PLC-γ1 regulates fibronectin assembly and cell aggregation

Phospholipase C-gamma 1 (PLC-gamma 1) mediates cell adhesion and migration through an undefined mechanism. Here, we examine the role of PLC-gamma 1 in cell-matrix adhesion in a hanging drop assay of cell aggregation. Plcg1 Null (-/-) mouse embryonic fibroblasts formed aggregates that were larger and significantly more resistant to dissociation than cells in which PLC-gamma 1 is re-expressed (Null+ cells). Aggregate formation Could be disrupted by inhibition of fibronectin interaction with integrins, indicating that fibronectin assembly may mediate aggregate formation. Fibronectin assembly was mediated by integrin alpha 5 beta 1 in both cell lines, while assays measuring fibronectin assembly revealed increased assembly in the Null cells. Null and Null+ cells exhibited equivalent fibronectin mRNA levels and equivalent levels of fibronectin protein in pulse-labeling experiments. However, levels of secreted fibronectin in the conditioned medium were increased in Null cells. The data implicates a negative regulatory role for PLC-gamma 1 in cell aggregation by controlling the secretion of fibronectin into the media and its assembly into fibrils. (C) 2009 Elsevier Inc. All rights reserved.