title: Tyrosine phosphorylation plays a role in increasing maspin protein levels and its cytoplasmic accumulation.
abstract: Maspin is a tumor suppressor with many biological activities, multiple ligands and different subcellular localizations. Its underlying molecular mechanism remains elusive. We hypothesized that phosphorylation might regulate maspin localization and function. Using two-dimensional gel electrophoresis with different focusing power followed by Western blot we identified four different maspin forms with the same molecular weight (42 kDa), but different isoelectric points. Three of these forms were sensitive to acidic phosphatase treatment, suggesting that they are phosphorylated. Sodium peroxidovanadate treatment, a protein-tyrosine phosphatase inhibitor, resulted in a rapid increase in maspin protein levels and cytoplasmic accumulation. These data show that there are three different maspin tyrosine phosphoforms. Inhibition of tyrosine phosphatases increased maspin protein levels and leads to its cytoplasmic accumulation.
authors: Departamento de Biologia Celular e Desenvolvimento, Instituto de Ciências Biomédicas, Av. Prof. Lineu Prestes, 1524, Universidade de São Paulo, São Paulo 05508-900, SP, Brazil ; Departamento de Bioquímica, Instituto de Química, Av. Prof. Lineu Prestes, 748, Universidade de São Paulo, São Paulo 05508-900, SP, Brazil.
authors: Mariana
authors: M
authors: Tamazato Longhi
authors: Nathalie
authors: N
authors: Cella
keywords: 2D-SDS-PAGE, two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis; Cytoplasmic accumulation; DTT, dithiothreitol; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; IEF, isoelectric focalization; Maspin; PTM, post-translational modification; Tumor suppressor; Tyrosine phosphorylation; serpin, serine protease inhibitor
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