Cdc42
WASP
PDB 1cee
Structure of
Cdc42 in
complex with the
GTPase-binding
domain of the
‘Wiskott-Aldrich
syndrome’
protein
List

Finish Breast Cancer Talk
 Look up Drugs affecting WAS and
structures
 Conclusion/ WAS
 Write whole speech
 PRACTICE PRACTICE PRACTICe
 Tuesday, 10-12 Eagleton Institute of
Politics
 1-4:30 I have 3 1/2 hours
Overview
Introduction
Function
Structure
Disease
Treatment
Conclusion
Introduction

CDC42 is a member of a small family of GTPases. Through the
action of GTPases, GTP (an essential for signal transduction
with G-proteins) is converted to GDP (guanosine diphosphate).

GTP-binding proteins together control the assembly,
organization, and disassembly of the actin cytoskeleton in
response to extracellular signals in eukaryotic cells.

The Cdc42 proteins bind to effector proteins

Diseases such as the Wiskott- Aldrich Syndrome or certain
forms of cancer,such as breast cancer are thought to arise due to
derangement or mutations of the Cdc42.
Function
“Cdc42 acts as a molecular switch in
signaling pathways that regulate
cytoskeletal architecture, gene expression,
and progression of the cell cycle. The
switch transmits different signals through
the GTP-dependent binding to effector
proteins containing a Cdc42/Rac interactive
binding (CRIB) motif”
Function

Regulators of the actin cytoskeleton

Control motility of mammalian cells

Transduce signals from extracellular
stimuli to intracellular signal transduction
pathways.
Signaling Pathway
Involving Cdc42
Cdc42
Re
Cdc42
GDP
GTPase
Cycle
Cdc42
GTP
Effectors
WASP
Regulates Actin
cytoskeleton
Cell morphology
Cell migration
Cell growth
Cell survival
Gene expression
Structure (By NMR Spectroscopy)




Structure of the Cdc42 complex binding through
GTP-dependent binding to effector proteins
containing a Cdc42/Rac interactive-binding
(CRIB) motif.
Chain A : GTP-binding Rho-like Protein
Chain B is the Wiskott-Aldrich Syndrome Protein
Fifty-five known interactions
The CDC42/Rac- binding domain is between
amino acids 201-321 on WASP.
Chain B: WASP
CRIB
Motif
Chain A: Cdc42
PDB 1cee
C
Switch I
Switch II
N
ß3
ß2
CRIB
C
N
PDB 1cee
Structure
Cdc42 residues Phe37, Asn39 and Ala41,
near the C terminus of switch I, form
main-chain hydrogen bonds to WASP
residues Val250, Val247/Ser 248 and
Lys 245. These interactions position the
Asp38 side chain of Cdc42 near WASP
residues His246 and His249. There is a
hydrogen bond from the Asp 38 to eiter
His 246 or His249 ring.
C
Switch I
Switch II
N
ß3
ß2
CRIB
C
N
PDB 1cee
I276
V36
L67
A274
V260
D38
F271
F37
H249
Y40
I21
L70
L270
L267
F56
T25
H246
PDB 1cee
WASP
H249
D38
F56
Hydrogen B
Y40
I21
Cdc42
H246
Structure

Hydrophobic interactions anchor WASP
residues 232-238 to the Cdc42 B2/B3
hairpin and alpha 5 helix.
 Interaction of the WASP GBD N terminus
and the Cdc42 B2/ B3 hairpin and alpha5
helix.
C
Switch I
Switch II
N
ß3
ß2
CRIB
C
N
Y51
I46
I238
D237
I233
I173
L177
L174
K235
Y51
I46
I173
L177
Hydrogen Bonds
D237
K235
E174
PDB 1cee
Gene Sequence
Binding Preference
Rac Cdc42
WASP
N-WASP
ACK
PAK65
STE20
MRCKb
230
192
502
67
329
1577
KKKISKADIGAPSΡ GFKHVS HVGWDPQNGFDVNNLDPDLRSLFSRAG IS
KKRLTKADIGTPS-- NFQHIG HVGWDPNTGFDLNN LDPELKNLFDMCGIS
VAGLSAQDISQPLQNSFI HTGHGDS DPRHCWGFP-DRIDE LY LGNPMDPP
KKEKERP EISLPS-- DFEHTI HVGF DAVTG-EFTGMPEQ WARLLQTSN IT
SSITTA LRISTPY-- NAKHIH HVGVDSKT GE-YTG LPEEWEKLLTSS G IS
DPELRSKMISNPTΡ NFN HVAHMG---PGD GMQV LMDLPLSVRPQPRRK
ISXPX---XFXHXXH
-277
-239
-550
-113
-375
-1620
+
+
-
CRIB motif
Cdc42
Rac1
RhoA
Ι SEYVPTV FDNYAVTVMIGG...AGQEDYDRLRPLSYPQT...VFDEAILAALEΙ
...GEYIPTVFDNYSANVMVDG...AGQEDYDRLRPLSYPQT...VFDEAIRAVLC...
...EVYVPTVFENY VADIEVDG...AGQEDYDRLRPLSYPDT...VFEMATRAALQ...
30
Switch I
48 59
Switch II
75 168
178
+
+
+
+
+
+
Wiskott- Aldrich Syndrome

Rare X-lined recessive disorder that affects cell
morphology and signal transduction in
hematopoietic cells
 Function of WASP is to serve as a bridge
between signaling and movement of the actin
filaments in the cytoskeleton.
 Researchers identified many different mutations
that interfere with the protein binding to Cdc42,
which is involved in regulation of the actin
cytoskeleton of lymphocytes. The actin
cytoskeleton is responsible for cellular functions
such as growth, endocytosis, exocytosis, and
cytokinesis.
Interaction

Show surface depiction of interaction
 Look for mutated ones
Drugs used and structures
Treatment

WAS is treated with a variety of therapeutic agents including antibiotics,
antivirals, antifungals, chemotherapeutic agents, immunoglobulins, and
corticosteroids.
 Examples: Prednisone, Methylprednisolone, fluocinolone, and immune
globulin.
Conclusion
References
Questions/Comments?