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Sorting nexin 6 enhances lamin a synthesis and incorporation into the nuclear envelope. PLoS One 2014; 9:e115571. [PMID: 25535984 PMCID: PMC4275242 DOI: 10.1371/journal.pone.0115571] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 10/21/2014] [Indexed: 01/20/2023] Open
Abstract
Nuclear lamins are important structural and functional proteins in mammalian cells, but little is known about the mechanisms and cofactors that regulate their traffic into the nucleus. Here, we demonstrate that trafficking of lamin A, but not lamin B1, and its assembly into the nuclear envelope are regulated by sorting nexin 6 (SNX6), a major component of the retromer that targets proteins and other molecules to specific subcellular locations. SNX6 interacts with lamin A in vitro and in vivo and links it to the outer surface of the endoplasmic reticulum in human and mouse cells. SNX6 transports its lamin A cargo to the nuclear envelope in a process that takes several hours. Lamin A protein levels in the nucleus augment or decrease, respectively, upon gain or loss of SNX6 function. We further show that SNX6-dependent lamin A nuclear import occurs across the nuclear pore complex via a RAN-GTP-dependent mechanism. These results identify SNX6 as a key regulator of lamin A synthesis and incorporation into the nuclear envelope.
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Synthesis, transport and incorporation into the nuclear envelope of A-type lamins and inner nuclear membrane proteins. Biochem Soc Trans 2012; 39:1758-63. [PMID: 22103521 DOI: 10.1042/bst20110653] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mammalian NE (nuclear envelope), which separates the nucleus from the cytoplasm, is a complex structure composed of nuclear pore complexes, the outer and inner nuclear membranes, the perinuclear space and the nuclear lamina (A- and B-type lamins). The NE is completely disassembled and reassembled at each cell division. In the present paper, we review recent advances in the understanding of the mechanisms implicated in the transport of inner nuclear membrane and nuclear lamina proteins from the endoplasmic reticulum to the nucleus in interphase cells and mitosis, with special attention to A-type lamins.
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Ben Yaou R, Navarro C, Quijano-Roy S, Bertrand AT, Massart C, De Sandre-Giovannoli A, Cadiñanos J, Mamchaoui K, Butler-Browne G, Estournet B, Richard P, Barois A, Lévy N, Bonne G. Type B mandibuloacral dysplasia with congenital myopathy due to homozygous ZMPSTE24 missense mutation. Eur J Hum Genet 2011; 19:647-54. [PMID: 21267004 DOI: 10.1038/ejhg.2010.256] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutation in ZMPSTE24 gene, encoding a major metalloprotease, leads to defective prelamin A processing and causes type B mandibuloacral dysplasia, as well as the lethal neonatal restrictive dermopathy syndrome. Phenotype severity is correlated with the residual enzyme activity of ZMPSTE24 and accumulation of prelamin A. We had previously demonstrated that a complete loss of function in ZMPSTE24 was lethal in the neonatal period, whereas compound heterozygous mutations including one PTC and one missense mutation were associated with type B mandibuloacral dysplasia. In this study, we report a 30-year longitudinal clinical survey of a patient harboring a novel severe and complex phenotype, combining an early-onset progeroid syndrome and a congenital myopathy with fiber-type disproportion. A unique homozygous missense ZMPSTE24 mutation (c.281T>C, p.Leu94Pro) was identified and predicted to produce two possible ZMPSTE24 conformations, leading to a partial loss of function. Western blot analysis revealed a major reduction of ZMPSTE24, together with the presence of unprocessed prelamin A and decreased levels of lamin A, in the patient's primary skin fibroblasts. These cells exhibited significant reductions in lifespan associated with major abnormalities of the nuclear shape and structure. This is the first report of MAD presenting with confirmed myopathic abnormalities associated with ZMPSTE24 defects, extending the clinical spectrum of ZMPSTE24 gene mutations. Moreover, our results suggest that defective prelamin A processing affects muscle regeneration and development, thus providing new insights into the disease mechanism of prelamin A-defective associated syndromes in general.
