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Autoinhibition of Bruton's tyrosine kinase (Btk) and activation by soluble inositol hexakisphosphate.

Wang Q, Vogan EM, Nocka LM, Rosen CE, Zorn JA, Harrison SC, Kuriyan J - Elife (2015)

Bottom Line: In addition to the expected activation of Btk by membranes containing phosphatidylinositol triphosphate (PIP3), we found that inositol hexakisphosphate (IP6), a soluble signaling molecule found in both animal and plant cells, also activates Btk.This activation is a consequence of a transient PH-TH dimerization induced by IP6, which promotes transphosphorylation of the kinase domains.Sequence comparisons with other Tec-family kinases suggest that activation by IP6 is unique to Btk.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.

ABSTRACT
Bruton's tyrosine kinase (Btk), a Tec-family tyrosine kinase, is essential for B-cell function. We present crystallographic and biochemical analyses of Btk, which together reveal molecular details of its autoinhibition and activation. Autoinhibited Btk adopts a compact conformation like that of inactive c-Src and c-Abl. A lipid-binding PH-TH module, unique to Tec kinases, acts in conjunction with the SH2 and SH3 domains to stabilize the inactive conformation. In addition to the expected activation of Btk by membranes containing phosphatidylinositol triphosphate (PIP3), we found that inositol hexakisphosphate (IP6), a soluble signaling molecule found in both animal and plant cells, also activates Btk. This activation is a consequence of a transient PH-TH dimerization induced by IP6, which promotes transphosphorylation of the kinase domains. Sequence comparisons with other Tec-family kinases suggest that activation by IP6 is unique to Btk.

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Structural details of the Src-like module of Btk.(A) The Src-like module of Btk forms a domain-swapped dimer in the crystal lattice, with one molecule per asymmetric unit. The SH3 domain and the kinase domain are intact, but the SH2 domain forms a domain-swapped dimer with another molecule. (B) Molecular details of the domain-swapped SH2 dimer in Btk and Grb2 (Schiering et al., 2000). The SH2 domain opens up at a position within the β-sheet, so that helix αB of one polypeptide chain packs against the β-sheet of the other. (C) Interactions between the SH2-kinase linker and the kinase domain. Leu 390 of the linker stabilizes the inactive conformation of the kinase domain by being sandwiched between residues Trp 421 and Tyr 461 in the kinase domain. (D) The ‘electrostatic switch’ in the Btk kinase domain. The active conformation of the Btk kinase domain is modeled from the crystal structure of Lck (PDB: 3LCK) (Yamaguchi and Hendrickson, 1996) using Modeller (Eswar et al., 2006). Activation entails a shuffling of salt-bridge and polar hydrogen-bond partners.DOI:http://dx.doi.org/10.7554/eLife.06074.004
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fig1s1: Structural details of the Src-like module of Btk.(A) The Src-like module of Btk forms a domain-swapped dimer in the crystal lattice, with one molecule per asymmetric unit. The SH3 domain and the kinase domain are intact, but the SH2 domain forms a domain-swapped dimer with another molecule. (B) Molecular details of the domain-swapped SH2 dimer in Btk and Grb2 (Schiering et al., 2000). The SH2 domain opens up at a position within the β-sheet, so that helix αB of one polypeptide chain packs against the β-sheet of the other. (C) Interactions between the SH2-kinase linker and the kinase domain. Leu 390 of the linker stabilizes the inactive conformation of the kinase domain by being sandwiched between residues Trp 421 and Tyr 461 in the kinase domain. (D) The ‘electrostatic switch’ in the Btk kinase domain. The active conformation of the Btk kinase domain is modeled from the crystal structure of Lck (PDB: 3LCK) (Yamaguchi and Hendrickson, 1996) using Modeller (Eswar et al., 2006). Activation entails a shuffling of salt-bridge and polar hydrogen-bond partners.DOI:http://dx.doi.org/10.7554/eLife.06074.004

Mentions: We determined the structure of a construct of mouse Btk spanning residues 214 to 659, which starts just before the SH3 domain and ends at the C terminus of full-length Btk. The structure resembles those described previously for autoinhibited, Src-like, non-receptor tyrosine kinases, with the SH2-kinase linker sandwiched between the SH3 domain and the small domain of the kinase (the N lobe of the kinase) (Figure 1B). The crystal structure has two molecules of Btk in the asymmetric unit, intertwined as a domain-swapped dimer in which each SH2 domain has pieces from two molecules (Figure 1—figure supplement 1A). The domain-swapped SH2 domain packs against the large domain of the kinase (the C lobe of the kinase), but Btk lacks a Src-like C-terminal tail to stabilize this interaction.


