RESUMO
BACKGROUND: Sialic-acid-binding immunoglobulin-like lectins (Siglecs) are the best-characterized immunoglobulin-type lectins. There is a growing amount of data linking Siglec and autoimmune diseases. The recently identified Siglec-9 inhibits T cell receptor (TCR)-mediated signaling which has been demonstrated by site-directed mutagenesis. In human Siglec-9, at least 8 nonsynonymous SNPs have been detected without functional studies. This study examined the SNP(s) related to TCR-mediated signaling. METHODS: Since the functions of Siglecs are modulated by their interaction with sialic-acid-containing carbohydrate groups, a molecular modeling analysis of carbohydrate binding interactions and an RBC binding analysis were performed using the 8 SNPs. The TCR-mediated signaling was analyzed with the downstream signaling molecules ZAP-70 and IL-2. RESULTS: This study revealed that an A391C polymorphism is the only mutant related to the binding. Jurkat T cells transfected with the A391C mutant reduced the inhibition of ZAP-70 phosphorylation and IL-2 production compared to cells transfected with the wild type. CONCLUSIONS: Siglec-9 A391C was the only polymorphism related to TCR-mediated signaling in human Siglec-9, resulting in less inhibition compared to the wild type.
Assuntos
Antígenos CD/genética , Lectinas/genética , Receptores de Antígenos de Linfócitos T/imunologia , Antígenos CD/imunologia , Western Blotting , Eritrócitos/imunologia , Citometria de Fluxo , Humanos , Interleucina-2/imunologia , Células Jurkat , Lectinas/imunologia , Modelos Moleculares , Mutagênese Sítio-Dirigida , Ácido N-Acetilneuramínico/imunologia , Fosforilação/imunologia , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/química , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico , Transdução de Sinais , Transfecção , Proteína-Tirosina Quinase ZAP-70/imunologiaRESUMO
A kinetic study is reported for reactions of Y-substituted phenyl X-substituted cinnamates (1a-e and 3a-g) and benzoates (2a-e and 4a-g) with a series of alicyclic secondary amines in 80 mol % H2O/20 mol % DMSO at 25.0 +/- 0.1 degrees C. Reactions of 2,4-dinitrophenyl X-substituted cinnamates (1a-e) and benzoates (2a-e) with amines result in linear Yukawa-Tsuno plots. The rho(X) values are much smaller for the reactions of 1a-e than for those of 2a-e. A distance effect and the nature of the reaction mechanism (i.e., a concerted mechanism for 1a-e) have been suggested to be responsible for the small rho(X) values. The Brønsted-type plots for the reactions of 2,4-dinitrophenyl X-substituted cinnamates (1a, 1c, and 1e) with amines are curved with a decreasing betanuc value from 0.65 to 0.3-0.4. The reactions of Y-substituted phenyl cinnamates (3a-g) with morpholine also result in a curved Brønsted plot, while the corresponding reactions of Y-substituted phenyl benzoates (4a-e) exhibit a linear Brønsted plot. It has been concluded that the curved Brønsted plots found for the reactions of the cinnamates (1a, 1c, 1e, and 3a-g) are not due to a change in the rate-determining step (RDS) but due to a normal Hammond effect for a concerted mechanism, that is, an earlier transition state (TS) for a more reactive amine or substrate.
