title: Alterations in activity of protein tyrosine phosphatase SH-PTP1 in autoimmune MRL/mpj-lpr/lpr mice.
abstract: Activities of protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) in autoimmune MRL/MpJ-lpr/lpr mice (lpr mice) were measured and compared with the activities in the tissues from MRL/MpJ-+/+ mice (+/+ mice) as the control. In the spleen and liver, PTK activities in cytosol and membrane fractions were about 1.7- and 1.3-fold, respectively, higher in lpr mice than +/+ mice. PTP activities in cytosol and membrane fractions from lpr mice were 1.7- and 1.3-fold, respectively, higher in spleen, and 2.5- and 1.3-fold, respectively, higher in liver compared with those of the controls. These results demonstrate that the mutation of lpr gene resulted in elevation of PTK and PTP activities. Then, we measured the amounts and activities of SH-PTP1, a cytosolic PTP playing a crucial role in intracellular signaling from Fas antigen. The amounts of SH-PTP1 were about 4-fold larger in thymus, spleen, and lymphnodes than in liver, but there was no marked difference in the amounts between lpr and +/+ mice. On the other hand, activity of SH-PTP1 was definitely lower in lpr spleen and lymphnodes than +/+ spleen, but several times higher in lpr liver than +/+ liver. Tyrosine phosphorylation levels of SH-PTP1 in spleen of lpr and +/+ mice were similar. However, in liver, it was less phosphorylated in lpr than in +/+ mice. This hypophosphorylation might cause the activation of SH-PTP1 activity in lpr liver.
authors.affiliation: Section of Biochemistry, Hokkaido University.
authors.forename: A
authors.initials: A
authors.lastname: Matsuda
authors.forename: S
authors.initials: S
authors.lastname: Matsuzawa
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Mizuno
authors.forename: K
authors.initials: K
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D015536:Down-Regulation; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000201:enzymology; D051379:Mice; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D015398:Signal Transduction; D013154:Spleen / Q000201:enzymology; D015854:Up-Regulation; D019014:fas Receptor / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D019014:fas Receptor; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse