Mock, Nm23: Same as Fig.1. The experiment procedure was described in the “”Methods”". Altered glycosylation integrin subunit in cells transfected with Nm23-H1 To further study whether the decrease of integrin β1 subunits on cell surface was due to post-transcriptional regulation, we compared the total expression level of cellular β1 subunit by western blotting. As previously reported, two bands are typically observed in western blots of β1 integrin [24], namely a 115 kD partially glycosylated precursor and a 130 kD fully glycosylated mature form. It was very interesting to find that the total amount of β1 subunit was also unaltered in Nm23/H7721
cells, but the ratio of mature to precursor integrin isoforms was decreased significantly, being 1:1.21 ± 0.39 in Nm23/H7721 cells Crenigacestat clinical trial compared with 1:0.33 ± 0.12 in Mock cells (Fig 5A). This result suggested that overexpression of Nm23-H1 did not change total expression levels of β1 integrin.
Instead, Nm23-H1 modulated the posttranslational processing of β1 integrin. Figure 5 Western blot analysis of α5 and β1 integrin subunits after transfected with nm23-H1 cDNA. A: Western blot profiles of α5 and β1 integrin Bucladesine subunits expression in mock and pcDNA/Nm23-H1 transfected cells. B: Expression of β1 integrin subunits in cell treated with tunicamycin. Mock, Nm23: Same as Fig.1. The experiment procedure was described in the “”Methods”". Three independent experiments of A and B were performed and the results were reproducible. To further demonstrate that the alterated expression of mature β1 subunit was due to aberrant glycosylation, rather than other post-transcriptional regulation, we treated the cells with tunicamycin, an N-glycosylation inhibitor, and observed the deglycosylated form of β1 subunit. As shown in Fig. 5B, both Nm23/H7721 and Mock/H7721
cells only showed one band of about 90 kD crossed with intergrin β1 subunit antibody. Their size corresponded to the completely deglycosylated core peptide of the β1 subunit and their levels were almost equal. So these results indicated that the reduction of cell surface integrin β1 subunits in cells transfected with Nm23-H1 might be due to the changes of glycosylation. Effect of Nm23-H1 overexpression on the phosphorylation of FAK FAK is associated Acetophenone with the intracellular domain of integrin β subunit and involved in signaling transduction for cell adhesion and migration [25]. We tested whether Nm23-H1 overexpression CH5183284 mouse affected phosphorylation of FAK on cells stimulated with fibronectin. As shown in Fig. 6, tyrosine autophosphorylation of FAK in Nm23-H1 transfected cells was decreased to 32.2 ± 6.4% (p < 0.01) compared with Mock cells. Figure 6 Phophorylation of FAK in mock and pcDNA/Nm23-H1 transfected cells. Mock, Nm23: Same as Fig.1. The experimental procedures of immuno-precipitation and Western blot were described in the “”Methods”".