Lectin binding to gp60 decreases specific albumin binding and transport in pulmonary artery endothelial monolayers
✍ Scribed by Alma Siflinger-Birnboim; Jan Schnitzer; Hazel Lum; Frank A. Blumenstock; Chien-Ping J. Shen; Peter J. Del Vecchio; Asrar B. Malik
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 938 KB
- Volume
- 149
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Theeffect of albumin binding to cultured bovine pulmonaryarteryendothelial cell (BPAEC) monolayers on the transendothelial flux of '251-labelled bovine serum albumin (BSA) was examined to determine its possible role on albumin transcytosis. The transport of '251-BSA tracer across BPAEC grown on gelatin-and fibronectin-coated filters (0.8 p m pore diam.) was affected by the presence of unlabelled BSA in the medium in that transendothelial '251-BSA permeability decreased, reaching a 40% reduction at BSA concentrations equal to or greater than 5 mgiml. BSA binding to BPAEC monolayers was saturated at concentration of 10 mg/ml with an apparent binding affinity of 6 x 1 0-7 M. In contrast, gelatin added to the medium altered neither '"I-BSA binding nor transport. Several lectins were tested for their ability to inhibit '"I-BSA binding and transport. One lectin, Ricinus communis (RCA), reduced '"I-BSA binding by 70% and transport by 40%. Other lectins, Ulex europaeus, Triticum vulgare, and Clycine max decreased neither '251-BSA binding nor transport. The reduction of I2'1-BSA transport by RCA was not observed in the presence of saturating levels of BSA, indicating that RCA influenced only the albumin-dependent component of transport. RCA, but not other lectins, precipitated a 60 kDa plasrnalemmal glycoprotein from cell lysates of surface radioiodinated BPAEC monolayers. This 60 kDa glycoprotein appears to be the equivalent of gp60 identified previously as an albumin binding glycoprotein in rat microvascular endothelium. In summary, approximately 40% of albumin transport across'BPAEC monolayers i s dependent on albumin binding. This component of albumin transport is inhibited by 80% by the binding of RCA to gp60. These results suggest that binding of albumin to gp60 on pulmonary artery endothelial cell membrane is a critical determinant of transendothelial albumin flux involving mechanisms such as plasmalemmal vesicular transcytosis.
Recent studies indicate that transendothelial flux of plasma molecules, such as insulin, transferrin, and albumin, may involve recognition by receptors located on the luminal side of the endothelial cell followed by transcytosis via plasmalemmal vesicles (Ghitescu,