title: Melanosome and erythrosome positioning regulates cAMP-induced movement in chromatophores from spotted triplefin, Grahamina capito.
abstract: This study investigated regulation of uniform positioning of melanosomes and erythrosomes in chromatophores from spotted triplefin Grahamina capito from New Zealand, by modulating levels of intracellular cAMP. Elevated cAMP levels, caused by forskolin treatment, inhibited aggregation and induced rapid dispersion of melanosomes and erythrosomes. The dispersing organelles moved to and accumulated at the cell periphery, leading to an abnormal hyperdispersed state with a melanosome- or erythrosome-depleted cell center. Minutes after hyperdispersion, these organelles reversed direction and moved towards the center again to finally distribute throughout the cells. When chromatophores with initially dispersed melanosomes or erythrosomes were treated with forskolin, no hyperdispersion was seen, but the erythrosomes aggregated slowly. Disassembly of actin by latrunculin resulted in a similar but constant hyperdispersed melanosome and erythrosome distribution. The results show that cAMP not only disperses but also aggregates melanosomes and erythrosomes, and that it is the intracellular position of these organelles that determine the directionality of the cAMP-induced movement. To ascertain the even distribution in the dispersed state, regulatory components associated with the actin cytoskeleton in the cell periphery might modify activity of cytoplasmic dynein or kinesin upon contact with dispersing melanosomes or erythrosomes.
authors.affiliation: Department of Zoophysiology, University of Göteborg, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Nilsson
mesh_terms: D000199:Actins / Q000037:antagonists & inhibitors / Q000187:drug effects; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002338:Carotenoids / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005399:Fishes / Q000502:physiology*; D066298:In Vitro Techniques; D020460:Melanosomes / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D012879:Skin Physiological Phenomena / Q000187:drug effects; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D013844:Thiazoles; D053778:Thiazolidines; D005576:Colforsin; D002338:Carotenoids; D000242:Cyclic AMP; C037067:latrunculin A; D009638:Norepinephrine