Transforming growth factor-β1 regulation of laminin γ1 and fibronectin expression and survival of mouse mesangial cells

The transforming growth factor-beta (TGF-beta) 1 is a mediator of extracellular matrix (ECM) gene expression in mesangial cells and the development of diabetic glomerulopathy. Here, we investigate the effects of TGF-beta 1 on laminin gamma 1 and fibronectin polypeptide expression and cell survival in mouse mesangial cells (MES-13). TGF-beta 1 ( 10 ng/ml) stimulates laminin-gamma 1 and fibronectin expression similar to two-fold in a time-dependent manner (0 - 48 h). TGF-beta 1 treatment also retards laminin-gamma 1 mobility on SDS-gels, and tunicamycin, an inhibitor of the N-linked glycosylation, blocks the mobility shift. TGF-beta 1 increases the binding of laminin gamma 1 to WGA-agarose and the binding is abolished by tunicamycin suggesting that laminin gamma 1 is modified by N-linked glycosylation. TGF-beta 1 also elevates fibronectin glycosylation but its mobility is not altered. The degradation of laminin gamma 1 and fibronectin proteins is reduced by their glycosylation. In addition, TGF-beta 1 enhances mesangial cell viability and metabolic activities initially ( 0 - 24 h); however, eventually leads to cell death ( 24 - 48 h). TGF-beta 1 elevates pro-apoptotic caspase-3 activity and decrease cell cycle progression factor cyclin D1 expression, which parallels cell death. These results indicate that TGF-beta 1 plays an important role in ECM expression, protein glycosylation and demise of mesangial cells in the diabetic glomerular mesangium.