Regulation of light-dependent Gqalpha translocation and morphological changes in fly photoreceptors.
Heterotrimeric G-proteins relay signals between membrane-bound receptors and downstream effectors. Little is known, however, about the regulation of Galpha subunit localization within the natural endogenous environment of a specialized signaling cell. Here we show, using live Drosophila flies, that light causes massive and reversible translocation of the visual Gqalpha to the cytosol, associated with marked architectural changes in the signaling compartment. Molecular genetic dissection together with detailed kinetic analysis enabled us to characterize the translocation cycle and to unravel how signaling molecules that interact with Gqalpha affect these processes. Epistatic analysis showed that Gqalpha is necessary but not sufficient to bring about the morphological changes in the signaling organelle. Furthermore, mutant analysis indicated that Gqbeta is essential for targeting of Gqalpha to the membrane and suggested that Gqbeta is also needed for efficient activation of Gqalpha by rhodopsin. Our results support the 'two-signal model' hypothesis for membrane targeting in a living organism and characterize the regulation of both the activity-dependent Gq localization and the cellular architectural changes in Drosophila photoreceptors.
Kosloff
Mickey
M
Department of Biological Chemistry and the Kühne Minerva Center for Studies of Visual Transduction, Institute of Life Sciences, The Hebrew University, Givat Ram, Jerusalem, 91904, Israel.
Elia
Natalie
N
Joel-Almagor
Tamar
T
Timberg
Rina
R
Zars
Troy D
TD
Hyde
David R
DR
Minke
Baruch
B
Selinger
Zvi
Z
D000199:Actins / Q000378:metabolism; D000818:Animals; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D003623:Dark Adaptation; D004331:Drosophila melanogaster / Q000378:metabolism* / Q000648:ultrastructure; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008027:Light; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D030781:Organisms, Genetically Modified; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism / Q000648:ultrastructure*; D021122:Protein Subunits / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D000199:Actins; D008840:Microfilament Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; C071058:moesin; D012243:Rhodopsin; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins