Boyle Robert Tew, McNamara John Campbell
Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil.
Pigment Cell Res. 2006 Feb;19(1):68-75. doi: 10.1111/j.1600-0749.2005.00277.x.
Chromatic adaptation in crustaceans results from the differential distribution of colored pigment granules within their chromatophores consequent to cell signaling by neurosecretory peptides. However, the force transducing, mechanochemical protein motors responsible for granule translocation, and their molecular mechanisms of action, are not well understood. The present study uses immunocytochemical techniques and a motility assay in vitro to demonstrate that protein motors from the kinesin and myosin superfamilies are stably associated with membrane-bounded pigment granules in the red, ovarian chromatophores of the freshwater, palaemonid shrimp, Macrobrachium olfersii. Monoclonal antibodies against conventional kinesin heavy chain, and an anti-myosin whole serum, labeled pigment-containing fragments prepared from homogenates of chromatophores with fully dispersed or aggregated pigments: this finding infers a permanent association between the protein motors and the pigment granules, and suggests that such motors may be regulated while bound to their cargos. The pigment aggregator appears to be a myosin since the anti-myosin whole serum attenuated hormonally triggered pigment aggregation in the motility assay in vitro, and induced pigment hyper-dispersion in some chromatophores. Western blots of the chromatophore-containing, ovarian tissue homogenate demonstrated protein bands consistent with myosin II and myosin XII, either of which may be the pigment aggregator. This study provides the first direct evidence for myosin and kinesin protein motors directly and stably associated with pigment granules in crustacean chromatophores, and may represent the first successful isolation of myosin class XII.
甲壳类动物的色适应是由神经分泌肽的细胞信号传导导致色素细胞内有色色素颗粒的差异分布引起的。然而，负责颗粒转运的力转导机械化学蛋白马达及其分子作用机制尚不清楚。本研究使用免疫细胞化学技术和体外运动测定法，证明来自驱动蛋白和肌球蛋白超家族的蛋白马达与淡水沼虾Macrobrachium olfersii红色卵巢色素细胞中膜结合的色素颗粒稳定相关。针对传统驱动蛋白重链的单克隆抗体和抗肌球蛋白全血清，标记了从色素完全分散或聚集的色素细胞匀浆中制备的含色素片段：这一发现推断蛋白马达与色素颗粒之间存在永久关联，并表明此类马达在与其货物结合时可能受到调节。色素聚集蛋白似乎是一种肌球蛋白，因为抗肌球蛋白全血清在体外运动测定中减弱了激素触发的色素聚集，并在一些色素细胞中诱导了色素过度分散。含色素细胞的卵巢组织匀浆的蛋白质印迹显示出与肌球蛋白II和肌球蛋白XII一致的蛋白条带，其中任何一种都可能是色素聚集蛋白。本研究为肌球蛋白和驱动蛋白蛋白马达直接且稳定地与甲壳类色素细胞中的色素颗粒相关联提供了首个直接证据，并且可能代表了首次成功分离出肌球蛋白XII类。
