Soluble extracellular domains of human SIRPα and CD47 expressed in Escherichia coli enhances the phagocytosis of leukemia cells by macrophages in vitro.
Signal regulatory protein (SIRP) α, a transmembrane protein belonging to the immunoglobulin superfamily, is a receptor for CD47. The interaction between SIRPα and CD47 plays an important role in regulating the phagocytosis of leukemia cells and leukemia stem cells (LSCs) by macrophages. Blocking antibodies against CD47 have been shown to promote phagocytosis of LSCs by macrophages. Here, we consider an alternative way to interrupt the interaction between CD47 and SIRPα. We expressed the extracellular domains of the human SIRPα (hSIRP(ext)) and the human CD47 (hCD47(ext)) in Escherichia coli as Trx fusion proteins, and purified them by using affinity chromatography. We show that the purified fusion protein Trx-SIRP(ext) could interact in vitro with Trx-hCD47(ext). Moreover, Trx-SIRP(ext) could effectively bind to Jurkat T-ALL cells, which expressed CD47 at a high level. CD47(ext), on the other hand, bound to human macrophages. In vitro phagocytosis assay showed that these fusion proteins could enhance the phagocytosis of Jurkat cells by macrophage, with Trx-hSIRP(ext) showed a higher efficiency than Trx-CD47(ext). These results indicated that the soluble Trx-hSIRP(ext) and Trx-CD47(ext) polypeptides could be alternative molecules to interrupt CD47-SIRPα interaction between leukemia cells and macrophages, and might be potentially useful for the targeted therapy of leukemia.
Department of Hematology, Fourth Military Medical University, Xi'an 710038, China.
Yan
Y
Lin
Xue-Qian
XQ
Yan
Fang
F
Yang
Xin-Wei
XW
Yang
Xun
X
Jiang
Xing-Cheng
XC
Zhao
Bing-Ke
BK
Zhu
Li
L
Liu
Hong-Yan
HY
Qin
Ying-Min
YM
Liang
Hua
H
Han
D000943:Antigens, Differentiation / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000494:pharmacology*; D051928:CD47 Antigen / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000494:pharmacology*; D004926:Escherichia coli / Q000235:genetics*; D006801:Humans; D019169:Jurkat Cells; D015458:Leukemia, T-Cell / Q000188:drug therapy / Q000276:immunology; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D010587:Phagocytosis / Q000187:drug effects*; D058849:Protein Refolding; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000494:pharmacology
D000943:Antigens, Differentiation; D051928:CD47 Antigen; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; C501920:SIRPA protein, human