Microfibril-associated MAGP-2 Stimulates Elastic Fiber Assembly

Elastic fibers are complex structures composed of a tropoelastin inner core and microfibril outer mantle guiding tropoelastin deposition. Microfibrillar proteins mainly include fibrillins and microfibril-associated glycoproteins (MAGPs). MAGP-2 exhibits developmental expression peaking at elastic fiber onset, suggesting that MAGP-2 mediates elastic fiber assembly. To determine whether MAGP-2 regulates elastic fiber assembly, we used an in vitro model featuring doxycycline-regulated cells conditionally overexpressing exogenous MAGP-2 and constitutively expressing enhanced green fluorescent protein-tagged tropoelastin. Analysis by immunofluorescent staining showed that MAGP-2 overexpression dramatically increased elastic fibers levels, independently of extracellular levels of soluble tropoelastin, indicating that MAGP-2 stimulates elastic fiber assembly. This was associated with increased levels of matrix-associated MAGP-2. Electron microscopy showed that MAGP-2 specifically associates with microfibrils and that elastin globules primarily colocalize with MAGP-2-associated microfibrils, suggesting that microfibril-associated MAGP-2 facilitates elastic fiber assembly. MAGP-2 overexpression did not change levels of matrix-associated fibrillin-1, MAGP-1, fibulin-2, fibulin-5, or emilin-1, suggesting that microfibrils and other elastic fiberassociated proteins known to regulate elastogenesis do not mediate MAGP-2-induced elastic fiber assembly. Moreover, mutation analysis showed that MAGP-2 does not stimulate elastic fiber assembly through its RGD motif, suggesting that integrin receptor binding does not mediate MAGP-2-induced elastic fiber assembly. Because MAGP-2 interacts with Jagged-1 that controls cell-matrix interaction and cell motility, two key factors in elastic fiber macroassembly, microfibril-associated MAGP-2 may stimulate elastic fiber macroassembly by targeting the release of elastin globules from the cell membrane onto developing elastic fibers. Elastic fibers are complex structures composed of a tropoelastin inner core and microfibril outer mantle guiding tropoelastin deposition. Microfibrillar proteins mainly include fibrillins and microfibril-associated glycoproteins (MAGPs). MAGP-2 exhibits developmental expression peaking at elastic fiber onset, suggesting that MAGP-2 mediates elastic fiber assembly. To determine whether MAGP-2 regulates elastic fiber assembly, we used an in vitro model featuring doxycycline-regulated cells conditionally overexpressing exogenous MAGP-2 and constitutively expressing enhanced green fluorescent protein-tagged tropoelastin. Analysis by immunofluorescent staining showed that MAGP-2 overexpression dramatically increased elastic fibers levels, independently of extracellular levels of soluble tropoelastin, indicating that MAGP-2 stimulates elastic fiber assembly. This was associated with increased levels of matrix-associated MAGP-2. Electron microscopy showed that MAGP-2 specifically associates with microfibrils and that elastin globules primarily colocalize with MAGP-2-associated microfibrils, suggesting that microfibril-associated MAGP-2 facilitates elastic fiber assembly. MAGP-2 overexpression did not change levels of matrix-associated fibrillin-1, MAGP-1, fibulin-2, fibulin-5, or emilin-1, suggesting that microfibrils and other elastic fiberassociated proteins known to regulate elastogenesis do not mediate MAGP-2-induced elastic fiber assembly. Moreover, mutation analysis showed that MAGP-2 does not stimulate elastic fiber assembly through its RGD motif, suggesting that integrin receptor binding does not mediate MAGP-2-induced elastic fiber assembly. Because MAGP-2 interacts with Jagged-1 that controls cell-matrix interaction and cell motility, two key factors in elastic fiber macroassembly, microfibril-associated MAGP-2 may stimulate elastic fiber macroassembly by targeting the release of elastin globules from the cell membrane onto developing elastic fibers. Elastic fibers are major insoluble extracellular matrix structures