Ryk binds to Cdc37. A, FLAG-tagged Cdc37 and Myc-tagged Ryk
were transfected into 293T cells. Binding of Cdc37 and Ryk was analyzed by
immunoprecipitation (IP) followed by Western blotting (IB)
using anti-Myc or anti-FLAG antibodies. FL, full-length. B,
a Western blot analysis of anti-FLAG and anti-Myc immunoprecipitates from
membrane and cytosolic extracts is shown. C, Cdc37 binds to the ICD
region of Ryk. 293T cells expressing Cdc37-FLAG were transfected with the
wild-type Ryk, Ryk ICD, or a control plasmid. An anti-Myc immunoprecipitate
from whole cell lysates was analyzed by Western blotting using anti-FLAG and
anti-Myc antibodies. D, Cdc37 recognizes the tyrosine kinase domain
of Ryk. A schematic of the wild-type and mutant of Ryk ICD constructs shows
that the Ryk tyrosine kinase domain consists of 11 conserved subdomains
(top panel). Each mutant was constructed by deletion of the indicated
subdomains. Wild-type and subdomain I/II-deleted mutants, but not other
mutants, bind Cdc37 (bottom panel). Plasmids encoding wild-type and
mutant ICD proteins or a control vector were cotransfected with FLAG-Cdc37.
Cell lysates were analyzed by immunoprecipitation and Western blotting with
anti-Myc or anti-FLAG antibodies. E, the fragment encoding amino
acids 367–579 of the Ryk kinase domains is sufficient to bind to Cdc37
directly. HA-tagged Ryk-(367–579) was purified from bacteria. Cdc37-FLAG
was purified by immunoprecipitation from 293T cells transfected with the
construct encoding Cdcd37-FLAG. A Coomassie Blue-stained SDS-polyacrylamide
gel containing purified proteins (top panel) confirms the purity of
the protein preparations. Arrows indicate purified
Ryk-(367–579) (lane 1) and Cdc37-FLAG (lane 2).
Purified protein samples were incubated under the indicated conditions, and
immunoprecipitation and Western blot analyses were performed using anti-HA or
anti-FLAG antibody (lower panel). F, the Cdc37 C terminus is
required for binding of Ryk. 293T cells expressing wild-type (WT)
Ryk-Myc were transfected with plasmids encoding either wild-type Cdc37-FLAG or
C-terminal (CT) deletion mutant (Cdc37ΔCT-FLAG). Anti-FLAG and
anti-Myc immunoprecipitates were subjected to Western blotting with anti-Myc
and anti-FLAG antibodies.