The association of type 1, type 2A and type 2B phosphatases with the human T lymphocyte plasma membrane

• Published in: Biochemical journal Vol. 256; no. 3; pp. 885 - 892
• Main Authors: Alexander, D R, Hexham, J M, Crumpton, M J
• Format: Journal Article
• Language: English
• Published: England 15.12.1988
• Subjects: Calcineurin; Calmodulin-Binding Proteins - metabolism; Cell Line; Cell Membrane - enzymology; Humans; Immunoblotting; lymphocytes T; man; Phosphopeptides - metabolism; Phosphoprotein Phosphatases - metabolism; Phosphorylase Phosphatase - metabolism; T-Lymphocytes - enzymology; T-Lymphocytes - ultrastructure
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2560885

Several putative plasma-membrane-associated components of the T-lymphocyte signal-transduction pathway are phosphorylated during the initial events of cellular activation. Little is known about the control of dephosphorylation of these components. We have shown by immunoblotting that the type 1 phosphatase, the type 2A phosphatase and type 2B phosphatase (calcineurin) are associated with the plasma membrane of normal human T lymphoblasts and the human T leukaemic cell line Jurkat 6. The type 1 phosphorylase phosphatase activity is present in a latent form which can be stimulated synergistically by deinhibitor and p-nitrophenyl phosphate. The PCSH form of the type 2A phosphatase appears to be the predominant oligomer in the plasma-membrane fraction. All three phosphatases can be extracted from membranes with Nonidet P40, but whereas the type 1c and type 2Ac phosphatases separate into the detergent-poor phase of Triton X-114, calcineurin separates into both detergent-rich and -poor phases. It is probable that one or more of these three plasma-membrane-associated phosphatases play regulatory roles in determining the phosphorylation state of membrane-bound proteins involved in human T-cell activation.