that provide connective tissues with flexibility and extensibility. These properties are critical to the functions of arteries, lung, skin, and all other dynamic tissues and have been essential requirements in the evolution of multicellular organisms. The importance of elastic fibers is highlighted by severe heritable connective tissue diseases caused by mutations in components of elastic fibers (1Milewicz D.M. Urban Z. Boyd C. Matrix Biol. 2000; 19: 471-480Crossref PubMed Scopus (150) Google Scholar). Elastic fibers are complex structures composed of two major components as follows: an inner core of amorphous cross-linked tropoelastin and an outer microfibril mantle composed of multiple proteins. Various other components of the elastic fiber localize at the elastin-microfibril or cell-elastic fiber interface (for review see Ref. 2Kielty C.M. Sherratt M.J. Shuttleworth C.A. J. Cell Sci. 2002; 115: 2817-2828Crossref PubMed Google Scholar), including fibulin-2, fibulin-5, and emilin-1. These elastic fiber-associated molecules are important mediators of elastic fiber assembly as deletion of these genes induces elastic fiber defects in mice (3Chu M. Communication: 2nd National Meeting of the American Society for Matrix Biology, San Diego, CA, November, 10-13, 2004, Abstr. 28.American Society for Matrix Biology. 2004; Google Scholar, 4Yanagisawa H. Davis E.C. Starcher B.C. Ouchi T. Yanagisawa M. Richardson J.A. Olson E.N. Nature. 2002; 415: 168-171Crossref PubMed Scopus (487) Google Scholar, 5Zanetti M. Braghetta P. Sabatelli P. Mura I. Doliana R. Colombatti A. Volpin D. Bonaldo P. Bressan G.M. Mol. Cell. Biol. 2004; 24: 638-650Crossref PubMed Scopus (142) Google Scholar). Microfibrils play an essential role in elastic fiber assembly by orchestrating deposition of tropoelastin onto the developing elastic fiber. Recent data have shown that a microfibril scaffold is required for deposition of tropoelastin into the extracellular matrix (6Kozel B.A. Ciliberto C.H. Mecham R.P. Matrix Biol. 2004; 23: 23-34Crossref PubMed Scopus (65) Google Scholar). This confirms previous ultrastructural studies showing that microfibrillar proteins are generally expressed prior to tropoelastin during development (7Mariencheck M.C. Davis E.C. Zhang H. Ramirez F. Rosenbloom J. Gibson M.A. Parks W.C. Mecham R.P. Connect. Tissue Res. 1995; 31: 87-97Crossref PubMed Scopus (75) Google Scholar) and that elastin in early stages of assembly is always associated with microfibrils in developing elastic tissues (8Cleary E.G. Gibson M.A. Int. Rev. Connect. Tissue Res. 1983; 10: 97-209Crossref PubMed Google Scholar, 9Greenlee Jr., T.K. Ross R. Hartman J.L. J. Cell Biol. 1966; 30: 59-71Crossref PubMed Scopus (297) Google Scholar). However, because of the structural and functional heterogeneity of microfibrils, the molecular basis of tropoelastin alignment by microfibrils remains unclear. In this respect, each microfibrillar component may selectively determine the structure of microfibrils and/or their function in tropoelastin alignment. The biological role of these microfibrillar molecules is still under investigation. Fibrillin-1 and -2 are the principal structural components of microfibrils in elastic fibers (10Sakai L.Y. Keene D.R. Engvall E. J. Cell Biol. 1986; 103: 2499-2509Crossref PubMed Scopus (889) Google Scholar, 11Zhang H. Apfelroth S.D. Hu W. Davis E.C. Sanguineti C. Bonadio J. Mecham R.P. Ramirez F. J. Cell Biol. 1994; 124: 855-863Crossref PubMed Scopus (318) Google Scholar). Mutation of fibrillin-1 in the Tight-skin (Tsk) mice induces major alterations in microfibril structures (12Gayraud B. Keene D.R. Sakai L.Y. Ramirez F. J. Cell Biol. 2000; 150: 667-680Crossref PubMed Scopus (80) Google Scholar, 13Lemaire R. Farina G. Kissin E. Shipley J.M. Bona C. Korn J.H. Lafyatis R. Arthritis Rheum. 2004; 50: 915-926Crossref PubMed Scopus (42) Google Scholar). They also have a function in tropoelastin deposition as they regulate tropoelastin coacervation (14Clarke A.W. Wise S.G. Cain S.A. Kielty C.M. Weiss A.S. Biochemistry. 2005; 44: 10271-10281Crossref PubMed Scopus (56) Google Scholar). They are large glycoproteins that have distinct but overlapping pattern of expression (15Zhang H. Hu W. Ramirez F. J. Cell Biol. 1995; 129: 1165-1176Crossref PubMed Scopus (255) Google Scholar). Fibrillin-2 is generally expressed earlier in development than fibrillin-1 and may be particularly important in elastic fiber formation (16Pereira L. Andrikopoulos K. Tian J. Lee S.Y. Keene D.R. Ono R. Reinhardt D.P. Sakai L.Y. Biery N.J. Bunton T. Dietz H.C. Ramirez F. Nat. Genet. 1997; 17: 218-222Crossref PubMed Scopus (309) Google Scholar). Apart from the fibrillins, MAGP-1 (microfibril-associated glycoprotein 1) is possibly the best candidate for an integral microfibril molecule important for structural integrity. It is associated with virtually all microfibrils and is widely expressed in mesenchymal and connective tissue cells throughout the development. MAGP-1 binds to amino-terminal exons 1-10 of fibrillin-1 (17Jensen S.A. Reinhardt D.P. Gibson M.A. Weiss A.S. J. Biol. Chem. 2001; 276: 39661-39666Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar) through its carboxyl-terminal region containing seven common cysteine residues (18Penner A.S. Rock M.J. Kielty C.M. Shipley J.M. J. Biol. Chem. 2002; 277: 35044-35049Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar). MAGP-1 forms ternary complexes with fibrillin-1 and decorin (19Trask B.C. Trask T.M. Broekelmann T. Mecham R.P. Mol. Biol. Cell. 2000; 11: 1499-1507Crossref PubMed Scopus (118) Google Scholar), as well as with biglycan and tropoelastin (20Reinboth B. Hanssen E. Cleary E.G. Gibson M.A. J. Biol. Chem. 2002; 277: 3950-3957Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). MAGP-1 also binds to the α3 chain of type VI collagen (21Finnis M.L. Gibson M.A. J. Biol. Chem. 1997; 272: 22817-22823Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar). MAGP-2, the other member of this small microfibrillar protein family, is a 170-173 residue protein structurally related to MAGP-1 mainly in its central region. MAGP-2 contains an RGD motif through which it specifically binds to the αvβ3 integrin (22Gibson M.A. Leavesley D.I. Ashman L.K. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) and interacts with an for receptor A. G. Shipley J.M. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). MAGP-2 is specifically associated with It binds to a carboxyl-terminal region of fibrillin-1 through its carboxyl-terminal region (18Penner A.S. Rock M.J. Kielty C.M. Shipley J.M. J. Biol. Chem. 2002; 277: 35044-35049Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar), as well as to amino-terminal and central of fibrillin-1 G. Gibson M.A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The role of MAGP-2 in microfibril structure remains because it exhibits of tissue and developmental However, it may have a function in matrix have shown that in of and mice is associated with increased MAGP-2 levels R. Farina G. Kissin E. Shipley J.M. Bona C. Korn J.H. Lafyatis R. Arthritis Rheum. 2004; 50: 915-926Crossref PubMed Scopus (42) Google Scholar) and that MAGP-2 stimulates expression of type R. Korn J.H. Shipley J.M. Lafyatis R. Arthritis Rheum. 2005; PubMed Scopus Google Scholar). that MAGP-2 may also microfibril function in as MAGP-2 is associated with microfibrils in developing M.A. G. Cleary E.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google MAGP-2 expression at the of of elastogenesis in this tissue M.A. M.L. Cleary E.G. J. PubMed Scopus (78) Google Scholar), and increased matrix-associated MAGP-2 in the of mice is associated with increased elastic fiber assembly. with MAGP-2 function in fibrillin-1 mutations to have been to the region that binds MAGP-2 Reinhardt D.P. Sakai L.Y. Matrix Biol. 2000; 19: PubMed Scopus (114) Google Scholar). In this cell conditionally overexpressing MAGP-2 and constitutively expressing used enhanced green fluorescent green fluorescent used enhanced green fluorescent green fluorescent tropoelastin, we that microfibril-associated MAGP-2 stimulates elastic fiber assembly independently of its RGD motif and microfibril assembly or matrix-associated levels of elastic fiber associated fibulin-2, fibulin-5, and emilin-1. and cells used in this from a that the a expressing a protein that binds to cells constitutively overexpressing tropoelastin by cells with a expression of tropoelastin with cells conditionally overexpressing MAGP-2 and constitutively tropoelastin by cells with a expression of MAGP-2 R. Korn J.H. Shipley J.M. Lafyatis R. Arthritis Rheum. 