Raman Microscopy and X-ray Diffraction, a Combined Study of Fibrillin-rich Microfibrillar Elasticity

Haston, J. Louise; Engelsen, Søren B.; Roessle, Manfred; Clarkson, John; Blanch, Ewan W.; Baldock, Clair; Kielty, Cay M.; Wess, Timothy James

doi:10.1074/jbc.m212854200

Cited by 28 publications

(23 citation statements)

References 25 publications

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“…We suggest that the structure of guanidine-extracted microfibrils more closely resemble microfibrils within tissues, because fibrillin-1 does not appear to be degraded in the guanidine-extracted microfibrils. Average bead-to-bead periodicities of guanidine-extracted microfibrils were around 50 nm, consistent with the measurements of antibody-induced periodicities of microfibrils in tissues (3,6) and x-ray diffraction studies of dissected ocular zonules (27). Stretching experiments of tissues containing microfibrils have demonstrated reversible elastic changes in microfibril periodicities.…”

Section: Discussionsupporting

confidence: 63%

“…Stretching experiments of tissues containing microfibrils have demonstrated reversible elastic changes in microfibril periodicities. Tissue extension (150%) of zonular microfibrils resulted in reversible periodicities up to 104 nm, and longer periodicities were not observed (27). In our studies, guanidine-extracted microfibrils extended only to 80 nm, but these microfibrils were not stretched.…”

Section: Discussionmentioning

confidence: 63%

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Effects of Fibrillin-1 Degradation on Microfibril Ultrastructure

Kuo

Isogai

Keene

et al. 2007

Journal of Biological Chemistry

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Current models of the elastic properties and structural organization of fibrillin-containing microfibrils are based primarily on microscopic analyses of microfibrils liberated from connective tissues after digestion with crude collagenase. Results presented here demonstrate that this digestion resulted in the cleavage of fibrillin-1 and loss of specific immunoreactive epitopes. The proline-rich region and regions near the second 8-cysteine domain in fibrillin-1 were easily cleaved by crude collagenase. Other sites that may also be cleaved during microfibril digestion and extraction were identified. In contrast to collagenase-digested microfibrils, guanidine-extracted microfibrils contained all fibrillin-1 epitopes recognized by available antibodies. The ultrastructure of guanidine-extracted microfibrils differed markedly from that of collagenase-digested microfibrils. Fibrillin-1 filaments splayed out, extending beyond the width of the periodic globular beads. Both guanidine-extracted and collagenase-digested microfibrils were subjected to extensive digestion by crude collagenase. Collagenase digestion of guanidine-extracted microfibrils removed the outer filaments, revealing a core structure. In contrast to microfibrils extracted from tissues, cell culture microfibrils could be digested into short units containing just a few beads. These data suggest that additional cross-links stabilize the long beaded microfibrils in tissues. Based on the microfibril morphologies observed after these experiments, on the crude collagenase cleavage sites identified in fibrillin-1, and on known antibody binding sites in fibrillin-1, a model is proposed in which fibrillin-1 molecules are staggered in microfibrils. This model further suggests that the N-terminal half of fibrillin-1 is asymmetrically exposed in the outer filaments, whereas the C-terminal half of fibrillin-1 is present in the interior of the microfibril.Microfibrils have been extracted from a variety of tissues and visualized by electron microscopy as distinctive beaded string structures (1, 2). The molecular composition of these structures is assumed to be complex. However, based upon immunolocalization of fibrillin to these structures (2, 3) and the shape of fibrillin monomers (4, 5), fibrillins are thought to be the major backbone components of these extracted microfibrils. Fibrillincontaining microfibrils are ubiquitous in the connective tissue space (6), providing architectural support as well as information essential for appropriate signaling during morphogenesis (7-9). In human disorders associated with fibrillins, the structural integrity of fibrillin microfibrils is required for the proper function of certain connective tissues (10). Therefore, determination of the organization of fibrillin molecules within the microfibril is important basic information.The organization of fibrillin molecules within microfibrils has been controversial. Both parallel (head-to-tail) (3, 4) and antiparallel (11) arrangements of fibrillin molecules within microfibrils have been...

