The Soluble Granulocyte-Macrophage Colony-Stimulating Factor Receptor's Carboxyl-Terminal Domain Mediates Retention of the Soluble Receptor on the Cell Surface through Interaction with the Granulocyte
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- 作者：Elizabeth W. Murray ; Carin Pihl ; Stephen M. Robbins ; Jay Prevost ; Arati Mokashi ; Sherry M. Bloomfield ; and Christopher B. Brown
- 刊名：Biochemistry
- 出版年：1998
- 出版时间：October 6, 1998
- 年：1998
- 卷：37
- 期：40
- 页码：14113 - 14120
- 全文大小：114K
- 年卷期：v.37,no.40(October 6, 1998)
- ISSN：1520-4995
文摘
The hematopoietic cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF)mediates its activity through binding to cell-surface receptors. The high-affinity GM-CSF receptor (GMR)consists of two transmembrane-anchored subunits: a ligand-specific, low-affinity subunit (GMR
); anda signal-transducing 
beta2.gif" BORDER=0 ALIGN="middle">-subunit (GMRbeta2.gif" BORDER=0 ALIGN="middle">). The human GMR subunit also exists in a soluble isoform(SOL) which antagonizes GM-CSF activity in vitro. Previous studies by us have shown that coexpressionof SOL and a mutated GMRbeta2.gif" BORDER=0 ALIGN="middle"> in BHK cells results in retention of SOL on the cell surface and theformation of an intermediate affinity binding complex (Kd approximately 300 pM). This paper investigatesthe mechanism of the retention of SOL on the cell surface. The data demonstrate that SOL is anchoredby a direct, ligand-independent interaction with GMRbeta2.gif" BORDER=0 ALIGN="middle"> which also occurs when SOL is coexpressedwith wild-type GMRbeta2.gif" BORDER=0 ALIGN="middle">. However, SOL and wild-type GMRbeta2.gif" BORDER=0 ALIGN="middle"> form a complex which binds GM-CSFwith high affinity (Kd = 39 pM), indistinguishable from the binding characteristics of the TM/GMRbeta2.gif" BORDER=0 ALIGN="middle">complex. The experiments further reveal that the interaction between SOL and GMRbeta2.gif" BORDER=0 ALIGN="middle"> is abrogated byremoval of the unique 16 amino acid carboxyl-terminal domain of SOL. Specific mutation of cysteine323 in this carboxyl-domain to alanine also eliminates the cell-surface retention of SOL identifying thisresidue as being necessary for the formation of the SOL/GMRbeta2.gif" BORDER=0 ALIGN="middle"> complex.
); anda signal-transducing beta2.gif" BORDER=0 ALIGN="middle">-subunit (GMRbeta2.gif" BORDER=0 ALIGN="middle">). The human GMR subunit also exists in a soluble isoform(SOL) which antagonizes GM-CSF activity in vitro. Previous studies by us have shown that coexpressionof SOL and a mutated GMRbeta2.gif" BORDER=0 ALIGN="middle"> in BHK cells results in retention of SOL on the cell surface and theformation of an intermediate affinity binding complex (Kd approximately 300 pM). This paper investigatesthe mechanism of the retention of SOL on the cell surface. The data demonstrate that SOL is anchoredby a direct, ligand-independent interaction with GMRbeta2.gif" BORDER=0 ALIGN="middle"> which also occurs when SOL is coexpressedwith wild-type GMRbeta2.gif" BORDER=0 ALIGN="middle">. However, SOL and wild-type GMRbeta2.gif" BORDER=0 ALIGN="middle"> form a complex which binds GM-CSFwith high affinity (Kd = 39 pM), indistinguishable from the binding characteristics of the TM/GMRbeta2.gif" BORDER=0 ALIGN="middle">complex. The experiments further reveal that the interaction between SOL and GMRbeta2.gif" BORDER=0 ALIGN="middle"> is abrogated byremoval of the unique 16 amino acid carboxyl-terminal domain of SOL. Specific mutation of cysteine323 in this carboxyl-domain to alanine also eliminates the cell-surface retention of SOL identifying thisresidue as being necessary for the formation of the SOL/GMRbeta2.gif" BORDER=0 ALIGN="middle"> complex.