Fibrillin-1 and Fibulin-2 Interact and Are Colocalized in Some Tissues

doi:10.1074/jbc.271.32.19489

Fibrillin-1 and Fibulin-2 Interact and Are Colocalized in Some Tissues*

From the ^‡ Shriners Hospital For Crippled Children, Portland, Oregon 97201,
^§ Max-Planck-Institut für Biochemie, D-82152 Martinsried, Federal Republic of Germany,
^¶ Department of Biochemistry and Molecular Biology and Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, and
^∥ Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, Oregon 97201

^” To whom correspondence should be addressed:
Shriners Hospital For Crippled Children, Portland, OR 97201.
Tel.: 503-221-3436; Fax: 503-221-3451.

Abstract

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 K_d = 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.

Footnotes

↵* This work was supported by Fellowship Re 1021/1-1 (to D. P. R.) and Sonderforschungsbereich 266 from the Deutsche Forschungsgemeinschaft, by Grant AR38923 (to M. L. .C) from the National Institutes of Health, and by the Shriners Hospitals. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

EGF

epidermal growth factor

ECM

extracellular matrix

cb

calcium binding

mAb

monoclonal antibody

PBS

phosphate-buffered saline

TBS

Tris-buffered saline.
- Received March 25, 1996.
- Revision received May 15, 1996.