2005; PubMed Scopus Google Scholar). and cells conditionally overexpressing MAGP-2 and MAGP-2, by cells with and R. Korn J.H. Shipley J.M. Lafyatis R. Arthritis Rheum. 2005; PubMed Scopus Google Scholar). cells conditionally overexpressing carboxyl-terminal fibrillin-1 by cells with expression of the fibrillin-1 was by a expression of was by the from R. Farina G. Kissin E. Shipley J.M. Bona C. Korn J.H. Lafyatis R. Arthritis Rheum. 2004; 50: 915-926Crossref PubMed Scopus (42) Google Scholar), to the region fibrillin-1, by a from was into in of a to the carboxyl-terminal of Cell cells for and cell and for the by and and proteins from by from cell and matrix in an to and with MAGP-2 R. Farina G. Kissin E. Shipley J.M. Bona C. Korn J.H. Lafyatis R. Arthritis Rheum. 2004; 50: 915-926Crossref PubMed Scopus (42) Google Scholar), fibrillin-1 from L. from B. or to The of a was or by was by through a and onto a membrane to for MAGP-2, tropoelastin, or as R. Korn J.H. Lafyatis R. Arthritis Rheum. 2002; PubMed Scopus Google Scholar). in for in at for with in and for with MAGP-2 from J. M. fibrillin-1 MAGP-1 from R. A. tropoelastin R. Korn J.H. Shipley J.M. Lafyatis R. J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar), or to or at a in with for and for with a or at a by an under fluorescent associated with and and of Elastic cells overexpressing MAGP-2 in tissue and in the of cells in for for with and with for for with with to and/or in for for with and with in for of was a in with a of and two The used to and to associated with and The used to MAGP-2 and to elastin associated with and cells for with prior to in in for with for for with with in for with for with by a in with The in and at for with and and a MAGP-2 Elastic in a to the molecular elastic fiber assembly, we used a cell that microfibrils but not elastic fibers because tropoelastin is not expressed Because these cells all components required to the of elastic but not tropoelastin they provide an in vitro for elastic fiber assembly in with expression of an exogenous tropoelastin To cells constitutively expressing tropoelastin cells with a expression of tropoelastin with to exogenous tropoelastin onto microfibrils was by and in the of in to the assembly of microfibrils in the matrix R. Korn J.H. Lafyatis R. Arthritis Rheum. 2002; PubMed Scopus Google Scholar). cells constitutively overexpressing tropoelastin showed a and of developing elastic fibers that a of elastin globules cells for to a showed a elastic fiber as elastic fibers in and not To the role of MAGP-2 in elastic fiber assembly, we cells conditionally overexpressing exogenous MAGP-2 under the of the M. H. Sci. A. PubMed Scopus Google Scholar). to constitutively a with a MAGP-2 expression under the of the In the of a cells showed levels of MAGP-2 in the In the of cells showed levels of MAGP-2 in the as expression of exogenous MAGP-2 is of MAGP-2 did not change expression or levels of tropoelastin and enhanced levels of exogenous MAGP-2 in the This is associated with a in levels of exogenous MAGP-2 not Because expression of exogenous MAGP-2 is by a this that the MAGP-2 To at the of MAGP-2 overexpression elastic fiber assembly, cells for with or in the of and elastic fibers by with cells cells with and expressing levels of MAGP-2, showed an and of elastic fibers associated with and elastin globules developing elastic fibers these large elastin globules that in a and In cells with and overexpressing exogenous MAGP-2, showed a and of elastic fibers Elastic fibers and and to be from the of the elastin globules and with the and of cells to elastic fibers assembly, indicating that the of MAGP-2 elastic fibers was not because of the or not These that MAGP-2 overexpression stimulates assembly of tropoelastin onto microfibrils, of extracellular levels of soluble tropoelastin to the matrix MAGP-2-induced Elastic with of the molecular basis of the of elastic fiber assembly by MAGP-2, cells also in for MAGP-2 by overexpressing exogenous MAGP-2 showed a in matrix-associated MAGP-2 with the cells expressing MAGP-2 a and in elastic fibers and matrix-associated MAGP-2 expression of exogenous MAGP-2 associated as they and in the of exogenous MAGP-2, the of elastic fibers also with matrix-associated MAGP-2 and MAGP-2-induced with MAGP-2-associated Microfibrils and Elastic analysis of elastic fibers by cells overexpressing MAGP-2 and tropoelastin was by associated with of MAGP-2 and or in with elastin and and MAGP-2 targeting specifically to microfibrils the matrix and This is with previous microscopy studies tissues showing of MAGP-2 to microfibrils M.A. G. Cleary E.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). structures of elastin associated with of microfibrils molecular for the of elastic fibers in in vitro a of MAGP-2-associated microfibrils was elastin globules primarily to MAGP-2-associated microfibrils not to microfibrils These globules by to targeting and to tropoelastin their elastin The of of these globules by the to is to a to the of and/or of of cross-linked elastin or showed not The of elastin globules with MAGP-2 molecules the matrix that MAGP-2 facilitates elastic fiber assembly from its matrix-associated as to its soluble To selectively the of matrix-associated and soluble MAGP-2 elastic fiber assembly, we of the of soluble MAGP-2 as an from to the matrix of cells not cells in from overexpressing MAGP-2 and elastic fibers by other for cells in showed in elastic fibers with cells in not Because soluble MAGP-2 to stimulate elastic fiber assembly in matrix-associated this the microscopy indicating that matrix-associated MAGP-2 mediates MAGP-2-induced elastic fiber assembly. Fibrillin-1 Matrix of fibrillin-1 binds MAGP-2 (18Penner A.S. Rock M.J. Kielty C.M. Shipley J.M. J. Biol. Chem. 2002; 277: 35044-35049Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar, C. I. D. T. L. J. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar), we whether matrix-associated fibrillin-1 regulates matrix assembly of MAGP-2. used cell conditionally overexpressing a fibrillin-1 deletion the carboxyl-terminal region was at by analysis of cells showed levels of but matrix-associated of this expression of of fibrillin-1 with and fibrillin-1 molecules showed that overexpression of dramatically matrix assembly of fibrillin-1 and analysis of an targeting and forms of fibrillin-1 showed levels of fibrillin-1 in cell and of cells overexpressing indicating that not the matrix by is This a of the extracellular of fibrillin-1 to of severe caused by fibrillin-1 M. Kielty C.M. B. J. Mol. Biol. 1995; PubMed Scopus Google Scholar). of matrix assembly of fibrillin-1 by dramatically levels of matrix-associated MAGP-2 Because overexpression of did not levels of soluble MAGP-2 to the matrix and because fibrillins are the known matrix proteins binding MAGP-2, this that matrix regulates matrix assembly of MAGP-2, by binding MAGP-2. This in that MAGP-2 overexpression stimulate elastic fiber assembly matrix assembly of MAGP-2 Elastic by Matrix of whether MAGP-2 stimulates elastic fiber assembly by matrix assembly of fibrillins, we at the of MAGP-2 overexpression matrix-associated fibrillin-1 in cells is not expressed in data not MAGP-2 overexpression was associated with an matrix-associated fibrillin-1 that with matrix-associated MAGP-2 and and elastic fibers and However, of MAGP-2 overexpression dramatically matrix-associated MAGP-2 and elastic as and it did not matrix-associated fibrillin-1 and These data that MAGP-2 does not stimulate elastic fiber assembly by matrix assembly of They also that in in vitro matrix-associated fibrillin-1 is but not for elastic fiber assembly, as it also required MAGP-2. MAGP-2 Elastic by of MAGP-1, or the molecular basis for MAGP-2-induced elastic fiber assembly, we whether elastic fiber components other than fibrillin-1 mediate the of MAGP-2 elastic including major structural components of microfibrils MAGP-1, as well as interface molecules fibulin-2, fibulin-5, and in elastogenesis (3Chu M. Communication: 2nd National Meeting of the American Society for Matrix Biology, San Diego, CA, November, 10-13, 2004, Abstr. 