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The Fyn-ADAP Axis: Cytotoxicity Versus Cytokine Production in Killer Cells.

Gerbec ZJ, Thakar MS, Malarkannan S - Front Immunol (2015)

Bottom Line: Specifically, the Fyn signaling axis represents a branch point for killer cell effector functions and provides a model for how cytotoxicity and cytokine production are differentially regulated.While the Fyn-PI(3)K pathway controls multiple functions, including cytotoxicity, cell development, and cytokine production, the Fyn-ADAP pathway preferentially regulates cytokine production in NK and T cells.In this review, we discuss how the structure of Fyn controls its function in lymphocytes and the role this plays in mediating two facets of lymphocyte effector function, cytotoxicity and production of inflammatory cytokines.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology and Immunotherapy, Blood Research Institute, Medical College of Wisconsin , Milwaukee, WI , USA ; Department of Microbiology, Immunology and Molecular Genetics, Medical College of Wisconsin , Milwaukee, WI , USA.

ABSTRACT
Lymphocyte signaling cascades responsible for anti-tumor cytotoxicity and inflammatory cytokine production must be tightly regulated in order to control an immune response. Disruption of these cascades can cause immune suppression as seen in a tumor microenvironment, and loss of signaling integrity can lead to autoimmunity and other forms of host-tissue damage. Therefore, understanding the distinct signaling events that exclusively control specific effector functions of "killer" lymphocytes (T and NK cells) is critical for understanding disease progression and formulating successful immunotherapy. Elucidation of divergent signaling pathways involved in receptor-mediated activation has provided insights into the independent regulation of cytotoxicity and cytokine production in lymphocytes. Specifically, the Fyn signaling axis represents a branch point for killer cell effector functions and provides a model for how cytotoxicity and cytokine production are differentially regulated. While the Fyn-PI(3)K pathway controls multiple functions, including cytotoxicity, cell development, and cytokine production, the Fyn-ADAP pathway preferentially regulates cytokine production in NK and T cells. In this review, we discuss how the structure of Fyn controls its function in lymphocytes and the role this plays in mediating two facets of lymphocyte effector function, cytotoxicity and production of inflammatory cytokines. This offers a model for using mechanistic and structural approaches to understand clinically relevant lymphocyte signaling.

No MeSH data available.


Related in: MedlinePlus

Specificity of the Fyn–ADAP interaction. (A) Surface and ribbon models show the Fyn SH2 domain bound to a pYEEI peptide motif. Green shading on the surface model represents the phosphotyrosine-binding pocket, while red shading represents the specificity-determining region. The ribbon model shows that the pYEEI peptide lies orthogonal to the β-sheet of the SH2 domain. This positions the phosphorylated tyrosine in a hydrophilic pocket in between the β-sheet and the αA helix. The linear conformation of the peptide allows residues C-terminal to the phosphotyrosine to interact with other regions of the SH2 domain, which increases specificity and affinity of the Fyn–substrate interaction. Both the surface and ribbon model are derived from PDB deposition 1AOT. (B) An exploded view of the primary binding pocket highlights the interaction between the phosphotyrosine and the conserved ArgβB5 of Fyn. Salt-bridge formation at this site contributes roughly 50% of the binding energy required for the SH2 peptide interaction. (C) Comparison of different SFKs bound to pYEEI motifs show varied interactions at the phosphotyrosine-binding pocket. Ribbon models of Fyn (left), Lck (center), and Src (right) highlight bond distances between ArgαA2 of the SH2 domain and a backbone carbonyl on the target peptide (#1). Bond distances show that ArgαA2 is capable of interacting with the backbone of the pYEEI motif in Src and Lck but not in Fyn. Ribbon models also show the distance between the backbone carbonyl of HisβD4 of the SH2 domain and backbone amide of the pYEEI motif (#2). These bond distances suggest that the structure of the Fyn SH2 domain places pYEEI motifs in a more extended conformation than that seen in Src or Lck. (D) Measurements obtained from PDB depositions show the distance between TyrβD5 of the SH2 domain and the glutamate residue in the +1 position from the phosphotyrosine. The shorter distance in Fyn (left) means that hydrogen bonding is possible between TyrβD5 and the +1 glutamate residue of the pYEEI motif, while bonding is based primarily on hydrophobic interactions (red dashes) in Lck (center) and Src (right). This may provide an explanation for the ability of Fyn to act as the sole kinase responsible for recruitment of ADAP, as less hydrophobic interactions would be possible between the SH2 domain and YDGI motif of ADAP. Measurements are based on PDB depositions 1AOT for Fyn, 1LKK for Lck, and 1SPS for Src.
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Figure 4: Specificity of the Fyn–ADAP interaction. (A) Surface and ribbon models show the Fyn SH2 domain bound to a pYEEI peptide motif. Green shading on the surface model represents the phosphotyrosine-binding pocket, while red shading represents the specificity-determining region. The ribbon model shows that the pYEEI peptide lies orthogonal to the β-sheet of the SH2 domain. This positions the phosphorylated tyrosine in a hydrophilic pocket in between the β-sheet and the αA helix. The linear conformation of the peptide allows residues C-terminal to the phosphotyrosine to interact with other regions of the SH2 domain, which increases specificity and affinity of the Fyn–substrate interaction. Both the surface and ribbon model are derived from PDB deposition 1AOT. (B) An exploded view of the primary binding pocket highlights the interaction between the phosphotyrosine and the conserved ArgβB5 of Fyn. Salt-bridge formation at this site contributes roughly 50% of the binding energy required for the SH2 peptide interaction. (C) Comparison of different SFKs bound to pYEEI motifs show varied interactions at the phosphotyrosine-binding pocket. Ribbon models of Fyn (left), Lck (center), and Src (right) highlight bond distances between ArgαA2 of the SH2 domain and a backbone carbonyl on the target peptide (#1). Bond distances show that ArgαA2 is capable of interacting with the backbone of the pYEEI motif in Src and Lck but not in Fyn. Ribbon models also show the distance between the backbone carbonyl of HisβD4 of the SH2 domain and backbone amide of the pYEEI motif (#2). These bond distances suggest that the structure of the Fyn SH2 domain places pYEEI motifs in a more extended conformation than that seen in Src or Lck. (D) Measurements obtained from PDB depositions show the distance between TyrβD5 of the SH2 domain and the glutamate residue in the +1 position from the phosphotyrosine. The shorter distance in Fyn (left) means that hydrogen bonding is possible between TyrβD5 and the +1 glutamate residue of the pYEEI motif, while bonding is based primarily on hydrophobic interactions (red dashes) in Lck (center) and Src (right). This may provide an explanation for the ability of Fyn to act as the sole kinase responsible for recruitment of ADAP, as less hydrophobic interactions would be possible between the SH2 domain and YDGI motif of ADAP. Measurements are based on PDB depositions 1AOT for Fyn, 1LKK for Lck, and 1SPS for Src.

