title: A novel role for p21-activated protein kinase 2 in T cell activation.
abstract: To identify novel components of the TCR signaling pathway, a large-scale retroviral-based functional screen was performed using CD69 expression as a marker for T cell activation. In addition to known regulators, two truncated forms of p21-activated kinase 2 (PAK2), PAK2DeltaL(1-224) and PAK2DeltaS(1-113), both lacking the kinase domain, were isolated in the T cell screen. The PAK2 truncation, PAK2DeltaL, blocked Ag receptor-induced NFAT activation and TCR-mediated calcium flux in Jurkat T cells. However, it had minimal effect on PMA/ionomycin-induced CD69 up-regulation in Jurkat cells, on anti-IgM-mediated CD69 up-regulation in B cells, or on the migratory responses of resting T cells to chemoattractants. We show that PAK2 kinase activity is increased in response to TCR stimulation. Furthermore, a full-length kinase-inactive form of PAK2 blocked both TCR-induced CD69 up-regulation and NFAT activity in Jurkat cells, demonstrating that kinase activity is required for PAK2 function downstream of the TCR. We also generated a GFP-fused PAK2 truncation lacking the Cdc42/Rac interactive binding region domain, GFP-PAK2(83-149). We show that this construct binds directly to the kinase domain of PAK2 and inhibits anti-TCR-stimulated T cell activation. Finally, we demonstrate that, in primary T cells, dominant-negative PAK2 prevented anti-CD3/CD28-induced IL-2 production, and TCR-induced CD40 ligand expression, both key functions of activated T cells. Taken together, these results suggest a novel role for PAK2 as a positive regulator of T cell activation.
authors.affiliation: Rigel Inc., 1180 Veterans Boulevard, South San Francisco, CA 94080, USA.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Chu
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.forename: X Charlene
authors.initials: XC
authors.lastname: Liao
authors.forename: Jorge
authors.initials: J
authors.lastname: Pardo
authors.forename: Haoran
authors.initials: H
authors.lastname: Zhao
authors.forename: Congfen
authors.initials: C
authors.lastname: Li
authors.forename: Marcy K
authors.initials: MK
authors.lastname: Mendenhall
authors.forename: Erlina
authors.initials: E
authors.lastname: Pali
authors.forename: Mary
authors.initials: M
authors.lastname: Shen
authors.forename: Simon
authors.initials: S
authors.lastname: Yu
authors.forename: Vanessa C
authors.initials: VC
authors.lastname: Taylor
authors.forename: Gregorio
authors.initials: G
authors.lastname: Aversa
authors.forename: Susan
authors.initials: S
authors.lastname: Molineaux
authors.forename: Donald G
authors.initials: DG
authors.lastname: Payan
authors.forename: Esteban S
authors.initials: ES
authors.lastname: Masuda
mesh_terms: D015703:Antigens, CD / Q000032:analysis / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D037181:Lectins, C-Type; D008213:Lymphocyte Activation; D009154:Mutation; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D054462:p21-Activated Kinases; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D015415:Biomarkers; D004268:DNA-Binding Proteins; D037181:Lectins, C-Type; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D011948:Receptors, Antigen, T-Cell; D014157:Transcription Factors; D054462:p21-Activated Kinases; D000099192:CD69 Antigens; C515907:PAK2 protein, human