Fibrillin assembly requires fibronectin.
Fibrillins constitute the major backbone of multifunctional microfibrils in elastic and nonelastic extracellular matrices. Proper assembly mechanisms are central to the formation and function of these microfibrils, and their properties are often compromised in pathological circumstances such as in Marfan syndrome and in other fibrillinopathies. Here, we have used human dermal fibroblasts to analyze the assembly of fibrillin-1 in dependence of other matrix-forming proteins. siRNA knockdown experiments demonstrated that the assembly of fibrillin-1 is strictly dependent on the presence of extracellular fibronectin fibrils. Immunolabeling performed at the light and electron microscopic level showed colocalization of fibrillin-1 with fibronectin fibrils at the early stages of the assembly process. Protein-binding assays demonstrated interactions of fibronectin with a C-terminal region of fibrillin-1, -2, and -3 and with an N-terminal region of fibrillin-1. The C-terminal half of fibrillin-2 and -3 had propensities to multimerize, as has been previously shown for fibrillin-1. The C-terminal of all three fibrillins interacted strongly with fibronectin as multimers, but not as monomers. Mapping studies revealed that the major binding interaction between fibrillins and fibronectin involves the collagen/gelatin-binding region between domains FNI(6) and FNI(9).
Sabatier
Laetitia
L
Faculty of Medicine, Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada H3A 2B2.
Chen
Daliang
D
Fagotto-Kaufmann
Christine
C
Hubmacher
Dirk
D
McKee
Marc D
MD
Annis
Douglas S
DS
Mosher
Deane F
DF
Reinhardt
Dieter P
DP
D000595:Amino Acid Sequence; D001665:Binding Sites; D002675:Child, Preschool; D003094:Collagen / Q000378:metabolism; D020405:Dermis / Q000166:cytology; D005109:Extracellular Matrix / Q000378:metabolism; D000071838:Fibrillin-1; D000071840:Fibrillin-2; D000071837:Fibrillins; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D005780:Gelatin / Q000378:metabolism; D006801:Humans; D008297:Male; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D025941:Protein Interaction Mapping; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000378:metabolism; D054392:Adipokines
D003094:Collagen; D000071838:Fibrillin-1; D000071840:Fibrillin-2; D000071837:Fibrillins; D005353:Fibronectins; D005456:Fluorescent Dyes; D005780:Gelatin; D008840:Microfilament Proteins; D010455:Peptides; D011994:Recombinant Proteins; C000605722:FBN1 protein, human; D054392:Adipokines; C000605723:FBN2 protein, human