Characterization of the Heparin/Heparan Sulfate Binding Site of the Natural Cytotoxicity Receptor NKp46

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• 作者：Alon Zilka ; Guy Landau ; Oren Hershkovitz ; Noga Bloushtain ; Ahuva Bar-Ilan ; Fabrice Benchetrit ; Eyal Fima ; Toin H. van Kuppevelt ; John T. Gallagher ; Sharona Elgavish ; and Angel Porgador
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：November 8, 2005
• 年：2005
• 卷：44
• 期：44
• 页码：14477 - 14485
• 全文大小：416K
• 年卷期：v.44,no.44(November 8, 2005)
• ISSN：1520-4995

文摘

NKp46 is a member of a group of receptors collectively termed natural cytotoxicity receptors(NCRs) that are expressed by natural killer (NK) cells. NCRs are capable of mediating direct killing oftumor and virus-infected cells by NK cells. We have recently shown that NKp46 recognizes the heparansulfate moieties of membranal heparan sulfate proteoglycans (HSPGs), thus enabling lysis of tumor cellsby NK cells. In the current study, we further examined the residues in NKp46 that may be involved inheparan sulfate binding on tumor cells. On the basis of both the electrostatic potential map and comparisonto the heparin binding site on human fibronectin, we predicted a continuous region containing the basicamino acids K133, R136, H139, R142, and K146 to be involved in NKp46 binding to heparan sulfate.Mutating these amino acids on NKp46D2 to noncharged amino acids retained its virus binding capacitybut reduced its binding to tumor cells with a 10-100 fold lower K_D when tested for direct binding toheparin. The minimal length of the heparin/heparan sulfate epitope recognized by NKp46 was eightsaccharides as predicted from the structure and proven by testing heparin oligomers. Testing selectivelymonodesulfated heparin oligomers emphasized the specific contributions of O-sulfation, N-sulfation, andN-acetylation to epitope recognition by NKp46. The characterization of heparan sulfate binding region inNKp46 offers further insight into the identity of the ligands for NKp46 and the interaction of NK andcancers.