title: Different associations of CD45 isoforms with STAT3, PKC and ERK regulate IL-6-induced proliferation in myeloma.
abstract: In response to interleukin 6 (IL-6) stimulation, both CD45RO and CD45RB, but not CD45RA, translocate to lipid rafts. However, the significance of this distinct translocation and the downstream signals in CD45 isoforms-participated IL-6 signal are not well understood. Using sucrose fractionation, we found that phosphorylated signal transducer and activator of transcription (STAT)3 and STAT1 were mainly localized in lipid rafts in response to IL-6 stimulation, despite both STAT3 and STAT1 localizing in raft and non-raft fractions in the presence or absence of IL-6. On the other hand, extracellular signal-regulated kinase (ERK), and phosphorylated ERK were localized in non-raft fractions regardless of the existence of IL-6. The rafts inhibitor significantly impeded the phosphorylation of STAT3 and STAT1 and nuclear translocation, but had little effect on (and only postponing) the phosphorylation of ERK. This data suggests that lipid raft-dependent STAT3 and STAT1 pathways are dominant pathways of IL-6 signal in myeloma cells. Interestingly, the phosphorylation level of STAT3 but not STAT1 in CD45+ cells was significantly higher compared to that of CD45- cells, while the phosphorylation level of ERK in CD45+ myeloma cells was relatively low. Furthermore, exogenously expressed CD45RO/RB significantly enhanced STAT3, protein kinase C (PKC) and downstream NF-κB activation; however, CD45RA/RB inhibited IL-6-induced ERK phosphorylation. CD45 also enhanced the nuclear localization of STAT3 but not that of STAT1. In response to IL-6 stimulation, CD45RO moved into raft compartments and formed a complex with STAT3 and PKC in raft fraction, while CD45RA remained outside of lipid rafts and formed a complex with ERK in non-raft fraction. This data suggests a different role of CD45 isoforms in IL-6-induced signaling, indicating that while CD45RA/RB seems inhibit the rafts-unrelated ERK pathway, CD45RO/RB may actually work to enhance the rafts-related STAT3 and PKC/NF-κB pathways.
authors.affiliation: Department of Oncology, ShengJing Hospital of China Medical University, Shenyang, Liaoning, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Harvard University, Cambridge, MA, United States of America.
authors.forename: Allison S
authors.initials: AS
authors.lastname: Li
authors.affiliation: He University, Shenyang, Liaoning, China.
authors.forename: Huanyu
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Oncology, ShengJing Hospital of China Medical University, Shenyang, Liaoning, China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Department of Oncology, ShengJing Hospital of China Medical University, Shenyang, Liaoning, China.
authors.forename: Dagang
authors.initials: D
authors.lastname: Guan
authors.affiliation: Department of Oncology, ShengJing Hospital of China Medical University, Shenyang, Liaoning, China.
authors.forename: Huawei
authors.initials: H
authors.lastname: Zou
mesh_terms: D017398:Alternative Splicing; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000032:analysis / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D017493:Leukocyte Common Antigens / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D009101:Multiple Myeloma / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D020033:Protein Isoforms / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology; D021381:Protein Transport; D050794:STAT1 Transcription Factor / Q000032:analysis / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000032:analysis / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D015850:Interleukin-6; D016328:NF-kappa B; D020033:Protein Isoforms; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D017493:Leukocyte Common Antigens