Copf Tijana
Department of Physiology and Cellular Biophysics, Columbia University Medical Center, 630 W. 168th St. P&S 12-403, NY 10032, USA; Institute of Molecular Biology and Biotechnology, Nikolaou Plastira 100, P.O Box 1385, GR-70013 Heraklion, Crete, Greece.
Dev Biol. 2014 Sep 15;393(2):282-297. doi: 10.1016/j.ydbio.2014.07.002. Epub 2014 Jul 11.
Dendrites develop morphologies characterized by multiple levels of complexity that involve neuron type specific dendritic length and particular spatial distribution. How this is developmentally regulated and in particular which signaling molecules are crucial in the process is still not understood. Using Drosophila class IV dendritic arborization (da) neurons we test in vivo the effects of cell-autonomous dose-dependent changes in the activity levels of the cAMP-dependent Protein Kinase A (PKA) on the formation of complex dendritic arbors. We find that genetic manipulations of the PKA activity levels affect profoundly the arbor complexity with strongest impact on distal branches. Both decreasing and increasing PKA activity result in a reduced complexity of the arbors, as reflected in decreased dendritic length and number of branching points, suggesting an inverted U-shape response to PKA. The phenotypes are accompanied by changes in organelle distribution: Golgi outposts and early endosomes in distal dendritic branches are reduced in PKA mutants. By using Rab5 dominant negative we find that PKA interacts genetically with the early endosomal pathway. We test if the possible relationship between PKA and organelles may be the result of phosphorylation of the microtubule motor dynein components or Rab5. We find that Drosophila cytoplasmic dynein components are direct PKA phosphorylation targets in vitro, but not in vivo, thus pointing to a different putative in vivo target. Our data argue that tightly controlled dose-dependent intra-neuronal PKA activity levels are critical in determining the dendritic arbor complexity, one of the possible ways being through the regulation of organelle distribution.
树突形成的形态具有多层次的复杂性，涉及特定神经元类型的树突长度和特定的空间分布。目前仍不清楚这在发育过程中是如何调控的，特别是哪些信号分子在这个过程中至关重要。我们利用果蝇IV类树突状分支（da）神经元在体内测试了环磷酸腺苷依赖性蛋白激酶A（PKA）活性水平的细胞自主剂量依赖性变化对复杂树突分支形成的影响。我们发现，对PKA活性水平的基因操作会深刻影响分支复杂性，对远端分支的影响最为强烈。PKA活性的降低和升高都会导致分支复杂性降低，表现为树突长度和分支点数量减少，这表明对PKA的反应呈倒U形。这些表型伴随着细胞器分布的变化：PKA突变体中远端树突分支中的高尔基体驻留站和早期内体减少。通过使用Rab5显性阴性，我们发现PKA与早期内体途径存在遗传相互作用。我们测试了PKA与细胞器之间的可能关系是否可能是微管动力蛋白动力蛋白成分或Rab5磷酸化的结果。我们发现果蝇细胞质动力蛋白成分在体外是PKA的直接磷酸化靶点，但在体内不是，因此指向一个不同的假定体内靶点。我们的数据表明，严格控制的剂量依赖性神经元内PKA活性水平对于确定树突分支复杂性至关重要，其中一种可能的方式是通过调节细胞器分布。
