title: Negative regulation of interleukin-2 and p38 mitogen-activated protein kinase during T-cell activation by the adaptor ALX.
abstract: Activation of naïve T cells requires synergistic signals produced by the T-cell receptor (TCR) and by CD28. We previously identified the novel adaptor ALX, which, upon overexpression in Jurkat T cells, inhibited activation of the interleukin-2 (IL-2) promoter by TCR/CD28, suggesting that it is a negative regulator of T-cell activation. To further understand the physiological role of ALX, ALX-deficient mice were generated. Purified T cells from ALX-deficient mice demonstrated increased IL-2 production, CD25 expression, and proliferation in response to TCR/CD28 stimulation. Enhanced IL-2 production and proliferation were also observed when ALX-deficient mice were primed in vivo with ovalbumin-complete Freund's adjuvant and then restimulated ex vivo. Consistent with our initial overexpression studies, these data demonstrate that ALX is a negative regulator of T-cell activation. While TCR/CD28-mediated activations of phosphotyrosine induction, extracellular signal-regulated kinase 1/2, Jun N-terminal protein kinase, IkappaB kinase alpha/beta, and Akt were unaltered, constitutive activation of p38 mitogen-activated protein kinase and its upstream regulators MKK3/6 were observed for ALX-deficient splenocytes. The phenotype of ALX-deficient mice resembled the phenotype of those deficient in the transmembrane adaptor LAX, and an association between ALX and LAX proteins was demonstrated. These results suggest that ALX, in association with LAX, negatively regulates T-cell activation through inhibition of p38.
authors.affiliation: Dept. of Pathology and Laboratory Medicine, University of Pennsylvania, 3620 Hamilton Walk, Philadelphia, PA 19104, USA.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Perchonock
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Fernando
authors.forename: William J
authors.initials: WJ
authors.lastname: Quinn
authors.forename: Chau T
authors.initials: CT
authors.lastname: Nguyen
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shapiro
authors.forename: Virginia Smith
authors.initials: VS
authors.lastname: Shapiro
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000375:Aging; D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D016923:Cell Death; D049109:Cell Proliferation; D015536:Down-Regulation / Q000235:genetics*; D007376:Interleukin-2 / Q000096:biosynthesis / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000276:immunology*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D013154:Spleen / Q000166:cytology / Q000201:enzymology; D013163:Splenomegaly; D013210:Staphylococcus / Q000276:immunology; D018089:Superantigens / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C509871:HSH2 protein, mouse; D007376:Interleukin-2; C501224:LAX protein, mouse; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D015375:Receptors, Interleukin-2; D018089:Superantigens; D048051:p38 Mitogen-Activated Protein Kinases