28.American Society for Matrix Biology. 2004; Google Scholar, 4Yanagisawa H. Davis E.C. Starcher B.C. Ouchi T. Yanagisawa M. Richardson J.A. Olson E.N. Nature. 2002; 415: 168-171Crossref PubMed Scopus (487) Google Scholar, 5Zanetti M. Braghetta P. Sabatelli P. Mura I. Doliana R. Colombatti A. Volpin D. Bonaldo P. Bressan G.M. Mol. Cell. Biol. 2004; 24: 638-650Crossref PubMed Scopus (142) Google Scholar). we at the of MAGP-2 overexpression matrix-associated MAGP-1, fibulin-2, and by and by cells overexpressing MAGP-2 showed an elastic fiber that with matrix-associated MAGP-1 and and and and However, of MAGP-2 overexpression dramatically elastic fiber levels, it did not matrix-associated levels of MAGP-1 and and and and MAGP-2 overexpression did not levels of These data that MAGP-2 does not stimulate elastic fiber assembly by matrix-associated levels of MAGP-1, fibulin-2, fibulin-5, or emilin-1, and their is to for a of overexpression does not elastic fiber assembly by cells conditionally overexpressing MAGP-2, and constitutively tropoelastin, for with or in the or the of Matrix and cell in and proteins for MAGP-2 and by Matrix of Elastic and MAGP-2 by MAGP-2 by the MAGP-2 contains an RGD a motif is known to be required in matrix assembly of proteins as as for C. J.A. Cell. 1995; Full Text PDF PubMed Scopus Google Scholar). To whether binding of MAGP-2 to integrin may mediate MAGP-2-induced elastic fiber assembly, we the RGD of MAGP-2 to and at the of this mutation elastic fiber assembly cells conditionally overexpressing this MAGP-2 to cells overexpressing MAGP-2, cells overexpressing MAGP-2 with a RGD showed a in matrix levels of MAGP-2 a and elastic fibers that These that the MAGP-2 RGD does not regulate elastic fiber assembly, suggesting that MAGP-2 does not stimulate elastic fiber assembly by with an integrin receptor as αvβ3 (22Gibson M.A. Leavesley D.I. Ashman L.K. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Moreover, because matrix assembly of MAGP-2 is increased overexpression of the MAGP-2 RGD this also that matrix assembly of MAGP-2 is not by its an in vitro model featuring levels of extracellular soluble tropoelastin we in this that stimulates elastic fiber assembly, independently of its RGD MAGP-2 did not stimulate elastic fiber assembly by microfibril assembly, as structural components of microfibrils, fibrillin-1 and MAGP-1, not by MAGP-2. Because is not expressed in of fibrillin-1 with MAGP-1 a of the microfibril because fibrillin-1 with elastic fibers also showed that MAGP-2 does not stimulate elastic fiber assembly by levels of fibulin-2, fibulin-5, and emilin-1. MAGP-2 is not known to to these we the that MAGP-2 its elastin deposition by the or ultrastructural of of possibly their interaction with tropoelastin or cell molecular into the of elastic fiber assembly by MAGP-2 by a and ultrastructural analysis of elastic fibers by cells in the or the of exogenous MAGP-2. In the of exogenous MAGP-2 the elastic fiber is by large tropoelastin globules that are specifically in a structure by elastic fibers and These large globules are also overexpression of MAGP-2, they to have into to elastic fibers. of elastin globules to the elastic fiber and from an by the interaction of the tropoelastin tropoelastin to in large B.A. Starcher B.C. J. Biol. Chem. Full Text PDF PubMed Google Scholar). Because these elastin globules are in cells overexpressing or not MAGP-2, this that MAGP-2 does not stimulate elastic fibers assembly by or of tropoelastin by important in elastic fiber assembly, in stages of fiber an for MAGP-2-induced elastic fiber assembly. However, shown that tropoelastin is not required for the deposition of tropoelastin