Spatiotemporal control of small GTPases with light using the LOV domain.

TitleSpatiotemporal control of small GTPases with light using the LOV domain.
Publication TypeJournal Article
Year of Publication2011
AuthorsWu YI, Wang X, He L, Montell D, Hahn KM
JournalMethods Enzymol
Date Published2011
KeywordsAnimals, Cell Movement, Cells, Cultured, Drosophila melanogaster, Female, Light, Microscopy, Monomeric GTP-Binding Proteins, Ovary, Phototropins, Protein Structure, Tertiary, rac GTP-Binding Proteins, Signal Transduction

<p>Signaling networks in living systems are coordinated through subcellular compartmentalization and precise timing of activation. These spatiotemporal aspects ensure the fidelity of signaling while contributing to the diversity and specificity of downstream events. This is studied through development of molecular tools that generate localized and precisely timed protein activity in living systems. To study the molecular events responsible for cytoskeletal changes in real time, we generated versions of Rho family GTPases whose interactions with downstream effectors is controlled by light. GTPases were grafted to the phototropin LOV (light, oxygen, or voltage) domain (Huala, E., Oeller, P. W., Liscum, E., Han, I., Larsen, E., and Briggs, W. R. (1997). Arabidopsis NPH1: A protein kinase with a putative redox-sensing domain. Science278, 2120-2123.) via an alpha helix on the LOV C-terminus (Wu, Y. I., Frey, D., Lungu, O. I., Jaehrig, A., Schlichting, I., Kuhlman, B., and Hahn, K. M. (2009). A genetically encoded photoactivatable Rac controls the motility of living cells. Nature461, 104-108.). The LOV domain sterically blocked the GTPase active site until it was irradiated. Exposure to 400-500nm light caused unwinding of the helix linking the LOV domain to the GTPase, relieving steric inhibition. The change was reversible and repeatable, and the protein could be returned to its inactive state simply by turning off the light. The LOV domain incorporates a flavin as the active chromophore. This naturally occurring molecule is incorporated simply upon expression of the LOV fusion in cells or animals, permitting ready control of GTPase function in different systems. In cultured single cells, light-activated Rac leads to membrane ruffling, protrusion, and migration. In collectively migrating border cells in the Drosophila ovary, focal activation of photoactivatable Rac (PA-Rac) in a single cell is sufficient to redirect the entire group. PA-Rac in a single cell also rescues the phenotype caused by loss of endogenous guidance receptor signaling in the whole group. These findings demonstrate that cells within the border cell cluster communicate and are guided collectively. Here, we describe optimization and application of PA-Rac using detailed examples that we hope will help others apply the approach to different proteins and in a variety of different cells, tissues, and organisms.</p>

Alternate JournalMethods Enzymol
PubMed ID21601095
PubMed Central IDPMC3407667
Grant ListR01 GM073164 / GM / NIGMS NIH HHS / United States
R01 GM057464 / GM / NIGMS NIH HHS / United States
S10 RR024550 / RR / NCRR NIH HHS / United States
R01 GM046425 / GM / NIGMS NIH HHS / United States
R01 GM046425-18A1 / GM / NIGMS NIH HHS / United States
R01 GM073164-08 / GM / NIGMS NIH HHS / United States