A role for cytoskeletal elements in the light-driven translocation of proteins in rod photoreceptors.
OBJECTIVE
Light-driven protein translocation is responsible for the dramatic redistribution of some proteins in vertebrate rod photoreceptors. In this study, the involvement of microtubules and microfilaments in the light-driven translocation of arrestin and transducin was investigated.


METHODS
Pharmacologic reagents were applied to native and transgenic Xenopus tadpoles, to disrupt the microtubules (thiabendazole) and microfilaments (cytochalasin D and latrunculin B) of the rod photoreceptors. Quantitative confocal imaging was used to assess the impact of these treatments on arrestin and transducin translocation. A series of transgenic tadpoles expressing arrestin truncations were also created to identify portions of arrestin that enable arrestin to translocate.


RESULTS
Application of cytochalasin D or latrunculin B to disrupt the microfilament organization selectively slowed only transducin movement from the inner to the outer segments. Perturbation of the microtubule cytoskeleton with thiabendazole slowed the translocation of both arrestin and transducin, but only in moving from the outer to the inner segments. Transgenic Xenopus expressing fusions of green fluorescent protein (GFP) with portions of arrestin implicates the C terminus of arrestin as an important portion of the molecule for promoting translocation. This C-terminal region can be used independently to promote translocation of GFP in response to light.


CONCLUSIONS
The results show that disruption of the cytoskeletal network in rod photoreceptors has specific effects on the translocation of arrestin and transducin. These effects suggest that the light-driven translocation of visual proteins at least partially relies on an active motor-driven mechanism for complete movement of arrestin and transducin.
Peterson
James J
JJ
Department of Ophthalmology, University of Florida, Gainesville, 32610, USA.
Orisme
Wilda
W
Fellows
Jonathan
J
McDowell
J Hugh
JH
Shelamer
Charles L
CL
Dugger
Donald R
DR
Smith
W Clay
WC
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D019393:Arrestin / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000633:toxicity; D015638:Cytochalasin D / Q000633:toxicity; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008027:Light; D018613:Microscopy, Confocal; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D021381:Protein Transport / Q000528:radiation effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D013827:Thiabendazole / Q000633:toxicity; D013844:Thiazoles / Q000633:toxicity; D053778:Thiazolidines; D015293:Transducin / Q000378:metabolism*; D014982:Xenopus laevis
D019393:Arrestin; D019086:Bridged Bicyclo Compounds, Heterocyclic; D011993:Recombinant Fusion Proteins; D013844:Thiazoles; D053778:Thiazolidines; D049452:Green Fluorescent Proteins; D015638:Cytochalasin D; D015293:Transducin; C037068:latrunculin B; D013827:Thiabendazole