Carboxy-terminal conversion of profibrillin to fibrillin at a basic site by PACE/furin-like activity required for incorporation in the matrix.
Fibrillin-1, the main component of 10-12 nm microfibrils of the extracellular matrix, is synthesized as profibrillin and proteolytically processed to fibrillin. The putative cleavage site has been mapped to the carboxy-terminal domain of profibrillin-1, between amino acids arginine 2731 and serine 2732, by a spontaneous mutation in this recognition site that prevents profibrillin conversion. This site contains a basic amino acid recognition sequence (R-G-R-K-R-R) for proprotein convertases of the furin/PACE family. In this study, we use a mini-profibrillin protein to confirm the cleavage in the carboxy-terminal domain by both fibroblasts and recombinantly expressed furin/PACE, PACE4, PC1/3 and PC2. Site-directed mutagenesis of amino acids in the consensus recognition motif prevented conversion, thereby identifying the scissile bond and characterizing the basic amino acids required for cleavage. Using a PACE/furin inhibitor, we show that wild-type profibrillin is not incorporated into the extracellular matrix until it is converted to fibrillin. Therefore, profibrillin-1 is the first extracellular matrix protein to be shown to be a substrate for subtilisin-like proteases, and the conversion of profibrillin to fibrillin controls microfibrillogenesis through exclusion of uncleaved profibrillin.
Raghunath
M
M
Department of Physiological Chemistry and Pathobiochemistry and of Medical Physics and Biophysics, University of Münster, Münster, Germany.
Putnam
E A
EA
Ritty
T
T
Hamstra
D
D
Park
E S
ES
Tschödrich-Rotter
M
M
Peters
R
R
Rehemtulla
A
A
Milewicz
D M
DM
D000818:Animals; D019556:COS Cells; D017931:DNA Primers; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism*; D000071837:Fibrillins; D045683:Furin; D008840:Microfilament Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D011498:Protein Precursors / Q000378:metabolism*; D011994:Recombinant Proteins; D013381:Subtilisins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism
D017931:DNA Primers; D000071837:Fibrillins; D008840:Microfilament Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D004533:Egtazic Acid; D013381:Subtilisins; D045683:Furin