Microfibril-associated glycoprotein-2 specifically interacts with a range of bovine and human cell types via alphaVbeta3 integrin.
Microfibril-associated glycoprotein (MAGP)-1 and MAGP-2 are small structurally related glycoproteins that are specifically associated with fibrillin-containing microfibrils. MAGP-2, unlike MAGP-1, contains an RGD motif with potential for integrin binding. To determine if the RGD sequence is active, a series of cell binding assays was performed. MAGP-2 was shown to promote the attachment and spreading of bovine nuchal ligament fibroblasts when coated onto plastic wells in molar quantities similar to those of fibronectin. In contrast, approximately 10-fold more MAGP-1 was required to support comparable levels of cell adhesion. The fibroblast binding to MAGP-2 was completely inhibited if the peptide GRGDSP or the MAGP-2-specific peptide GVSGQRGDDVTTVTSET was added to the reaction medium at a 10 microM final concentration. The control peptide GRGESP had no effect on the interaction. These findings indicate that the cell interaction with MAGP-2 is an RGD-mediated event. A monoclonal antibody to human alphaVbeta3 integrin (LM609) almost completely blocked cell attachment to MAGP-2 when added to the medium at 0.5 microgram/ml, whereas two monoclonal antibodies specific for the human beta1 integrin subunit, 4B4 (blocking) and QE2.E5 (activating), had no effect even at 10 microgram/ml. Fetal bovine aortic smooth muscle cells, ear cartilage chondrocytes, and arterial endothelial cells and human skin fibroblasts and osteoblasts were also observed to adhere strongly to MAGP-2. In addition, each cell type was able to spread on MAGP-2 substrate, with the exception of the endothelial cells, which remained spherical after 2 h of incubation. The binding of each cell type was blocked when the anti-alphaVbeta3 integrin antibody was included in the assay, indicating that alphaVbeta3 integrin is the major receptor for MAGP-2 on several cell types. Thus, MAGP-2 may mediate interactions between fibrillin-containing microfibrils and cell surfaces during the development of a variety of tissues.
Gibson
M A
MA
Department of Pathology, University of Adelaide, Adelaide, South Australia 5005. mgibson@medicine.adelaide.edu.au
Leavesley
D I
DI
Ashman
L K
LK
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002417:Cattle; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D003285:Contractile Proteins / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D011485:Protein Binding; D000072260:RNA Splicing Factors; D019030:Receptors, Vitronectin / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D003285:Contractile Proteins; D016326:Extracellular Matrix Proteins; D009842:Oligopeptides; D000072260:RNA Splicing Factors; D019030:Receptors, Vitronectin; C016598:microfibrillar protein; C047981:arginyl-glycyl-aspartic acid