Title :
Mac-2 binding protein is a cell-adhesive
protein of the extracellular matrix which self-assembles into ring-like structures and binds
beta1 integrins, collagens and
fibronectin
Abstract :
- Human Mac-2 binding protein ( M2BP ) was prepared in recombinant form from the culture medium of 293 kidney cells and consisted of a 92 kDa subunit
- The protein was obtained in a native state as indicated by CD spectroscopy, demonstrating alpha-helical and beta-type structure, and by protease resistance and immunological analysis
- It was highly modified by N- and O-glycosylation but not by glycosaminoglycans
- Ultracentrifugation showed non-covalent association into oligomers with molar masses of 1000-1500 kDa
- Electron microscopy showed ring-like shapes with diameters of 30-40 nm
- M2BP bound in solid-phase assays to collagens IV, V and VI, fibronectin and nidogen, but not to fibrillar collagens I and III or other basement membrane proteins
- The protein also mediated adhesion of cell lines at comparable strength with laminin
- Adhesion to M2BP was inhibited by antibodies to integrin beta1 subunits but not to alpha2 and alpha6 subunits , RGD peptide or lactose
- This distinguishes cell adhesion of M2BP from that of laminin and excludes involvement of lactose-binding galectin-3
- Immunological assays demonstrated variable secretion by cultured human cells of M2BP , which was detected in the extracellular matrix of several mouse tissues