1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics

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

  1. Qi Wang
  2. Erik M Vogan
  3. Laura M Nocka
  4. Connor E Rosen
  5. Julie A Zorn
  6. Stephen C Harrison
  7. John Kuriyan  Is a corresponding author
  1. Howard Hughes Medical Institute, University of California, Berkeley, United States
  2. Beryllium Inc, United States
  3. University of California, Berkeley, United States
  4. Harvard Medical School, Howard Hughes Medical Institute, United States
https://doi.org/10.7554/eLife.06074
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Cite this article
  1. Qi Wang
  2. Erik M Vogan
  3. Laura M Nocka
  4. Connor E Rosen
  5. Julie A Zorn
  6. Stephen C Harrison
  7. John Kuriyan
(2015)
Autoinhibition of Bruton's tyrosine kinase (Btk) and activation by soluble inositol hexakisphosphate
eLife 4:e06074.
https://doi.org/10.7554/eLife.06074
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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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Author details

  1. Qi Wang

    Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
    Competing interests
    No competing interests declared.

  2. Erik M Vogan

    Beryllium Inc, Boston, United States
    Competing interests
    No competing interests declared.

  3. Laura M Nocka

    Department of Chemistry, University of California, Berkeley, Berkeley, United States
    Competing interests
    No competing interests declared.

  4. Connor E Rosen

    Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
    Competing interests
    No competing interests declared.

  5. Julie A Zorn

    Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
    Competing interests
    No competing interests declared.

  6. Stephen C Harrison

    Laboratory of Molecular Medicine, Harvard Medical School, Howard Hughes Medical Institute, Boston, United States
    Competing interests
    Stephen C Harrison, Reviewing editor, eLife.

  7. John Kuriyan

    Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
    For correspondence
    jkuriyan@mac.com
    Competing interests
    John Kuriyan, Senior editor, eLife.

Copyright

© 2015, Wang et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Qi Wang
  2. Erik M Vogan
  3. Laura M Nocka
  4. Connor E Rosen
  5. Julie A Zorn
  6. Stephen C Harrison
  7. John Kuriyan
(2015)
Autoinhibition of Bruton's tyrosine kinase (Btk) and activation by soluble inositol hexakisphosphate
eLife 4:e06074.
https://doi.org/10.7554/eLife.06074

Share this article

https://doi.org/10.7554/eLife.06074

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Further reading

    1. Biochemistry and Chemical Biology
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    Stimulation of the catalytic activity of the tyrosine kinase Btk by the adaptor protein Grb2

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    The Tec-family kinase Btk contains a lipid-binding Pleckstrin homology and Tec homology (PH-TH) module connected by a proline-rich linker to a ‘Src module’, an SH3-SH2-kinase unit also found in Src-family kinases and Abl. We showed previously that Btk is activated by PH-TH dimerization, which is triggered on membranes by the phosphatidyl inositol phosphate PIP3, or in solution by inositol hexakisphosphate (IP6) (Wang et al., 2015, https://doi.org/10.7554/eLife.06074). We now report that the ubiquitous adaptor protein growth-factor-receptor-bound protein 2 (Grb2) binds to and substantially increases the activity of PIP3-bound Btk on membranes. Using reconstitution on supported-lipid bilayers, we find that Grb2 can be recruited to membrane-bound Btk through interaction with the proline-rich linker in Btk. This interaction requires intact Grb2, containing both SH3 domains and the SH2 domain, but does not require that the SH2 domain be able to bind phosphorylated tyrosine residues – thus Grb2 bound to Btk is free to interact with scaffold proteins via the SH2 domain. We show that the Grb2-Btk interaction recruits Btk to scaffold-mediated signaling clusters in reconstituted membranes. Our findings indicate that PIP3-mediated dimerization of Btk does not fully activate Btk, and that Btk adopts an autoinhibited state at the membrane that is released by Grb2.

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