Structural basis for c-KIT inhibition by the suppressor of cytokine signaling 6 (SOCS6) ubiquitin ligase

TY - JOUR

T1 - Structural basis for c-KIT inhibition by the suppressor of cytokine signaling 6 (SOCS6) ubiquitin ligase

AU - Zadjali, Fahad

AU - Pike, Ashley C W

AU - Vesterlund, Mattias

AU - Sun, Jianmin

AU - Wu, Chenggang

AU - Li, Shawn S C

AU - Rönnstrand, Lars

AU - Knapp, Stefan

AU - Bullock, Alex N

AU - Flores Morales, Amilcar

PY - 2011/1/7

Y1 - 2011/1/7

N2 - The c-KIT receptor tyrosine kinase mediates the cellular response to stem cell factor (SCF). Whereas c-KIT activity is important for the proliferation of hematopoietic cells, melanocytes and germ cells, uncontrolled c-KIT activity contributes to the growth of diverse human tumors. Suppressor of cytokine signaling 6 (SOCS6) is a member of the SOCS family of E3 ubiquitin ligases that can interact with c-KIT and suppress c-KIT-dependent pathways. Here, we analyzed the molecular mechanisms that determine SOCS6 substrate recognition. Our results show that the SH2 domain of SOCS6 is essential for its interaction with c-KIT pY568. The 1.45-Å crystal structure of SOCS6 SH2 domain bound to the c-KIT substrate peptide (c-KIT residues 564-574) revealed a highly complementary and specific interface giving rise to a high affinity interaction (K(d) = 0.3 µm). Interestingly, the SH2 binding pocket extends to substrate residue position pY+6 and envelopes the c-KIT phosphopeptide with a large BG loop insertion that contributes significantly to substrate interaction. We demonstrate that SOCS6 has ubiquitin ligase activity toward c-KIT and regulates c-KIT protein turnover in cells. Our data support a role of SOCS6 as a feedback inhibitor of SCF-dependent signaling and provides molecular data to account for target specificity within the SOCS family of ubiquitin ligases.

AB - The c-KIT receptor tyrosine kinase mediates the cellular response to stem cell factor (SCF). Whereas c-KIT activity is important for the proliferation of hematopoietic cells, melanocytes and germ cells, uncontrolled c-KIT activity contributes to the growth of diverse human tumors. Suppressor of cytokine signaling 6 (SOCS6) is a member of the SOCS family of E3 ubiquitin ligases that can interact with c-KIT and suppress c-KIT-dependent pathways. Here, we analyzed the molecular mechanisms that determine SOCS6 substrate recognition. Our results show that the SH2 domain of SOCS6 is essential for its interaction with c-KIT pY568. The 1.45-Å crystal structure of SOCS6 SH2 domain bound to the c-KIT substrate peptide (c-KIT residues 564-574) revealed a highly complementary and specific interface giving rise to a high affinity interaction (K(d) = 0.3 µm). Interestingly, the SH2 binding pocket extends to substrate residue position pY+6 and envelopes the c-KIT phosphopeptide with a large BG loop insertion that contributes significantly to substrate interaction. We demonstrate that SOCS6 has ubiquitin ligase activity toward c-KIT and regulates c-KIT protein turnover in cells. Our data support a role of SOCS6 as a feedback inhibitor of SCF-dependent signaling and provides molecular data to account for target specificity within the SOCS family of ubiquitin ligases.

KW - Amino Acid Sequence

KW - HEK293 Cells

KW - Humans

KW - Models, Molecular

KW - Molecular Sequence Data

KW - Phosphopeptides

KW - Protein Tyrosine Phosphatase, Non-Receptor Type 11

KW - Proto-Oncogene Proteins c-kit

KW - Signal Transduction

KW - Stem Cell Factor

KW - Substrate Specificity

KW - Suppressor of Cytokine Signaling Proteins

KW - Ubiquitination

KW - src Homology Domains

U2 - 10.1074/jbc.M110.173526

DO - 10.1074/jbc.M110.173526

M3 - Journal article

C2 - 21030588

SN - 0021-9258

VL - 286

SP - 480

EP - 490

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

IS - 1

ER -