title: 1alpha, 25-dihydroxy-vitamin D3 alters Syk activation through FcgammaRII in monocytic THP-1 cells.
abstract: In monocytes and macrophages, activation of the tyrosine kinase Syk is an essential step in the biochemical cascade linking aggregation of receptors for immunoglobulin G (FcgammaR) to initiation of effector functions. An increase in Syk activation during differentiation of myeloid cells by different agents has been reported. We studied the activation state of Syk in response to FcgammaRII crosslinking in monocytic cells before and after in vitro differentiation with 1alpha, 25-dihydroxy-vitamin D3. We show here that while in undifferentiated THP-1 cells clustering of FcgammaRII induces significant phosphorylation and activation of Syk, in THP-1 cells differentiated in vitro by 1alpha, 25-dihydroxy-vitamin D3, FcgammaRII crosslinking induced a decrease in Syk activity. In vitro differentiation did not induce changes in the expression of FcgammaRII isoforms. The observed effect on Syk activation though FcgammaRII could be mediated by differentiation-induced changes in the expression and basal activation level of Syk, as well as changes in the association of Syk with the tyrosine phosphatase SHP-1. These results suggest that the biochemical signaling pathways induced by FcgammaRII could be dependent on the differentiation state of the cell.
authors.affiliation: Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Cuidad Universitaria, D. F., 04510 México.
authors.forename: José
authors.initials: J
authors.lastname: Agramonte-Hevia
authors.forename: Claudia
authors.initials: C
authors.lastname: Hallal
authors.forename: Claudia
authors.initials: C
authors.lastname: Garay-Canales
authors.forename: Christian
authors.initials: C
authors.lastname: Guerra-Araiza
authors.forename: Ignacio
authors.initials: I
authors.lastname: Camacho-Arroyo
authors.forename: Enrique
authors.initials: E
authors.lastname: Ortega Soto
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009000:Monocytes / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*; D012756:Sheep; D000072377:Syk Kinase; D014638:Vanadates / Q000494:pharmacology; D018909:src Homology Domains
chemical_list: D003432:Cross-Linking Reagents; D017931:DNA Primers; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D020033:Protein Isoforms; D017452:Receptors, IgG; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D002117:Calcitriol