Transmembrane Signaling By Receptor Protein Kinases In Plants

植物的分化深受环境因素的影响。我们研究的长期目标是了解细胞外信号如何与植物细胞机制相互作用以影响生长和发育。最近的证据有力地表明植物细胞具有具有内在蛋白激酶活性的质膜受体。植物受体样蛋白激酶（RLK）在结构上与动物多肽生长因子受体相关；然而，植物RLKs似乎都是丝氨酸/苏氨酸蛋白激酶。植物RLKs的多样性反映在它们的结构和功能特性上，为研究植物细胞信号传导开辟了广阔的新领域，对植物细胞感知和响应细胞外刺激的机制具有深远的意义。我们的具体目的是表征拟南芥中一种受体样蛋白激酶（RLK5）的体外和体内生化特性。我们已经证明，这种跨膜蛋白激酶的重组融合蛋白会对几个位点进行自磷酸化，并且自磷酸化对于与细胞靶点的相互作用至关重要。其中一个靶点KAPP（激酶相关蛋白磷酸酶）包含三个结构域：氨基末端膜插入信号、激酶相互作用结构域和磷酸化蛋白磷酸酶结构域。KAPP与RLK5的相互作用需要RLK5磷酸化。这种结合机制让人联想到src同源2蛋白与动物中活化的生长因子受体的相互作用。本研究将明确RLK5的自磷酸化位点，并探讨KAPP结合RLK5的功能意义。RLK5介导的细胞内信号传导的其他成分也将被确定。预计这些研究结果将为植物感知环境的分子机制以及环境信号如何调节生长和发育过程提供基础和新的见解。植物的分化深受环境因素的影响。我们研究的长期目标是了解细胞外信号如何与植物细胞机制相互作用以影响生长和发育。最近的证据有力地表明植物细胞具有具有内在蛋白激酶活性的质膜受体。植物受体样蛋白激酶（RLK）在结构上与动物多肽生长因子受体相关；然而，植物RLKs似乎都是丝氨酸/苏氨酸蛋白激酶。植物RLKs的多样性反映在它们的结构和功能特性上，为研究植物细胞信号传导开辟了广阔的新领域，对植物细胞感知和响应细胞外刺激的机制具有深远的意义。我们的具体目的是表征拟南芥中一种受体样蛋白激酶（RLK5）的体外和体内生化特性。我们已经证明，这种跨膜蛋白激酶的重组融合蛋白会对几个位点进行自磷酸化，并且自磷酸化对于与细胞靶点的相互作用至关重要。这项工作现在将进一步研究自磷酸化的性质以及它在信号事件序列中的重要性。预计这些研究结果将为植物感知环境的分子机制以及环境信号如何调节生长和发育过程提供基础和新的见解。＊＊＊

MCB-9417732 Walker Differentiation in plants is profoundly affected by environmental factors. The long term goal of our research is to understand how extracellular signals interact with the plant cellular machinery to influence growth and development. Recent evidence strongly suggests that plant cells have plasma membrane receptors with intrinsic protein kinase activity. The plant receptor-like protein kinases (RLK) are structurally related to the animal polypeptide growth factor receptors; however, the plant RLKs all appear to be serine/threonine protein kinases. Diversity among plant RLKs, reflected in their structural and functional properties, has opened up a broad new area of investigation into cellular signaling in plants with far-reaching implications for the mechnaisms by which plant cells perceive and respond to extracellular stimuli. Our specific aims are to characterize the biochemical properties, both in vitro and in vivo, of one receptor-like protein kinase (RLK5) from Arabidopsis thaliana. We have shown that a recombinant fusion protein of this transmembrane protein kinase will autophosphorylate several sites and that autophosphorylation is critical for interaction with cellular targets. One of these targets, KAPP (kinase associated protein phosphatase) contains three domains: an amino-terminal membrane insertion signal, a kinase interaction domain and phosphoprotein phosphatase domain, Interaction of KAPP with RLK5 requires RLK5 phosphorylation. This mechanism of binding is reminiscent of the interaction of src homology 2 containing proteins with activated growth factor receptors in animals. The research proposed here will define the autophosphorylation sites in RLK5 and investigate the functional significance of KAPP binding to RLK5. Additional components for RLK5 mediated intracellular signaling will also be identified. It is anticipated that results from these studies will yield fundamental and new insights into the molecular mech anisms of how plants perceive their environment and how growth and developmental processes are regulated by environmental signals. %%% Differentiation in plants is profoundly affected by environmental factors. The long term goal of our research is to understand how extracellular signals interact with the plant cellular machinery to influence growth and development. Recent evidence strongly suggests that plant cells have plasma membrane receptors with intrinsic protein kinase activity. The plant receptor-like protein kinases (RLK) are structurally related to the animal polypeptide growth factor receptors; however, the plant RLKs all appear to be serine/threonine protein kinases. Diversity among plant RLKs, reflected in their structural and functional properties, has opened up a broad new area of investigation into cellular signaling in plants with far-reaching implications for the mechnaisms by which plant cells perceive and respond to extracellular stimuli. Our specific aims are to characterize the biochemical properties, both in vitro and in vivo, of one receptor-like protein kinase (RLK5) from Arabidopsis thaliana. We have shown that a recombinant fusion protein of this transmembrane protein kinase will autophosphorylate several sites and that autophosphorylation is critical for interaction with cellular targets. The work will now further investigate the nature of the autophosphorylation and how it is important in the signaling sequence of events. It is anticipated that results from these studies will yield fundamental and new insights into the molecular mechanisms of how plants perceive their environment and how growth and developmental processes are regulated by environmental signals. ***