Abstract
Microglia are resident macrophages in the central nervous system. In response to injuries or inflammation, microglia are stimulated to exhibit drastic changes in morphology and functions, and called as "activated microglia". Activated microglia proliferate vigorously, migrate and accumulate to the site of the inflammation, and phagocytose pathogens and cellular debris. Further, activate microglia produce various bioactive molecules to assist repair and regeneration of the nervous system. In this report, to elucidate molecular mechanisms of microglia activation, we focused on motility and phagocytosis of microglia. Motility and phagocytosis are underlain by dynamic remodeling of the action cytoskeleton. Microglia exhibit extremely active motility and phagocytosis, suggesting existence of microglia-specific regulatory mechanisms. We therefore analyzed signaling molecules involved in regulation of the actin cytoskeleton of activated microglia. Iba1 is a small calcium-binding protein expressed specifically in microglia. We previously reported that expression of Iba1 is upregulated during microglia activation, and that Iba1 is involved in motility and phagocytosis of microglia. Furthermore, Iba1 was shown to be cooperating with a small G protein, Rac, in regulation of the actin cytoskeleton. Herein, we demonstrated intracellular behavior of these signaling molecules by using visualizing system such as green fluorescent protein (GFP). [Jpn J Physiol 54 Suppl:S78 (2004)]
