Cell adhesion and proliferation mediated through the G1 domain of versican.

We have demonstrated previously that versican stimulated cell proliferation through the G3 domain. In these experiments, we show that versican mini-gene-transfected cell lines exhibited decreased cell-substratum interaction and increased cell proliferation. Exogenous addition of growth medium containing the versican gene product produced the same results. Because the G1 domain of versican is structurally similar to the G1 domain of aggrecan and to link protein, both of which play role in cell adhesion, we hypothesized that versican's proliferative effects may be a consequence of its ability to reduce cell adhesion, and may be mediated through the G1 domain. To investigate this, we expressed a G1 construct in NIH3T3 cells and showed that it reduced cell adhesion and enhanced cell proliferation. We then demonstrated that deletion of the G1 domain from versican greatly, but not completely, reversed the effects of versican: G1-deletion mutants of versican show slightly reduced amounts of cell adhesion and slightly increased rates of proliferation. We concluded that versican can stimulate cell proliferation via two mechanisms: through two EGF-like motifs in the G3 domain which play a role in stimulating cell growth, and through the G1 domain, which destabilizes cell adhesion and facilitates cell growth. We purified the G1 product with an affinity column and demonstrated that it reduced cell adhesion and enhanced cell proliferation.