The protein tyrosine phosphatase CD45 is required for interleukin 6 signaling in U266 myeloma cells.
The objective of this study was to examine whether CD45 mediates interleukin 6 (IL-6) signaling in human multiple myeloma (MM) cells. We chose U266 MM cells as a study model and isolated cells into CD45+ and CD45- subpopulations. CD45+ and CD45- U266 cells were cocultured with bone marrow stromal cells (BMSCs). IL-6-induced proliferation in CD45+ U266 cells was inhibited by vanadate, a potent protein tyrosine phosphatase inhibitor. However, IL-6-independent CD45- U266 cell growth was not affected by vanadate. CD45+ U266 cells, but not CD45- U266 cells, have the capability of cell adhesion concomitant with actin filament polymerization at the adherent cells. Adhesion of CD45+ U266 cells to BMSCs was impaired by vanadate. We clarified the signaling differences between CD45+ and CD45- U266 cells in response to IL-6. In CD45+ U266 cells, IL-6 increased tyrosine phosphorylation of gp130 and STAT3 and stimulated the level of Mcl-1 protein expression. An association between CD45 and the Src-family protein tyrosine kinase, Lyn, was maintained in the presence of IL-6; the formation of the CD45/Lyn complex was impaired by vanadate. Additionally, IL-6-induced Lyn kinase activity in CD45+ U266 cells was increased by the cross-linking of CD45, and this increase was due to the dephosphorylation of Tyr507 at Lyn. In conclusion, IL-6-dependent MM cells require CD45 to initiate IL-6 signaling and to maintain Lyn kinase activity, both of which are essential for cell proliferation and cell adhesion.
Blood and Marrow Transplant and Hematologic Malignancy Program, Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, West Virginia 26506, USA.
Qun
Q
Zhou
Yuan
Y
Yao
Solveig G
SG
Ericson
D000199:Actins / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002469:Cell Separation; D018920:Coculture Techniques; D050822:Cytokine Receptor gp130; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology*; D017493:Leukocyte Common Antigens / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D009101:Multiple Myeloma / Q000473:pathology*; D009363:Neoplasm Proteins / Q000502:physiology*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D017154:Stromal Cells / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D019061:src-Family Kinases / Q000737:chemistry / Q000378:metabolism*
D000199:Actins; D015703:Antigens, CD; D004268:DNA-Binding Proteins; C494199:IL6ST protein, human; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D050822:Cytokine Receptor gp130; D019000:Phosphotyrosine; D014638:Vanadates; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D017493:Leukocyte Common Antigens