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Membrane Recruitment of Tec Kinase by RANKL Activates NFATc1 in Osteoclasts
Author(s) -
Sarmasik Aliye,
Wang Guangqing,
Wang Kent Z.Q.,
Auron Philip E.,
Galson Deborah L.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a249-a
Subject(s) - tec , bruton's tyrosine kinase , rankl , microbiology and biotechnology , kinase , chemistry , nfat , syk , downregulation and upregulation , osteoclast , tyrosine kinase , phosphorylation , signal transduction , cancer research , transcription factor , activator (genetics) , receptor , biology , biochemistry , ionosphere , physics , astronomy , gene
RANKL stimulation of osteoclastogenesis has been shown to require a costimulatory signal by the ITAM bearing adapter‐receptor complex DAP12/TREM2. The molecular mechanism by which the RANK and ITAM signals are integrated to upregulate and activate the Ca 2+ ‐regulated transcription factor NFATc1 is unknown. Overexpression of the protein tyrosine kinases Tec or Btk in RAW264.7 cells is sufficient to induce NFATc1 activation and upregulation of the osteoclast‐specific calcitonin receptor P3 promoter (P3). Use of the inhibitors, U73122 and CsA, demonstrated that Tec/Btk activation of both PLCγ and calcineurin were required to upregulate P3. Mutation of various functional regions of Tec demonstrated that: inactivation of the PH domain, thereby preventing membrane recruitment, eliminates the ability of Tec to activate P3; an intact SH2 domain is required for Tec activation of P3; kinase‐inactive Tec maintained significant activity; and NFATc1 activation did not require an intact SH3 domain or proline‐containing motifs. Live imaging showed that RANKL recruits Tec PH‐EGFP to the membrane, but not Btk PH‐EGFP. Furthermore, a Btk inhibitor, LFM‐A13 blocked Btk, but not Tec activation of P3 and had no effect on osteoclast differentiation. We propose that Tec kinase integrates signals from RANKL/RANK and ITAMs in osteoclasts and is required to generate the signal strength necessary to activate NFATc1.