Tyrosine phosphatase activity of lymphoma CD45 (GP180) is regulated by a direct interaction with the cytoskeleton

V. B. Lokeshwar, L. Y.W. Bourguignon

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Abstract

GP180 is one of the major transmembrane glycoproteins in mouse T-lymphoma cells. This molecule is an isoform of CD45 and is known to contain an intrinsic protein tyrosine phosphatase (PTPase) activity. Using several complementary biochemical techniques, we have found that fodrin (a spectrin- like protein) is preferentially co-isolated with CD45 (GP180), suggesting that a complex between CD45 (GP180) and the cytoskeleton exists in mouse T- lymphoma cells. Furthermore, we have determined that this CD45 (GP180)-fodrin complex is dissociated by high salt treatment. Using in vitro binding assays, we have shown that CD45 (GP180) binds directly and specifically to fodrin (K(d) ≃ 1.1 nM) or spectrin (K(d) ≃ 3.2 nM) in a saturable manner. Additional analyses indicate that a 48-kDa phosphopeptide of CD45 (GP180) contains the fodrin/spectrin-binding domain. Most importantly, the direct binding of fodrin/spectrin to CD45 (GP180) is found to significantly stimulate the PTPase activity of CD45. Enzyme kinetic analysis indicates that fodrin and spectrin increase the V(max) of CD45 (GP180)-mediated dephosphorylation by 7.5 and 3.2-fold, respectively, without significantly changing the K(m) value. These results strongly suggest that the cytoskeletal proteins, fodrin and spectrin, play an important role in the regulation of the CD45 (GP180) PTPase activity during lymphocyte activation.

Original languageEnglish (US)
Pages (from-to)21551-21557
Number of pages7
JournalJournal of Biological Chemistry
Volume267
Issue number30
StatePublished - Jan 1 1992

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Cytoskeleton
Phosphoric Monoester Hydrolases
Spectrin
Tyrosine
Lymphoma
Protein Tyrosine Phosphatases
T-Cell Lymphoma
Phosphopeptides
Enzyme kinetics
Cytoskeletal Proteins
Lymphocytes
Lymphocyte Activation
fodrin
Assays
Glycoproteins
Protein Isoforms
Salts
Chemical activation
Molecules
Enzymes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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Tyrosine phosphatase activity of lymphoma CD45 (GP180) is regulated by a direct interaction with the cytoskeleton. / Lokeshwar, V. B.; Bourguignon, L. Y.W.

In: Journal of Biological Chemistry, Vol. 267, No. 30, 01.01.1992, p. 21551-21557.

Research output: Contribution to journalArticle

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