title: Pigment granule translocation in red ovarian chromatophores from the palaemonid shrimp Macrobrachium olfersi (Weigmann, 1836): functional roles for the cytoskeleton and its molecular motors.
abstract: The binding of red pigment concentrating hormone (RPCH) to membrane receptors in crustacean chromatophores triggers Ca²⁺/cGMP signaling cascades that activate cytoskeletal motors, driving pigment granule translocation. We investigate the distributions of microfilaments and microtubules and their associated molecular motors, myosin and dynein, by confocal and transmission electron microscopy, evaluating a functional role for the cytoskeleton in pigment translocation using inhibitors of polymer turnover and motor activity in vitro. Microtubules occupy the chromatophore cell extensions whether the pigment granules are aggregated or dispersed. The inhibition of microtubule turnover by taxol induces pigment aggregation and inhibits re-dispersion. Phalloidin-FITC actin labeling, together with tannic acid fixation and ultrastructural analysis, reveals that microfilaments form networks associated with the pigment granules. Actin polymerization induced by jasplaquinolide strongly inhibits RPCH-induced aggregation, causes spontaneous pigment dispersion, and inhibits pigment re-dispersion. Inhibition of actin polymerization by latrunculin-A completely impedes pigment aggregation and re-dispersion. Confocal immunocytochemistry shows that non-muscle myosin II (NMMII) co-localizes mainly with pigment granules while blebbistatin inhibition of NMMII strongly reduces the RPCH response, also inducing spontaneous pigment dispersion. Myosin II and dynein also co-localize with the pigment granules. Inhibition of dynein ATPase by erythro-9-(2-hydroxy-3-nonyl) adenine induces aggregation, inhibits RPCH-triggered aggregation, and inhibits re-dispersion. Granule aggregation and dispersion depend mainly on microfilament integrity although microtubules may be involved. Both cytoskeletal polymers are functional only when subunit turnover is active. Myosin and dynein may be the molecular motors that drive pigment aggregation. These mechanisms of granule translocation in crustacean chromatophores share various features with those of vertebrate pigment cells.
authors.affiliation: Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil.
authors.forename: Sarah Ribeiro
authors.initials: SR
authors.lastname: Milograna
authors.affiliation: Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil.
authors.forename: Márcia Regina
authors.initials: MR
authors.lastname: Ribeiro
authors.affiliation: Departamento de Biologia Celular, Molecular e Bioagentes Patogênicos, FMRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil.
authors.forename: Munira Muhammad Abdel
authors.initials: MM
authors.lastname: Baqui
authors.affiliation: Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil. Electronic address: mcnamara@ffclrp.usp.br.
authors.forename: John Campbell
authors.initials: JC
authors.lastname: McNamara
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001938:Brazil; D022081:Cell Surface Extensions / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D004398:Dyneins / Q000037:antagonists & inhibitors / Q000378:metabolism; D005260:Female; D007447:Invertebrate Hormones / Q000378:metabolism*; D008387:Marine Toxins / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009218:Myosins / Q000037:antagonists & inhibitors / Q000378:metabolism; D024507:Nonmuscle Myosin Type IIA / Q000037:antagonists & inhibitors / Q000378:metabolism; D024501:Nonmuscle Myosin Type IIB / Q000037:antagonists & inhibitors / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010053:Ovary / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D033541:Palaemonidae / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D010860:Pigments, Biological / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D045483:Rivers; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D007447:Invertebrate Hormones; D008387:Marine Toxins; D009842:Oligopeptides; D010860:Pigments, Biological; D050257:Tubulin Modulators; C022059:red pigment-concentrating hormone; D024507:Nonmuscle Myosin Type IIA; D024501:Nonmuscle Myosin Type IIB; D009218:Myosins; D004398:Dyneins; D011761:Pyrrolidonecarboxylic Acid
keywords: Actin; Confocal microscopy; Crustacean chromatophore; Dynein; Functional inhibition assays; Non-muscle myosin II; Pigment granule transport; Tubulin