B and T lymphocyte attenuator-mediated signal transduction provides a potent inhibitory signal to primary human CD4 T cells that can be initiated by multiple phosphotyrosine motifs.
The B and T lymphocyte attenuator (BTLA) is a recently identified member of the CD28 family of cell receptors. Initial reports demonstrated that mice deficient in BTLA expression were more susceptible to experimental autoimmune encephalomyelitis, indicating that BTLA was likely to function as a negative regulator of T cell activation. However, cross-linking of BTLA only resulted in a 2-fold reduction of IL-2 production, questioning the potency with which BTLA engagement blocks T cell activation. We established a model in which BTLA signaling could be studied in primary human CD4 T cells. We observed that cross-linking of a chimeric receptor consisting of the murine CD28 extracellular domain and human BTLA cytoplasmic tail potently inhibits IL-2 production and completely suppresses T cell expansion. Mutation of any BTLA tyrosine motifs had no effect on the ability of BTLA to block T cell activation. Only mutation of all four tyrosines rendered the BTLA cytoplasmic tail nonfunctional. We performed structure-function studies to determine which factors recruited to the BTLA cytoplasmic tail correlated with BTLA function. Using pervanadate as a means to phosphorylate the BTLA cytoplasmic tail, we observed both Src homology protein (SHP)-1 and SHP-2 recruitment. However, upon receptor engagement, we observed only SHP-1 recruitment, and mutations that abrogated SHP-1 recruitment did not impair BTLA function. These studies question whether SHP-1 or SHP-2 have any role in BTLA function and caution against the use of pervanadate as means to initiate signal transduction cascades in primary cells.
Chemnitz
Jens M
JM
Abramson Family Cancer Research Institute and Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Lanfranco
Anthony R
AR
Braunstein
Inbal
I
Riley
James L
JL
D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D018106:CD28 Antigens / Q000235:genetics / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D049109:Cell Proliferation; D019281:Dimerization; D006131:Growth Inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D009154:Mutation; D019000:Phosphotyrosine / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects / Q000276:immunology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D014638:Vanadates / Q000494:pharmacology
C482586:BTLA protein, human; D018106:CD28 Antigens; D006131:Growth Inhibitors; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; C076715:pervanadate; D019000:Phosphotyrosine; D014638:Vanadates; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse