Complement-mediated phagocytosis--the role of Syk.
Phagocytosis is a central event in the innate immune responses that are triggered by the association between ligands on the surface of pathogens and receptors on the membrane of phagocytes. Particularly, complement-mediated phagocytosis is accomplished by specific recognition of bound complement components by the corresponding complement receptors on the phagocytes. The protein-tyrosine kinase, Syk, plays a central role in Fcgamma receptor-mediated phagocytosis in the adaptive immune system. From recent studies using a macrophage-like differentiated cell line and serum-treated zymosan, it was found that Syk also plays an essential role in complement-mediated phagocytosis in innate immunity. Serum-treated zymosan particles promptly attached to the cells and were subsequently engulfed via complement receptor3. During this process, Syk became tyrosine-phosphorylated and accumulated around the nascent phagosomes. The transfer of Syk-siRNA or dominant-negative Syk (DN-Syk) into macrophages resulted in impaired engulfment of pathogen. Collectively, Syk is required for the engulfment of pathogen in complement-mediated phagocytosis.
Tohyama
Yumi
Y
Himeji Dokkyo University, Hyogo, and Hyogo Prefectural Institute of Public Health and Environmental Sciences, Kobe, Japan. ytohyama@himeji-du.ac.jp
Yamamura
Hirohei
H
D000818:Animals; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D010587:Phagocytosis / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D000072377:Syk Kinase
D047908:Intracellular Signaling Peptides and Proteins; D003165:Complement System Proteins; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase