Increased expression of integrin α3 and α6 RNA and cell surface receptor protein in response to aggrecan. Quantifications of the results are given in Table 1. A, Northern analysis of integrin total RNA. The expression of RNA for α3 and α6 integrin is increased in neurons cultured on substrata containing both laminin and aggrecan (LM/PG) relative to those cultured on laminin alone (LM). The blots were stripped and reprobed for GAPDH as a loading control.B, Western analysis of biotinylated cell-surface integrin protein. Neurons cultured on substrata containing laminin and aggrecan (LM/PG) show an increase in the expression of laminin receptors integrin α3 and α6 at the cell surface relative to those cultured on laminin alone (LM), whereas the expression of these receptors does not increase in neurons cultured on substrata containing fibronectin and aggrecan (FN/PG) when compared with those cultured on fibronectin alone (FN).