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Microglia-specific localisation of a novel calcium binding protein, Iba1
1Department of Neurochemistry, National Institute of Neuroscience, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187, Japan.
Abstract:
Recently it has been shown that mRNA of Iba1 (ionized calcium binding adaptor molecule 1), which was a novel calcium binding protein cDNA-cloned by our group, is specifically expressed in microglia in cultures of rat brain cells [Imai et al. Biophys. Biochem. Res. Commun., 224 (1996) 855-862]. In the present study, immunocytochemical and immunohistochemical examinations demonstrated that Iba1 protein is expressed in microglia alone both in cultured brain cells and in the brain, respectively. In a mixed cell culture of embryonic rat brain, immunocytochemically positive for Iba1 protein were the microglia but it was not detectable in neurons, astroglia, or oligodendroglia. Immunohistochemical staining of adult rat brain sections showed Iba1 protein to be specifically localised in ramified microglia. In addition, immunohistochemical staining and immunoblot analysis of activated microglia in the facial nucleus after facial nerve axotomy shows that expression of Iba1 protein was upregulated and peaked at 7 days. These results indicated that localisation of Iba1 protein is restricted to microglia both in vitro and in vivo, and that Iba1 protein plays a role in regulating the function of microglia, especially in the activated microglia.
Insights
Ionized calcium binding adaptor molecule 1 (Iba1) protein is specifically expressed in microglia, both in cell cultures and in the brain. Iba1 protein expression is upregulated in activated microglia, suggesting a role in microglial function.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Ionized calcium binding adaptor molecule 1 (Iba1) mRNA is known to be specifically expressed in microglia.
- Iba1 is a novel calcium-binding protein identified in rat brain cells.
Purpose of the Study:
- To confirm the specific expression of Iba1 protein in microglia.
- To investigate the role of Iba1 protein in microglial function, particularly in activated states.
Main Methods:
- Immunocytochemistry and immunohistochemistry were used to detect Iba1 protein.
- Western blot analysis (immunoblot) was performed on activated microglia.
Main Results:
- Iba1 protein was immunocytochemically detected exclusively in microglia in mixed embryonic rat brain cell cultures.
- Immunohistochemical staining confirmed Iba1 protein localization in ramified microglia in adult rat brain sections.
- Iba1 protein expression was significantly upregulated in activated microglia following facial nerve axotomy, peaking at 7 days.
Conclusions:
- Iba1 protein is specifically localized to microglia in both in vitro and in vivo conditions.
- Iba1 protein plays a role in regulating microglial function, especially in activated microglia.