Fibrillin-1 and fibulin-2 interact and are colocalized in some tissues.
Microfibrils 10-12 nm in diameter are found in elastic and non-elastic tissues with fibrillin as a major component. Little is known about the supramolecular structure of these microfibrils and the protein interactions it is based on. To identify protein binding ligands of fibrillin-1, we tested binding of recombinant fibrillin-1 peptides to different extracellular matrix proteins in solid phase assays. Among the proteins tested, only fibulin-2 showed significant binding to rF11, the N-terminal half of fibrillin-1, in a calcium-dependent manner. Surface plasmon resonance demonstrated high affinity binding with a Kd = 56 nM. With overlapping recombinant fibrillin-1 peptides, the binding site for fibulin-2 was narrowed down to the N terminus of fibrillin-1 (amino acid positions 45-450). Immunofluorescence in tissues demonstrated colocalization of fibrillin and fibulin-2 in skin, perichondrium, elastic intima of blood vessels, and kidney glomerulus. Fibulin-2 was not present in ocular ciliary zonules, tendon, and the connective tissue around kidney tubules and lung alveoli, which all contain fibrillin. Immunogold labeling of fibulin-2 on microfibrils in skin was found preferentially at the interface between microfibrils and the amorphous elastin core, suggesting that in vivo the interaction between fibrillin-1 and fibulin-2 is regulated by cellular expression and deposition as well as by protein-protein interactions.
Reinhardt
D P
DP
Shriners Hospital For Crippled Children, Portland, Oregon 97201, USA.
Sasaki
T
T
Dzamba
B J
BJ
Keene
D R
DR
Chu
M L
ML
Göhring
W
W
Timpl
R
R
Sakai
L Y
LY
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D002648:Child; D017931:DNA Primers; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D000071838:Fibrillin-1; D000071837:Fibrillins; D006801:Humans; D007700:Kinetics; D008297:Male; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D012867:Skin / Q000378:metabolism / Q000648:ultrastructure; D013045:Species Specificity; D054392:Adipokines
D002135:Calcium-Binding Proteins; D017931:DNA Primers; D016326:Extracellular Matrix Proteins; D000071838:Fibrillin-1; D000071837:Fibrillins; D008840:Microfilament Proteins; D011994:Recombinant Proteins; C000605722:FBN1 protein, human; D054392:Adipokines; C000605724:Fbn1 protein, mouse; C084612:fibulin 2