Experimental Cell Research 170 (1987) 290-299 Specific Modulation of Surface Receptors in J.774 Macrophages by Anchorage M. A. VENTURA,’ F. LOUACHE,’ M. ROUIS,’ D. ERLICH,3 S. GOLDSTEIN,3 U. TESTA and P. THOMOPOULOS’,* ‘U-282 INSERM and ‘U-91 INSERM, H6pital Henri Mondor, 94010 CrCteil, ‘Laboratoire de Biochimie (INSERM), Facult.6 de Medecine Saint-Antoine, F-75012 Paris, France, and “Laboratorio di Ematologia, Istituto Superiore di Sanitir, Rome, Italy The 5.774 murine macrophage cells were cultured in suspension in Teflon flasks. When allowed to attach on culture plastic dishes, a 2-3-fold increase in transferrin binding was observed. This occurred in 10 min, reached a steady state at 60 min, remained stable for several hours and was reversible after resuspension of the cells at 37°C.The phenomenon was not dependent on the synthesis of new protein. An opposite change of acetyl LDL receptors was observed, with a threefold decrease of the binding 1 h after the attachment of the cells. The increase of transferrin binding affected almost equally the cell surface and the intracellular sites; therefore it could not be related to a simple shift between these two compartments. It is suggested that the attachment of the cells induced a recruitment of binding sites from a ‘silent’ pool of receptors. Serum factors, as well as phorbol esters and db-CAMP potentiated the effect of anchorage. @ 1987 Academic PRSS, IK. It is well established that several functions of cells are regulated by cell-surface contact. The attachment of cells to a solid substrate is followed by an obvious change in cell shape, which switches from a globular to a spread morphology [ 11. The cellular growth [l, 21, the migratory activity [3] and the metastatic capability of tumour cells [4] are profoundly altered; the expression of differentiation markers is influenced by the adherence [5, 61; DNA, RNA and protein synthesis are affected, as well as the post-translational processing of membrane and secret- ed proteins [7-l 11. The fluidity of the plasma membrane [ 121 and the transmem- brane signalling [l, 21 are also dependent on the substrate upon which the cultures are maintained. Cells of the mononuclear phagocyte system provide a useful model for studies on the attachment; they naturally switch during their life from a circulating form suspended in blood, the monocyte, to a fixed form, the tissue macrophage; they attach quite rapidly on glass or plastic and can be modulated by various agents that affect their rate of spreading and other biological properties [ 131.In addition, normal mononuclear phagocytes or macrophage cell lines can be cultured on * To whom offprint requests should be sent. Address: U-282 INSERM, Hbpital Henri Mondor, 94010 Creteil, France. 290 Copyright @ 1987 by Academic Press, Inc. All rights of reproduction in any form reserved 0014-4827187 $03.00