Calmodulin immunolocalization in outer segments of Xenopus laevis photoreceptors.
Because adaptation of vertebrate photoreceptors to light is mediated by changes in the level of calcium in their outer segments (OS), proteins that bind calcium are important in phototransduction. This study has used immunofluorescence to investigate the distribution of the calcium-binding protein calmodulin within photoreceptor OS dissociated from amphibian ( Xenopus laevis) retinas. The OS of rods and cones had a streak of fluorescence to calmodulin at the ciliary axoneme. The OS of rods (but not cones) also displayed regularly spaced puncta of anti-calmodulin fluorescence along longitudinal lines coinciding with their multiple incisures. This location of calmodulin immunofluorescence closely matches the known location of microtubules within the OS of amphibian rods and cones. These findings provide evidence that calmodulin is closely associated with the microtubules of both the axonemal and incisural cytoskeletal systems in OS, and suggest that this association is important for calmodulin function in photoreceptors.
Eckmiller
Marion S
MS
C. and O. Vogt Brain Research Institute, University Clinic, Heinrich Heine University of Düsseldorf, Postfach 101007, 40001 Düsseldorf, Germany. eckmill@hirn.uni-duesseldorf.de
D000818:Animals; D002147:Calmodulin / Q000032:analysis*; D005455:Fluorescent Antibody Technique; D017949:Retinal Cone Photoreceptor Cells / Q000737:chemistry*; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry*; D014982:Xenopus laevis
D002147:Calmodulin