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Updated: Aug 17, 2026

Co-immunoprecipitation Assay for Studying Functional Interactions Between Receptors and Enzymes
Published on: September 28, 2018
The CD28 and CTLA-4 receptors associate with the serine/threonine phosphatase PP2A
E Chuang1, T S Fisher, R W Morgan
1Gwen Knapp Center for Lupus and Immunobiology Research, University of Chicago, Illinois 60637, USA.
Abstract:
CD28 and CTLA-4 are related members of a family of T lymphocyte cell surface receptors that function to regulate T cell activation. We have found that the cytoplasmic domains of both CTLA-4 and CD28 can associate with members of the PP2A family of serine/threonine phosphatases. The association of PP2A with CD28 was negatively regulated by tyrosine phosphorylation of the CD28 cytoplasmic domain. Inhibition of PP2A activity in Jurkat leukemia T cells by treatment with okadaic acid or by expression of a dominant-negative mutant enhanced T cell activation induced by CD28 engagement. Interactions between cell surface receptors such as CTLA-4 and CD28 and serine/threonine phosphatases may represent a novel mechanism for modulating the intracellular signal transduction pathways associated with cell activation.
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