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Section: Discussionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 63%

Effects of Fibrillin-1 Degradation on Microfibril Ultrastructure

Kuo

Isogai

Keene

et al. 2007

Journal of Biological Chemistry

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“…Interestingly, fibrillin is not always associated with elastic fibers. Fibrillin can often be found by itself, in which it may independently function as a mechanical, load-bearing but highly extensible scaffold [40]. Numerous domains in fibrillin exist for binding integrins, heparan sulafate proteoglycans, and growth factors, which point to substantial roles for alone fibrillin and mature elastic fibers in mediating cell signaling and adhesion [41].…”

Section: Elastic Fibers Comprise a Significant Portion Of The Ventricmentioning

confidence: 99%

Extracellular Matrix Organization, Structure, and Function

Wiltz¹,

Arevalos²,

Balaoing³

et al. 2013

Calcific Aortic Valve Disease

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“…The identification of a second MAGP-2 attachment site at the shoulder region of the microfibrils suggests that MAGP-2 aggregates may be involved in the fusion of the two arms by cross-linking two parallel bundles of fibrillin monomers at this point of the interbead substructure. The microfibrils are considered to have some capacity for elasticity (16,17), although recent evidence indicates that they are relatively stiff structures (18). The extent of cross-linking of MAGPs within the microfibril may influence the degree of unfolding permitted to the fibrillin monomers and thus MAGPs may control microfibril extensibility.…”

Section: Fig 6 Magp-2 Is Periodically Associated Along the Microfibmentioning

confidence: 99%

“…The fibrillin molecules appear to be arranged within the microfibrils as parallel bundles of 4 -8 molecules joined in series in a head-to-tail manner. However, the precise organization of the fibrillin monomers remains to be elucidated, and several models for the molecular architecture of the microfibrils have been proposed (15)(16)(17)(18). Recent evidence suggests that fibrillins 1 and 2 can form separate microfibrils but that the proteins can also occur within the same microfibril (14).…”

mentioning

confidence: 99%

MAGP-2 Has Multiple Binding Regions on Fibrillins and Has Covalent Periodic Association with Fibrillin-containing Microfibrils

Hanssen

Hew

Moore

et al. 2004

Journal of Biological Chemistry

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The interactions of microfibril-associated glycoprotein (MAGP)-2 have been investigated with fibrillins and fibrillin-containing microfibrils. Solid phase binding assays were conducted with recombinant fragments covering fibrillin-1 and most of fibrillin-2. MAGP-2, and its structure relative MAGP-1, were found to bind two fragments spanning the N-terminal half of fibrillin-1 and an N-terminal fragment of fibrillin-2. Blocking experiments indicated that MAGP-2 had a binding site(s) close to the N terminus of the fibrillin-1 molecule that was distinct from that for MAGP-1 and an additional, more central binding site(s) that may be shared by the two MAGPs. Immunogold labeling of developing nuchal ligament tissue showed that MAGP-2 had regular covalent and periodic (about 56 nm) association with fibrillin-containing microfibrils of elastic fibers in this tissue. Further analysis of isolated microfibrils indicated that MAGP-2 was attached at two points along the microfibril substructure, "site 1" on the "beads" and "site 2" at the "shoulder" of the interbead region close to where the two "arms" fuse. In contrast, MAGP-1 was located only on the beads. Comparison of the MAGP-2 binding data with known fibrillin epitope maps of the microfibrils showed that site 1 correlated with the N-terminal MAGP-2 binding region, and site 2 correlated with the second, more central, MAGP-2 binding region on the fibrillin-1 molecule. Of particular note, immunolabeling at site 2 was markedly decreased, relative to that at site 1, on extended microfibrils with beadto-bead periods over 90 nm, suggesting that site 2 may move toward the beads when the microfibril is stretched. The study points to MAGP-2 being an integral component of some populations of fibrillin-containing microfibrils. Moreover, the identification of multiple MAGP-binding sequences on fibrillins supports the concept that MAGPs may function as molecular cross-linkers, stabilizing fibrillin monomers in folded conformation within or between the microfibrils, and thus MAGPs may be implicated in the modulation of the elasticity of these structures.

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Raman Microscopy and X-ray Diffraction, a Combined Study of Fibrillin-rich Microfibrillar Elasticity

Cited by 28 publications

References 25 publications

Effects of Fibrillin-1 Degradation on Microfibril Ultrastructure

Effects of Fibrillin-1 Degradation on Microfibril Ultrastructure

Extracellular Matrix Organization, Structure, and Function

MAGP-2 Has Multiple Binding Regions on Fibrillins and Has Covalent Periodic Association with Fibrillin-containing Microfibrils

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