Mentions: All SFKs contain a highly conserved SH2 domain with a preference for binding pYEEI phosphopeptide motifs (56). Roughly half of the binding energy for this interaction is derived from contact between the phosphotyrosine residue and a hydrophilic binding pocket located between the N-terminal α-helix and central β-sheet of SH2 domains (Figure 4A) (27, 57). The base of this pocket is formed by an Arg residue in the β-sheet that mediates electrostatic interactions with the phosphotyrosine (Figure 4B). This pocket is conserved across SH2 domains and provides the basis for SH2–phosphotyrosine interactions (58).


The Fyn-ADAP Axis: Cytotoxicity Versus Cytokine Production in Killer Cells.

Gerbec ZJ, Thakar MS, Malarkannan S - Front Immunol (2015)

Specificity of the Fyn–ADAP interaction. (A) Surface and ribbon models show the Fyn SH2 domain bound to a pYEEI peptide motif. Green shading on the surface model represents the phosphotyrosine-binding pocket, while red shading represents the specificity-determining region. The ribbon model shows that the pYEEI peptide lies orthogonal to the β-sheet of the SH2 domain. This positions the phosphorylated tyrosine in a hydrophilic pocket in between the β-sheet and the αA helix. The linear conformation of the peptide allows residues C-terminal to the phosphotyrosine to interact with other regions of the SH2 domain, which increases specificity and affinity of the Fyn–substrate interaction. Both the surface and ribbon model are derived from PDB deposition 1AOT. (B) An exploded view of the primary binding pocket highlights the interaction between the phosphotyrosine and the conserved ArgβB5 of Fyn. Salt-bridge formation at this site contributes roughly 50% of the binding energy required for the SH2 peptide interaction. (C) Comparison of different SFKs bound to pYEEI motifs show varied interactions at the phosphotyrosine-binding pocket. Ribbon models of Fyn (left), Lck (center), and Src (right) highlight bond distances between ArgαA2 of the SH2 domain and a backbone carbonyl on the target peptide (#1). Bond distances show that ArgαA2 is capable of interacting with the backbone of the pYEEI motif in Src and Lck but not in Fyn. Ribbon models also show the distance between the backbone carbonyl of HisβD4 of the SH2 domain and backbone amide of the pYEEI motif (#2). These bond distances suggest that the structure of the Fyn SH2 domain places pYEEI motifs in a more extended conformation than that seen in Src or Lck. (D) Measurements obtained from PDB depositions show the distance between TyrβD5 of the SH2 domain and the glutamate residue in the +1 position from the phosphotyrosine. The shorter distance in Fyn (left) means that hydrogen bonding is possible between TyrβD5 and the +1 glutamate residue of the pYEEI motif, while bonding is based primarily on hydrophobic interactions (red dashes) in Lck (center) and Src (right). This may provide an explanation for the ability of Fyn to act as the sole kinase responsible for recruitment of ADAP, as less hydrophobic interactions would be possible between the SH2 domain and YDGI motif of ADAP. Measurements are based on PDB depositions 1AOT for Fyn, 1LKK for Lck, and 1SPS for Src.
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Figure 4: Specificity of the Fyn–ADAP interaction. (A) Surface and ribbon models show the Fyn SH2 domain bound to a pYEEI peptide motif. Green shading on the surface model represents the phosphotyrosine-binding pocket, while red shading represents the specificity-determining region. The ribbon model shows that the pYEEI peptide lies orthogonal to the β-sheet of the SH2 domain. This positions the phosphorylated tyrosine in a hydrophilic pocket in between the β-sheet and the αA helix. The linear conformation of the peptide allows residues C-terminal to the phosphotyrosine to interact with other regions of the SH2 domain, which increases specificity and affinity of the Fyn–substrate interaction. Both the surface and ribbon model are derived from PDB deposition 1AOT. (B) An exploded view of the primary binding pocket highlights the interaction between the phosphotyrosine and the conserved ArgβB5 of Fyn. Salt-bridge formation at this site contributes roughly 50% of the binding energy required for the SH2 peptide interaction. (C) Comparison of different SFKs bound to pYEEI motifs show varied interactions at the phosphotyrosine-binding pocket. Ribbon models of