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Davies BSJ, Fong LG, Yang SH, Coffinier C, Young SG. The posttranslational processing of prelamin A and disease. Annu Rev Genomics Hum Genet 2009; 10:153-74. [PMID: 19453251 DOI: 10.1146/annurev-genom-082908-150150] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Human geneticists have shown that some progeroid syndromes are caused by mutations that interfere with the conversion of farnesyl-prelamin A to mature lamin A. For example, Hutchinson-Gilford progeria syndrome is caused by LMNA mutations that lead to the accumulation of a farnesylated version of prelamin A. In this review, we discuss the posttranslational modifications of prelamin A and their relevance to the pathogenesis and treatment of progeroid syndromes.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, University of California, Los Angeles, California 90095, USA.
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Coutinho HDM, Falcão-Silva VS, Gonçalves GF, da Nóbrega RB. Molecular ageing in progeroid syndromes: Hutchinson-Gilford progeria syndrome as a model. IMMUNITY & AGEING 2009; 6:4. [PMID: 19379495 PMCID: PMC2674425 DOI: 10.1186/1742-4933-6-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 04/20/2009] [Indexed: 01/09/2023]
Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder that belongs to a group of conditions called laminopathies which affect nuclear lamins. Mutations in two genes, LMNA and ZMPSTE24, have been found in patients with HGPS. The p.G608G LMNA mutation is the most commonly reported mutation. The aim of this work was to compile a comprehensive literature review of the clinical features and genetic mutations and mechanisms of this syndrome as a contribution to health care workers. This review shows the necessity of a more detailed clinical identification of Hutchinson-Gilford progeria syndrome and the need for more studies on the pharmacologic and pharmacogenomic approach to this syndrome.
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Affiliation(s)
- Henrique Douglas M Coutinho
- Laboratório de Pesquisa em Produtos Naturais, Departamento de Ciências físicas e Biológicas, Centro de Ciências Biológicas e da Saúde, Universidade Regional do Cariri, Crato (CE), Brazil.
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Mazereeuw-Hautier J, Wilson LC, Mohammed S, Smallwood D, Shackleton S, Atherton DJ, Harper JI. Hutchinson-Gilford progeria syndrome: clinical findings in three patients carrying the G608G mutation in LMNA and review of the literature. Br J Dermatol 2007; 156:1308-14. [PMID: 17459035 DOI: 10.1111/j.1365-2133.2007.07897.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature ageing disorder that belongs to a group of conditions called laminopathies which affect nuclear lamins. Classical and atypical forms of HGPS have been reported and there are clinical overlaps with mandibulo-acral dysplasia and restrictive dermopathy. To date, mutations in two genes, LMNA and ZMPSTE24, have been found in patients with HGPS. The p.G608G LMNA mutation is the most commonly reported mutation. Correlations between genotype and phenotype in children with progeroid syndromes are beginning to emerge. OBJECTIVES To establish whether the LMNA p.G608G mutation is associated with a particular phenotype of HGPS. METHODS We reviewed the clinical features and skin histology of three children with HGPS associated with the p.G608G LMNA mutation, and compared our findings with those reported in the literature. RESULTS Our patients shared a very similar presentation and clinical course. Skin changes were the earliest finding in all three. Skin histology showed nonspecific changes only. CONCLUSIONS The LMNA p.G608G mutation results in a uniform phenotype through early to mid-childhood, in keeping with that described in classical HGPS. Skin changes are the earliest distinctive clinical finding and should prompt careful physical and radiological examination for other features of HGPS. Skin biopsy for histology is not a useful investigation when a diagnosis of HGPS is suspected.
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Affiliation(s)
- J Mazereeuw-Hautier
- Department of Dermatology, Great Ormond Street Hospital for Children NHS Trust, Great Ormond Street, London, UK.
