title: Rac1 modulates stimulus-evoked Ca(2+) release in neuronal growth cones via parallel effects on microtubule/endoplasmic reticulum dynamics and reactive oxygen species production.
abstract: The small G protein Rac regulates cytoskeletal protein dynamics in neuronal growth cones and has been implicated in axon growth, guidance, and branching. Intracellular Ca(2+) is another well known regulator of growth cone function; however, effects of Rac activity on intracellular Ca(2+) metabolism have not been well characterized. Here, we investigate how Rac1 activity affects release of Ca(2+) from intracellular endoplasmic reticulum (ER) stores stimulated by application of serotonin (5-hydroxytriptamine). We also address how Rac1 effects on microtubule assembly dynamics affect distribution of Ca(2+) release sites. Multimode fluorescent microscopy was used to correlate microtubule and ER behavior, and ratiometric imaging was used to assess intracellular Ca(2+) dynamics. We report that Rac1 activity both promotes Ca(2+) release and affects its spatial distribution in neuronal growth cones. The underlying mechanism involves synergistic Rac1 effects on microtubule assembly and reactive oxygen species (ROS) production. Rac1 activity modulates Ca(2+) by 1) enhancing microtubule assembly which in turn promotes spread of the ER-based Ca(2+) release machinery into the growth cone periphery, and 2) by increasing ROS production which facilitated inositol 1,4,5-trisphosphate-dependent Ca(2+) release. These results cast Rac1 as a key modulator of intracellular Ca(2+) function in the neuronal growth cone.
authors: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven CT 06520, USA.
authors: Xiao-Feng
authors: XF
authors: Zhang
authors: Paul
authors: P
authors: Forscher
mesh_terms: D000818:Animals; D001048:Aplysia / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D020439:Growth Cones / Q000378:metabolism* / Q000648:ultrastructure; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D012701:Serotonin; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D020830:rac1 GTP-Binding Protein; D002118:Calcium