Fyn (left), Lck (center), and Src (right) highlight bond distances between ArgαA2 of the SH2 domain and a backbone carbonyl on the target peptide (#1). Bond distances show that ArgαA2 is capable of interacting with the backbone of the pYEEI motif in Src and Lck but not in Fyn. Ribbon models also show the distance between the backbone carbonyl of HisβD4 of the SH2 domain and backbone amide of the pYEEI motif (#2). These bond distances suggest that the structure of the Fyn SH2 domain places pYEEI motifs in a more extended conformation than that seen in Src or Lck. (D) Measurements obtained from PDB depositions show the distance between TyrβD5 of the SH2 domain and the glutamate residue in the +1 position from the phosphotyrosine. The shorter distance in Fyn (left) means that hydrogen bonding is possible between TyrβD5 and the +1 glutamate residue of the pYEEI motif, while bonding is based primarily on hydrophobic interactions (red dashes) in Lck (center) and Src (right). This may provide an explanation for the ability of Fyn to act as the sole kinase responsible for recruitment of ADAP, as less hydrophobic interactions would be possible between the SH2 domain and YDGI motif of ADAP. Measurements are based on PDB depositions 1AOT for Fyn, 1LKK for Lck, and 1SPS for Src.
Mentions: All SFKs contain a highly conserved SH2 domain with a preference for binding pYEEI phosphopeptide motifs (56). Roughly half of the binding energy for this interaction is derived from contact between the phosphotyrosine residue and a hydrophilic binding pocket located between the N-terminal α-helix and central β-sheet of SH2 domains (Figure 4A) (27, 57). The base of this pocket is formed by an Arg residue in the β-sheet that mediates electrostatic interactions with the phosphotyrosine (Figure 4B). This pocket is conserved across SH2 domains and provides the basis for SH2–phosphotyrosine interactions (58).

Bottom Line: Specifically, the Fyn signaling axis represents a branch point for killer cell effector functions and provides a model for how cytotoxicity and cytokine production are differentially regulated.While the Fyn-PI(3)K pathway controls multiple functions, including cytotoxicity, cell development, and cytokine production, the Fyn-ADAP pathway preferentially regulates cytokine production in NK and T cells.In this review, we discuss how the structure of Fyn controls its function in lymphocytes and the role this plays in mediating two facets of lymphocyte effector function, cytotoxicity and production of inflammatory cytokines.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology and Immunotherapy, Blood Research Institute, Medical College of Wisconsin , Milwaukee, WI , USA ; Department of Microbiology, Immunology and Molecular Genetics, Medical College of Wisconsin , Milwaukee, WI , USA.

ABSTRACT
Lymphocyte signaling cascades responsible for anti-tumor cytotoxicity and inflammatory cytokine production must be tightly regulated in order to control an immune response. Disruption of these cascades can cause immune suppression as seen in a tumor microenvironment, and loss of signaling integrity can lead to autoimmunity and other forms of host-tissue damage. Therefore, understanding the distinct signaling events that exclusively control specific effector functions of "killer" lymphocytes (T and NK cells) is critical for understanding disease progression and formulating successful immunotherapy. Elucidation of divergent signaling pathways involved in receptor-mediated activation has provided insights into the independent regulation of cytotoxicity and cytokine production in lymphocytes. Specifically, the Fyn signaling axis represents a branch point for killer cell effector functions and provides a model for how cytotoxicity and cytokine production are differentially regulated. While the Fyn-PI(3)K pathway controls multiple functions, including cytotoxicity, cell development, and cytokine production, the Fyn-ADAP pathway preferentially regulates cytokine production in NK and T cells. In this review, we discuss how the structure of Fyn controls its function in lymphocytes and the role this plays in mediating two facets of lymphocyte effector function, cytotoxicity and production of inflammatory cytokines. This offers a model for using mechanistic and structural approaches to understand clinically relevant lymphocyte signaling.

No MeSH data available.


Related in: MedlinePlus