Cylindrical substratum induces different patterns of actin microfilament bundles in nontransformed and in ras-transformed epitheliocytes.

The influence of the cylindrical substratum surface on the actin microfilament bundle and the extracellular matrix (fibronectin and laminin) patterns in nontransformed epithelial cells of the IAR-2 rat line and in their N-ras-transformed descendants, IAR-ras-c4 cells, was studied. The cells were cultured on substrata with cylindrical surfaces-fused quartz glass fibers with a diameter of 32 microm. Quantitative analysis of actin microfilament bundle alignment and immunomorphological study of fibronectin and laminin were used. IAR-2 epitheliocytes on the cylindrical substrata formed straight actin microfilament bundles and fibronectin- or laminin-positive fibrils aligned predominantly transversely to the cylinder axis. In contrast, in the majority of IAR-ras-c4 cells on the cylindrical substrata, the revealed straight microfilament bundles and the fibrils of the extracellular matrix were oriented approximately longitudinally to the cylinder axis; a small part of the transformed cells formed microfilament bundles and extracellular matrix patterns similar to those in the normal epitheliocytes on the cylindrical substrata. These results show that transformed epitheliocytes that acquired polarized morphology react to the curvature of the cylindrical substratum surface by actin cytoskeleton and extracellular matrix reorganization changes essentially different from those characteristic of normal discoid epitheliocytes on the cylindrical substrata, but similar to those observed in normal polarized cells, e.g., fibroblasts.