onto developing elastic fiber (6Kozel B.A. Ciliberto C.H. Mecham R.P. Matrix Biol. 2004; 23: 23-34Crossref PubMed Scopus (65) Google Scholar). of elastic fiber assembly by MAGP-2 to be increased elastic fibers in exogenous have a structure than in with fibers in the of as deposition of soluble tropoelastin onto microfibrils to the as with exogenous MAGP-2 (6Kozel B.A. Ciliberto C.H. Mecham R.P. Matrix Biol. 2004; 23: 23-34Crossref PubMed Scopus (65) Google Scholar). it that MAGP-2 elastic fiber assembly by tropoelastin with analysis of expression in cells MAGP-2 overexpression showed change in expression of and two of its protein and not molecular of the of elastic fiber assembly by MAGP-2 is the of elastin and MAGP-2-associated This that MAGP-2 controls elastic fiber assembly from its matrix-associated The in that be a interaction of matrix-associated MAGP-2 with However, from cell overexpressing MAGP-2 and tropoelastin did not binding of MAGP-2 to elastin not with previous binding studies the that showed interaction of MAGP-2 with fibrillins but not elastin (18Penner A.S. Rock M.J. Kielty C.M. Shipley J.M. J. Biol. Chem. 2002; 277: 35044-35049Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar). MAGP-2 tropoelastin deposition through elastic fiber-associated Fibrillin-1 is a candidate because it binds MAGP-2 and tropoelastin (14Clarke A.W. Wise S.G. Cain S.A. Kielty C.M. Weiss A.S. Biochemistry. 2005; 44: 10271-10281Crossref PubMed Scopus (56) Google Scholar, A.S. Rock M.J. Kielty C.M. Shipley J.M. J. Biol. Chem. 2002; 277: 35044-35049Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar, C. I. D. T. L. J. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). binding of MAGP-2 to fibrillin-1 may stimulate matrix assembly of fibrillin-1, which in stimulate tropoelastin deposition onto However, we that MAGP-2 overexpression does not assembly of matrix-associated To the of matrix-associated MAGP-2 regulates elastic fiber assembly, alignment of elastin globules onto microfibrils have to be The in microscopy have shown the of cells the of cell elastic fiber assembly A. J. B.A. Mecham R.P. Davis E.C. J. Cell. PubMed Scopus Google Scholar, B.A. A. J. Davis E.C. M.A. Mecham R.P. J. Cell. PubMed Scopus (139) Google Scholar). microscopy shown that elastic fiber assembly is a that and to the of small cell tropoelastin globules that in with to the of these globules onto elastic fiber they into structures that be into data do not that MAGP-2 because elastin globules are in cell whether or not MAGP-2 is MAGP-2 the of elastic fiber macroassembly microfibril-associated elastin globules into MAGP-2 overexpression be associated with alterations in data of major microfibril structural fibrillin-1 and MAGP-1, suggesting MAGP-2 does not this of MAGP-2 may regulate the early stages of elastic fiber macroassembly, including of tropoelastin globules from the cell membrane onto the developing fiber. In that as the cell interacts with a elastic the tropoelastin globules the cell are the of elastic fiber and into the structure B.A. A. J. Davis E.C. M.A. Mecham R.P. J. Cell. PubMed Scopus (139) Google Scholar). The molecular basis of elastic fiber is not known but cell-matrix interaction MAGP-2. with this MAGP-2 interacts with Jagged-1 A. G. Shipley J.M. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar), a protein and an for its receptor J. G. Cell. 1995; Full Text PDF PubMed Scopus Google Scholar), which a critical role in matrix of interaction and cell C. I. D. T. L. J. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). matrix-associated MAGP-2 regulate elastic fiber assembly by binding cells release of elastin globules from the cell onto the fiber. have that MAGP-2 stimulates type collagen expression R. Korn J.H. Shipley J.M. Lafyatis R. Arthritis Rheum. 2005; PubMed Scopus Google Scholar). This a function of MAGP-2 in Because collagen and elastic fibers are widely expressed and play key in structural and of connective MAGP-2 as a critical of the extracellular matrix and may have a connective tissue and of Cell and of and of of for their in