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Protein Prenylation: An (Almost) Comprehensive Overview on Discovery History, Enzymology, and Significance in Physiology and Disease. MONATSHEFTE FUR CHEMIE 2006. [DOI: 10.1007/s00706-006-0534-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Denecke J, Brune T, Feldhaus T, Robenek H, Kranz C, Auchus RJ, Agarwal AK, Marquardt T. A homozygousZMPSTE24null mutation in combination with a heterozygous mutation in theLMNAgene causes Hutchinson-Gilford progeria syndrome (HGPS): insights into the pathophysiology of HGPS. Hum Mutat 2006; 27:524-31. [PMID: 16671095 DOI: 10.1002/humu.20315] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder normally caused by a spontaneous heterozygous mutation in the LMNA gene that codes for the nuclear lamina protein lamin A. Several enzymes are involved in the processing of its precursor, prelamin A, to the mature lamin A. A functional knockout of one of the enzymes involved in prelamin A processing, the zinc metalloprotease ZMPSTE24, causes an even more severe disorder with early neonatal death described as restrictive dermatopathy (RD). This work describes a HGPS patient with a combined defect of a homozygous loss-of-function mutation in the ZMPSTE24 gene and a heterozygous mutation in the LMNA gene that results in a C-terminal elongation of the final lamin A. Whereas the loss of function mutation of ZMPSTE24 normally results in lethal RD, the truncation of LMNA seems to be a salvage alteration alleviating the clinical picture to the HGPS phenotype. The mutations of our patient indicate that farnesylated prelamin A is the deleterious agent leading to the HGPS phenotype, which gives further insights into the pathophysiology of the disorder.
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Affiliation(s)
- Jonas Denecke
- Department of Pediatrics, University Hospital of Munster, Munster, Germany.
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Maraldi NM, Lattanzi G, Capanni C, Columbaro M, Mattioli E, Sabatelli P, Squarzoni S, Manzoli FA. Laminopathies: A chromatin affair. ACTA ACUST UNITED AC 2006; 46:33-49. [PMID: 16857244 DOI: 10.1016/j.advenzreg.2006.01.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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10
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van Steensel MAM, Frank J. Lamin Processing Comes of Age. J Invest Dermatol 2005; 125:xii-xiii. [PMID: 16297177 DOI: 10.1111/j.0022-202x.2005.23871.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Young SG, Fong LG, Michaelis S. Prelamin A, Zmpste24, misshapen cell nuclei, and progeria--new evidence suggesting that protein farnesylation could be important for disease pathogenesis. J Lipid Res 2005; 46:2531-58. [PMID: 16207929 DOI: 10.1194/jlr.r500011-jlr200] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prelamin A undergoes multistep processing to yield lamin A, a structural protein of the nuclear lamina. Prelamin A terminates with a CAAX motif, which triggers farnesylation of a C-terminal cysteine (the C of the CAAX motif), endoproteolytic release of the last three amino acids (the AAX), and methylation of the newly exposed farnesylcysteine residue. In addition, prelamin A is cleaved a second time, releasing 15 more residues from the C terminus (including the farnesylcysteine methyl ester), generating mature lamin A. This second cleavage step is carried out by an endoplasmic reticulum membrane protease, ZMPSTE24. Interest in the posttranslational processing of prelamin A has increased with the recognition that certain progeroid syndromes can be caused by mutations that lead to an accumulation of farnesyl-prelamin A. Recently, we showed that a key cellular phenotype of these progeroid disorders, misshapen cell nuclei, can be ameliorated by inhibitors of protein farnesylation, suggesting a potential strategy for treating these diseases. In this article, we review the posttranslational processing of prelamin A, describe several mouse models for progeroid syndromes, explain the mutations underlying several human progeroid syndromes, and summarize recent data showing that misshapen nuclei can be ameliorated by treating cells with protein farnesyltransferase inhibitors.
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Affiliation(s)
- Stephen G Young
- Division of Cardiology, Department of Internal Medicine, University of California, Los Angeles, CA 90095, USA.
