A molecular and structural mechanism for G protein-mediated microtubule destabilization.
The heterotrimeric, G protein-coupled receptor-associated G protein, Gα(s), binds tubulin with nanomolar affinity and disrupts microtubules in cells and in vitro. Here we determine that the activated form of Gα(s) binds tubulin with a K(D) of 100 nm, stimulates tubulin GTPase, and promotes microtubule dynamic instability. Moreover, the data reveal that the α3-β5 region of Gα(s) is a functionally important motif in the Gα(s)-mediated microtubule destabilization. Indeed, peptides corresponding to that region of Gα(s) mimic Gα(s) protein in activating tubulin GTPase and increase microtubule dynamic instability. We have identified specific mutations in peptides or proteins that interfere with this process. The data allow for a model of the Gα(s)/tubulin interface in which Gα(s) binds to the microtubule plus-end and activates the intrinsic tubulin GTPase. This model illuminates both the role of tubulin as an "effector" (e.g. adenylyl cyclase) for Gα(s) and the role of Gα(s) as a GTPase activator for tubulin. Given the ability of Gα(s) to translocate intracellularly in response to agonist activation, Gα(s) may play a role in hormone- or neurotransmitter-induced regulation of cellular morphology.
Department of Physiology and Biophysics, University of Illinois, Chicago, Illinois 60612, USA.
Rahul H
RH
Davé
Witchuda
W
Saengsawang
Manu
M
Lopus
Sonya
S
Davé
Leslie
L
Wilson
Mark M
MM
Rasenick
D020816:Amino Acid Motifs; D000818:Animals; D002417:Cattle; D004789:Enzyme Activation / Q000502:physiology; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012756:Sheep
D019205:GTP-Binding Protein alpha Subunits, Gs