Three-dimensional collagen regulates collagen gene expression by a mechanism that requires serine/threonine kinases and is independent of mechanical contraction

Integrin alpha1 beta1, one of the cellular collagen receptors, can particip ate in the regulation of collagen accumulation by acting as a negative feed back regulator. The molecular mechanism behind this phenomenon has been unk nown. We have plated cells inside three-dimensional collagen and analyzed a set of chemical inhibitors for various signal transduction pathways. Only two wide-spectrum serine/threonine kinase inhibitors, H-7 and iso-H-7 could prevent the downregulation of alpha1(I) collagen mRNA levels in cells expo sed to three-dimensional collagen. In monolayer iso-H-7 slightly down-regul ated collagen gene expression, indicating that inside collagen it affected integrin signaling rather than having a direct stimulatory effect on collag en mRNA levels. The effect of iso-H-7 was not dependent on its ability to i nhibit protein kinases A, C, or G. H-7 and iso-H-7 could also inhibit colla gen gel contraction, but this mechanism was independent of collagen gene re gulation. Three dimensional collagen could also up-regulate the mRNA levels of several matrix metalloproteinases (MMPs) but H-7 and iso-H-7 had no eff ect on the regulation of MMP genes. Our data indicate that three-dimensiona l collagenous matrix regulates distinct cellular signaling pathways and tha t collagen gene regulation is independent of the other effects of the matri x. (C) 2000 Academic Press.