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Corrigan D, Kuszczak D, Rusinol A, Thewke D, Hrycyna C, Michaelis S, Sinensky M. Prelamin A endoproteolytic processing in vitro by recombinant Zmpste24. Biochem J 2005; 387:129-38. [PMID: 15479156 PMCID: PMC1134940 DOI: 10.1042/bj20041359] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The nuclear lamins form a karyoskeleton providing structural rigidity to the nucleus. One member of the lamin family, lamin A, is first synthesized as a 74 kDa precursor, prelamin A. After the endopeptidase and methylation reactions which occur after farnesylation of the CAAX-box cysteine, there is a second endoproteolysis that occurs 15 amino acids upstream from the C-terminal farnesylated cysteine residue. Studies with knockout mice have implicated the enzyme Zmpste24 (Face-1) as a suitable candidate to perform one or both of these proteolytic reactions. Evidence has been presented elsewhere establishing that Zmpste24 possesses a zinc-dependent CAAX endopeptidase activity. In the present study, we confirm this CAAX endopeptidase activity with recombinant, membrane-reconstituted Zmpste24 and show that it can accept a prelamin A farnesylated tetrapeptide as substrate. To monitor the second upstream endoproteolytic cleavage of prelamin A, we expressed a 33 kDa prelamin A C-terminal tail in insect cells. We demonstrate that this purified substrate possesses a C-terminal farnesylated and carboxyl-methylated cysteine and, therefore, constitutes a valid substrate for assaying the second endoproteolytic step in lamin A maturation. With this substrate, we demonstrate that insect cell membranes bearing recombinant Zmpste24 can also catalyse the second upstream endoproteolytic cleavage.
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Affiliation(s)
- Douglas P. Corrigan
- *Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Box 70581, Johnson City, TN 37614-0581, U.S.A
| | - Danuta Kuszczak
- *Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Box 70581, Johnson City, TN 37614-0581, U.S.A
| | - Antonio E. Rusinol
- *Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Box 70581, Johnson City, TN 37614-0581, U.S.A
| | - Douglas P. Thewke
- *Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Box 70581, Johnson City, TN 37614-0581, U.S.A
| | - Christine A. Hrycyna
- †Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, U.S.A
| | - Susan Michaelis
- ‡Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 N Wolfe St., Baltimore, MD 21205, U.S.A
| | - Michael S. Sinensky
- *Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Box 70581, Johnson City, TN 37614-0581, U.S.A
- To whom correspondence should be addressed (email )
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Maske CP, Hollinshead MS, Higbee NC, Bergo MO, Young SG, Vaux DJ. A carboxyl-terminal interaction of lamin B1 is dependent on the CAAX endoprotease Rce1 and carboxymethylation. J Cell Biol 2003; 162:1223-32. [PMID: 14504265 PMCID: PMC2173957 DOI: 10.1083/jcb.200303113] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 08/13/2003] [Indexed: 11/24/2022] Open
Abstract
The mammalian nuclear lamina protein lamin B1 is posttranslationally modified by farnesylation, endoproteolysis, and carboxymethylation at a carboxyl-terminal CAAX motif. In this work, we demonstrate that the CAAX endoprotease Rce1 is required for lamin B1 endoproteolysis, demonstrate an independent pool of proteolyzed but nonmethylated lamin B1, as well as fully processed lamin B1, in interphase nuclei, and show a role for methylation in the organization of lamin B1 into domains of the nuclear lamina. Deficiency in the endoproteolysis or methylation of lamin B1 results in loss of integrity and deformity of the nuclear lamina. These data show that the organization of the nuclear envelope and lamina is dependent on a mechanism involving the methylation of lamin B1, and they identify a potential mechanism of laminopathy involving a B-type lamin.
