Retinoids and phorbol esters alter release of fibronectin from enucleated cells.

Abstract

Addition of 12-tetradecanoylphorbol 13-acetate (TPA) to cultures of intact Swiss mouse 3T3 fibroblasts induced a dose-dependent increase in ornithine decarboxylase (OrnDCase) activity. Over the same concentration range, 10-9 to 10-6 M, TPA induced the release of radioactively labeled fibronectin (FN) from the cells into the culture medium. Retinoic acid, a derivative of vitamin A, inhibited in a dose-dependent manner both the increase in OrnDCase activity and the release of FN induced by TPA. To examine the effects of TPA and retinoic acid in enucleated cells, the cells were treated with 7.5 ,.g of cytochalasin B per ml of medium during centrifugation at 10,000 X g for 35 min at 370C. In a series offive experiments, the treated cells were 94.7 ± 4.8% (± SEM) enucleated as measured by [3H]thymidine incorporation and verified by Giesma staining for nuclei. In the enucleated cells, TPA did not induce increased OrnDCase activity but did induce FN release in a dose-dependent fashion over the same concentration range effective for FN release from intact cells. Moreover, addition of retinoic acid to the enucleated cells inhibited the phorbol ester-induced release of FN in a dose-dependent manner. A series of phorbol ester derivatives showed the same order of activity in causing FN release from the enucleated cells as reported for inducing OrnDcase activity in intact cells or in promoting mouse skin tumors in vivo. Similarly, several retinoids were tested for their ability to inhibit the phorbol ester-induced release of FN from enucleated cells. The efficacy of the retinoids in preventing FN release paralleled their activity in inhibiting phorbol ester-induced OrnDCase activity and skin tumor promotion, as reported in the literature. We conclude that at least one aspect of tumor promotion induced by phorbol esters-the loss of FN-does not require the cell nucleus, and further, that retinoids can inhibit this aspect of tumor promotion without nuclear involvement.From the recent work of Liau et al. demonstrating the binding of retinol to chromatin (1) and that of Fuchs and Green on the regulation of specific messenger RNA by retinol (2), one can safely conclude that in its normal physiological function, vitamin

Retinoic acid inhibits calmodulin binding to human erythrocyte membranes and reduces membrane Ca2(+)-adenosine triphosphatase activity.

“…The mechanisms of the actions of retinoic acid and its parent, retinol, appear to be nuclear (21,22) as well as extranuclear (23). In the present studies we have shown that retinoic acid, but not retinol, is a "calmodulin antagonist" in the context of the activation of human red cell Ca2+-ATPase by calmodulin.…”

Spatial and temporal pattern of expression of the cellular retinoic acid-binding protein and the cellular retinol-binding protein during mouse embryogenesis.

“…The retinoids exert profound effects on development and differentiation in a wide variety of systems (1)(2)(3)(4)(5)(6)(7). In the developing chick limb, retinoic acid has the ability to change the positional information of cells in a very precise manner: for example, application of retinoic acid to the side opposite the zone of polarizing activity causes digit pattern duplication (8,9).…”

Role of protein kinase C in diacylglycerol-mediated induction of ornithine decarboxylase and reduction of epidermal growth factor binding.

“…5) Although protein kinase C appears to be involved in these responses, the mechanism by which they are affected is not identical. ODCase induction involves a nuclear event, whereas reduction of EGF binding does not (5)(6)(7)17). We hypothesize that activation of protein kinase C transmits a signal to the nucleus, which results in enhanced transcription of the ODCase gene and increased ODCase synthesis.…”

“…A strong correlation exists between the induction of ODCase and the promotion of tumor formation (4,(12)(13)(14)(15)(16). Unlike the inhibition of EGF binding (5)(6)(7)(8), ODCase induction requires nuclear events (17).…”