Rab1A/B and Rab2, partitioned between the cytosol and microsomes. In SOJ-6 cells Rab1A/B and Rab2 also partitioned between the cytosol and microsomes, but Rab6 was strictly associated with microsome membranes, suggesting a specific defect of Rab6 cycling in human SOJ-6 cells. The apparent defect of cycling in these cells is not due to the expression of a defective Rab6 since its correct sequence was confirmed. We further demonstrated that AR4-2J and SOJ-6 cells express the Rab-GDIbeta and Rab-GDIalpha isoforms, respectively. However, the sequence of Rab-GDIbeta, which may be the main form expressed by SOJ-6 cells, identified a few substitutions located in regions that are essential for Rab-GDI function. We conclude that the deficient secretion of BSDL by SOJ-6 cells could be due to the expression of defective Rab-GDIbeta. In spite of the alterations in Rab-GDIbeta, membrane proteins such as CD71 and NHE3 were correctly localized to the cell plasma membrane of SOJ-6 cells, suggesting that two functional distinct secretory pathway coexist in pancreatic cells.
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Affiliation(s)
- N Caillol
- INSERM Unité 260-Faculté de Médecine-Timone, 27 bld Jean Moulin, 13385 Marseille cedex 05 France
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45
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Abstract
BACKGROUND Rab geranylgeranyltransferase (RabGGT) catalyzes the addition of two geranylgeranyl groups to the C-terminal cysteine residues of Rab proteins, which is crucial for membrane association and function of these proteins in intracellular vesicular trafficking. Unlike protein farnesyltransferase (FT) and type I geranylgeranyltransferase, which both prenylate monomeric small G proteins or short peptides, RabGGT can prenylate Rab only when Rab is in a complex with Rab escort protein (REP). RESULTS The crystal structure of rat RabGGT at 2.0 A resolution reveals an assembly of four distinct structural modules. The beta subunit forms an alpha-alpha barrel that contains most of the residues in the active site. The alpha subunit consists of a helical domain, an immunoglobulin (Ig)-like domain, and a leucine-rich repeat (LRR) domain. The N-terminal region of the alpha subunit binds to the active site in the beta subunit; residue His2alpha directly coordinates a zinc ion. The prenyl-binding pocket of RabGGT is deeper than that in FT. CONCLUSIONS LRR and Ig domains are often involved in protein-protein interactions; in RabGGT they might participate in the recognition and binding of REP. The binding of the N-terminal peptide of the alpha subunit to the active site suggests an autoinhibition mechanism that might contribute to the inability of RabGGT to recognize short peptides or Rab alone as its substrate. Replacement of residues Trp102beta and Tyr154beta in FT by Ser48beta and Leu99beta, respectively, in RabGGT largely determine the different lipid-binding specificities of the two enzymes.
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Affiliation(s)
- H Zhang
- Department of Biochemistry, Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas, 75235-9050, USA
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46
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Tolmachova T, Ramalho JS, Anant JS, Schultz RA, Huxley CM, Seabra MC. Cloning, mapping and characterization of the human RAB27A gene. Gene 1999; 239:109-16. [PMID: 10571040 DOI: 10.1016/s0378-1119(99)00371-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Choroideremia (CHM) is an X-linked retinal degenerative disease that results from mutations in Rab Escort Protein-1 (REP1). REP1 acts in the prenylation of Rab GTPases, regulators of intracellular protein trafficking. Rab27a is unique among Rabs in that it is selectively unprenylated in CHM cells, suggesting that the degenerative process in CHM may result from unprenylation and consequent loss-of-function of Rab27a. As a first step towards the analysis of the Rab27a protein in patients, we report here the characterization of the human RAB27A gene. The putative protein encoded by this gene shares 96% identity with the previously cloned rat homologue. The RAB27A gene comprises five coding exons and two non-coding exons, of which one is alternatively used, and spans approximately 65 kb of DNA. There are three alternative poly-A addition sites in the long 3' UTR and also six potential single-nucleotide polymorphisms. The gene is located on chromosome 15q15-21.1, as determined by fluorescent in situ hybridization, and between markers D15S209 and AFM321ZD5 by radiation hybrid mapping.
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Affiliation(s)
- T Tolmachova
- Molecular Genetics, Division of Biomedical Sciences, Imperial College School of Medicine, London, UK
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47
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Hayakawa M, Fujiki K, Hotta Y, Ito R, Ohki J, Ono J, Saito A, Nakayasu K, Kanai A, Ishidoh K, Kominami E, Yoshida K, Kim KC, Ohashi H. Visual impairment and REP-1 gene mutations in Japanese choroideremia patients. Ophthalmic Genet 1999; 20:107-15. [PMID: 10420196 DOI: 10.1076/opge.20.2.107.2285] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Choroideremia (CHM), an X-linked recessive hereditary disease, is an intractable chorioretinal dystrophy. The rate of disease progression of CHM reportedly shows considerable variability. A number of mutations involving the gene that codes for Rab escort protein-1 (REP-1) have been detected in CHM patients. We have analyzed REP-1 gene mutations of Japanese CHM patients. The present study was designed to investigate the clinical variability and the genotype to phenotype relationship in 15 Japanese CHM patients referred to the Department of Ophthalmology of Juntendo University Hospital. The clinical investigation of visual acuity, visual field, color vision and refraction revealed inter-individual variability. Mutation analyses of the REP-1 gene revealed 10 types of mutations in 13 patients from 11 families, including an insertion, small deletions, nonsense mutations and an A to CC mutation. In 13 CHM patients with detectable REP-1 gene mutations, no relationship of genotype to phenotype was detected. At present, we consider the REP-1 genotype to be an unreliable prognostic factor for counseling of CHM patients. In two patients from one family, no mutations were detected in coding regions of the REP-1 gene. These patients may have intron mutations of the REP-1 gene, not detectable by the techniques employed in this study, or other causative genes. Both were observed to have somewhat slower disease progression than the other 13 patients. More advanced analyses are necessary to answer questions regarding the genotype-phenotype relationship in CHM patients.
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Affiliation(s)
- M Hayakawa
- Department of Ophthalmology, Juntendo University School of Medicine, Tokyo, Japan
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48
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Abstract
The regulatory function of the Ras-like GTPases in diverse cellular processes, such as growth, cell movement, and protein trafficking, is critically dependent on targeting to the proper cellular membrane. Prenylation of Ras, Rho/Rac, and Rab GTPases, defined as the covalent addition of isoprenyl groups to cysteine residues near or at their carboxyl terminus, is the first and necessary step that leads to membrane binding and targeting of these proteins. Recent progress on the molecular mechanisms of prenylation, membrane association, and targeting of Ras, Rho/Rac, and Rab proteins will be reviewed here. The detailed understanding of these targeting mechanisms may allow future development of specific therapeutic agents that interfere with the function of each one of these proteins.
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Affiliation(s)
- M C Seabra
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235, USA.
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