When platelet-derived growth factor (PDGF) binds to its receptors a number of biochemical reactions are elicited in the cell. Several models have been presented for the effects of ligand-induced receptor conformation and aggregation on signal transduction but little is known about the direct effects on receptor diffusion. This study concerns the lateral mobility of PDGF receptors in fibroblasts. It was assessed with fluorescence recovery after photobleaching (FRAP), using rhodaminated receptor antibodies or Fab-fragments of the antibody as ligands. The aims of the investigation were: (a) to compare the lateral mobility of membrane receptors of human fibroblasts labelled with either antibodies against the PDGF receptor or Fab-fragments of the same antibodies, and (b) to study the effects of serum or PDGF on the mobility of the receptors. Human foreskin fibroblasts (AG 1523) were grown on coverslips either under standard or under serum-free conditions yielding “normal” and “starved” cells, respectively. Two parameters of the diffusion were evaluated; the diffusion coefficient (D) and the mobile fraction (R) of the receptors. We found that normal fibroblasts had a smaller diffusion coefficient and a lower mobile fraction compared to starved cells using antibodies for receptor labelling. The addition of PDGF, just before the measurement, increased the D and R for normal cells, while starved cells, showing higher initial values, displayed slightly reduced values of D and R. After the addition of serum, D increased and R remained low for normal cells, whereas for starved cells both D and R increased to upper limits of 11.0×10−10 cm2s−1 and >90% respectively. In general, the D and R values, both in normal and starved cells, were higher for cells labelled with Fab-fragments than for antibody-labelled cells. The results are discussed in relation to the natural complexity of the receptor, and how PDGF, serum, antibodies and Fab-fragments might interfere with receptor structure, aggregation state and membrane diffusion characteristics.
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February 01 1991
Lateral diffusion of PDGF β-receptors in human fibroblasts
Pia Ljungquist-Höddelius;
Pia Ljungquist-Höddelius
aDepartment of Cell Biology, Faculty of Heath Sciences, University of Linköping, S-581 85 Linköping, Sweden
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Margareta Lirvall;
Margareta Lirvall
aDepartment of Cell Biology, Faculty of Heath Sciences, University of Linköping, S-581 85 Linköping, Sweden
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Åke Wasteson;
Åke Wasteson
aDepartment of Cell Biology, Faculty of Heath Sciences, University of Linköping, S-581 85 Linköping, Sweden
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Karl-Eric Magnusson
Karl-Eric Magnusson
bDepartment of Medical Microbiology, Faculty of Heath Sciences, University of Linköping, S-581 85 Linköping, Sweden
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Publisher: Portland Press Ltd
Received:
October 08 1990
Revision Requested:
November 19 1990
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© 1991 Plenum Publishing Corporation
1991
Biosci Rep (1991) 11 (1): 43–52.
Article history
Received:
October 08 1990
Revision Requested:
November 19 1990
Citation
Pia Ljungquist-Höddelius, Margareta Lirvall, Åke Wasteson, Karl-Eric Magnusson; Lateral diffusion of PDGF β-receptors in human fibroblasts. Biosci Rep 1 February 1991; 11 (1): 43–52. doi: https://doi.org/10.1007/BF01118604
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