Dynamic Association of CD45 with Detergent-Insoluble Microdomains in T Lymphocytes

Abstract

The receptor-like protein tyrosine phosphatase CD45 is essential for TCR signal transduction. Substrates of CD45 include the protein tyrosine kinases p56lck and p59fyn, both of which have been shown to be enriched in detergent-insoluble microdomains. Here we find that there is a cholesterol-dependent association between CD45 and the raft-associated protein linker for activation of T cells, suggesting that CD45 and linker for activation of T cells may colocalize in lipid rafts. Consistent with this observation, we find that ∼5% of total CD45 can be detected in Triton X-100-insoluble buoyant fractions of sucrose gradients, demonstrating that CD45 is not excluded from lipid rafts. Upon stimulation of T cells with anti-CD3, there is a reduction in the amount of CD45 found associating with lipid rafts. Our data suggest that CD45 is present in lipid rafts in T cells before activation, perhaps to activate raft-associated p56lck, allowing membrane-proximal signaling events to proceed. Furthermore, the reduction in CD45 content of lipid rafts after CD3 stimulation may serve to limit the amounts of activated p56lck in rafts and thus possibly the duration of T cell responses.

Altered lipid raft–associated proximal signaling and translocation of CD45 tyrosine phosphatase in B lymphocytes from patients with systemic lupus erythematosus

“…Previous studies on whether CD45 translocates into LRs have yielded inconsistent results. The results of some studies have suggested that CD45 is excluded, while others have suggested that human leukemia cells and granulocytes transiently express CD45 in LRs (14,(31)(32)(33)(34). More recently, we observed that CD45 translocates into LRs in T cells from patients with SLE but not healthy controls (35).…”

Selective internalization of monoclonal antibodies by B‐cell chronic lymphocytic leukaemia cells

“…Thus, the effect of Fcc-bearing immunotherapeutic agents may be significantly influenced by cells. Receptor-mediated modulation of antigen expression may also occur via the clustering and internalization of membrane microdomains, known as lipid rafts, that contain antigens such as CD20 and CD45 (Edmonds & Ostergaard, 2002). Finally, antibodies with an identical idiotype, that is specific for either the same or an overlapping epitope on a cell surface antigen, can display different internalization properties .…”

Changes in the Role of the CD45 Protein Tyrosine Phosphatase in Regulating Lck Tyrosine Phosphorylation during Thymic Development

“…In addition to factors that regulate the basal capacity or potential activity of CD45, CD45 protein tyrosine phosphatase activity and/or CD45 access to substrates may be further regulated following T cell activation (32,(52)(53)(54). These data suggest that the regulation of CD45 functional activity is likely to be complex and that different modes of regulation may be involved depending on the state of T cell activation and stage of development.…”

“…Initial reports in tumor cell lines suggested that raft-resident Lck was constitutively hyperphosphorylated due to the exclusion of CD45 from rafts and presumably due to raft targeting of Csk tyrosine kinase by PAG/cbp (30). However, more recent reports have suggested that a small percentage of CD45 has access to lipid raft domains and may regulate raft-resident Lck tyrosine phosphorylation (31,32). To clarify this issue in primary cells, we purified lipid raft and nonraft cell fractions from CD45 ϩ/Ϫ and CD45 Ϫ/Ϫ thymocytes by sucrose density gradient centrifugation.…”