A Three-dimensional Collagen Lattice Induces Protein Kinase C-ζ Activity: Role in α2 Integrin and Collagenase mRNA Expression

A three-dimensional collagen lattice can provide skin fibroblasts with a cell culture environment that simulates normal dermis. Such a collagen matrix environment regulates interstitial collagenase (type I metalloproteinase [MMP-1], collagenase-1) and collagen receptor alpha2 subunit mRNA expression in both unstimulated or platelet-derived growth factor-stimulated dermal fibroblasts (Xu, J., and R.A.F. Clark. 1996. J. Cell Biol. 132:239-249). Here we report that the collagen gel can signal protein kinase C (PKC)-zeta activation in human dermal fibroblasts. An in vitro kinase assay demonstrated that autophosphorylation of PKC-zeta immunoprecipitates was markedly increased by a collagen matrix. In contrast, no alteration in PKC-zeta protein levels or intracellular location was observed. DNA binding activity of nuclear factor kappaB (NF-kappaB), a downstream regulatory target of PKC-zeta, was also increased by fibroblasts grown in collagen gel. The composition of the NF-kappaB/Rel complexes that contained p50, was not changed. The potential role of PKC-zeta in collagen gel-induced mRNA expression of collagen receptor alpha2 subunit and human fibroblast MMP-1 was assessed by the following evidence. Increased levels of alpha2 and MMP-1 mRNA in collagen gel-stimulated fibroblasts were abrogated by bisindolylmaleimide GF 109203X and calphostin C, chemical inhibitors for PKC, but retained when cells were depleted of 12-myristate 13-acetate (PMA)-inducible PKC isoforms by 24 h of pretreatment with phorbol PMA. Antisense oligonucleotides complementary to the 5' end of PKC-zeta mRNA sequences significantly reduced the collagen lattice-stimulated alpha2 and MMP-1 mRNA levels. Taken together, these data indicate that PKC-zeta, a PKC isoform not inducible by PMA or diacylglycerol, is a component of collagen matrix stimulatory pathway for alpha2 and MMP-1 mRNA expression. Thus, a three-dimensional collagen lattice maintains the dermal fibroblast phenotype, in part, through the activation of PKC-zeta.