PATHWAYS OF RECEPTOR SIGNALING AND CHEMOTAXIS

受体信号传导和趋化性的途径

• 批准号: 7593426
• 负责人: ALAN R KIMMEL
• 金额: $ 46.55万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7593426
• 关键词: Accounting; Actins; Adenylate Cyclase; Binding; Biological Process; CAR receptor; Cell Polarity; Cell Surface Receptors; Cells; Chemicals; Chemotactic Factors; Chemotaxis; Complex; Condition; Cyclic AMP; Cyclic AMP Receptors; Cyclic AMP-Dependent Protein Kinases; Cytoskeleton; Development; Dictyostelium; Eukaryota; Eukaryotic Cell; Family; Feedback; GTP-Binding Proteins; Gene Expression; Growth and Development function; Heterotrimeric GTP-Binding Proteins; Individual; Ligand Binding; Ligands; MAPK1 gene; Mammalian Cell; Mediating; Mitogen-Activated Protein Kinases; Neurotransmitters; Pathway interactions; Phosphorylation; Phosphotransferases; Physiological Processes; Production; Range; Receptor Signaling; Regulation; Serine; Signal Pathway; Signal Transduction; System; Threonine; Transmembrane Domain; Variant; Work; chemokine; chemokine receptor; extracellular; morphogens; neutrophil; polarized cell; receptor; response; Accounting; Actins; Adenylate Cyclase; Binding; Biological Process; CAR receptor; Cell Polarity; Cell Surface Receptors; Cells; Chemicals; Chemotactic Factors; Chemotaxis; Complex; Condition; Cyclic AMP; Cyclic AMP Receptors; Cyclic AMP-Dependent Protein Kinases; Cytoskeleton; Development; Dictyostelium; Eukaryota; Eukaryotic Cell; Family; Feedback; GTP-Binding Proteins; Gene Expression; Growth and Development function; Heterotrimeric GTP-Binding Proteins; Individual; Ligand Binding; Ligands; MAPK1 gene; Mammalian Cell; Mediating; Mitogen-Activated Protein Kinases; Neurotransmitters; Pathway interactions; Phosphorylation; Phosphotransferases; Physiological Processes; Production; Range; Receptor Signaling; Regulation; Serine; Signal Pathway; Signal Transduction; System; Threonine; Transmembrane Domain; Variant; Work; chemokine; chemokine receptor; extracellular; morphogens; neutrophil; polarized cell; receptor; response

Chemotactic cells orient and move directionally in very shallow chemical gradients. As cells polarize, distinct structural and signaling components become spatially restricted to the leading edge or rear of cells. Feedback loops downstream of receptor signaling integrate both activating and inhibiting pathways to establish cell polarity within such gradients. While much effort has focused on defining activating pathways, inhibitory networks have been largely unexplored. Many receptor-mediated pathways in eukaryotes adapt/deactivate to persistent stimulation. While the MAP kinase ERK2 in Dictyostelium has been assumed to adapt to continuous engagement of cAMP with its 7-transmembrane, cell surface receptor CAR, we have shown, to the contrary, that ERK2 remains active under such conditions. The upstream phosphorylation pathway that is responsible for ERK2 activation transiently responds to CAR stimulation, whereas ERK2 de-phosphorylation (deactivation) is inhibited by continuous stimulation. We argue that the net result is persistently active ERK2 when the extracellular cAMP concentration is constant and that the oscillating production/destruction of secreted cAMP in chemotaxing cells accounts for the observed oscillatory activity of ERK2. We also showed that CAR-dependent pathways that control ERK2 activation/deactivation function independently of G proteins and of ligand-induced production of intracellular cAMP and the consequent activation of PKA. This regulation enables ERK2 to function both in an oscillatory manner, critical for chemotaxis, and in a persistent manner, necessary for gene expression, as secreted cAMP increases during later development. This work redefines mechanisms of ERK2 regulation by CAR signaling in Dictyostelium and establishes new implications for control of signal-relay during chemotaxis. 7-TMRs activate multiple downstream signaling cascades via heterotrimeric G protein-dependent and -independent pathways and control a wide range of biological processes. Upon ligand binding, 7-TMRs become phosphorylated at cytoplasmic serine and threonine residues by specific receptor kinases, functioning to uncouple heterotrimeric G protein pathways from receptor signaling and to activate G protein-independent pathways. In Dictyostelium, CAR signaling regulates chemotaxis and both G protein-dependent and -independent signaling cascades. Since the CARs become phosphorylated upon cAMP binding, we analyzed the ability of cells that only express non-phosphorylatable CAR variants to respond to cAMP. These cells were defective in adenylyl cyclase adaptation and in cell polarization and chemotaxis. While receptor phosphorylation is known to uncouple certain G protein-mediated signaling pathways from 7-TMRs in mammalian cells, our studies are the first to show that such mechanisms also function in pathways that regulate chemotaxis.

趋化细胞定向并在非常浅的化学梯度中方向移动。随着细胞极化，不同的结构和信号传导成分在空间上限制在细胞的前缘或后部。受体信号下游的反馈环会整合激活和抑制途径，以在此类梯度内建立细胞极性。尽管很多努力集中在定义激活途径上，但抑制网络在很大程度上没有探索。 真核生物中许多受体介导的途径适应/停用以持续刺激。尽管已假定Dictyostelium中的MAP激酶ERK2适应CAMP与其7跨膜，细胞表面受体车的连续参与，但相反，我们已经表明，在这种情况下ERK2保持活跃。负责ERK2激活的上游磷酸化途径会瞬时响应汽车刺激，而ERK2去磷酸化（停用）被连续刺激抑制。我们认为，当细胞外cAMP浓度恒定并且在趋化型趋化型cAMP中振荡/破坏趋化细胞中的振荡/破坏是ERK2的振荡活性时，净结果是持续活跃的ERK2。我们还表明，控制ERK2激活/失活的CAR依赖性途径独立于G蛋白和配体诱导的细胞内cAMP的产生以及随之而来的PKA激活。该调节使ERK2能够以振荡的方式起作用，对趋化性至关重要，并且以持续的方式（基因表达）的持续方式起作用，因为分泌的营地在以后的发育过程中增加。这项工作重新定义了dictyostelium中CAR信号调节ERK2调节的机制，并确立了对趋化过程中信号延迟控制的新含义。 7-TMR通过异三聚体G蛋白依赖性和非依赖性途径激活多个下游信号级联，并控制广泛的生物学过程。配体结合后，7-TMR通过特定的受体激酶在细胞质丝氨酸和苏氨酸残基上磷酸化，从而从受体信号传导和激活G蛋白独立的途径中脱离异位三聚体G蛋白途径。在Dictyostelium中，CAR信号传导调节趋化性以及G蛋白依赖性和非依赖性信号级联反应。由于汽车在cAMP结合时会磷酸化，因此我们分析了仅表达非磷酸化汽车变体对cAMP响应cAMP的细胞的能力。这些细胞在腺苷酸环化酶适应以及细胞极化和趋化性方面有缺陷。虽然已知受体磷酸化可以使哺乳动物细胞中7-TMR的某些G蛋白介导的信号通路取消，但我们的研究是第一个表明这种机制在调节趋化性的途径中也起作用。