Control of AKR fibroblast phenotype by fibronectin: regulation of cell-surface fibronectin binding receptor by fibronectin.
Results of previous studies show that the expression of fibronectin and its cell-surface fibronectin binding receptor is coregulated in 3-methylchloranthrene transformation of normal AKR-2B cells to form AKR-MCA cells and in N,N,-dimethylformamide (DMF) induction of differentiation of transformed AKR-MCA cells (1990, J. Cell. Physiol., 143:445). In this study, we tested the coregulation hypothesis by transfection experiments using an antisense fibronectin expression vector. We determined the effect of antisense fibronectin RNA expression on untransformed AKR-2B cells, and on the responses of transformed AKR-MCA cells to DMF treatment. Expression of antisense fibronectin RNA in AKR-2B cells down-modulated fibronectin production, reduced adhesion to extracellular fibronectin, and altered cellular morphology. Saturation binding and Scatchard analyses using radiolabelled fibronectin revealed a concurrent down-modulation of cell-surface fibronectin binding sites, but the binding affinity of the receptor for the ligand was not affected. Immunoblotting and immunostaining revealed down-modulation of the expression of alpha 5 beta 1 integrins. Expression of antisense fibronectin RNA in AKR-MCA cells down-modulated the ability of DMF to restore normal fibronectin production, cell-surface fibronectin binding receptor, adhesion to extracellular fibronectin, and cellular morphology. These studies show that both fibronectin and its cell-surface fibronectin binding receptor were tightly regulated during transformation and induction of differentiation in these cells, that the ligand and its cell-surface fibronectin binding receptor worked together to bring about phenotypic changes, and that fibronectin production regulated the expression of its cell-surface fibronectin binding receptor.
Division of Laboratory Medicine, University of Texas, M.D. Anderson Cancer Center, Houston 77030.
S
S
Huang
J
J
Varani
S
S
Chakrabarty
D000818:Animals; D002448:Cell Adhesion; D002455:Cell Division; D048429:Cell Size; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology*; D005353:Fibronectins / Q000502:physiology*; D015870:Gene Expression; D051379:Mice; D008806:Mice, Inbred AKR; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000235:genetics; D017469:Receptors, Fibronectin / Q000378:metabolism*
D005353:Fibronectins; D016372:RNA, Antisense; D012333:RNA, Messenger; D017469:Receptors, Fibronectin