Autoinhibition of Bruton's tyrosine kinase (Btk) and activation by soluble inositol hexakisphosphate.

Wang Q, Vogan EM, Nocka LM, Rosen CE, Zorn JA, Harrison SC, Kuriyan J - Elife (2015)

Structural details of the Src-like module of Btk.(A) The Src-like module of Btk forms a domain-swapped dimer in the crystal lattice, with one molecule per asymmetric unit. The SH3 domain and the kinase domain are intact, but the SH2 domain forms a domain-swapped dimer with another molecule. (B) Molecular details of the domain-swapped SH2 dimer in Btk and Grb2 (Schiering et al., 2000). The SH2 domain opens up at a position within the β-sheet, so that helix αB of one polypeptide chain packs against the β-sheet of the other. (C) Interactions between the SH2-kinase linker and the kinase domain. Leu 390 of the linker stabilizes the inactive conformation of the kinase domain by being sandwiched between residues Trp 421 and Tyr 461 in the kinase domain. (D) The ‘electrostatic switch’ in the Btk kinase domain. The active conformation of the Btk kinase domain is modeled from the crystal structure of Lck (PDB: 3LCK) (Yamaguchi and Hendrickson, 1996) using Modeller (Eswar et al., 2006). Activation entails a shuffling of salt-bridge and polar hydrogen-bond partners.DOI:http://dx.doi.org/10.7554/eLife.06074.004
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384635&req=5

fig1s1: Structural details of the Src-like module of Btk.(A) The Src-like module of Btk forms a domain-swapped dimer in the crystal lattice, with one molecule per asymmetric unit. The SH3 domain and the kinase domain are intact, but the SH2 domain forms a domain-swapped dimer with another molecule. (B) Molecular details of the domain-swapped SH2 dimer in Btk and Grb2 (Schiering et al., 2000). The SH2 domain opens up at a position within the β-sheet, so that helix αB of one polypeptide chain packs against the β-sheet of the other. (C) Interactions between the SH2-kinase linker and the kinase domain. Leu 390 of the linker stabilizes the inactive conformation of the kinase domain by being sandwiched between residues Trp 421 and Tyr 461 in the kinase domain. (D) The ‘electrostatic switch’ in the Btk kinase domain. The active conformation of the Btk kinase domain is modeled from the crystal structure of Lck (PDB: 3LCK) (Yamaguchi and Hendrickson, 1996) using Modeller (Eswar et al., 2006). Activation entails a shuffling of salt-bridge and polar hydrogen-bond partners.DOI:http://dx.doi.org/10.7554/eLife.06074.004
Mentions: We determined the structure of a construct of mouse Btk spanning residues 214 to 659, which starts just before the SH3 domain and ends at the C terminus of full-length Btk. The structure resembles those described previously for autoinhibited, Src-like, non-receptor tyrosine kinases, with the SH2-kinase linker sandwiched between the SH3 domain and the small domain of the kinase (the N lobe of the kinase) (Figure 1B). The crystal structure has two molecules of Btk in the asymmetric unit, intertwined as a domain-swapped dimer in which each SH2 domain has pieces from two molecules (Figure 1—figure supplement 1A). The domain-swapped SH2 domain packs against the large domain of the kinase (the C lobe of the kinase), but Btk lacks a Src-like C-terminal tail to stabilize this interaction.

Bottom Line: In addition to the expected activation of Btk by membranes containing phosphatidylinositol triphosphate (PIP3), we found that inositol hexakisphosphate (IP6), a soluble signaling molecule found in both animal and plant cells, also activates Btk.This activation is a consequence of a transient PH-TH dimerization induced by IP6, which promotes transphosphorylation of the kinase domains.Sequence comparisons with other Tec-family kinases suggest that activation by IP6 is unique to Btk.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.

ABSTRACT
Bruton's tyrosine kinase (Btk), a Tec-family tyrosine kinase, is essential for B-cell function. We present crystallographic and biochemical analyses of Btk, which together reveal molecular details of its autoinhibition and activation. Autoinhibited Btk adopts a compact conformation like that of inactive c-Src and c-Abl. A lipid-binding PH-TH module, unique to Tec kinases, acts in conjunction with the SH2 and SH3 domains to stabilize the inactive conformation. In addition to the expected activation of Btk by membranes containing phosphatidylinositol triphosphate (PIP3), we found that inositol hexakisphosphate (IP6), a soluble signaling molecule found in both animal and plant cells, also activates Btk. This activation is a consequence of a transient PH-TH dimerization induced by IP6, which promotes transphosphorylation of the kinase domains. Sequence comparisons with other Tec-family kinases suggest that activation by IP6 is unique to Btk.

Show MeSH