Identification of the cytoskeletal regulatory protein α-adducin as a target of T cell receptor signaling

• Published in: Molecular immunology 2004-06, Vol.41 (4), p.435-447
• Main Authors: Lu, Qingjun, Liu, Xuebin, Trama, Jason, Roti, Michelle A, Go, William Y, Ho, Steffan N
• Format: Article
• Language: English
• Subjects: Adducin; Animals; Calmodulin-Binding Proteins - biosynthesis; Calmodulin-Binding Proteins - chemistry; Calmodulin-Binding Proteins - genetics; Calmodulin-Binding Proteins - physiology; Cellular activation; Cytochalasin D - pharmacology; Cytoskeleton; Cytoskeleton - drug effects; Cytoskeleton - ultrastructure; Epitopes - immunology; Gene Expression Regulation; Immunologic Memory; Lymphocyte Activation; Mice; Phosphorylation; Protein Kinase C - metabolism; Protein Processing, Post-Translational; Rats; Rats, Sprague-Dawley; Receptors, Antigen, T-Cell - immunology; Recombinant Fusion Proteins - physiology; Signal transduction; Signal Transduction - physiology; T lymphocyte; T-Lymphocytes - immunology; T-Lymphocytes - ultrastructure
• ISSN: 0161-5890; 1872-9142
• DOI: 10.1016/j.molimm.2004.03.028

Quiescent T lymphocytes reorganize the actin cytoskeleton subsequent to interaction with antigen presenting cells bearing the appropriate peptide antigen. Although both biochemical and genetic evidence indicate that T cell receptor-dependent cytoskeletal reorganization is critical to T cell activation, the mechanisms that mediate this process remain poorly defined. In this study, the cytoskeletal regulatory protein α-adducin was identified as a novel target of TCR signaling in primary T lymphocytes through the biochemical purification of an unknown 120 kDa protein (p120) defined by a fortuitously cross-reactive phospho-sensitive antiserum. The epitope identified by this antiserum defines a previously unrecognized site of phosphorylation localized to amino acids 590–620. Both TCR cross-linking and exposure to phorbol ester resulted in the phosphorylation-dependent elimination of this epitope. However, while phorbol ester induced rapid phosphorylation of both the phospho-sensitive epitope and the functionally defined major protein kinase C site present near the carboxy-terminus (serine 724) of α-adducin, only the phospho-sensitive epitope was modified upon activation through the TCR. Moreover, inhibition of actin polymerization by cytochalasin D blocked this modification. Of particular importance, α-adducin was not expressed in T cell lines, was completely down-regulated in primary T cells within 24 h of activation and was reduced in quiescent memory T cells. These results suggest a model in which reorganization of the unique cytoskeletal network that defines a primary quiescent T lymphocyte is mediated in part through the TCR-dependent modification and subsequent down-regulation of α-adducin, thereby resulting in a cytoskeletal architecture compatible with T cell effector and memory functions.