The Tiam1 guanine nucleotide exchange factor is auto-inhibited by its pleckstrin homology coiled-coil extension domain.

Autor: Xu Z; From the Department of Biochemistry., Gakhar L; From the Department of Biochemistry.; Protein Crystallography Facility, and., Bain FE; From the Department of Biochemistry., Spies M; From the Department of Biochemistry.; Holden Comprehensive Cancer Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242., Fuentes EJ; From the Department of Biochemistry, ernesto-fuentes@uiowa.edu.; Holden Comprehensive Cancer Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.
Jazyk: angličtina
Zdroj: The Journal of biological chemistry [J Biol Chem] 2017 Oct 27; Vol. 292 (43), pp. 17777-17793. Date of Electronic Publication: 2017 Sep 07.
DOI: 10.1074/jbc.M117.799114
Abstrakt: T-cell lymphoma invasion and metastasis 1 (Tiam1) is a Dbl-family guanine nucleotide exchange factor (GEF) that specifically activates the Rho-family GTPase Rac1 in response to upstream signals, thereby regulating cellular processes including cell adhesion and migration. Tiam1 contains multiple domains, including an N-terminal pleckstrin homology coiled-coiled extension (PH n -CC-Ex) and catalytic Dbl homology and C-terminal pleckstrin homology (DH-PH c ) domain. Previous studies indicate that larger fragments of Tiam1, such as the region encompassing the N-terminal to C-terminal pleckstrin homology domains (PH n -PH c ), are auto-inhibited. However, the domains in this region responsible for inhibition remain unknown. Here, we show that the PH n -CC-Ex domain inhibits Tiam1 GEF activity by directly interacting with the catalytic DH-PH c domain, preventing Rac1 binding and activation. Enzyme kinetics experiments suggested that Tiam1 is auto-inhibited through occlusion of the catalytic site rather than by allostery. Small angle X-ray scattering and ensemble modeling yielded models of the PH n -PH c fragment that indicate it is in equilibrium between "open" and "closed" conformational states. Finally, single-molecule experiments support a model in which conformational sampling between the open and closed states of Tiam1 contributes to Rac1 dissociation. Our results highlight the role of the PH n -CC-Ex domain in Tiam1 GEF regulation and suggest a combinatorial model for GEF inhibition and activation of the Rac1 signaling pathway.
(© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)
Databáze: MEDLINE
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