TY - JOUR
T1 - A two-state allosteric model for autoinhibition rationalizes WASP signal integration and targeting
AU - Buck, Matthias
AU - Xu, Wei
AU - Rosen, Michael K.
N1 - Funding Information:
We thank Daoqi You for technical assistance with protein preparation, Daisy Leung and Drs Rama Ranganathan and Harald Schwalbe for critical reading of the manuscript, and Dr Annette S. Kim for helpful discussion. M.K.R. is supported by the National Institutes of Health (GM56322) and the Welch Foundation (I1544). M.B. was the recipient of an NIH postdoctoral fellowship (GM20502).
PY - 2004/4/23
Y1 - 2004/4/23
N2 - Remodeling of the actin cytoskeleton is controlled by signaling pathways that include the Wiskott-Aldrich syndrome protein (WASP). WASP is regulated by autoinhibition, and the intramolecular contacts that inactivate the protein can be relieved through binding to the Rho-family GTPase Cdc42. Here, we show that the allosteric regulation of WASP can be quantitatively described by a two-state equilibrium between an active, largely unfolded conformation that is able to stimulate the Arp2/3 complex, and an inactive, folded conformation. The model is parameterized by the stability of WASP against unfolding and by the Cdc42 affinities of WASP constructs that mimic the unfolded and folded conformations. The model is consistent with NMR spectra of GTPase-bound WASP, and accurately predicts changes of amide hydrogen exchange behavior and Cdc42 affinity as a function of WASP stability. The results provide a thermodynamic rationale for the GTPase-independent recruitment of WASP and other autoinhibited effectors to their sites of activity. They also explain how basal activity is suppressed and confirm that WASP needs to integrate multiple cooperative inputs for maximal activation. Our analysis suggests that, in general, simple modulation of a two-state equilibrium may determine several regulatory functions, allowing the generation of complex signaling behavior in vivo.
AB - Remodeling of the actin cytoskeleton is controlled by signaling pathways that include the Wiskott-Aldrich syndrome protein (WASP). WASP is regulated by autoinhibition, and the intramolecular contacts that inactivate the protein can be relieved through binding to the Rho-family GTPase Cdc42. Here, we show that the allosteric regulation of WASP can be quantitatively described by a two-state equilibrium between an active, largely unfolded conformation that is able to stimulate the Arp2/3 complex, and an inactive, folded conformation. The model is parameterized by the stability of WASP against unfolding and by the Cdc42 affinities of WASP constructs that mimic the unfolded and folded conformations. The model is consistent with NMR spectra of GTPase-bound WASP, and accurately predicts changes of amide hydrogen exchange behavior and Cdc42 affinity as a function of WASP stability. The results provide a thermodynamic rationale for the GTPase-independent recruitment of WASP and other autoinhibited effectors to their sites of activity. They also explain how basal activity is suppressed and confirm that WASP needs to integrate multiple cooperative inputs for maximal activation. Our analysis suggests that, in general, simple modulation of a two-state equilibrium may determine several regulatory functions, allowing the generation of complex signaling behavior in vivo.
KW - Allosteric
KW - Cytoskeleton/Cdc42 GTPase
KW - GBD, GTPase binding domain
KW - Signal transduction
KW - VCA, verprolin homology region, central hydrophobic and acidic C-terminal region of WASP
KW - WASP, Wiskott-Aldrich syndrome protein
KW - Wiskott-Aldrich
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U2 - 10.1016/j.jmb.2004.02.036
DO - 10.1016/j.jmb.2004.02.036
M3 - Article
C2 - 15066431
AN - SCOPUS:1842505060
SN - 0022-2836
VL - 338
SP - 271
EP - 285
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 2
ER -