CD36 mediates binding of soluble thrombospondin-1 but not cell adhesion and haptotaxis on immobilized thrombospondin-1.
In this study, we examined the binding of soluble TSP1 (and ox-LDL) to CD36-transfected cells and the mechanisms by which immobilized TSP1 mediated attachment and haptotaxis (cell migration towards a substratum-bound ligand) of these transfected cells. CD36 cDNA transfection of NIH 3T3 cells clearly induced a dramatic increase in binding of both soluble [125I]-TSP1 and [125I]-ox-LDL to the surface of CD36-transfected cells, indicating that there was a gain of function with CD36 transfection in NIH 3T3 cells. Despite this gain of function, mock- and CD36-transfected NIH 3T3 cells attached and migrated to a similar extent on immobilized TSP1. An anti-TSP1 oligoclonal antibody inhibited CD36-transfected cell attachment to TSP1 while function blocking anti-CD36 antibodies, alone or in combination with heparin, did not. A series of fusion proteins encompassing cell-recognition domains of TSP1 was then used to delineate mechanisms by which NIH 3T3 cells adhere to TSP1. Although CD36 binds soluble TSP1 through a CSVTCG sequence located within type 1 repeats, 18,19CD36-transfected NIH 3T3 cells did not attach to immobilized type 1 repeats while they did adhere to the N-terminal, type 3 repeats (in an RGD-dependent manner) and the C-terminal domain of TSP1. Conversely, Bowes melanoma cells attached to type 1 repeats and the N- and C-terminal domains of TSP1. However, CD36cDNA transfection of Bowes cells did not increase cell attachment to type 1 repeats compared to that observed with mock-transfected Bowes cells. Moreover, a function blocking anti-CSVTCG peptide antibody did not inhibit the attachment of mock- and CD36-transfected Bowes cells to type 1 repeats. It is suggested that CD36/TSP1 interaction does not occur upon cell-matrix adhesion and haptotaxis because TSP1 undergoes conformational changes that do not allow the exposure of the CD36 binding site.
Magnetto
S
S
INSERM Research Unit 403, Hôpital Edouard Herriot, Lyon, France.
Bruno-Bossio
G
G
Voland
C
C
Lecerf
J
J
Lawler
J
J
Delmas
P
P
Silverstein
R
R
Clezardin
P
P
D016475:3T3 Cells; D000818:Animals; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002633:Chemotaxis; D008545:Melanoma; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D012995:Solubility; D019700:Thrombospondin 1 / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D018955:CD36 Antigens; D009842:Oligopeptides; D011994:Recombinant Proteins; D019700:Thrombospondin 1; C047981:arginyl-glycyl-aspartic acid