Probst W C, Cropper E C, Heierhorst J, Hooper S L, Jaffe H, Vilim F, Beushausen S, Kupfermann I, Weiss K R
Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY 10029.
Proc Natl Acad Sci U S A. 1994 Aug 30;91(18):8487-91. doi: 10.1073/pnas.91.18.8487.
Acting through a cAMP-cAMP-dependent protein kinase (cAPK) cascade, members of two neuropeptide families, the small cardioactive peptides and myomodulins, modulate contraction amplitude and relaxation rate in the accessory radula closer (ARC) muscle of the marine mollusc Aplysia californica. An approximately 750-kDa phosphoprotein was identified in the ARC muscle as the major substrate for cAPK activated either by application of neuropeptides or by peptides released by motorneuron stimulation at physiological frequencies. Immunoblot and immunoelectron microscopy experiments revealed the widespread presence of this protein in Aplysia muscles and its colocalization with contractile filaments in the ARC muscle. Sequence analysis of proteolytic peptide fragments derived from the protein indicated that it is structurally related to the muscle protein twitchin. Finally, the level of neuropeptide-induced phosphorylation of the protein correlated well with peptidergic modulation of the relaxation rate of the muscle. We propose that twitchin in Aplysia, and perhaps in other species, may mediate the modulation of the relaxation rate of muscle contractions.
通过环磷酸腺苷-环磷酸腺苷依赖性蛋白激酶（cAPK）级联反应，两个神经肽家族（小的具有心脏活性的肽和肌调节素）的成员调节海洋软体动物加州海兔辅助齿舌闭合肌（ARC）的收缩幅度和舒张速率。在ARC肌肉中鉴定出一种约750 kDa的磷蛋白，它是通过应用神经肽或在生理频率下运动神经元刺激释放的肽激活的cAPK的主要底物。免疫印迹和免疫电子显微镜实验表明，这种蛋白在海兔肌肉中广泛存在，并且在ARC肌肉中与收缩细丝共定位。对该蛋白衍生的蛋白水解肽片段的序列分析表明，它在结构上与肌肉蛋白肌动蛋白调节蛋白相关。最后，神经肽诱导的该蛋白磷酸化水平与肌肉舒张速率的肽能调节密切相关。我们提出，海兔以及其他物种中的肌动蛋白调节蛋白可能介导肌肉收缩舒张速率的调节。
