Identification of the cytoskeletal regulatory protein alpha-adducin as a target of T cell receptor signaling.
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 alpha-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 alpha-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, alpha-adducin was not expressed in T cell lines, was completely down-regulated in primary T cells within 24h 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 alpha-adducin, thereby resulting in a cytoskeletal architecture compatible with T cell effector and memory functions.
Lu
Qingjun
Q
Department of Pathology, UCSD School of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0644, USA.
Liu
Xuebin
X
Trama
Jason
J
Roti
Michelle A
MA
Go
William Y
WY
Ho
Steffan N
SN
D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure*; D000939:Epitopes / Q000276:immunology; D005786:Gene Expression Regulation; D007156:Immunologic Memory; D008213:Lymphocyte Activation; D051379:Mice; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000648:ultrastructure; D000099291:Adducins
D002148:Calmodulin-Binding Proteins; D015638:Cytochalasin D; D000939:Epitopes; D011493:Protein Kinase C; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D000099291:Adducins