The chemokine receptor CXCR4 and its endogenous ligand SDF-1 are expressed in the neurogenic regions of the adult brain and are critical for guiding neurogenesis and migration of neural stem and progenitor cells. Recent evidence indicates that chemokines also regulate the proliferative and restorative response of the brain following focal cell death in brain injuries and neurological diseases. Activated chemokine receptors stimulate several cellular effectors, of which the mobilization of Ca2+ is a key signaling process necessary for its biological effects. As a multifunctional second messenger, Ca2+ activates distinct genetic programs that control many processes such as the proliferation of neural progenitor cells (NPCs), NPC migration, and differentiation of NPCs into mature neurons and glia. However, how NPCs generate Ca2+ signals in response to chemokines and other regulatory factors remains unknown. Our preliminary studies indicate that store-operated Ca2+ release-activated Ca2+ channels (CRAC channels) are a major mechanism for chemokine-driven Ca2+ signals in NPCs. We further find that ablation of CRAC channel expression or pharmacological blockade suppresses chemokine-mediated Ca2+ signaling, NPC proliferation, and chemokine-mediated migration of NPCs to their terminal destinations. Based on this evidence, we hypothesize that CRAC channels are essential regulators of chemokine-mediated Ca2+ signaling and directed migration of NPCs. We propose the three specific aims to address this question: 1) Define the expression of STIM1/Orai1 proteins in the neurogenic regions of the brain. How does this correlate with the known expression of the CXCR4 receptor? 2) Elucidate the contribution of CRAC channels for the generation of complex Ca2+ signals by the chemokine, SDF1. 3) Determine the role of CRAC channels for chemokine-mediated migration of NPCs and neuroblasts. We will approach these questions using a multidisciplinary approach that combines in-depth protein expression studies using confocal microscopy, electrophysiology and Ca2+ imaging using 2-photon laser scanning microscopy, and in vitro and in vivo cell migration assays. Collectively, results from these studies will advance our understanding of the physiological role of CRAC channels for the directed migration of neural progenitors and aid the quest for developing new therapies for brain repair following injuries and in neurodegenerative diseases.
The goal of this project is to understand how chemokines, which regulate the migration of neural stem cells, synergize with store-operated Ca2+ channels to control the migration of neural stem cells to their terminal brain destinations. Findings from these studies will provide new mechanistic insights into the signaling mechanisms controlling migration of neural progenitors and could yield new therapeutic strategies to treat brain injuries and neurodegenerative diseases.
| Toth, Anna B; Shum, Andrew K; Prakriya, Murali (2016) Regulation of neurogenesis by calcium signaling. Cell Calcium 59:124-34 |
