ATP and calmodulin dependent actomyosin aggregates induced by cytochalasin D in goldfish retinal ganglion cell axons in vitro.
Growing retinal ganglion cell (RGC) axons of the goldfish have mobile varicosities, which play a role in rapid bulk redistribution of axoplasm (Koenig, Kinsman, Repasky, and Sultz, 1985; Edmonds and Koenig, 1987). Varicosities contain a tubulo-vesicular SER embedded in an actin-containing cytomatrix (Koenig et al., 1985). Cytochalasin D (CD) induces the formation of focal cytoskeletal aggregates throughout preterminal axons and especially in varicosities. The aggregates are visible when labelled with fluoroscein isothiocyanate (FITC)-conjugated phalloidin. Double-labelling experiments show that Texas red-myosin or rhodamine isothiocyanate (RITC)-calmodulin immunofluorescence co-localizes with FITC-phalloidin-labelled aggregates. Formation of aggregates is blocked by calmidazolium, a calmodulin antagonist. Axon models permeabilized with digitonin retain the capacity to form focal aggregates in response to CD, when ATP or adenosine-5'-O(3-thiotriphosphate) (ATP-gamma S) is present in the permeabilization buffer, but not when 5'-adenylylimidodiphosphate (AMP-PNP) is present. The latter result indicates that formation of focal aggregates depends on ATP. The findings suggest that the formation of focal aggregates in immature axons is a manifestation of actomyosin interactions after free actin-filament ends are generated by CD treatment.
Edmonds
B T
BT
Department of Physiology, State University of New York, Buffalo 14214.
Koenig
E
E
D000205:Actomyosin / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology* / Q000502:physiology; D000818:Animals; D002147:Calmodulin / Q000502:physiology*; D002478:Cells, Cultured; D003530:Cyprinidae / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology*; D006054:Goldfish / Q000378:metabolism* / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D012160:Retina / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D002147:Calmodulin; D007093:Imidazoles; D015638:Cytochalasin D; C031938:calmidazolium; D000255:Adenosine Triphosphate; D000205:Actomyosin