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Affiliation(s)
- Christopher P Maske
- Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE, UK
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14
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Bergo MO, Gavino B, Ross J, Schmidt WK, Hong C, Kendall LV, Mohr A, Meta M, Genant H, Jiang Y, Wisner ER, Van Bruggen N, Carano RAD, Michaelis S, Griffey SM, Young SG. Zmpste24 deficiency in mice causes spontaneous bone fractures, muscle weakness, and a prelamin A processing defect. Proc Natl Acad Sci U S A 2002; 99:13049-54. [PMID: 12235369 PMCID: PMC130584 DOI: 10.1073/pnas.192460799] [Citation(s) in RCA: 337] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Zmpste24 is an integral membrane metalloproteinase of the endoplasmic reticulum. Biochemical studies of tissues from Zmpste24-deficient mice (Zmpste24(-/-)) have indicated a role for Zmpste24 in the processing of CAAX-type prenylated proteins. Here, we report the pathologic consequences of Zmpste24 deficiency in mice. Zmpste24(-/-) mice gain weight slowly, appear malnourished, and exhibit progressive hair loss. The most striking pathologic phenotype is multiple spontaneous bone fractures-akin to those occurring in mouse models of osteogenesis imperfecta. Cortical and trabecular bone volumes are significantly reduced in Zmpste24(-/-) mice. Zmpste24(-/-) mice also manifested muscle weakness in the lower and upper extremities, resembling mice lacking the farnesylated CAAX protein prelamin A. Prelamin A processing was defective both in fibroblasts lacking Zmpste24 and in fibroblasts lacking the CAAX carboxyl methyltransferase Icmt but was normal in fibroblasts lacking the CAAX endoprotease Rce1. Muscle weakness in Zmpste24(-/-) mice can be reasonably ascribed to defective processing of prelamin A, but the brittle bone phenotype suggests a broader role for Zmpste24 in mammalian biology.
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Affiliation(s)
- Martin O Bergo
- Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, CA 94141-9100, USA.
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Hofemeister H, Kuhn C, Franke WW, Weber K, Stick R. Conservation of the gene structure and membrane-targeting signals of germ cell-specific lamin LIII in amphibians and fish. Eur J Cell Biol 2002; 81:51-60. [PMID: 11893082 DOI: 10.1078/0171-9335-00229] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Targeting of nuclear lamins to the inner nuclear membrane requires CaaX motif-dependent posttranslational isoprenylation and carboxyl methylation. We previously have shown that two variants of lamin LIII (i.e., LIII and LIIIb) in amphibian oocytes are generated by alternative splicing and differ greatly in their membrane association. An extra cysteine residue (as a potential palmitoylation site) and a basic cluster in conjunction with the CaaX motif function as secondary targeting signals responsible for stable membrane association of lamin LIIIb. cDNA sequencing and genomic analysis of the zebrafish Danio rerio lamin LIII uncovers a remarkable conservation of the genomic organization and of the two secondary membrane-targeting signals in amphibians and fish. The expression pattern of lamin LIII genes is also conserved between amphibians and fish. Danio lamin LIII is expressed in diplotene oocytes. It is absent from male germ cells but is expressed in Sertoli cells of the testis. In addition, we provide sequence information of the entire coding sequence of zebrafish lamin A, which allows comparison of all major lamins from representatives of the four classes of vertebrates.
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Kale TA, Raab C, Yu N, Dean DC, Distefano MD. A photoactivatable prenylated cysteine designed to study isoprenoid recognition. J Am Chem Soc 2001; 123:4373-81. [PMID: 11457220 DOI: 10.1021/ja0012016] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein prenylation, involving the alkylation of a specific C-terminal cysteine with a C(15) or C(20) isoprenoid unit, is an essential posttranslational modification required by most GTP-binding proteins for normal biological activity. Despite the ubiquitous nature of this modification and numerous efforts aimed at inhibiting prenylating enzymes for therapeutic purposes, the function of prenylation remains unclear. To explore the role the isoprenoid plays in mediating protein-protein recognition, we have synthesized a photoactivatable, isoprenoid-containing cysteine analogue (2) designed to act as a mimic of the C-terminus of prenylated proteins. Photolysis experiments with 2 and RhoGDI (GDI), a protein which interacts with prenylated Rho proteins, suggest that the GDI is in direct contact with the isoprenoid moiety. These results, obtained using purified GDI as well as Escherichia coli (E. coli) crude extract containing GDI, suggest that this analogue will be an effective and versatile tool for the investigation of putative isoprenoid binding sites in a variety of systems. Incorporation of this analogue into peptides or proteins should allow for even more specific interactions between the photoactivatable isoprenoid and any number of isoprenoid binding proteins.
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Affiliation(s)
- T A Kale
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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17
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Moir RD, Yoon M, Khuon S, Goldman RD. Nuclear lamins A and B1: different pathways of assembly during nuclear envelope formation in living cells. J Cell Biol 2000; 151:1155-68. [PMID: 11121432 PMCID: PMC2190592 DOI: 10.1083/jcb.151.6.1155] [Citation(s) in RCA: 289] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/1999] [Accepted: 10/06/2000] [Indexed: 01/31/2023] Open
Abstract
At the end of mitosis, the nuclear lamins assemble to form the nuclear lamina during nuclear envelope formation in daughter cells. We have fused A- and B-type nuclear lamins to the green fluorescent protein to study this process in living cells. The results reveal that the A- and B-type lamins exhibit different pathways of assembly. In the early stages of mitosis, both lamins are distributed throughout the cytoplasm in a diffusible (nonpolymerized) state, as demonstrated by fluorescence recovery after photobleaching (FRAP). During the anaphase-telophase transition, lamin B1 begins to become concentrated at the surface of the chromosomes. As the chromosomes reach the spindle poles, virtually all of the detectable lamin B1 has accumulated at their surfaces. Subsequently, this lamin rapidly encloses the entire perimeter of the region containing decondensing chromosomes in each daughter cell. By this time, lamin B1 has assembled into a relatively stable polymer, as indicated by FRAP analyses and insolubility in detergent/high ionic strength solutions. In contrast, the association of lamin A with the nucleus begins only after the major components of the nuclear envelope including pore complexes are assembled in daughter cells. Initially, lamin A is found in an unpolymerized state throughout the nucleoplasm of daughter cell nuclei in early G1 and only gradually becomes incorporated into the peripheral lamina during the first few hours of this stage of the cell cycle. In later stages of G1, FRAP analyses suggest that both green fluorescent protein lamins A and B1 form higher order polymers throughout interphase nuclei.
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Affiliation(s)
- Robert D. Moir
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Miri Yoon
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Satya Khuon
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
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Hofemeister H, Weber K, Stick R. Association of prenylated proteins with the plasma membrane and the inner nuclear membrane is mediated by the same membrane-targeting motifs. Mol Biol Cell 2000; 11:3233-46. [PMID: 10982413 PMCID: PMC14988 DOI: 10.1091/mbc.11.9.3233] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Targeting of nuclear lamins to the inner nuclear envelope membrane requires a nuclear localization signal and CaaX motif-dependent posttranslational modifications, including isoprenylation and carboxyl methylation. These modifications, although necessary for membrane targeting, are not sufficient to mediate stable association with membranes. We show that two variants of lamin B3 (i.e., B3a and B3b) exist in Xenopus oocytes. They are encoded by two alternatively spliced, developmentally regulated mRNAs. The two lamin variants differ greatly in their membrane association in meiotically matured eggs. The presence of an extra cysteine residue (as a potential palmitoylation site) and a basic cluster in conjunction with the CaaX motif function as secondary targeting signals responsible for the stable membrane association of lamin B3b in Xenopus eggs. Moreover, transfection experiments with Green Fluorescent Protein lamin tail chimeras and with a Green Fluorescent Protein N-Ras chimera show that these secondary motifs are sufficient to target proteins to the inner nuclear membrane and/or the plasma membrane. Implications for the intracellular trafficking of doubly lipidated proteins are discussed.
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Affiliation(s)
- H Hofemeister
- Max Planck Institute for Biophysical Chemistry, Department of Biochemistry, D-37018 Göttingen, Germany
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Abstract
Post-translational modification of proteins with isoprenoids was first recognized as a general phenomenon in 1984. In recent years, our understanding, including mechanistic studies, of the enzymatic reactions associated with these modifications and their physiological functions has increased dramatically. Of particular functional interest is the role of prenylation in facilitating protein-protein interactions and membrane-associated protein trafficking. The loss of proper localization of Ras proteins when their farnesylation is inhibited has also permitted a new target for anti-malignancy pharmaceuticals. Recent advances in the enzymology and function of protein prenylation are reviewed in this article.
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Affiliation(s)
- M Sinensky
- Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614-0581, USA.
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