Characterization of Microfibrillar-associated Protein 4 (MFAP4) as a Tropoelastin- and Fibrillin-binding Protein Involved in Elastic Fiber Formation

• Published in: The Journal of biological chemistry 2016-01, Vol.291 (3), p.1103-1114
• Main Authors: Pilecki, Bartosz, Holm, Anne T., Schlosser, Anders, Moeller, Jesper B., Wohl, Alexander P., Zuk, Alexandra V., Heumüller, Stefanie E., Wallis, Russell, Moestrup, Soren K., Sengle, Gerhard, Holmskov, Uffe, Sorensen, Grith L.
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; analytical ultracentrifugation; Animals; calcium-binding protein; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Desmosine - metabolism; Elastic Tissue - metabolism; elastin; Extracellular Matrix Proteins - chemistry; Extracellular Matrix Proteins - genetics; Extracellular Matrix Proteins - metabolism; fibrillin; Fibrillin-1; Fibrillins; Glycobiology and Extracellular Matrices; Glycoproteins - chemistry; Glycoproteins - genetics; Glycoproteins - metabolism; Humans; Ligands; Male; Mice, Inbred C57BL; Mice, Mutant Strains; microfibrillar-associated protein 4; Microfibrils - metabolism; Microfilament Proteins - chemistry; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Models, Molecular; Mutation; Peptide Fragments - chemistry; Peptide Fragments - genetics; Peptide Fragments - metabolism; Protein Interaction Domains and Motifs; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein Multimerization; Protein Transport; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; site-directed mutagenesis; surface plasmon resonance (SPR); Tropoelastin - chemistry; Tropoelastin - genetics; Tropoelastin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.681775

MFAP4 (microfibrillar-associated protein 4) is an extracellular glycoprotein found in elastic fibers without a clearly defined role in elastic fiber assembly. In the present study, we characterized molecular interactions between MFAP4 and elastic fiber components. We established that MFAP4 primarily assembles into trimeric and hexameric structures of homodimers. Binding analysis revealed that MFAP4 specifically binds tropoelastin and fibrillin-1 and -2, as well as the elastin cross-linking amino acid desmosine, and that it co-localizes with fibrillin-1-positive fibers in vivo. Site-directed mutagenesis disclosed residues Phe241 and Ser203 in MFAP4 as being crucial for type I collagen, elastin, and tropoelastin binding. Furthermore, we found that MFAP4 actively promotes tropoelastin self-assembly. In conclusion, our data identify MFAP4 as a new ligand of microfibrils and tropoelastin involved in proper elastic fiber organization.